Study of terrestrial diatoms in corticolous assemblages from deciduous trees in Central Europe with descriptions of two new Luticola D.G.Mann taxa

Mateusz Rybak; Paweł Czarnota; Teresa Noga

doi:10.3897/phytokeys.221.95248

Research Article

Study of terrestrial diatoms in corticolous assemblages from deciduous trees in Central Europe with descriptions of two new Luticola D.G.Mann taxa

Mateusz Rybak^‡, Paweł Czarnota^‡, Teresa Noga^‡

‡ University of Rzeszów, Rzeszów, Poland

Corresponding author: Mateusz Rybak ( matrybak91@gmail.com )

Academic editor: Kalina Manoylov

This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Citation: Rybak M, Czarnota P, Noga T (2023) Study of terrestrial diatoms in corticolous assemblages from deciduous trees in Central Europe with descriptions of two new Luticola D.G.Mann taxa. PhytoKeys 221: 1-40. https://doi.org/10.3897/phytokeys.221.95248

Abstract

Although many studies have examined the algae associated with various habitats in tree trunks, the diatoms in these environments are still poorly studied. Studies of corticolous algae mainly focus on green algae and cyanobacteria, which are usually immediately visible, while diatoms are mostly overlooked or not reported. During the research, 143 species of diatoms were identified, including two new representatives of the genus Luticola: L. bryophila sp. nov. with relatively large central area and short distal raphe endings and L. confusa sp. nov. characterized by the presence of small depressions on central raphe endings. Both are described herein based on light and scanning electron microscopy observations and compared to similar taxa based on literature data. Basic morphological data for almost all the diatom taxa are noted, and their habitat requirements, and photographic documentation are also presented. The present research showed that the occurrence of diatom assemblages on tree trunks is influenced by various factors like host tree species, the area where the host tree grows, and the availability of suitable microhabitats within the trunk. However, the species composition of this assemblages depends mainly on the tree species.

Keywords

Bacillariophyceae, bark chemistry, bryosphere, corticolous habitats, diversity, taxonomy

Introduction

Despite over a century of study on terrestrial algae (West and West 1894; Fritsch 1907; Petersen 1915, 1928, 1935; Beyens 1989), less is still known about these ecological groups than is known about algae from aquatic environments. Most research on terrestrial algae is floristic (Dodd and Stoermer 1962; Schlichting 1975; Camburn 1983; McMillan and Rushforth 1985; Hoffmann 1989), while few works focus on their ecology (Ress 2012; Foets et al. 2021).

Many different terms are used to name algal assemblage in their terrestrial environments depending on environmental conditions and available water sources (Ress 2012; Furey et al. 2020). Bark-associated assemblages that inhabit raised objects that receive moisture exclusively from the atmosphere are categorized as euaerial. The terms epiphylophyte and epiphloeophyte are used to refer to bark-associated algae. The former describes algae growing on leaf surfaces, while the latter describes algae inhabiting tree bark often in association with bryophytes and lichens (Chapman and Chapman 1973; Awasthi 2015; Sivakumar 2016). The term corticophiles is also sometimes used in reference to algal communities growing directly on tree barks (Kawecka and Eloranta 1994; Bhakta et al. 2014; Narasimha Rao 2017).

Bark surfaces create special microclimatic niches for algae. Thanks to cracks, they retain moisture, protect against wind, and provide shade and nutrients that are compounds from accumulated dust which dissolve in rainwater (Kawecka and Eloranta 1994). Algae inhabiting tree trunks have been the subject of a few studies, most of which focused on green algae and cyanobacteria (Foerester 1971; Wylie and Schlichting 1973; Mrozińska 1990; Thompson and Wujek 1997; Salleh and Milow 1999; Czerwik and Mrozińska 2000; Neustupa 2003, 2005; Soni and Shukla 2006; Neustupa and Škaloud 2008, 2010; Lemes-Da-Silva et al. 2010; Bhakta et al. 2014; Kharkongor and Ramanujam 2014; Štifterová and Neustupa 2015; Narasimha Rao 2017; Ambika and Krishnamurthy 2018). In research on bark-associated algae, diatoms have been reported rarely to date and are usually only listed as single taxa in species’ lists (Neustupa and Škaloud 2010; Neustupa and Štifterová 2013; Kharkongor and Ramanujam 2014; Štifterová and Neustupa 2015; Nirmala et al. 2016; Eldrin 2019). Lakatos and co-authors (Lakatos et al. 2004) studied diatoms inhabiting the thallus of the arboreal lichen Coenogonium linkii Ehrenb., and during this research they noted 18 taxa. Research conducted by Qin et al. (2016) was focused on diatoms associated with arboreal bryophytes growing on trees in Wuhan, and they collected samples mainly from Cinnamomum camphora Ness & Eberm and they noted 76 taxa represented 13 genera. Studies on diatoms inhabiting arboreal mosses from the Indo-Burma biodiversity hot spot showed the presence of 56 species from 21 genera (Cheran et al. 2022). The only work from Europe is based on preliminary results from samples collected from a single tree Despite the small number of samples, 47 species have been identified (Rybak et al. 2018). In all these works, each studied sample contained only few species (usually fewer than 20) and were dominated by species from genera like: Luticola, Humidophila, Pinnularia and Orthoseira.

The aim of the study was to investigate the taxonomic diversity and ecological requirements of diatoms inhabiting various microhabitats on trunks of deciduous trees in Central Europe in areas confronting various degrees of human impact. Additionally, preferences of diatoms for host tree species and microhabitats within trunks were determined.

Methods

Samples were collected in 2017 and 2018 four times each year in the first half of April and June, and the second half of August and October from heights of 20 cm (referred to as trunk base) and 150 cm above ground level from several tree trunk microhabitats, i.e., bare bark, moss clumps, bark covered with lichens, bark with visible mats of algae (Fig. 1), at eight sampling sites and from the same trees of the following taxa: sycamore maple (Acer pseudoplatanus L.), linden (Tilia spp. L.), and poplar (Populus spp. L.). The designated sites included city centers (sites 1 and 4), small peripheral estates (sites 2 and 5), park complexes in suburban areas (sites 3 and 6), and the buffer zones of two national parks: Magurski National Park (site 7) and Gorczański National Park (site 8) (Table 1). Samples in form of bark pieces, together with overgrowing epiphytes, were chipped off using a hammer and chisel and placed in paper envelopes to avoid mold. During the collection of materials, no visible signs of the presence of diatoms (like slime or different color stains) were noted on the surface.

Figure 1.

Types of studied microhabitats on the example of sycamore maple. Bare bark (A), bark covered by green algae (B, C), bark with lichen covering (D) and bark covered by bryophytes (E).

Table 1.

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List of studied sites with the sampled tree taxa and microhabitat type over their trunk.

Site	Tree species	Coordinates	Studied microhabitat
1	Acer pseudoplatanus L.	50°34'09.1"N, 22°03'57.5"E	bare bark, lichens
	Tilia platyphyllos Scop.	50°34'04.1"N, 22°04'01.9"E	bare bark, lichens
	Populus nigra L. ‘Italica’	50°34'08.5"N, 22°03'56.8"E	bare bark, mosses, lichens
2	Acer pseudoplatanus L.	50°34'12.1"N, 22°04'20.4"E	lichens
	Tilia cordata Mill.	50°34'12.2"N, 22°04'20.8"E	lichens
	Populus nigra L.	50°34'16.4"N, 22°04'18.6"E	bare bark, mosses, lichens
3	Acer pseudoplatanus L.	50°36'13.2"N, 22°02'01.7"E	bare bark, mosses, green algae mats
	Tilia cordata Mill.	50°35'58.2"N, 22°01'49.7"E	bare bark, mosses
	Populus nigra L.	50°35'59.0"N, 22°01'49.6"E	bare bark, mosses
4	Acer pseudoplatanus L.	50°01'06.7"N, 22°01'01.5"E	bare bark, lichens
	Tilia platyphyllos Scop.	50°01'18.4"N, 22°00'56.7"E	bare bark, lichens
	Populus nigra L. ‘Italica’	50°01'18.8"N, 22°01'00.6"E	bare bark, mosses, lichens
5	Acer pseudoplatanus L.	50°00'08.9"N, 22°01'54.1"E	bare bark, mosses
	Tilia cordata Mill.	50°00'11.0"N, 22°01'54.1"E	bare bark, mosses
	Populus nigra L.	50°00'09.5"N, 22°01'48.3"E	bare bark, mosses, lichens, green algae mats
6	Acer pseudoplatanus L.	50°00'36.3"N, 21°59'16.0"E	bare bark, mosses
	Tilia cordata Mill.	50°00'39.1"N, 21°59'20.5"E	bare bark, mosses
	Populus alba L.	50°00'42.6"N, 21°59'23.6"E	bare bark, mosses, green algae mats
7	Acer pseudoplatanus L.	49°30'10.3"N, 21°29'31.1"E	bare bark, mosses, green algae mats
	Tilia cordata Mill.	49°30'42.8"N, 21°29'57.0"E	bare bark, mosses, lichens
	Populus tremula L.	49°30'58.1"N, 21°29'38.3"E	bare bark, mosses
8	Acer pseudoplatanus L.	49°37'01.8"N, 20°04'07.0"E	bare bark, mosses, lichens
	Tilia cordata Mill.	49°37'01.4"N, 20°04'06.7"E	bare bark, mosses, lichens
	Populus nigra L.	49°37'02.8"N, 20°04'14.3"E	bare bark, mosses, lichens

The samples were also used to prepare filtrates for pH and conductivity analyses. The filtrates were obtained by soaking bare bark pieces in deionized water (1:10 by weight) for 24 hours. The intact pieces of bark were used to obtain a solution similar to that forming on the bark surface that is a source of water and nutrients for corticolous organisms; in the case of trees completely covered by epiphytic mosses, the material together with them was used to obtain filtrates. Electrolytic conductivity and pH were measured with a MARTINI pH56 pH meter and a MARTINI EC59 conductometer (Milwaukee Electronics Kft.). The ions’ content was determined using a Thermo scientific DIONEX ICS–5000+DC device in the Departmental Laboratory of Analysis of Environmental Health and Materials of Agricultural Origin at the University of Rzeszów.

