Bauhinia gorgonae Killip ex R.S. Cowan (1961: 281–282

Juárez, Pedro, Flores, Rodolfo & Blanco, Mario A., 2018, Bauhinia proboscidea (Fabaceae: Cercidoideae), a new species from Costa Rica and Panama, with notes on B. beguinotii, B. gorgonae and B. pansamalana, Phytotaxa 361 (1), pp. 25-40 : 36

Bauhinia gorgonae Killip ex R.S. Cowan (1961: 281–282 , f. 2c–d). Bauhinia beguinotii var. gorgonae (Killip ex R.S.

Cowan) Wunderlin (1973: 570).

Type:— COLOMBIA. Nariño [actually Valle del Cauca]: dense forest along stream, east side of Isla Gorgona , 50–100 m, 11 February 1939 (fl.), Killip & Garcia-Barriga 33170 (holotype: US!; isotypes: BC!, BM!, COL!, US!) .

Distribution and habitat:— Bauhinia gorgonae is endemic to Gorgona Island ( Isla Gorgona) of the Department of Nariño, Colombia, located 35 km off the Colombian Pacific coast ( Fig. 3 ). The few available herbarium specimens indicate elevations of 50–305 m (the highest point in the island reaches 338 m). The island is covered by tropical wet forest without a dry season, with an average annual precipitation of 6891 mm. See additional comments below.

Comments:— Bauhinia gorgonae has been considered as a variety of B. beguinotii ( B. beguinotii var. gorgonae Wunderlin 1973 ; see also Wunderlin 1976, 1983, 1986, Quiñones 2005, Castellanos & Lewis 2012). However, the leaves of B. gorgonae are consistently divided for more than one third of their length, sometimes even completely divided in two separate leaflets, while leaves in B. beguinotii are entire or only slightly bifid apically (sinus less than one sixth the length of the leaf blade). The flowers of both species are very similar; however, five of the ten stamens of B. beguinotii (the shorter ones) are connate for ca. three fourths of their length, forming a prominent “staminate ligule” ( Wunderlin 1983, Fig. 1E in Torres Colín 1999), but in B. gorgonae the shorter stamens appear to be connate for less than a fourth of their length ( Fig. 2d in Cowan 1961). The fruits of B. gorgonae have not been documented.

Wunderlin (1976, 1983, 1986) stated that B. gorgonae and B. beguinotii are distinguished only in the degree of leaf lobing, and that further work would likely demonstrate the intraspecific variability of this character. We agree that the degree of leaf lobing is variable in many species of Bauhinia s.l. (especially in lianescent Schnella , even in the same plant); however, the available herbarium specimens and our own observations in the field and from cultivated plants indicate that the leaf shape of B. beguinotii in Costa Rica and Panama described above is fairly constant, and that markedly divided leaves are never produced in any developmental stage in this species.

Given the consistent difference in leaf shape, the apparent difference in the degree of connation of the shorter stamens, and their allopatric distribution (with resulting reproductive isolation), we consider B. gorgonae and B. beguinotii as different species.

Two sterile specimens from Gorgona Island, misidentified as B. gorgonae (Fernández Alonso 7393 and Lozano 5189, both at COL), are lianescent and represent species of Schnella .

Bauhinia beguinotii var. gorgonae was reported for Venezuela by Stergios et al. (2008), unvouchered and as with “unknown geographical distribution”. This erroneous report is likely based on the original description of B. gorgonae in a Venezuelan journal ( Cowan 1961), even when the protologue only cited specimens from Isla Gorgona in Colombia. This also led to the erroneous report of B. beguinotii from Venezuela by Ulloa Ulloa et al. (2017).

According to the classification of tribe Cercideae of Wunderlin et al. (1987), both Bauhinia beguinotii and B. gorgonae belong in series Decandrae Wunderlin, Larsen & Larsen (1987: 14 , characterized by 10 fertile stamens), of subgenus Bauhinia section Amaria .

