Two new species of Harpalyce are described from Cuba, H. revoluta sp. nov. from a serpentine area in the northern part of E. Cuba and H. marianensis sp. nov. from calcareous areas in the southern part of E. Cuba. Both have relatively small flowers, with an up to 6 mm long standard, and 2–3 mm long wings. Harpalyce marianensis is further characterized by strongly suberous (corky) young branches of a spongy consistence, deeply furrowed longitudinally, and by leaflets covered with a particular type of orange, apparently disk-shaped, sessile glands abaxially. Harpalyce revoluta, moreover, has suborbicular or broadly elliptic leaflets with a strongly recurved or sometimes revolute margin, secondary veins inconspicuous on either side; the foliar glands, by their morphology and anatomy, are of a different type. An epitype is designated for the name Harpalyce and its type, H. formosa; the distribution of both new species and their close relatives is mapped, and an updated identification key is offered, to cater for all 16 currently recognised Cuban species.

Se describen dos nuevas especies de Harpalyce para Cuba oriental, H. revoluta sp. nov. de las áreas de serpentina del norte y H. marianensis sp. nov. de áreas de formaciones calcáreas del sur. Ambas se caracterizan por tener flores pequeñas, con estandarte de hasta 6 mm de largo y alas de hasta 3 mm de largo. Harpalyce marianensis se distingue además por sus ramas jóvenes fuertemente suberosas, de consistencia esponjosa, profundamente surcadas longitudinalmente, y los folíolos cubiertos abaxialmente por un tipo particular de glándulas sésiles anaranjadas. Harpalyce revoluta, por su parte, tiene folíolos suborbiculares o anchamente ovales, con margen fuertemente recurvado o hasta revoluto, con venas secundarias inconspicuas en ambas caras, y glándulas foliares, por su morphología y anatomía, son de un tipo distinto. Se designa un epitipo para el nombre Harpalyce y su tipo, H. formosa. Se presenta un mapa de distribución de las nuevas especies y las relacionadas con ellas y se ofrece una clave de identificación actualizada, que incluye las 16 especies cubanas actualmente reconocidas.

Brongniartieae, Eastern Cuba, Fabaceae, Harpalyce, leaf gland morphology, limestone substrate, serpentine

Brongniartieae, Cuba oriental, Fabaceae, Harpalyce, morfología de glándulas foliares, serpentinas, substratos calcáreos

Harpalyce DC. is one of those genera that, so to say, sprouts new species on a regular basis, with apparently increasing frequency. The phenomenon is not limited to Cuba, but can also be observed in the two other, disjunct areas in which the genus occurs: Central Mexico to Nicaragua in Central America, and large parts of Brazil (São-Mateus 2018; São-Mateus et al. 2019; Rankin and González 2021). In Cuba, it is due to a variety of factors, among which are the occurrence in small populations of only a few individuals, long overlooked by collectors; and the fact that many collected specimens are incomplete, often lacking flowers and fruits, and unsuited for identification below the species group level, so that undescribed species often remain unrecognised in the herbaria.

In Cuba, from where 16 species (including the two present, new ones) are now known, Harpalyce was first collected by Charles Wright in the 1860s. The species described by Grisebach (1866) based on Wright’s material remained the single Cuban one for well over half a century. In the 1920s, five more species were added, consequent to the intense collecting activities of the Swede E. L. Ekman and North American botanists based in New York. Cuban botanists recognised three more species, all described in 1950. Borhidi and Muñiz (1977) added no less than 5 species (not counting synonyms) based on the collections of local botanists kept in Cuban herbaria. Just recently, describing a new species of our own, we published an update of the genus for Cuba (Rankin and González 2021). Even then, we realised that our digest was by no means final, as several sterile specimens exist in Cuban herbaria, including the type material for species described by Borhidi and Muñiz (1977; see Rankin and González 2021) that cannot be placed reliably in the framework of the species so far described. Further field investigations are planned which, if successful, will yield complete, fertile material from the very same or nearby populations. Therefore, be warned: as soon as the so far incompletely known plants have been located and collected, further descriptions of new taxa will likely be forthcoming.