A modified method by Qin et al. (2016) was used to obtain clean diatom material. For the purpose of separating bryophytes and diatoms from the bark surface, a part of the material collected was placed in beakers to which 50 ml 30% hydrogen peroxide (H₂O₂) was added, and these were left at room temperature for 48 hours. In the next step, bark fragments were rinsed with deionized water, and the resulting solution was collected in the same beaker in which the bark was digested. To obtain clean diatom valves, the solution was centrifuged to remove excess hydrogen peroxide and again digested in a mixture of sulfuric acid (H₂SO₄) and potassium dichromate (K₂Cr₂O₇) until the organic matter was completely dissolved. In the last step, the burning mixture was removed by centrifugation with distilled water (at 2500 rpm).

Light microscope slides were prepared by applying the cleaned diatom suspension to cover-slips that were left to dry. The dried material was mounted in synthetic Pleurax resin, Brunel Microscopes ltd. (refractive index 1.75). To better define the species composition of the assemblages analyzed, two microscope samples on coverslips were mounted on a single slide. In total, 647 samples were collected and analyzed. The diatoms were identified under a Carl Zeiss Axio Imager.A2 light microscope (LM) with a Zeiss AxioCam ICc 5 camera at 1000× magnification. For Scanning Electron Microscope (SEM) observations, the samples were coated in a Turbo-Pumped Sputter Coater Quorum Q 150OT ES with a 20 nm layer of gold and viewed under a Hitachi SU 8010 microscope.

Two microscope slides were made from each collected sample. Diatoms were identified in both slides by observations in all possible adjacent transects. During species identification, all identified valves were counted until a number of 400 was reached. Identification of species was continued for species composition also after reaching the assumed limit of 400 valves. The dominance structure and similarity analysis were determined only for samples for which a minimum of 200 valves were counted. Species with a minimum share of 10% in the assemblages were considered dominants. The remaining samples were considered unrepresentative because of the insufficient development of assemblages or their complete absence. To present the morphological variability of the observed taxa, valves dimensions were measured under light microscope using AxioVision SE62 Rel. 4.9.1 software. For range dimension of commonly occurred taxa ca. 50 specimens were measured including the biggest and the smallest observed specimens. In the case of rare taxa (observed in <10 samples) each observed specimen was measured.

Diatom diversity was analyzed using the Shannon diversity index (H’) and the Evenness index (J’). Principal Component Analysis (PCA) was performed to determine the similarity of diatom assemblages. Prior to analysis, diatom data were square root transformed. Redundancy analysis (RDA, gradient length = 1.9 SD) was performed to determine the effect of bark chemistry on diatom assemblages, but none of the parameters showed statistically significant effects on the assemblages studied (p> 0.05). All analyses (PCA, RDA) were performed using Canoco 5 (Ter Braak and Šmilauer 2012).

Student’s t-test was used to analyze the significance of differences in the chemical parameters of the samples, and values at p<0.05 were considered statistically significant. All calculations were performed using Statistica 13.3 software.

Diatom terminology and identification were based on Round et al. (1990), Krammer and Lange-Bertalot (1986, 1988, 1991a, b), Krammer (2000), Lange-Bertalot (1993), Lange-Bertalot et al. (2003, 2011, 2017), Levkov et al. (2013, 2017, 2019) and Houk et al. (2017).

Results

Chemical analyses

The pH of the analyzed filtrates indicated slightly acid to neutral condition of the barks of the tree species examined. The electrolytic conductivity values measured in the filtrates of all the trees analyzed indicated a very wide range (from 49 µm cm^-1 to 5 846 µS cm^-1), regardless of sampling height (Table 2). Statistically significant differences in the parameters measured for samples taken from heights of 20 and 150 cm were noted for pH in linden and poplar and for electrolytic conductivity in sycamore maple. On the other hand, the analysis of chemical parameters of permeates depending on tree species was not statistically significantly different. The parameters measured did not differ significantly among the tree species studied (Table 2).

Table 2.

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Chemical parameters measured in filtrates obtained from bark of studied trees, given range (minimum and maximum), and median (brackets), bold indicates value for samples from trunk bases. * – indicates a parameter in which differences between the studied heights were statistically significant (p> 0.05).

Tree taxon	Acer	Tilia	Populus
pH	5.3–7.3 (6.3)	4.7–7.3 (6.0)*	4.8–7.5 (6.3)*
pH	4.8–7.5 (6.4)	4.8–7.5 (6.4)*	5.1–7.4 (6.5)*
Cond. [μS cm^–1]	49–2305 (167)*	49–462 (202)	52–2305 (323.1)
Cond. [μS cm^–1]	64–604 (228)*	69–5846 (338)	39–1199 (332.1)
Cl- [mg/l]	0.5–29.9 (3.3)	1.1–20.7 (6.3)	0.442–103.7 (9.4)
Cl- [mg/l]	0.5–14.5 (3.3)	0.2–71.7 (9.0)	0.232–98.6 (8.8)
NO₃- [mg/l]	<0.001–4.6 (1.5)	<0.001–4.6 (2.5)	<0.001–159.3 (3.4)
NO₃- [mg/l]	<0.001–16.5 (1.2)	<0.001–89.9 (5.2)	<0.001–42.2 (2.3)
PO₄^3- [mg/l]	<0.001–44.8 (11.1)	<0.001–34.8 (10.1)*	<0.001–36.7 (8.8)*
PO₄^3- [mg/l]	2.7–42.5 (14.1)	<0.001–39.2 (16.3)*	<0.001–64.0 (14.3)*
SO₄^2- [mg/l]	0.7–55.5 (7.2)	<0.001–61.5 (18.6)	<0.001–400.9 (20.9)
SO₄^2- [mg/l]	0.9–14.9 (6.5)	0.6–3 278.2 (66.7)	0.2–10.7 (20.8)
Na⁺ [mg/l]	0.3–12.4 (2.5)	0.4–12.2 (3.1)*	0.273–59.2 (6.8)
Na⁺ [mg/l]	0.3–18.5 (3.4)	0.3–21.0 (5.7)*	0.3–55.3 (7.4)
K⁺ [mg/l]	10.2–137.9 (33.7)	9.509–68.1 (35.9)	7.8–752.2 (86.3)
K⁺ [mg/l]	11.2–161.4 (38.4)	<0.001–1510.2 (65.8)	<0.001–386.3 (75.2)
Ca²⁺ [mg/l]	0.6–48.2 (6.7)	0.1–26.4 (10.6)	0.3–56.5 (8.5)
Ca²⁺ [mg/l]	0.2–34.7 (8.0)	0.3–317.7 (16.4)	0.3–28.9 (8.7)
Mg²⁺ [mg/l]	0.2–18.5 (2.4)	0.3–10.6 (2.7)	0.1–37.1 (3.5)
Mg²⁺ [mg/l]	0.1–14.0 (2.6)	0.6–62.8 (3.8)	0.2–10.7 (3.0)
NH₄⁺ [mg/l]	<0.001–28.5 (3.8)*	0.1–23.7 (5.6)	<0.001–12.3 (2.3)*
NH₄⁺ [mg/l]	0.7–32.8 (7.3)*	<0.001–228.9 (12.7)	<0.001–103.0 (5.8)*

Taxonomic results

Description of new species

Luticola bryophila M.Rybak, Czarnota & Noga, sp. nov.

Fig. 2

Description

Rectangular in girdle view. Valves linear to linear lanceolate with weakly protracted and moderately rounded apices, smaller specimens without protracted apices. Valve length 10–25 µm, and valve width 4–6 µm. Axial area narrow linear, slightly expanded near central area. Central area wide and rounded, bordered by 3–4 areolae. Ghost areolae commonly present in central area. Round isolated pore located half way between valve center and margin. Raphe branch straight with both endings clearly curved to site opposite to isolated pore. Distal raphe endings short, not continuing onto mantle. Internal raphe slit simple and straight, distal endings form slightly developed helictoglossae. Striae number 18–20 in 10 µm composed of 2–3 same sized, rounded to slightly elongated areolae. Single row of areolae present also on valve mantle. Internally areolae covered by hymen forming continuous strip, separated by not thickened virgae. Internally small lipped opening of isolated pore visible. Marginal channel located on valve face/mantle junction occluded by hymenes and visible internally.

Figure 2.

Luticola bryophila sp. nov., LM microphotographs of girdle view (A) and size diminution series (B–X), black frame indicate the holotype specimen. SEM microphotographs (Y–AB) of valve in external (Y–AA) and internal view (AB). Scale bars: 10 µm (A–X); 5 µm (Y–AB).

Type material

Holotype : Slide SZCZ 28844 and unmounted material with the same number stored in A. Witkowski Diatom Collection of the Institute of Marine and Environmental Sciences, University of Szczecin, holotype specimen designated here in Fig. 3K

Figure 3.

Luticola confusa sp. nov., LM microphotographs of size diminution series (A–X), black frame indicate the holotype specimen. SEM microphotographs (Y–AB), valve in external (Y–AA) and internal view (AB). Scale bars: 10 µm (A–X); 5 µm (Y, Z, AB),

Isotype : Slide no. 2017/18 and unmounted material with the same number at the University of Rzeszów, Poland.

