Research Article |
Corresponding author: Rajesh Tandon ( tandon.raj@gmail.com ) Academic editor: Marco Pellegrini
© 2019 Remya Krishnan, Priyanka Khanduri, Rajesh Tandon.
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:
Krishnan R, Khanduri P, Tandon R (2019) Zeylanidium manasiae, a new species of Podostemaceae based on molecular and morphological data from Kerala, India. PhytoKeys 124: 23-38. https://doi.org/10.3897/phytokeys.124.33453
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We present the description of Zeylanidium manasiae (Podostemaceae), a new species from Kerala, India, which is proposed based on molecular, macro- and micromorphological data. This species is characterised by its ribbon-like dichotomous thallus, floriferous shoots produced along the margins and dichotomy of the thallus, inflorescence with two bracts, unequal stigmatic lobes, ellipsoid fruits and large seeds.
Internal transcribed spacer, Malpighiales, Podostemoideae, rheophyte, taxonomy
Podostemaceae represents a very distinct family of fresh water aquatic angiosperms, with unique evolutionary, ecological, morphological, developmental and embryological attributes (
The genus, Zeylanidium (Tul.) Engl. (subfamily Podostemoideae), is characterised by plants with crustose or ribbon-shaped thalli and caducous leaves. The flowering shoots in these species may be located either in the sinuses of the thallus lobes or borne randomly on the dorsal surface of the thallus (
Zeylanidium is currently represented by seven species: Z. olivaceum Engl., Z. johnsonii Engl., Z. lichenoides Engl., Z. maheshwarii C.J.Mathew & V.K.Satheesh, Z. sessile (Willis) C.D.K.Cook & Rutish, Z. crustaceum M.Kato and the recently described Z. tailichenoide M.Kato & Koi (
During field studies in the riverine areas of Kerala, India, between 2014 and 2016, a new morphological variant of Zeylanidium was found. The ribbon-shaped specimens with solitary flowering shoots appeared morphologically similar to Z. lichenoides, but the fruits were remarkably distinct in size and shape. Detailed morphological and molecular studies revealed that the specimens were different from the remaining species on several other characters. Hence, the specimens are documented and described here as a new species, Zeylanidium manasiae. A detailed description with photographic documentation, illustrations, phylogenetic placement within Podostemaceae and an identification key are provided.
Plant specimens were collected from Thommenkuthu waterfalls, Thodupuzha, Idukki, Kerala, India (9°57'21.59"N 76°50'01.87"E, Fig.
Morphometric differences between Zeylanidium lichenoides and Z. manasiae.
Characters | Z. manasiae | Z. lichenoides |
Flower length excluding pedicel (mm) | 2.38 ± 0.47 | 1.84 ± 0.10 |
Anther length (mm) | 0.50 ± 0.06 × 0.37 ± 0.05 | 0.4 ± 0.16 × 0.47 ± 0.02 |
Pollen production per flower | 4273 ± 941 | 4363 ± 92 |
Pollen size | ||
Polar diameter of the dyad (µm) | 30.25 ± 2.41 | 32.08 ± 1.42 |
Equatorial diameter of the dyad (µm) | 19.62 ± 1.99 | 21.01 ± 1.54 |
Shape of the pollen | Sub-prolate | Sub-prolate |
Ovule production per flower | 78 ± 13.70 | 59 ± 9.27 |
Pollen: Ovule ratio | 55:1 | 74:1 |
Capsule size (mm) | 1.96 ± 0.25 × 0.84 ± 0.10 | 1.2 ± 0.20 × 0.8 ± 0.13 |
Seed number per fruit | 60.1 ± 15.63 | 49 ± 15 |
Seed size (µm) | 248.75 ± 12.70 × 136 ± 8.90 | 207 ± 1.70 × 108 ± 1.20 |
Ovule:seed ratio | 1.30 | 1.20 |
For anatomical details, flower buds of desired specimens were fixed in Karnowsky’s fixative (
For palynological and seed micromorphological studies, anthers and seeds, respectively, were fixed in Karnowsky’s fixative, dehydrated in a graded series of cold acetone (10–100%, 30 min interval each), critical point dried (CPD), mounted on aluminium stubs and coated with gold-palladium alloy before making observations. The samples were examined by using a scanning electron microscope (SEM, JEOL, JSM-6610LV) at the Department of Botany, University of Delhi, India.
Genomic DNA was extracted using DNeasy plant mini kit (Qiagen, Amsterdam, Netherlands). DNA amplification and sequencing of the entire ITS region (ITS1, 5.8S and ITS2) were performed using the primers ITS 1 and ITS 2 (
ITS sequences of Z. manasiae and Z. maheshwarii were added to a dataset consisting of 39 species of Podostemaceae, produced by
ITS sequences of all the taxa were aligned using ClustalX ver. 2.0.11 (
DNA sequencing of the ITS region of Z. manasiae generated a sequence with 907 bp. This sequence aligned in the genus Zeylanidium, confirming its generic identity (Fig.