The original and complementary literature dealing with Harpalyce (Fabaceae, Brongniartieae) was consulted. In addition to the ca. 170 materials studied earlier (Rankin and González 2021), about 80 specimens (including duplicates) of Cuban Harpalyce belonging to the herbaria B, HAJB, JE, and PAL-Gr were examined, not counting the digital images of other specimens (including types) available online and housed in relevant herbaria such as A, GH, GOET, HAC, HAJB, K, MO, NY, P, S, UC, and US (see also Rankin and González 2021 and its Appendix 1 [https://doi.org/10.3372/wi.51.51204]). Herbarium codes follow Thiers (2022+). Georeferenced specimen label data were incorporated into the Flora Database of the Republic of Cuba (Greuter 2003); geographical coordinates were used to generate a distribution map, using the mapping software QIGS for Windows, version 3.16.

Leaf glands were studied using the stereo-zoom microscope system Olympus SZX16; the photographs were taken using the microscope’s camera Olympus DP72 and its CellSens Standard software. Cross cuts of the lamina were obtained by razor-cutting manually mature leaflets, previously soaked soap water at room temperature. Unstained cuts in aqueous solution were studied at 200× and 400× magnification by optical microscopy using a Carl Zeiss Axioscop instrument.

Description of two new Cuban species of Harpalyce

 Harpalyce marianensis R.Rankin, P.A.González & Greuter, sp. nov.

urn:lsid:ipni.org:names:77318009-1

Type material

Holotype. Cuba – Guantánamo Prov. • San Antonio del Sur, Abra de Mariana en el barranco, 5 km al noroeste de San Antonio del Sur; [20.08828°N, 74.85846°W]; A. Álvarez de Zayas et al. HFC 43077; montes secos, caliza; 11 May 1980; JE 28983.

Isotypes. Cuba • Same collection data as for preceding; B 100364878 [http://herbarium.bgbm.org/object/B100364878]; HAJB 1289, 1290; JE 28984.

Other material examined

Cuba – Guantánamo Prov. • San Antonio del Sur, manigua costera cerca de Playa Baitiquirí; [20.02482°N, –74.85226°W]; May 1968, Bisse & Köhler HFC 9259; HAJB, JE; Baitiquirí, en el camino a la Mina del Yeso; [20.02482°N, 74.85226°W]; 11 Apr. 1972; Bisse & Berazaín HFC 21818; HAJB, JE; Abra de Mariana, loma al oeste del barranco; [20.08828°N, 74.85846°W]; 6 Feb. 1978; Bisse et al. HFC 36575; B 100362446, HAJB, JE; Abra de Mariana, loma al oeste del Abra; [20.08828°N, 74.85846°W]; 9 Feb. 1979; Berazaín et al. HFC 39129; B 100361112, HAJB, JE.