Type locality

Stalowa Wola, Podkarpacie Province, Poland, 50°34'16.4"N, 22°04'18.6"E, leg. M. Rybak.

Etymology

The name refers to the occurrence of the species mainly in terrestrial bryophytes.

Distribution

Species observed at most of the sites studied, always in single specimens, mainly in samples of bryophytes from trunk bases.

Similar species

Luticola sparsipunctata Levkov, Metzeltin & Pavlov (Levkov et al. 2013, p. 222); Luticola tenuis Levkov, Metzeltin & Pavlov (Levkov et al. 2013, p. 236).

Luticola confusa M.Rybak & Czarnota, sp. nov.

Fig. 3

Description

Valves elliptic to elliptic-lanceolate with rounded apices, rectangular in girdle view. Valve length 9–22 µm, and valve width 4.5–5.5 µm. Axial area narrow and linear, central area elliptic bordered by 3–4 areolae. Round isolated pore located halfway between valve center and margin. Raphe branch straight. Proximal raphe endings deflected to site opposite to stigma with small rounded depressions. Distal raphe endings hooked continuing onto valve mantle. Internally raphe slit simple and straight, distal endings form slightly developed helictoglossae. Striae number 20–22 in 10 µm composed mainly of 4 areolae, single row of areolae also present on valve mantle. On apices row of mantle areolae interrupted by distal raphe endings. Internally areolae covered by hymen forming continuous strip, separated by not thickened virgae. Internally small lipped opening of isolated pore visible. Marginal channel located on valve face/mantle junction occluded by hymenes and visible internally.

Type material

Holotype : Slide SZCZ28845 and unmounted material with the same number stored in A. Witkowski Diatom Collection of the Institute of Marine and Environmental Sciences, University of Szczecin, holotype specimen designated here in Fig. 4O.

Figure 4.

Number of diatom taxa identified during the research on each of the examined trees on each site and value of Eveness index (J’) and Shannon index (H’). 1–8 number of sampling site.

Isotype : Slide no. 2018/454 and unmounted material with the same number at the University of Rzeszów, Poland.

Type locality

Stalowa Wola, Podkarpacie Province, Poland, 50°36'13.2"N, 22°02'01.7"E, leg. M. Rybak.

Etymology

The name refers to possible past confusions in identification of the species described with other small taxa with elliptic-lanceolate valves.

Distribution

Species observed at all sites studied, always in the form of individual specimens. It mainly occurred in samples taken from the base of the trunks of the trees studied.

Similar species

Luticola imbricata (W.Bock) Levkov, Metzeltin and Pavlov (Levkov et al. 2013, p. 134); L. pseudoimbricata Levkov, Metzeltin & Pavlov (Levkov et al. 2013, p. 134); L. obscura Levkov, Tofilovska, C.E.Wetzel, Mitić-Kopanja & Ector (Levkov et al. 2017).

Diversity and composition of diatom assemblages

During the study 143 diatom taxa representing 39 genera were identified (Table 3, Figs 2, 3, 5–22). Most of them belonged to the genera Luticola (27), Pinnularia (13), and Stauroneis (10) (Table 3). Among the taxa identified, only a few species were found commonly in the materials studied and had noticeable shares in the communities. In most of the trees studied significantly more species were recorded in samples taken from the trunk bases (Fig. 4).

Figure 5.

LM microphotographs of Orthoseira dendroteres in girdle view (A) and in size diminution series (B–E) and O. roeseana (F–K). SEM microphotographs of Orthoseira dendroteres (L) and O. roeseana (M, N). Scale bars: 10 µm.

Figure 6.

LM microphotographs of Achnanthes coarctata (A–I), Meridion circulare (J), Pseudostaurosira brevistriata (K), Eunotia botuliformis (L, M), Cocconeis pediculus (N, O), C. lineata (P, K), Lemnicola hungarica (R, S), Planothidium lanceolatum (T–X) and P. frequentissimum (Y–AC). Scale bar: 10 µm.

Figure 7.

LM microphotographs of Navicula neowiesneri (A–L), N. pseudowiesneri (M–S), N. gregaria (T, U), N. veneta (V, W), N. tenelloides (X), N. bjoernoeyaensis (Y), N. lundii (Z–AF), Placoneis hambergii (AG, AH), Sellaphora subseminulum (AI–AP) and S. harderii (AQ–AX). Scale bar: 10 µm.

Figure 8.

LM microphotographs of Humidophila contenta (A–G), H. gallica (H–P), H. brekkaensis (Q–Z), H. irata (AA–AF), H. perpusilla (AG–AL), Fallacia insociabilis (AM–AS), F. enigmatica (AT), Microcostatus aerophilus (AU–AZ), Mayamaea excelsa (BA, BB), M. atomus (BC–BJ), M. asellus (BK–BM), M. fossalis (BN–BP), M. permitis (BQ–BS), Cavinula cocconeiformis (BT) and Geissleria ignota (BU, BV). Scale bar: 10 µm.

Figure 9.

LM microphotographs of Luticola acidoclinata (A–H), L. poulickovae (I), L. cohnii (J, K), L. pseudokotschyi (L), L. spinifera (M–O), L. pitranensis (P–S), L. rotunda (T–AA), Luticola sp. (AB–AD), L. imbricata (AE–AJ), L. micra (AK–AP), L. cf. vesnae (AR–AX) and L. obscura (AY–BD). Scale bar: 10 µm.

Figure 10.

LM microphotographs of Luticola sparsipunctata in size diminution series (A–M). SEM microphotographs of external (N) and internal view (O). White arrowheads indicate a discontinuity in hymenes, Scale bars: 10 µm (A–M), 5 µm (N, O).

Figure 11.

LM microphotographs of Luticola nivalis (A–G), L. pseudonivalis (H–J), L. binodeformis (K), L. pulchra (L–S), L. kemalii (T–V), L. lecohui (W–AA), L. vanheurckii (AB–AE), L. undulata (AF), L. nivaloides (AG–AM), L. cholnokyi (AN, AO), L. ventricosa MT1 (AP–AV) and L. ventricosa MT2 (AW–BA). Scale bar: 10 µm.

Figure 12.

SEM microphotographs of Luticola spinifera (A, B), Luticola sp. (C), L. acidoclinata (D), L. ventricosa MT2 (E) and L. obscura (F). Scale bars: 10 µm (D); 5 µm (A–C, E, F).

Figure 13.

SEM microphotographs of Luticola nivaloides (A), L. nivalis (B), L. pulchra (C), L. vanheurckii (D), L. pseudonivalis (E) and L. lecouhui (F). Scale bars: 10 µm (B); 5 µm (A, C–F).

Figure 14.

SEM microphotographs of Humidophila gallica (A), H. perpusilla (B), H. contenta (C), Microcostatus aerophilus (D), Fallacia insociabilis (E), Navicula neowiesneri (F), Stauroneis thermicola (G) and S. parathermicola (H). Scale bars: 5 µm (B–H); 3 µm (A).

Figure 15.

LM microphotographs of Muelleria islandica (A–D), M. undulata (E–M), M. terrestris (N–R), M. sasaensis (S–W) and Neidium perforatum (X–AC). SEM microphotography of N. perforatum (AD). Scale bar: 10 µm (A–AC); 5 µm (AD).

Figure 16.

SEM microphotographs of Muelleria undulata (A–D) and M. terrestris (E–H). Scale bars: 10 µm (E, F), 5 µm (A, B, G, H); 3 µm (C, D).

Figure 17.

LM microphotographs of Stauroneis saprophila (A–C), S. obtusa (D–I), S. thermicola (J–P), S. parathermicola (K–S), S. leguminopsis (T), S. aff. lundii (U, V), S. muriella (W), S. laterostrata (X–AC), and S. borichii (AD–AI). Scale bar: 10 µm.

Figure 18.

LM microphotographs of Cosmioneis pusilla (A), Pinnularia microstauron var. angusta (B), P. brebissonii (C, D), P. isselana (E–G), P. cuneola (H–M) and Halamphora montana (N–S). Scale bar: 10 µm.

Figure 19.

LM microphotographs of Pinnularia borealis var. borealis (A–E), P. borealis var. subislandica (F–H), P. dubitabilis (I), P. sinistra (J–M), P. schoenfelderi (N–R), P. frauenbergiana var. caloneiopsis (S–U), P. obscura (V–AC), Caloneis cf. langebertalotioides (AD–AH), P. perirrorata (AI–AL), C. vasileyevae (AM–AP) and C. lancettula (AQ–AT). Scale bar: 10 µm.

Figure 20.

LM microphotographs of Hantzschia abundans (A–E), H. amphioxys (F–J), H. subrupestris (K–P), H. dorgaliensis (R) and H. stepposa (S). Scale bar: 10 µm.

Figure 21.

LM microphotographs of Hantzschia calcifuga in size diminution series (A–J). Scale bar: 10 µm.

Figure 22.

LM microphotographs of Tryblionella apiculata (A, B), T. debilis (C–E), Nitzschia harderi (F–I), N. solgensis (J), N. amphibia (K–M), N. amphibia f. apiculata (N–P), N. communis (Q), N. cf. frustulum (R–T), N. pusilla (U–Z), Surirella angusta (AA–AD), S. minuta (AE, AF) and S. terricola (AG–AJ). Scale bar: 10 µm.

Table 3.

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Complete list of documented diatom taxa with measured dimension ranges (Length / Width; striae/10µm), frequency of occurrence in samples (Freq. [%]), minimum and maximum relative abundance (Min-Max) at sycamore maples (Acer), lindens (Tilia) and poplars (Populus). Bold indicates data from samples collected at 20 cm above ground level. + idicates observation of species in sample with unrepresentative assemblages.