It can be distinguished from the closely related Z. lichenoides by the position of floriferous shoots along the margins of thallus, two bracts per floriferous shoot, unequal stigmatic lobes, larger fruits, ellipsoidal capsule and larger seeds.
INDIA. Kerala: Idduki district, Thommenkuthu Waterfalls, River Kaliyar, 9°57'21.59"N 76°50'01.87"E, 64 m alt., 31 Dec 2015, R. Krishnan & P. Khanduri 8010 (holotype:
Herbs rheophtytic, annual. Thallus 3.79 ± 0.44 mm wide, green to yellow, ribbon-shaped, dorsiventrally flattened, dichotomously branched, attached to the substrate by disc-shaped haptera, 1.14 ± 0.92 mm diam. Leaves produced at the margins and sinuses/branch points of the thallus, in pairs, caducous; blades 2.5–6.75 × 0.26 ± 0.03 mm, subulate, flattened, lacking a midrib. Floriferous shoots produced both marginally and at the branch points of the thallus, solitary, horizontally appressed to the thallus, composed of 2 subulate bracts subtending a single flower, successive shoots 3.56 ± 0.87 mm apart; bracts 2.25–8.20 mm long, caducous, with long caducous apices. Spathella 1.98 ± 0.30 mm long, obovoid, membranous, non-vascularised, persistent, enveloping the flower at pre-anthesis, rupturing longitudinally or irregularly at anthesis. Flowers green, bisexual, zygomorphic, achlamydeous, erect; pedicel measuring 8.32 ± 2.32 mm long in a mature flower; tepals 2, one on either side of the andropodium, 0.83 ± 0.21 mm long, filiform; stamens 2, borne on an andropodium, 0.74 ± 0.15 mm long at anthesis, elongating to 3.67 ± 0.74 mm long at post-anthesis, branched approximately ¼ from the apex, each branch measuring 0.13 ± 0.04 mm long at anthesis, elongating to 0.80 ± 0.10 mm long at post-anthesis, anthers 0.50 ± 0.06 × 0.37 ± 0.12 mm, quadrangular, base bilobed, lobes subequal, dehiscence introrsely rimose; 4273 ± 941 pollen dyads per flower, 30.25 ± 2.42 × 19.62 ± 1.99 µm, tricolpate, microechinate; gynoecium bicarpellate, syncarpic, ovary 2.07 ± 0.28 mm long, ellipsoidal, anisolobous, membranous septum separating two unequal locules, ovules 78 ± 14, anatropous, borne on a swollen axile placenta, style absent, stigma bifid, stigmatic lobes unequal, subconical, the longer 0.48 ± 0.06 × 0.10 ± 0.01 mm, the shorter 0.42 ± 0.06 × 0.08 ± 0.01 mm. Capsule dehiscent, loculicidal capsule measuring 1.96 ± 0.25 × 0.84 ± 0.10 mm and pedicel elongates to 15.55 ± 2.21 mm, bivalved, brown, ellipsoidal, longitudinally ridged, ridges 6, 3 on each valve, one valve persistent, the other deciduous. Seeds 60 ± 15.50 per capsule, 248.75 ± 12.70 × 136 ± 8.90 µm, spermoderm reticulate, cells rectangular with wavy striations.
Floral parts of Z. manasiae were anatomically investigated. The spathella is non-vascularised and consists of thick-walled polygonal cells. The anthers are of bithecous type, have secretory tapetum and each locule contains pollen dyads. The ovary is pluriovulate and divided into two unequal locules by an apical septum. The ovules are anatropous, bitegmic and tenuinucellate that are borne on a bulbous axile placenta (Fig.
The dyads of Z. manasiae are of the acalymmate type and measure 30.25 ± 2.41 µm in length and 19.62 ± 1.99 µm in width. Individual pollen grains are sub-prolate in shape with tricolpate aperture. The exine wall has microechinate ornamentation. The echinations on the apertural surface are larger than those on the non-apertural surface (Fig.
Zeylandium manasiae A habitat and habit showing plants on exposed rock surface (arrows) B habit of the plant showing solitary horizontally appressed flowering shoots C ventral surface of the thalli with haptera (arrows) D thalli bearing floriferous shoots on margins and point of branching E a young flower bud covered by bracts F floriferous shoot with flower subtended by two bracts. A pair of leaves can also be seen (arrows) G flower with spathella removed showing an anther and two tepals (arrows) H longitudinal section of floral bud enclosed in a spathella (sp). The ovary is bilocular and divided into two unequal halves by an apical septum (arrows). Numerous anatropous ovules (ov) are borne on a swollen placenta (p). One of the anthers in section shows a copious amount of dyad pollen I forked andropodium with two anthers J a mature capsule K a dehisced capsule showing persistent valve L comparative fruit morphology of congenerics. (Left to right) Z. maheshwarii, Z. lichenoides, Z. olivaceum and Z. manasiae M Comparative morphology of stigma. (Left to right) Z. maheshwarii, Z. lichenoides, Z. olivaceum and Z. manasiae. Scale bars: 2 mm (B); 3 mm (C); 2 mm (D); 1 mm (E); 2 mm (F); 0.5 mm (G); 0.2 mm (H); 0.5 mm (I); 1 mm (J); 1 mm (K); 5 mm (L).