Shrubs or small trees; young branches very suberous (corky), with a spongy appearance, deeply longitudinally ridged (Fig. 1), ferruginous-pubescent, old branches also suberous, but glabrescent. Stipules not seen, probably early shed. Leaves imparipinnate, normally alternate, or frequently subopposite, 4–7.5 cm long; petiole 10–18 mm long, densely ferruginous-pubescent; rachis 2–5.5 cm long, ferruginous-pubescent; leaflets (5-)7–9(-11) per leaf, coriaceous; lamina elliptic to narrowly elliptic, with a rounded base, the tip rounded or slightly emarginate, sometimes shortly mucronulate; the margin entire, mostly flat; adaxially glabrous, shiny (when dry), abaxially subglabrous except on the midvein; the leaflets, abaxially, are densely covered with showy orange, apparently disk-shaped glands of “type A” (the plump, apically flattened gland body is sessile in a wide open depression of the mesophyll: Fig. 2A, B); leaflet midvein sunk adaxially, prominent and ferruginous-pubescent abaxially, glabrescent with age, secondary veins in 6–9 pairs, ± conspicuous abaxially; lateral leaflets in opposite pairs, with a 1–1.5 mm long, thick, ferruginous-pubescent petiolule, the lamina 1.2–2.5(-3) × 0.8–1(-1.3) cm; terminal leaflet with a 1.5–2.5 mm long, thick and ferruginous-pubescent petiolule, the lamina 2–3.3 × 0.8–1.5 cm. Inflorescence terminal, many-flowered (with ≤ 50 flowers), 4–4.5 cm long, densely ferruginous-pubescent; bracts c. 1 mm long, densely ferruginous-pubescent; pedicels ≤ 2.5 cm long, ferruginous pubescent. Flowers zygomorphic. Calyx lips narrowly triangular, acute, outside densely covered with ferruginous hairs and sessile glands, inside glabrous or with scattered hairs; vexillary calyx lip (Fig. 3A) 3–3.2 × 0.5–0.6 cm, carinal calyx lip (Fig. 3B) 3.4–3.5 × 0.5–0.6 cm; petals membranaceous (when dry); standard (Fig. 3C) with a c. 2 mm long claw, the blade orbicular or broadly elliptic, apically rounded, 5–6 mm in diameter; wings (Fig. 3D) with a c. 2 mm long claw, the blade ± triangular, 2–3 × c. 2 mm, apparently lacking a basal auricle; keel petals (Fig. 3E) with a c. 2 mm long claw, the blades not connate, 2.3–2.5 × 0.2–0.3 cm, with a basal auricle on the vexillar side. Stamens 10; filaments 1.8–2.2 cm long, basally fused into a tube, distally free for 4–5 mm; anthers ± sagittate, c. 1.5 mm long (when dry). Pistil 3–3.2 cm long; ovary fusiform, laterally compressed, 7–8 × 1.5–2 mm, glabrous, 6–7-ovulate; style filiform, curved, 2.3–2.5 cm long, glabrous. Legume linear, 3–3.3 × c. 1 cm, brown, tipped with a c. 2 mm long mucro. Seeds up to 6 per legume, 4 × 1.5 mm (when dry).

Figure 1. 

Flowering branch of Harpalyce marianensis. Drawing by PAGG from an isotype specimen (JE 28983).

Figure 2. 

A–D leaf glands of Harpalyce marianensis (A, B from holotype specimen) and H. revoluta (C, D from specimen HFC 44956, B 100374694) A, C surface view B, D cross section. Preparations and photographs by Bibiana Moncada, Berlin. Scale bars: 100 μm.

Figure 3. 

A–E analysis of the perianth of Harpalyce marianensis A vexillary calyx lip, from inside B carinal calyx lip, from outside C standard, frontal view D wing E keel, lateral view. Drawings by PAGG from a flower of an isotype specimen (JE 28983).

Phenology

Collected in flower and with fruits in April and May.

Etymology

Named after the type locality, Abra de Mariana.

Distribution

Southern part of E Cuba, province Guantánamo, municipality San Antonio del Sur: Abra de Mariana and Baitiquirí. Grows in dry scrub vegetation on limestone substrate. Fig. 4.

Figure 4. 

Distribution of the two new species and of related, small-flowered Harpalyce species with free keel petals endemic to E Cuba.

Affinities and diagnostic features

Harpalyce marianensis has morphological affinities with H. revoluta (see below) and other Cuban species that have a relatively small (≤ 8–9 mm in length or diameter), orbicular to broadly elliptic standard and free keel petals, such as: Harpalyce ekmanii Urb., H. villosa Britton & P. Wilson, and H. baracoensis Borhidi & O.Muñiz, particularly with H. ekmanii, with which it also shares glabrous or subglabrous leaflets; however, H. ekmanii has larger leaflets (2.5–7.5 × 1.5–3 cm vs 1.2–3.3 × 0.8–1.5 cm). Harpalyce marianensis has pronounced suberous young branches with a spongy consistence and deep longitudinal ridges, a feature that is not found in H. ekmanii. Also, H. marianensis grows in dry scrub on limestone in the southern part of E Cuba, whereas H. ekmanii grows in rainforest, pine woods or dry scrub on ultramaphic soils such as serpentines in the northern portion of E Cuba.