Taxa	Dimensions	Acer		Tilia		Populus
Taxa	Dimensions	Freq.	Min-Max	Freq.	Min-Max	Freq.	Min-Max
*Achnanthes coarctata* (Brébisson & W.Smith) Grunow	15–32 / 4–7;	21	0.21–0.48	22	0.31–0.32	27	0.22–1.42
*Achnanthes coarctata* (Brébisson & W.Smith) Grunow	11–13	8	0.30–0.34	25	0.10–2.47	20	0.19–1.38
*Achnanthidium minutissimum* (Kützing) Czarnecki	5–18 / 3;	11	0.24–0.48	4	+	8	–
*Achnanthidium minutissimum* (Kützing) Czarnecki	21–22	9	0.21–0.31	12	0.32–7.41	15	0.19–0.49
*Amphora pediculus* (Kützing) Grunow	7–10 / 2.7–3;	–	–	–	–	–	–
*Amphora pediculus* (Kützing) Grunow	17–18	1	0.32	5	0.41	1	+
*Aulacoseira* spp.	–	14	0.25–0.31	9	0.20	5	0.12–0.34
*Aulacoseira* spp.		20	0.07–0.23	16	0.18–0.32	10	0.17–0.33
*Caloneis aerophila* W.Bock	12–19 / 3.5–4.5;			1	+
*Caloneis aerophila* W.Bock	19–23			–	–
*Caloneis lancettula* (Schulz) Lange-Bertalot & Witkowski	13–25 / 4–4.5;	4	0.37–0.48	1	+	2	–
	23–26	2	0.17–0.21	3	+	3	0.65
Caloneis cf. langebertalotioides Reichardt	17–26 / 4.5–5;	1	0.31	–	+	1	+
Caloneis cf. langebertalotioides Reichardt	26	–	0.25	1	0.41	3	0.17–0.29
*Caloneis leptosoma* (Grunow) Krammer	23.5–32.5 / 5–6;	–	–	–	–
*Caloneis leptosoma* (Grunow) Krammer	14–16	1	0.26	1	+
*Caloneis vasileyevae* Lange-Bertalot, Genkal & Vekhov	12–18 / 4–4.5;			1	+
*Caloneis vasileyevae* Lange-Bertalot, Genkal & Vekhov	27–30			–	–
*Cavinula cocconeiformis* (W.Gregory & Greville) D.G.Mann & A.J.Stickle	21–23.5 / 10;	1	0.30
	27	–	–
*Cocconeis euglypta* Ehrenberg	8–15 / 7–10;			1	+	1	+
*Cocconeis euglypta* Ehrenberg	14–22			6	+	–	–
*Cocconeis lineata* Ehrenberg	8–15 / 8–11;	5	0.26–0.37	4	+	2	0.32
*Cocconeis lineata* Ehrenberg	14–26	1	0.17	9	0.31–2.47	3	0.23
*Cocconeis pediculus* Ehrenberg	17–26 / 8–11;			2	+	–	–
*Cocconeis pediculus* Ehrenberg	18			4	0.32	1	0.47
*Cocconeis pseudolineata* (Geitler) Lange-Bertalot	7–20 / 7–11;	–	–	2	+	–	–
*Cocconeis pseudolineata* (Geitler) Lange-Bertalot	15	1	0.29	1	+	1	0.23
*Cosmioneis pusilla* (W.Smith) D.G.Mann & A.J.Stickle	22.5–26 / 13–15;					1	+
*Cosmioneis pusilla* (W.Smith) D.G.Mann & A.J.Stickle	15–16					–	–
*Cyclostephanos dubius* (Hustedt) Round	–	22	0.16–0.50	19	+	14	0.22–0.37
*Cyclostephanos dubius* (Hustedt) Round		17	0.22–0.48	26	0.31–2.47	8	0.17–0.37
*Epithemia adnata* (Kützing) Brébisson	17–22.5 / 7–9;	3	0.21–0.33	–	–	1	+
*Epithemia adnata* (Kützing) Brébisson	14	2	0.17–0.23	1	0.41	2	0.49
*Eunotia botuliformis* F.Wild, Nörpel & Lange-Bertalot	6–26 / 3–3.5;	–	–	–	–
*Eunotia botuliformis* F.Wild, Nörpel & Lange-Bertalot	16–19	8	0.21–0.37	1	+
*Eunotia minor* (Kützing) Grunow	12.5–31.5 / 4–6;			1	+	–	–
*Eunotia minor* (Kützing) Grunow	10–12			–	–	1	0.33
*Fallacia enigmatica* (H.Germain) Lange-Bertalot & Werum	8.8 / 2–2.2;			–	–	2	–
	not visible in LM			1	+	–	+
*Fallacia insociabilis* (Krasske) D.G.Mann	6.5–21 / 4.5–6.5;	2	0.31–0.66	1	–	2	0.47
*Fallacia insociabilis* (Krasske) D.G.Mann	22–25	11	0.17–1.30	6	0.41	3	0.22–0.49
*Geissleria ignota* (Krasske) Lange-Bertalot & Metzeltin	22.5–24 / 5;					–	–
	13–14					1	0.16
*Gomphonella olivacea* (Hornemann) Rabenhorst	12–23 / 5–6;	1	0.32	–	–	–	–
*Gomphonella olivacea* (Hornemann) Rabenhorst	10–11	–	–	1	+	1	+
*Gomphonema acuminatum* Ehrenberg	22 / 7;	1	0.24	–	–
*Gomphonema acuminatum* Ehrenberg	12	–	–	1	+
*Gomphonema amoenum* Lange-Bertalot	30–35 / 9–10;	1	0.31			–	–
*Gomphonema amoenum* Lange-Bertalot	10–11	1	0.32			1	0.24
*Gomphonema drutelingense* Reichardt	20–24.5 / 6.5–7;					–	–
*Gomphonema drutelingense* Reichardt	11					1	+
*Gomphonema micropus* Kützing	20–26 / 7–7.5;	2	0.13	1	+	1	+
*Gomphonema micropus* Kützing	10–12	4	0.26–0.29	7	0.20–1.23	4	0.32–0.93
*Gomphonema parvulum* (Kützing) Kützing	10–15 / 6–7;	1	0.24–	–	–	2	–
*Gomphonema parvulum* (Kützing) Kützing	11–13	–		2	+	1	0.31
*Halamphora montana* (Krasske) Levkov	12–20 / 3.5–5.5;	18	0.20–0.34	13	0.31–0.32	16	0.17–3.79
*Halamphora montana* (Krasske) Levkov	not visible in LM	21	0.17–2.08	16	0.10–0.41	16	0.17–0.65
*Hantzschia abundans* Lange-Bertalot	35–74.5 / 6–9.5;	47	0.21–2.81	51	0.30–0.61	51	0.12–6.16
*Hantzschia abundans* Lange-Bertalot	19–20	43	0.17–9.95	77	0.20–2.40	65	0.16–6.92
*Hantzschia amphioxys* (Ehrenberg) Grunow	12–45 / 4.5–7;	88	0.20–23.13	84	0.30–2.76	87	0.12–93.90
*Hantzschia amphioxys* (Ehrenberg) Grunow	21–27	94	0.14–58.82	99	0.20–29.94	91	0.16–88.10
*Hantzschia calcifuga* Reichardt & Lange-Bertalot	28–85 / 6.5–7.7;	18	0.21–23.18	20	+	18	0.17–0.47
*Hantzschia calcifuga* Reichardt & Lange-Bertalot	16–19	37	0.18–4.02	25	0.18–4.12	22	0.22–21.80
*Hantzschia dorgaliensis* Lange-Bertalot, Cavacini, Tagliaventi & Alfinito	60 / 6.7;					–	–
	18–19					1	+
Hantzschia aff. stepposa Maltsev & Kulikovskiy	33 / 5;					–	–
Hantzschia aff. stepposa Maltsev & Kulikovskiy	25					1	+
*Hantzschia subrupestris* Lange-Bertalot	26.7–81 / 6.7–9;	9	0.25–0.66	10	+	13	0.35–0.95
*Hantzschia subrupestris* Lange-Bertalot	14–17	15	0.18–2.99	16	0.20–0.65	20	0.16–1.01
*Humidophila brekkaensis* (Petersen) Lowe et al.	8–19.5 / 6–6.5;	1	–	1	+	2	–
*Humidophila brekkaensis* (Petersen) Lowe et al.	not visible in LM	5	0.24–12.5	5	+	3	0.34
*Humidophila contenta* (Grunow) Lowe et al.	5–13 / 2.5–3.2;	53	0.20–23.13	32	7.50–58.51	40	0.56–59.25
*Humidophila contenta* (Grunow) Lowe et al.	not visible in LM	68	0.02–34.05	52	0.30–79.22	72	0.23–81.77
*Humidophila gallica* (W.Smith) Lowe et al.	4–10 / 2–3;	2	0.31	9	0.20	10	0.35–10.90
*Humidophila gallica* (W.Smith) Lowe et al.	not visible in LM	3	0.22–0.34	7	+	15	0.22–4.12
*Humidophila irata* (Krasske) Lowe et al.	15–21 / 6.2–6.5;	6	0.24–0.31	2	+	2	0.24
*Humidophila irata* (Krasske) Lowe et al.	not visible in LM	25	0.17–1.01	17	0.10–0.41	6	0.19–0.22
*Humidophila perpusilla* (Grunow) Lowe et al.	6–13.5 / 4–5;			1	+	5	0.84
*Humidophila perpusilla* (Grunow) Lowe et al.	not visible in LM			2	+	10	2.21–19.06
*Lemnicola hungarica* (Grunow) Round & Basson	8–13 / 4–6;	–	–	1	+	–	–
*Lemnicola hungarica* (Grunow) Round & Basson	18–21	1	0.25–0.34	2	+	1	0.49
*Luticola acidoclinata* Lange-Bertalot	10–32 / 4.8–8.7;	81	0.31–98.77	50	2.50–38.21	55	1.02–97.33
*Luticola acidoclinata* Lange-Bertalot	18–23	87	0.26–99.91	69	1.62–94.12	68	7.73–91.22
*Luticola binodeformis* Levkov, Metzeltin & Pavlov	12–15.5 / 4–4.5;					–	–
*Luticola binodeformis* Levkov, Metzeltin & Pavlov	21–22					1	0.33
*Luticola blancoi* Levkov, Tofilovska, C.E.Wetzel, Mitić-Kopanja & Ector	18–21 / 6.5;			–	–	–	–
	20–21			1	+	1	+
*Luticola bryophila* M.Rybak, Czarnota & Noga, sp. nov.	10–25 / 4–6;	5	0.26	8	+	5	0.24
*Luticola bryophila* M.Rybak, Czarnota & Noga, sp. nov.	18–20	14	0.17–0.66	11	0.25–0.65	17	0.22–7.73
*Luticola cholnokyi* Levkov, Metzeltin & Pavlov	15–18 / 6.5;	–	–
*Luticola cholnokyi* Levkov, Metzeltin & Pavlov	20–21	1	0.16