Conservation status:—Because of its restricted AOO (estimated at 4 km 2), Bauhinia gorgonae fits in the category of Endangered [EN B2ab (ii, iv)]. For this placement we have taken into account that the only known locality where this species occurs is currently a protected area, the Gorgona Island Natural National Park of Colombia. We used the same inferred geographical coordinates for all four available collections (indicated for St. George Exped. 360, below).

Additional specimens examined:— COLOMBIA. Valle del Cauca: Gorgona Island, 800 ft, [2º58’06” N, 78º11’04” W], 7 July 1924 (fl.), St. George Exped. 360 (Kelsall s.n.) (US) ; Gorgona Island, 1000 ft, 10 July 1924 (fl.), St. George Exped. 380 (Cheeseman s.n.) ( US) ; Gorgona Island, sea level, 20 October 1924 (fl.), St. George Exped. 628 ( Collenette s.n.) ( K, US) .

Notes on the Neotropical triandrous species of Bauhinia :—Including the species described here, only four Neotropical species of Bauhinia with three fertile stamens are known. Bauhinia proboscidea and B. pansamalana are quite similar and differ mostly in their leaf proportions and the dimensions of their reproductive characters ( Table 1). The other triandrous neotropical Bauhinia species are: B. coulteri Macbride (1919: 59) , a species of open oak-pine, juniper, or deciduous forest of central Mexico with shortly bilobate leaves, pink (rarely white), sessile, narrowly elliptic petals, and 2–10-flowered racemose inflorescences, and B. pinheiroi Wunderlin (1987: 62) , a rare species found exclusively in eastern Atlantic Brazilian coastal forest ( Vaz et al. 2010) with divaricate bilobed leaves, yellowishwhite, shortly clawed petals, and 24–30-flowered racemose or paniculate inflorescences. These species are related to B. pansamalana (and B. proboscidea ) because of their three fertile stamens and their pollen morphology ( Torres Colín 1999). According to Wunderlin et al.´s (1987) classification, modified by Wunderlin (2006), B. pansamalana , B. pinheroi and B. proboscidea belong in Bauhinia series Remotae , but B. coulteri belongs in its own monotypic section Coulterae Wunderlin, Larsen & Larsen (1987: 12) , also of section Bauhinia . A key to the triandrous Neotropical Bauhinia species is provided below.

Figures

FIGURE 1. Bauhinia proboscidea. A. Fruiting branch. B. Perfect (hermaphrodite) flower; note recurved fertile stamens and incurved style. C. Staminate flower; note apically incurved fertile stamens. D. Apex of staminodes and bases of free portion of filaments of fertile stamens in staminate flower. E. Apex of fertile stamen filaments and anthers of staminate flower. F. Floral diagram of perfect flower. G. Pair of intrastipular spines at a node (leaf scar on opposite side of stem, not visible), with liquid secretion. A based on type specimen (Juaìrez 420, USJ, CR, MO); B–F based on photographs of Juárez 1241 (USJ). Drawn by P. Juaìrez.

FIGURE 2. Bauhinia proboscidea. A. Staminate flower. B. Perfect (hermaphrodite) flower. C. Apex of fertile stamens of staminate flower with incurved filaments and open anthers. D. Detail of perfect flower, showing recurved fertile anthers and pistil with incurved style. E. Detail of staminodes (red and yellow, with white abortive anthers), filaments of fertile stamens (dark red) and pistillode (green) in staminate flower. F. Immature fruits. G. Two-flowered inflorescence, with one perfect flower and one staminate flower; the perfect flower (left) has already shed its petals. H. Detail of stem node showing intrastipular spine with liquid secretion. F from Flores et al. 3835 (PMA) by R. Flores; all other photos from Juárez 1241 (USJ) by P. Juárez.

FIGURE 3. Distribution map of Bauhinia beguinotii, B. gorgonae, B. pansamalana and B. proboscidea, according to the localities of available herbarium collections with geographic coordinates (indicated or inferred, see text).