Sterile plants or specimens of Harpalyce marianensis might be confused with H. maisiana León & Alain, a species that also occurs in limestone areas of southern E. Cuba, but these two can be distinguished from each other through the colour of the glands on the adaxial face of the leaflets, yellow in H. maisiana vs orange in H. marianensis. When in flower, they can be easily told apart: the standard is oblanceolate, 1 × 0.2–0.3 cm and apically slightly emarginate in H. maisiana but orbicular or broadly elliptic, 5–6 mm in diameter or length and apically rounded in H. marianensis; the keel petals are partially connate in the apical third and 1.2–1.3 × 0.2–0.3 cm in H. maisiana, but totally free and 2.3–2.5 × 0.2–0.3 cm in H. marianensis.

 Harpalyce revoluta P.A.González, R.Rankin & Greuter, sp. nov.

urn:lsid:ipni.org:names:77318010-1

Type material

Holotype. Cuba – Holguín Prov. • Cuchillas de Moa; alrededores del aserrío La Melba; A. Álvarez de Zayas et al. HFC 42194; charrascales altos con Bonnetia cubensis; [20.51944°N, 74.81778°W]; alt.450–500 m; 28 Apr. 1980; B 100364586 [http://herbarium.bgbm.org/object/B100364586].

Isotypes. Cuba • Same collection data as for preceding; HAJB 1286-1288, JE 28985.

Other material examined

Cuba – Holguín Prov. • Moa; La Melba; charrascal cerca del aserrío; [20.51944°N, 74.81778°W]; Mar. 1968; Bisse & Köhler HFC 7066; HAJB, JE; La Melba, charrascal cerca del aserrío; [20.51944°N, 74.81778°W]; Mar. 1968; Bisse & Köhler HFC 7626; HAJB, JE; La Melba; charrascal cerca del aserrío; [20.51944°N, 74.81778°W]; 22 Dec. 1968; Bisse & Lippold HFC 11062, 11329; HAJB, JE; Cayo Probado; orillas de las cabezadas del río Jiguaní; [20.48864°N, 74.82188°W]; 3 Apr. 1972; Bisse & Berazaín HFC 21968; B 100462873, HAJB, JE; alrededores del aserrío La Melba; [20.51944°N, 74.81778°W]; 25 Apr. 1981; Bisse et al. HFC 44956; B 100374694, HAJB, JE.