*Luticola cohnii* (Hilse) D.G.Mann	17.5–28.5 / 8.5–10;	–	–	–	–
*Luticola cohnii* (Hilse) D.G.Mann	20–21	1	0.31	1	+
*Luticola confusa* M.Rybak & Czarnota, sp. nov.	9–22 / 4.5–6;	20	0.24–0.32	13	–	20	0.35–3.32
*Luticola confusa* M.Rybak & Czarnota, sp. nov.	20–22	25	0.18–10.45		0.18-2.00	19	0.17–0.53
*Luticola imbricata* (W.Bock) Levkov, Metzeltin & Pavlov	15–17 / 5.5–7;	–	–	1	+	–	–
	20	2	0.30–0.66	1	+	1	+
*Luticola kemalii* Solak & Levkov	12–16 / 5.6–7;	2		–	–	2	+
*Luticola kemalii* Solak & Levkov	20–22	–		1	+	2	0.28
*Luticola lecohui* Levkov, Tofilovska, C.E.Wetzel, Mitic-Kopanja & Ector	15–23.5 / 7–8;	1	+	1	+
	20–21	–	–	1	+
*Luticola micra* Levkov, Metzeltin & Pavlov	7.5–13 / 3.8–4.5;	6	0.24–0.32	5	0.30–0.31	7	0.24–0.28
*Luticola micra* Levkov, Metzeltin & Pavlov	22–24	9	0.20–0.52	5	0.28–0.30	2	0.19
*Luticola nivalis* (Ehrenberg) D.G.Mann	10–21 / 5.8–7.5;	16	0.28–0.36	15	0.32	21	0.17–0.95
*Luticola nivalis* (Ehrenberg) D.G.Mann	19–21	17	0.25–0.68	9	0.10	33	0.22–0.69
*Luticola nivaloides* (W.Bock) Denys & De Smet	15–23.5 / 6.5–8;	1	0.48	1	+	6	0.47
*Luticola nivaloides* (W.Bock) Denys & De Smet	18–19	–	–	4	0.32	8	0.17–0.29
*Luticola obscura* Levkov, Tofilovska, C.E.Wetzel, Mitić-Kopanja & Ector	10–24.5 / 5–7;	20	0.48–0.48	28	0.30–0.31	15	0.34
	19–22	26	0.17–2.24	36	0.18–1.53	29	0.19–7.54
*Luticola pitranensis* Levkov, Metzeltin & Pavlov	15–22.5 / 5.5–6.5;	–	–
*Luticola pitranensis* Levkov, Metzeltin & Pavlov	20–22	2	0.17–0.20
*Luticola poulickovae* Levkov, Metzeltin & Pavlov	22 / 6;	–	–
*Luticola poulickovae* Levkov, Metzeltin & Pavlov	21	1	+
*Luticola pulchra* (McCall) Levkov, Metzeltin & Pavlov	10–20 / 5.9–6.4;	1	0.32	7	0.31	15	1.90
*Luticola pulchra* (McCall) Levkov, Metzeltin & Pavlov	20–24	6	0.22–0.34	9	0.25–0.30	13	0.19–0.33
*Luticola pseudonivalis* (W.Bock) Levkov, Metzeltin & Pavlov	13.2–16.5 / 5–6;	4	+	2	0.31	1	0.47
	24	1	0.28	–	–	–	–
*Luticola rotunda* Solak & Levkov	12–15.5 / 6–6.5;	2	0.20–0.31	1	+	2	–
*Luticola rotunda* Solak & Levkov	19–20	8	0.31–0.68	1	+	1	0.22–0.29
*Luticola sparsipunctata* Levkov, Metzeltin & Pavlov	9.5–27 / 4.5–7;	14	0.28–0.40	19	0.31	25	0.12–1.42
*Luticola sparsipunctata* Levkov, Metzeltin & Pavlov	18–20	24	0.17–3.67	27	0.18–0.34	32	0.19–7.80
*Luticola spinifera* (W.Bock) L.Denys & W.H.De Smet	12–14 / 7–8;					1	+
*Luticola spinifera* (W.Bock) L.Denys & W.H.De Smet	16					–	–
*Luticola undulata* (Hilse) D.G.Mann	19–22.5 / 7.5–7.8;			–	–	–	–
*Luticola undulata* (Hilse) D.G.Mann	24–25			1	+	1	0.49
*Luticola vanheurckii* Van de Vijver & Levkov	14.5–19 / 5.5–7.3;			10	+	6	+
*Luticola vanheurckii* Van de Vijver & Levkov	18–21			16	0.25–0.65	3	0.22–0.29
*Luticola ventricosa* (Kützing) D.G.Mann MT1	10–23 / 5.5–7;	20	0.23–0.40	16	0.30–0.31	15	0.24–3.79
*Luticola ventricosa* (Kützing) D.G.Mann MT1	19–22	11	0.22–10.95	17	0.25–0.32	27	0.17–2.07
*Luticola ventricosa* (Kützing) D.G.Mann MT2	9.2–22 / 5–7;	10	0.26–0.61	23	0.30–0.31	35	0.12–1.42
*Luticola ventricosa* (Kützing) D.G.Mann MT2	19–22	13	0.02–0.82	43	0.19–62.21	31	0.19–0.69
*Luticola* cf. *vesnae* Levkov, Metzeltin & Pavlov	10–23.7 / 5–7.2;	8	0.16–0.25	7	+	9	0.12–0.34
*Luticola* cf. *vesnae* Levkov, Metzeltin & Pavlov	20–24	24	0.18–7.12	18	0.18–0.32	13	0.28–0.97
*Luticola* sp. 1	14–18 / 5.5–7;	–	–	1	0.31	2	0.25
*Luticola* sp. 1	18–23	9	0.34–0.37	9	0.32–0.41	5	0.16–0.19
*Luticola* sp. 2	-	–	+	–	–	–1	+
*Luticola* sp. 2		1	0.28	1	+	1	0.28
*Mayamaea asellus* (Weinhold & Hustedt) Lange-Bertalot	12–16.5 / 5.5–6;	1	0.32	2	+	4	+
*Mayamaea asellus* (Weinhold & Hustedt) Lange-Bertalot	16–18	4	+	7	0.25–0.32	2	0.28–0.29
*Mayamaea atomus* (Kützing) Lange-Bertalot	7–13 / 4–5;	5	+	9	0.31	7	0.22–0.95
*Mayamaea atomus* (Kützing) Lange-Bertalot	18–22	23	0.17–6.86	37	0.25–0.41	15	0.17–0.49
*Mayamaea excelsa* (Krasske) Lange-Bertalot	11–14.5 / 5–7;	2	0.22	–	–	1	+
*Mayamaea excelsa* (Krasske) Lange-Bertalot	16–17	5	0.26–0.31	7	+	3	0.26–0.33
Mayamaea fossalis var. fossalis (Krasske) Lange-Bertalot	9–11.5 / 3–4;	1	+	1	+	1	+
	17–19	3	0.17–0.41	4	+	1	0.33
Mayamaea fossalis var. obsidialis (Hustedt) Lange-Bertalot	9–11 / 4.5;			–	–
	18			3	0.18
*Mayamaea permitis* (Hustedt) K.Bruder & Medlin	7–12 / 3.5–4.5;	1	+	111	1	2	+
*Mayamaea permitis* (Hustedt) K.Bruder & Medlin	ca. 35	7	0.17–2.69	11	0.20	2	0.19
*Meridion circulare* (Greville) C.Agardh	13–24 / 5–6	3	0.20–0.31	7	+	2	0.24
*Meridion circulare* (Greville) C.Agardh	13–24 / 5–6	2	+	9	0.41	1	+
*Microcostatus aerophilus* Stanek-Tarkowska, Noga, C.E.Wetzel & Ector	6–9.5 / 2.5–3.5;	1	+	–	–
	not visible in LM	–	–	5	+
*Muelleria islandica* (Østrup) Lange-Bertalot	19.5–30 / 6.7–7.7;	2	+	2	+	3	+
*Muelleria islandica* (Østrup) Lange-Bertalot	22–25	5	0.17–0.35	3	+	2	+
*Muelleria sasaensis* Levkov, Vidaković, Cvetkoska, Mitić-Kopanja, Krstić, Van de Vijver & Hamilton	22.5–29.5 / 5.8–6.2;	–	–	3	+	1	–
	23–24	3	0.24–1.49	1	+	3	0.25
*Muelleria terrestris* (J.B.Petersen) Spaulding & Stoermer	23.5–26 / 5.2–6;	3	0.24	2	+	3	+
	18–19	3	0.23–0.64	3	0.50	3	v
*Muelleria undulata* (Krasske) Levkov, Hamilton & Van de Vijver	12–22 / 4.3–5;	3	+	1	+	–	–
	26–28	3	0.17–3.98	–	–	2	+
*Navicula bjoernoeyaensis* Metzeltin, Witkowski & Lange-Bertalot	17–18 / 3;	1	+	–	–	1	0.34
	18	–	–	1	+	3	0.23
*Navicula gregaria* Donkin	15.5–22 / 6–7;	–	–	1	+	1	0.12
*Navicula gregaria* Donkin	16	1	0.31	1	0.41	3	0.29–0.43
*Navicula lundii* Reichardt	14–25 / 4.2–6;	–	–			11	0.47
*Navicula lundii* Reichardt	15	2	0.24–0.50				0.24
*Navicula neowiesneri* Chaudev & Kulikovskyi	12–32 / 4.5–6;	38	0.16–0.80	36	0.20–0.32	43	0.12–5.69
*Navicula neowiesneri* Chaudev & Kulikovskyi	11–13	35	0.18–2.03	40	0.18–1.75	38	0.17–4.14
*Navicula pseudowiesneri* Chaudev & Kulikovskyi	11–24 / 4–5;	30	0.16–0.62	21	0.18–0.24	22	0.12–1.12
*Navicula pseudowiesneri* Chaudev & Kulikovskyi	11–13	35	0.18–2.03	23	0.18–1.02	12	0.17–0.35
*Navicula tenelloides* Hustedt	14–18 / 3–3.5;	–	–	1	+	1	+
*Navicula tenelloides* Hustedt	16	1	0.25	1	0.41	–	–
*Navicula veneta* Kützing	12–25.5 / 4.5–5.5;	1	+	–	–	1	0.12
*Navicula veneta* Kützing	13–16	2	0.32–0.41	2	0.32	4	0.22–0.49
*Neidium alpinum* Hustedt	15–29 / 4.5–5;			–	–
*Neidium alpinum* Hustedt	ca. 37			1	+
*Neidium perforatum* Schimanski	15.5–26 / 4.5–5.5;	2	0.31–0.33
*Neidium perforatum* Schimanski	21–23	6	0.18–0.37
*Nitzschia amphibia* Grunow	9–28 / 4–5.5;	9	0.21–0.48	6	0.31	8	0.34–0.47
*Nitzschia amphibia* Grunow	15–18	7	0.25–0.41	7	0.32	8	0.24–0.49
Nitzschia amphibia f. rostrata Hustedt	12–15 / 3.5–4;	1		–	–	–	–
Nitzschia amphibia f. rostrata Hustedt	18–20	–		1	0.32	1	+
*Nitzschia communis* Rabenhorst	15–20 / 4;	1	0.24			1	+
*Nitzschia communis* Rabenhorst	not visible in LM	–	–			3	0.22–0.29
*Nitzschia harderi* Hustedt	19–36 / 3–4;	1	0.25