INDIA. Kerala: Idduki district, Thommenkuthu Waterfalls, River Kaliyar, 9°54'00"N 76°46'00"E, 64 m alt., 23 Dec 2016, R. Krishnan 8080, (
The specific epithet ‘manasiae’ honours the late Dr. Manasi Ram née Ghosh for her contributions to the study of embryology and systematics of Santalaceae (
Zeylanidium manasiae is highly endemic and is known from only one location so far, i.e. Thommenkuthu waterfalls (Figs
This species is currently known to occur from a single location in Kerala and, hence, we suggest its placement in the Data Deficient category of
Flowering and fruiting occurs from December to January when the water level recedes to partly expose the rocks.
Zeylanidium manasiae is a ribbon-shaped, dichotomously branched species, which produces leaves and flowering shoots at the margins and sinuses of the thallus. Based on morphological studies, its closest relative is Z. lichenoides, which is also a ribbon-shaped species. However, Z. manasiae can be easily distinguished from it on the basis of a number of characters (Table
Zeylanidium tailichenoides and Z. sessile, the other two ribbon-shaped species in the genus, can be easily distinguished from Z. manasiae on the basis of (i) unilocular ovary in Z. tailichenoides vs. bilocular ovary in Z. manasiae; and (ii) sessile flowers and smooth capsules in Z. sessile vs. pedunculate flowers and ribbed capsules in Z. manasiae. The remaining congenerics (i.e. Z. olivaceum, Z. maheshwarii, Z. johnsonii and Z. crustaceum) have crustose thallus with leaves and flowering shoots scattered on the dorsal surface and, hence, are distinct from Z. manasiae.
Palynological studies also revealed the presence of tricolpate apertures with micro-echinate exine ornamentation. These characters are similar to the other Zeylanidium species, which confirms its generic placement. The structure of the pistil further supports generic identity of the species, since the anisolobous ovary is a characteristic feature of Zeylanidium. This characteristic feature separates the genus from Polypleurum.
Molecular phylogenetic analysis places Z. manasiae in a clade of Zeylanidium members which includes Z. olivaceum, Z. maheshwarii and Z. lichenoides. This corroborates the morphological studies done in the present work. The Zeylanidium clade is sister to Polypleurum within the subfamily of Podostemoideae.
1 | Thallus ribbon-like; shoots at the sinuses of the thallus or along the margins of the thallus | 2 |
– | Thallus crustose; shoots scattered on the dorsal surface of the thallus | 5 |
2 | Flowers sessile; spathella apex round; capsule smooth | Z. sessile |
– | Flowers pedicellate; spathella apex acute or obtuse; capsules ribbed | 3 |
3 | Shoots present along the margins and sinuses of the thallus; bracts 2 per floriferous shoot; spathella apex obtuse; stigmatic lobes unequal; capsules ellipsoidal | Z. manasiae |
– | Shoots restricted to the sinuses of thallus; bracts 4–6 per floriferous shoot; spathella apex acute; stigmatic lobes equal; capsules globose | 4 |
4 | Spathella apex papillate; ovary 2-locular | Z. lichenoides |
– | Spathella apex smooth; ovary 1-locular | Z. tailichenoides |
5 | Shoots dimorphic; primary shoot with a tuft of over 20 leaves; secondary shoots with 4–6 leaves | Z. olivaceum |
– | Shoots monomorphic with 4–6 leaves | 6 |
6 | Leaves up to 10 cm long; bracts 3–4; gynophore absent | Z. johnsonii |
– | Leaves 3–5 mm long; bracts more than 4; gynophore present | 7 |
7 | Bracts 4–6; stigma bilobed; capsules 8-ribbed | Z. crustaceum |
– | Bracts 6–8; stigma multilobed; capsules 6-ribbed | Z. maheshwarii |
Based on the evidence drawn from the present work, it is clear that Z. manasiae should be recognised as a new species of Zeylanidium. The recognition of Z. manasiae brings the total number of Zeylanidium species to eight. The finding of new species of Zeylanidium indicates that the region is splendidly diverse but remains poorly explored.
RK is thankful to the University Grants Commission for the grant of Junior Research Fellowship. Financial assistance from the DU-Research and Development Grant to RT is gratefully acknowledged. Dr. Jyotishman Deka is acknowledged for making the distribution map. The authors would like to thank reviewers Rafael Felipe Almeida, Claudia Bove and an anonymous reviewer for constructive criticism. The authors would also like to thank the handling editor Marco Pellegrini for his valuable comments to improve the text.
Other examined material
Data type: species data
Comparative morphology of species of Zeylanidium s.l.
Data type: measurement
Source locality, Herbarium Vouchers and GenBank accession numbers of newly incorporated species in the analysis
Data type: species data