Shrubs or small trees; young branches pubescent, old branches (Fig. 5) suberous and glabrescent. Stipules not seen, probably early shed. Leaves imparipinnate, normally alternate, sometimes subopposite, 3–7 cm long; petiole 0.5–10 mm long, very thick particularly at the basis, pubescent; rachis 2–6 cm long, pubescent, glabrescent with age; leaflets 7–11 per leaf, rigidly coriaceous, opposite or very rarely subopposite; lamina mostly suborbicular or ± broadly elliptic, with a rounded or obtuse base, the tip emarginate; margin entire, recurved to strongly revolute; the surface shiny (when dry), adaxially glabrous, abaxially glabrous except on the midvein and beset with well-spaced yellow to orange, somewhat funnel-shaped glands of “type B” (in which the obconical gland body is stalked in the bottom of a mesophyll cavity, barely protruding through its narrowed opening; Fig. 2C, D); leaflet midvein sunk adaxially, prominent and with some scattered hairs abaxially, secondary veins inconspicuous on both faces; lateral leaflets with a c. 1 mm long, thick and ferruginous-pubescent petiolule, the lamina 0.6–1.2 × 0.5–1 cm, terminal leaflets with petiolule 1–3 mm long, thick and ferruginous pubescent, lamina 1–2 × 0.8–1 cm. Inflorescence terminal, with ≤ ca. 20 flowers, 2–4 cm long, densely ferruginous-pubescent; peduncle 1–1.5 cm long, densely ferruginous-pubescent, bracts linear, 2.5–3 mm long, densely ferruginous-pubescent; pedicels 1–1.5 cm long, densely ferruginous-pubescent. Flowers (Fig. 5) zygomorphic. Calyx lips narrowly triangular, acute, outside densely covered with ferruginous hairs and sessile glands, inside glabrous and with scattered glands; vexillary calyx lip (Fig. 6A) 2.1 × 0.3 cm, carinal calyx lip (Fig. 6B) 2.3 × 0.4 cm; petals membranaceous (when dry); standard (Fig. 6C) with a 2–2.5 mm long claw, the blade broadly elliptic, apically rounded, c. 3.5 × 2.5 mm; wings (Fig. 6D) with a c. 2 mm long claw, the blade ± triangular, c. 2 × 2 mm, apparently lacking a basal auricle; keel petals (Fig. 6E) with a 2–3 mm long claw, the blades not connate, 1.2–1.3 × c. 0.2 cm, with an auricle on the vexillar side. Stamens 10; filaments 1.7–2 cm long, basally fused into a tube, distally free for 4–5 mm; anthers sagittate, c. 1.5 × 0.7 mm (when dry). Pistil c. 2.3 cm long; ovary fusiform, laterally compressed, 4 × 1–1.5 mm, glabrous; style filiform, 1.9–2 cm long, glabrous. Legume (immature) linear, 13–14 × 3–3.5 mm. Seeds not seen.

Figure 5. 

Branch with immature fruits of Harpalyce marianensis. Drawing by PAGG from the holotype specimen.

Figure 6. 

A–E analysis of the perianth of Harpalyce revoluta A vexillary calyx lip, from inside B carinal calyx lip, from outside C standard, frontal view D wing E keel, lateral view. Drawings by PAGG from a flower of specimen HFC 44956, B 100374694.

Phenology

When collected in late April, the type material was in flower and with immature fruits. Some other specimens seen, collected in April as well, similarly were in flower and with immature fruits.

Distribution

Northern part of E Cuba, province Holguín. Grows in rainforest, pine woods or xeromorphic scrub on ultramaphic substrate (serpentine). Fig. 4.

Etymology

The epithet refers to the characteristic, revolute leaflet margin.

Affinities and diagnostic features

Harpalyce revoluta, shows morphological affinities with H. marianensis (see above) and other Cuban species that have a relatively small (≤ 8–9 mm in length or diameter), orbicular to broadly elliptic standard and free keel petals, particularly with H. ekmanii, with which it shares glabrous or subglabrous leaflets; however, in H. ekmanii the leaflets are much larger (2.5–7.5 × 1.5–3 cm vs 0.6–2 × 0.5–1 cm), with flat (vs recurved to revolute) margins, and the sessile glands on the abaxial leaf face are fairly dense, less spaced. The size and shape of the standard relates H. revoluta to H. villosa, but the latter has leaflets that, particularly when young, are densely hairy abaxially, not glabrous except on the loosely hairy midvein, as in H. revoluta.

As we stated in the introduction, the two new species here described are likely not the last addition to the genus. There are incomplete specimens in the Cuban herbaria, HAC and HAJB in particular, that in all likelihood represent new, undescribed species, which we shall duly name as soon as we succeed in relocating them in the field and collect complete, fertile material; furthermore, in view of the species definition we here adopt, following the tradition established by other authors, any newly discovered Harpalyce population is likely to represent a new taxon.

The question may be asked legitimately: is such a narrow species definition practical and defendable? We ignore whether our species are valid under a biological species concept. For all we know, they might all, or at least some of them, be freely interbreeding when brought together. Without much experimental work involving artificial crossing, it is impossible to know whether and to which extent evolutionary divergence has succeeded in establishing genetic barriers and cross-incompatibility between morphologically distinct populations. We are similarly ignorant of the extent of genetic isolation, if any, for many and indeed most species currently recognised in polymorphic Cuban genera. It is therefore legitimate to recognise morphologically distinguishable populations as separate taxa, and currently, no workable alternative to this course is available.