*Nitzschia harderi* Hustedt	not visible in LM	1	1.48
*Nitzschia pusilla* Grunow	7–22 / 2.5–3.5;	5	0.21–0.36	5	0.20	2	+
*Nitzschia pusilla* Grunow	not visible in LM	11	0.18–1.59	5	0.10	7	0.22–0.33
Nitzschia cf. frustulum (Kützing) Grunow	4–16.5 / 3;	15	0.25–0.36	9	–	4	0.12
Nitzschia cf. frustulum (Kützing) Grunow	25–27	6	0.30	16	0.32–0.34	14	0.22–6.45
*Nitzschia solgensis* Cleve-Euler	11.5–24 / 3–4;	1	0.24	–	–	3	0.33
*Nitzschia solgensis* Cleve-Euler	21–23	2	0.30	1	+	3	0.19–0.29
Nitzschia cf. supralitorea Lange-Bertalot	10–20 / 2.5–3.5;			–	–	2	1.42
Nitzschia cf. supralitorea Lange-Bertalot	27–30			1	+	–	–
*Nitzschia linearis* W.Smith	50–55 / 6;					–	–
*Nitzschia linearis* W.Smith	28–29					2	0.22–1.74
*Orthoseira dendroteres* (Ehrenberg) Genkal & Kulikovskiy	Ø – 7–26;	36	0.24–95.69	7	+	9	0.17–3.59
	20–22	39	0.23–95.36	17	0.82	16	0.17–72.02
*Orthoseira roeseana* (Rabenhorst) Pfitzer	Ø – 8–24;	4	0.24–0.71	2	+	1	0.17
*Orthoseira roeseana* (Rabenhorst) Pfitzer	8–12	8	0.17–3.55	–	–	4	0.26–2.85
Pantocsekiella cf. ocellata (Pantocsek) K.T.Kiss & E.Ács	–	6	0.24–0.34	2	+	6	0.12–0.33
		10	0.02–0.20	6	+	11	0.19–0.33
Pinnularia borealis var. borealisEhrenberg	22–42 / 8–9.5;	68	0.21–58.21	52	0.30–1.81	57	1.63–97.80
Pinnularia borealis var. borealisEhrenberg	ca. 5	80	0.03–52.24	79	0.30–86.57	67	0.24–66.32
Pinnularia borealis var. subislandica Krammer	35–40 / 8.5–9;	–	–	1	+	1	0.47
Pinnularia borealis var. subislandica Krammer	ca. 5	3	0.26–0.32	2	0.30	3	0.29–0.65
*Pinnularia brebissonii* (Kützing) Rabenhorst	10–34 / 9–12;	1	+	1	+	2	+
*Pinnularia brebissonii* (Kützing) Rabenhorst	10–13	3	0.22–0.34	1	+	2	0.22–0.29
*Pinnularia cuneola* Reichardt	24.5–30 / 7–8;	9	0.28–0.34	3	+	9	0.34
*Pinnularia cuneola* Reichardt	10–11	7	0.23–0.32	11	0.30–0.41	9	0.17–0.49
*Pinnularia dubitabilis* Hustedt	40 / 9;	–	–
*Pinnularia dubitabilis* Hustedt	ca. 5	1	+
Pinnularia aff. frauenbergiana var. caloneiopsis Lange-Bertalot & M.Werum	13–22 / 4–4.5;	3	+	1	+	2	+
	17–18	2	0.33–1.35	2	+	1	0.29
*Pinnularia isselana* Krammer	30–45 / 7–9;	2	0.28–0.36	2	+	1	0.24–0.47
*Pinnularia isselana* Krammer	10–12	–	–	10	0.32–0.41	5	0.24–0.49
Pinnularia microstauron var. angusta Krammer	42–44 / 6.5–7;			1	+
Pinnularia microstauron var. angusta Krammer	12–13			–	–
Pinnularia microstauron var. rostrata Krammer	35 / 6.5;			1	+
Pinnularia microstauron var. rostrata Krammer	11			–	–
*Pinnularia obscura* Krasske	9–35 / 3–5;	5559	0.21–1.95	29	0.20–0.31	3	0.24–1.90
*Pinnularia obscura* Krasske	10–13		0.02–26.48	73	0.18–9.48	38	0.16–2.03
*Pinnularia perirrorata* Krammer	12–25 / 4;	–	–	1	+
*Pinnularia perirrorata* Krammer	16–18	5	0.25–0.27	7	0.30
*Pinnularia schoenfelderi* Krammer	19–34 / 5–6.5;	10	0.22–0.50	11	+	6	0.33
*Pinnularia schoenfelderi* Krammer	14–16	11	0.22–0.37	20	0.32–2.47	7	0.23–0.32
*Pinnularia sinistra* Krammer	17–35 / 4.5–6;	3	0.21–0.36	1	+	2	+
*Pinnularia sinistra* Krammer	11–13	6	0.27–0.37	8	0.18	2	+
*Placoneis hambergii* (Hustedt) K.Bruder	14–22 / 5–7;	1	+	–	–
*Placoneis hambergii* (Hustedt) K.Bruder	13–16	4	0.26–0.30	3	0.41
*Planothidium frequentissimum* (Lange-Bertalot) Lange-Bertalot	4–25 / 3.5–6;	6	0.16–0.36	5	0.31	8	0.22–2.37
	14–17	5	0.21–0.30	22	0.30–2.47	11	0.19–1.69
*Planothidium lanceolatum* (Brébisson & Kützing) Lange-Bertalot	7–25 / 4–6.5;	5	0.21–0.30	5	0.30	2	0.12
	13–15	3	0.29–0.30	8	0.30–3.29	7	0.22–3.72
*Rhoicosphenia abbreviata* (C.Agardh) Lange-Bertalot	–			–	–	–	–
*Rhoicosphenia abbreviata* (C.Agardh) Lange-Bertalot				1	+	1	+
*Reimeria sinuata* (W.Gregory) Kociolek & Stoermer	9–14 / 3.5–5.5;	–	–	–	–
*Reimeria sinuata* (W.Gregory) Kociolek & Stoermer	9–13	1	0.29	1	+
*Sellaphora atomoides* (Grunow) Wetzel & Van de Vijver	6–12 / 3–4;	5	0.31–0.36	7	+	4	0.12–1.42
*Sellaphora atomoides* (Grunow) Wetzel & Van de Vijver	22–25	8	0.17–0.41	14	0.41	8	0.12–0.33
*Sellaphora harderi* (Hustedt) J.Foets & C.E.Wetzel	5.5–12 / 3–4;	–	–	–	–	1	+
*Sellaphora harderi* (Hustedt) J.Foets & C.E.Wetzel	32–35	1	0.28	2	+	–	–
*Sellaphora nana* (Hustedt) Lange-Bertalot, Cavacini, Tagliaventi & Alfinito	15–18.5 / 4–4.5;	2	0.30	–	–	1	0.47
	38	1	0.41	3	+	–	–
*Sellaphora nigri* (De Notaris) C.E.Wetzel & Ector	5–10 / 4;					1	0.47
*Sellaphora nigri* (De Notaris) C.E.Wetzel & Ector	28–30					1	+
*Sellaphora subseminulum* (Hustedt) Wetzel	7–14 / 3.2–3.8;	1	+	2	0.31	1	+
*Sellaphora subseminulum* (Hustedt) Wetzel	23–25	8	0.19–1.23	15	0.41–3.29	5	0.22–0.34
*Stauroneis borrichii* (J.B.Petersen) J.W.G.Lund	10–26 / 3.8–5;	19	0.22–0.33	22	0.20	18	0.17–0.95
*Stauroneis borrichii* (J.B.Petersen) J.W.G.Lund	22–26	40	0.20–9.97	43	0.10–1.19	26	0.19–0.49
*Stauroneis laterostrata* Hustedt	19–26 / 6.5–8.5;	–	–			5	+
*Stauroneis laterostrata* Hustedt	17–20	8	0.17–2.01			5	+
*Stauroneis leguminopsis* Lange-Bertalot & Krammer	20–22 / 4.5;	–	–
*Stauroneis leguminopsis* Lange-Bertalot & Krammer	24	1	0.31
*Stauroneis* aff. *lundii* Hustedt	14–19 / 4–5;	2	0.20	4	+	4	0.17–0.22
*Stauroneis* aff. *lundii* Hustedt	23–24	16	0.22–0.59	12	0.32–1.03	4	0.22–0.29
*Stauroneis muriella* J.W.G.Lund	16–20 / 3–4;	1	+	2		–	–
*Stauroneis muriella* J.W.G.Lund	22–26	2	0.26	1		1	+
*Stauroneis obtusa* Lagerstedt	15–28 / 6–8;	1	+	3	+	2	+
*Stauroneis obtusa* Lagerstedt	19–23	4	0.30–6.25	5	0.41	2	+
*Stauroneis parathermicola* Lange-Bertalot	8–18 / 3–4.5;	2	0.32–0.34	1	+	2	+
*Stauroneis parathermicola* Lange-Bertalot	20–23	10	0.17–1.01	12	0.82	2	0.22–0.24
*Stauroneis saprophila* M.Rybak, Noga & Ector	30–35/ 8.5–9.5;	3	0.48	1	+	3	+
*Stauroneis saprophila* M.Rybak, Noga & Ector	15–17	2	0.48	2	+	4	0.22–0.49
*Stauroneis separanda* Lange-Bertalot & Werum	13–14 / 3.8–4.2;	1	0.30	1	+
*Stauroneis separanda* Lange-Bertalot & Werum	ca. 28	1	0.30	1	+
*Stauroneis thermicola* (J.B.Petersen) J.W.G.Lund	8–18 / 3–4.5;	18	0.21–0.37	7	+	2	0.12
*Stauroneis thermicola* (J.B.Petersen) J.W.G.Lund	20–23	28	0.18–4.39	31	0.10–0.32		0.22–0.33
*Surirella angusta* Kützing	16.5–42.5 / 6–9;	3	+	1	+	2	0.12–0.47
*Surirella angusta* Kützing	24–27	–	–	2	0.30	7	0.16–1.16
*Surirella minuta* Brébisson & Kützing	9–34.5 / 8–10;	–	–	2	+	2	+
*Surirella minuta* Brébisson & Kützing	26–28	1	0.25	6	0.41	3	0.29–0.23
*Surirella terricola* Lange-Bertalot & E.Alles	11–18.1 / 6.4;	10	0.21–0.36	97	+	2	+
*Surirella terricola* Lange-Bertalot & E.Alles	18–23	10	0.23–0.34		0.41	3	0.28–0.32
*Tryblionella apiculata* W.Gregory	20–24 / 4.5–5.5;					–	–
*Tryblionella apiculata* W.Gregory	17					2	0.49–1.08
*Tryblionella debilis* Arnott & O’Meara	12–23.5 / 7–8.5;	–	–	11	+	–	–
*Tryblionella debilis* Arnott & O’Meara	not visible in LM	1	+		+	3	0.22–0.49
*Tryblionella hungarica* (Grunow) Frenguelli	35–42 / 5.2–6;			–	–	–	–
*Tryblionella hungarica* (Grunow) Frenguelli	8–10			1	0.25	2	0.22–0.29

Of the 647 samples collected, only in 197 were numerous occurrences of diatoms observed. Diatoms did not occur, or occurred only, as individual valves in all samples from barks covered with lichens or algal mats. Numerous diatom assemblages were observed in 74 of 283 samples from bare bark (27 from 20 cm above ground level and 47 from 150 cm above ground level). Numerous assemblages were also observed in 123 of 231 moss samples collected (43 from 20 cm above ground level and 80 from 150 cm above ground level).

Higher values of both indices studied (H’ and J’) were usually recorded for bare bark samples, and higher values of both of these indices were also recorded for samples collected from trunk bases (Fig. 4). When more than one microhabitat from a single tree was analyzed in the same season, higher values of both indexes were noted for bare bark (Fig. 4).

Principal component analysis (PCA) revealed considerable variability in the diatom assemblages. The gradient length in analysis was 2.7. The first ordination axis explained 33.48% of the variation, the second 25.00%, the third 14.02%, and the fourth 10.14% (Fig. 23). The diatom communities from sites located in city centers and small peripheral estates (sites 1, 2, 4, 5) where the trees were exposed are grouped on the left, bottom corner of the graph. Assemblages from park complexes and the buffer zones of national parks (site 3 and 6–8) form two distinct groups. Samples from sycamore maples are grouped on the bottom right, while assemblages from lindens and poplars are grouped on the left top corner. The seasons in which the research was conducted did not affect the grouping of the tested samples.

Figure 23.

PCA ordination of analyzed samples determined by relative diatom assemblage composition on studied tree taxa.

Discussion

Characteristics of the habitat

Tree barks, thanks to their porosity, can absorb rainwater; therefore the solution on its surface is usually slightly acidic. On the other hand, pH reactions often depend on bark structures, which differ depending on tree species (Zimny 2006). A slightly acidic or close to neutral reaction is typical of the barks of most deciduous tree species, in contrast to conifers, which usually have more acidic barks (Barkman 1958; Steindor et al. 2011; Štifterová and Neustupa 2015). Additionally, the reaction of barks also can decrease with tree age (Grodzińska 1979).

Of the 647 samples collected, only 197 had developed diatom communities, and only single valves were found in the remaining samples. The almost complete or complete absence of diatoms was observed in bark samples covered with visible mats of green algae. Other studies focusing on corticolous algae assemblages, in which only a few species of diatoms have been found (Neustupa and Škaloud 2010; Neustupa and Štifterová 2013; Štifterová and Neustupa 2015), confirm that this microhabitat is not conducive to their development. A similar situation occurred in bark samples covered with lichens. The low number of diatoms in these two microhabitats could be the result of competition for resources with arboreal cyanobacteria and green algae, or it could result from the allelopathic effects of algae and/or lichens on diatoms (Bhattacharyya et al. 2016; Goga et al. 2018).

Although trees growing as close as possible to each other were selected at the sites and materials from analogous microhabitats were collected from them, differences in the frequency of occurrence of diatom assemblages were clearly notable. On bare bark, diatom assemblages were found mainly in materials collected from maples and poplars at locations closest to natural sites (parks and national park buffer zones). However, diatoms were not found or only single specimens were observed in bare bark samples from site 7 (the buffer zone of Magura National Park). This was the only site where samples were collected from aspen poplar (Populus tremula L.), and it is possible that the bark of this host tree is an unfavorable habitat for diatoms. In urban conditions the trunks of poplars and maples were poorly inhabited by diatoms, and their diversity was concentrated in microhabitats created by bryophytes. Regardless of site, lindens seemed to be unsuitable for diatoms; they were abundant on this host tree only in single samples. The tree species-dependent bark water-holding capacity, which is related to bark features such as stability, texture, thickness, and hardness, directly influenced the intensity of desiccation and were important determinants of the distribution of various organisms overgrowing bark including algae (Valová and Bieleszová 2008; Büdel 2011; Ellis 2012).

Materials from moss microhabitats were more than half of the samples in which large numbers of diatoms were found (123 out of 197 samples). This result is similar to the study by Lindo and Gonzalez (2010) in which the bryophytes overgrowing various substrates (bryosphere), thanks to their structure that permits the accumulation of mineral particles and rainwater, create conditions for the development of different groups of organisms. Only samples of bryophytes from linden and poplar trunks in urban sites, and again from aspen at site 7, contained a few diatoms.

The developed diatom assemblages in the microhabitats analyzed were more often recorded in samples taken from trunk bases than from a height of 150 cm above ground level, and more species were also noted in samples collected from trunk bases (Table 2). This could have been because of the greater availability of moisture from condensation, or it could have been related to the higher share of soil diatoms from the vicinity of the trees. However, the height above ground level did not influence the differences in taxonomic composition between samples from different heights within the tree trunk (Fig. 23).