The role of small, isolated populations in evolution and speciation in higher plants has been studied by Runemark in the Aegean archipelago of Greece. He has coined the expression “reproductive drift” (Runemark 1969, 1970) to describe and explain this phenomenon. His ideas have not received the attention that they deserve, and we would like to encourage others to apply them to understand and explain the polymorphism observed in Cuban species complexes with a comparable fragmented population structure which, in the case of Cuba, is usually associated with edaphic specialisation to small and scattered habitats which, for biological purposes, are comparable to archipelagos of small islands in a sea of generalistic environmental conditions.

Concerning the general evolutionary context in which the Cuban populations are to be seen, it is useful to be mindful of the results and conclusions of recent phylogenetic studies (São Mateus 2018). That work was based on sequence analyses of both nuclear ribosomal and plastid DNA of an impressive sampling of taxa from Brasil (Harpalyce sect. Brasilienses Arroyo) and Mexico (H. sect. Harpalyce) but only a single one from Cuba (two accessions of, allegedly, H. cubensis Griseb., which in fact, however, both belong to H. suberosa Urb.) representing H. sect. cubenses Rydb.). By São Mateus’ (2018) results, the genus Harpalyce and, presumably, its three geographically vicariant sections are natural, monophyletic taxa, with H. sect. Brasilienses being the sister clade of the two remaining sections, which are in turn sisters to each other (a rather shaky assumption, as long as a single Cuban taxon has been studied). The genus is old, assumed to be of Oligocene origin (> 30 Ma b.p.). Divergence of the northern sections from the Brazilian clade is also old (> 20 Ma b.p.). Species diversification, however, is fairly young, basically post-Miocene, an assumption that obviously, for Cuba, remains to be verified by the study of a larger number of taxa.

A further promising field of additional studies that we propose to follow up in the near future has opened up through the preliminary study of leaf glands of the new species here described. We found that the slight but obvious difference of the gland pattern they presented was based on obvious structural differences, to be observed on leaf transects, which have led to the definition of two distinct gland types that we have named “type A” and “type B”. Screening the remaining species of the genus for the presence in them of these gland types, and of possible further types yet to be defined, is a promising field of study. Preliminary results of leaf surface studies indicate that the “type A” glands of Harpalyce marianensis are also found in H. ekmanii, H. maisiana as well as H. greuteri R.Rankin & P.A.González (not discussed here); whereas “type B” glands of H. revoluta occur in H. cristalensis Borhidi & O.Muñiz. The scattered glands of the leaves of H. villosa, H. baracoensis, and H. acunae Borhidi & O.Muñiz, hidden by dense indumentum, might represent yet another type.

We express our gratitude to the herbaria B and HAJB, their technicians and curators for facilitating the study of specimens; to Alelí Morales and Wildee Alonso from HAJB, who provided information on, and photos of, some specimens; to Bibiana Moncada, Berlin, for providing preparations and micrographs of the leaf surface and leaf transects; to Michael Rodewald who edited the original illustrations; to H. Manitz for the loan of Harpalyce specimens housed in JE; and to Eddy Martínez Quesada and Isis Hernández from Camagüey, Cuba, for generating the distribution map based on our data. The revision of materials in the herbaria B and JE was possible thanks to scholarships awarded by the Verein der Freunde des Botanischen Gartens und des Botanischen Museums Berlin-Dahlem to Pedro A. González in 2022. This contribution to the taxonomic revision of Harpalyce for “Flora de la República de Cuba” is one of the results of the Cuban national project PN223LH010-018 “Estudios taxonómicos y fitogeográficos en familias de la flora cubana”, which involves the National Botanical Garden of Cuba and other Cuban institutions. Thanks to the Stiftung Herbarium Greuter for bearing the publication cost.