Comparison of novel taxa to similar species

Both of the newly described Luticola represent a group of small taxa with elliptic-lanceolate to linear elliptic valves. Many taxa representing this morphological group have been identified previously as L. mutica, which is a brackish species (Levkov et al. 2013). Consequently, many modern reports of L. mutica, especially those from terrestrial and freshwater habitats, require systematic verification.

Luticola bryophila sp. nov. is most similar to the two European species L. sparsipunctata and L. tenuis. All three taxa share similar sizes and striae densities. The newly described species of the genus Luticola commonly shows ghost areolae in the central area, which are absent in both of the other taxa. Additionally, L. bryophila can be easily separated from L. tenuis based on distal raphe endings, which are short and deflected and not hooked and do not continue onto the valve mantle. Luticola sparsipunctata shows two morphotypes with different distal raphe ending morphology. The first of them has a hooked end that continues onto the valve mantle raphe endings, while the second has short and only deflected raphe endings (Levkov et al. 2013, pl. 33). However, L. sparsipunctata can also be easily distinguished from L. bryophila by the more lanceolate valve shape and the different striae morphology that manifests in the small areolae near the raphe slit and the large areolae near the valve edge (Levkov et al. 2013, p. 222; Fig. 11N), while in L. bryophila the areolae in striae are of the same size. Moreover, the internal view of the valve differs in both species. In L. bryophila the hymenes form a continuous strip on the striae, while in L. sparsipunctata the hymenes are interrupted and cover only the areolae, not the whole striae (Levkov et al. 2013, pl. 33, fig. 7; Fig. 11O).

Luticola confusa sp. nov. is highly similar in valve and central area shape and striae pattern to L. imbricata, L. pseudoimbricata, and L. obscura. The new species can be distinguished from L. imbricata based on its less lanceolate, narrower valves (5–9 µm width in L. imbricata vs. 4–6 µm in L. confusa) (Levkov et al. 2013, p. 134) and by small depressions on the proximal raphe endings, while they are absent in L. imbricata (Levkov et al. 2017, figs 191, 192). Compared to L. obscura, which has hooked distal raphe endings terminating on the valve face, L. confusa forms hooked distal raphe endings that continue onto the valve mantle (Levkov et al. 2017, fig 169, 170). L. obscura also lacks small depressions on the proximal raphe endings, while they are present in L. confusa. The structure of raphe endings also distinguishes L. confusa from L. pseudoimbricata. Both taxa share the same valve dimensions, but L. pseudoimbricata has a raphe with slightly deflected proximal endings and distal raphe endings terminate on the valve face (Levkov et al. 2013, pls 16, 1–5).

Diversity and composition of the assemblages analyzed

During the study 143 diatom taxa were identified, but most of them were found in single samples and often their share did not exceed 1% of communities. Only 16 species were common in the samples studied (in over 20% of the samples), of which 13 species formed numerous populations (from 10% in assemblages to practically monocultures). The vast majority of the species recorded were taxa commonly identified in various terrestrial environments, mainly in soils (Lund 1946; Ettl and Gärtner 1995; Kerckvoorde et al. 2000; Stanek-Tarkowska et al. 2013; Noga et al. 2014; Barragán et al. 2018; Foets et al. 2021), but also on raised objects like cave walls (Claus 1955, 1964; Krammer and Lange-Bertalot 1991b; Poulíčková and Hašler 2007; Falasco et al. 2014), and on cliffs and walls overgrown by mosses (Round 1957; Casamatta et al. 2002; Lowe et al. 2007; Ress and Lowe 2014).

Assemblages noted on the trunks of all the trees studied growing in city centers and small peripheral estates were dominated by species able to develop in low moisture habitats with high osmotic stress (Hantzschia abundans, H. amphioxys, Humidophila contenta, Pinnularia borealis, P. obscura) (Lange-Bertalot et al. 2017; Foets et al. 2021). Several co-dominant species were present at these sites, which resulted in higher values of the H’ and J’ indexes.

Similar assemblage structures were also noted on linden and poplar at sites located in suburban park complexes and national park buffer zones. It seems that corticolous assemblages consisting mainly of drought-resistant diatom taxa are typical of these tree species regardless of the degree of tree cover in the area in which they grow. Qin et al. (2016), who studied diatoms inhabiting arboreal mosses (collected from Cinnamomum camphora Ness et Eberm., Quercus aliena Blume and Pterocarya stenoptera D.CD.) in Wuhan, also found numerous specimens of P. borealis, H. amphioxys, O. dendroteres, and H. contenta. These species were also reported in works concerning mainly corticophilic green algae and cyanobacteria, (Neustupa and Škaloud 2010; Neustupa and Štifterová 2013; Štifterová and Neustupa 2015), which indicates that they are common elements of microalgal corticolous biofilms.

Assemblages from sycamore maple (except those from city centers) were distinctly different from those inhabiting linden and poplars because of the strong domination of just one species, which often formed near monocultures (Fig. 23). In parks, assemblages on sycamore were dominated (especially in the case of bryophyte samples) by Luticola acidoclinata, a taxon commonly inhabiting moss clumps even in conditions of high osmotic stress, that are able to survive on highly saline soils (Levkov et al. 2013, 2017). Conversely, on the same host tree species in national park buffer zones with huge tree density, the main dominant species was Orthoseira dendroteres, which is typical of more shaded and wet habitats like caves and riparian zones of streams (Poulíčková and Hašler 2007; Škaloud 2009; Czerwik-Marcinkowska and Mrozińska 2011; Czerwik-Marcinkowska et al. 2015; Barragán et al. 2018). The mass development of both taxa resulted in the tremendous homogenization of assemblages reflected in the very low (even 0) values of the H’ and J’ indexes (Fig. 4).

Additionally, many diatom species often common in terrestrial and aerophytic habitats (numerous representatives of the genera Luticola, Mayamaea, and Muelleria; Microcostatus aerophilus; Stauroneis borrichii; S. parathermicola; S. termicola; Sellaphora harderi; S. nana, S. subseminulum) rarely developed in the environments studied. They were either observed in single samples or their share in assemblages did not exceed a few percent (Levkov et al. 2013; Stanek-Tarkowska et al. 2013; Noga et al. 2014; Barragán et al. 2018; Foets et al. 2021). The habitat conditions seemed to be too harsh for the development of these species in larger numbers, or the species could have found suitable conditions on different host trees that were not examined in the current study.

Except for taxa commonly reported from terrestrial habitats, diatoms that usually occur in aquatic environments were noted. The most common were centric taxa such as Aulacoseira spp., Pantocsekiella sp. and Cyclostephanos dubius that are recorded in freshwater planktonic assemblages. They were observed mainly as single, often damaged, frustules, but were observed in 25% of the samples analyzed. Freshwater species associated with epiphytic and epilithic communities (Achnanthidium minutissimum, Cocconeis spp., Gomphonema spp., Pseudostaurosira brevistriata) were also observed in the materials examined; however, they were noted significantly less frequently than planktonic taxa. Vacht et al. (2014), Martínez-Carreras et al. (2015) and Barragán et al. (2018) also observed typical aquatic diatoms (especially centric ones) in terrestrial environments. Their presence in the environments studied could have resulted from aerosol transmission, which is thought to be the most effective means of dispersing aerosolized microalgal cells, colonies, or whole filaments (Sharma et al. 2007; Harper and McKay 2010; Van Eaton et al. 2013; Sahu and Tangutur 2015; Tesson et al. 2016). Similar natural wind-borne “contamination” in terrestrial habitats was observed by Gottschling et al. (2020), who reported the presence of dinophyte DNA in soil samples. Based on the methods used in the present research, it is not possible to state unequivocally which of the identified species actually live in the habitats examined, only thrive there, or were only empty valves deposited in the bark cracks that were examined.

Conclusions

The present research showed that the occurrence of diatom assemblages on tree trunks is influenced by many factors, such as host tree species and the area in which these trees grow, high above soil as well as the presence of suitable microhabitats within trunks. Additionally, diatom assemblage composition was mainly influenced by the tree species.

The current research focused on communities developing on only a few tree species occurring naturally in Europe. Further research involving other tree taxa is necessary for developing a better understanding of corticolous diatom assemblages.

Acknowledgements

The first author would like to acknowledge prof. Agata Z. Wojtal and prof. Małgorzata Bąk for a detailed review of his doctoral thesis, which was the basis for the preparation of this article. The authors would also like to acknowledge Dr Kalina Manoylov (editor) and an anonymous reviewers for their work with the manuscript and their suggestions which helped to prepare the final version. The work was supported by the program of the Minister of Science and Higher Education under the program “Regional Initiative of Excellence” 2019–2023, project number 026/RID/2018/19.

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﻿Abstract

Keywords

﻿Introduction

﻿Methods

﻿Results

﻿Chemical analyses

﻿Taxonomic results

﻿Description of new species

﻿Luticola bryophila M.Rybak, Czarnota & Noga, sp. nov.

Description

Type material

Type locality

Etymology

Distribution

Similar species

﻿ Luticola confusa M.Rybak & Czarnota, sp. nov.

Description

Type material

Type locality

Etymology

Distribution

Similar species

﻿Diversity and composition of diatom assemblages

﻿Discussion

﻿Characteristics of the habitat

﻿Comparison of novel taxa to similar species

﻿Diversity and composition of the assemblages analyzed

﻿Conclusions

﻿Acknowledgements

﻿References

Abstract

Introduction

Methods

Results

Chemical analyses

Taxonomic results

Description of new species

Luticola bryophila M.Rybak, Czarnota & Noga, sp. nov.

Luticola confusa M.Rybak & Czarnota, sp. nov.

Diversity and composition of diatom assemblages

Discussion

Characteristics of the habitat

Comparison of novel taxa to similar species

Diversity and composition of the assemblages analyzed

Conclusions

Acknowledgements

References