Leucothrinax morrisii (Wendland) Lewis & Zona (2008: 87)

Henderson, Andrew, 2023, A revision of Coccothrinax, Hemithrinax, Leucothrinax, Thrinax, and Zombia (Arecaceae), Phytotaxa 614 (1), pp. 1-115 : 95-96

3.1. Leucothrinax morrisii (Wendland) Lewis & Zona (2008: 87) .

Thrinax morrisii Wendland (1892: 104) .

Lectotype (designated by Moya 2019):— ANGUILLA. Without locality, January 1891, D. Morris s.n. (lectotype K!)

Thrinax microcarpa Sargent (1896: 162) . Type:— USA. Florida, No Name Key, March [no year given], A. Curtiss 2679*** (holotype NY!, isotypes A!, FI!, K!, LE n.v., LE image!, US!) .

Thrinax keyensis Sargent (1899: 86) . Type:— USA. Florida, Marquesas Key , 1886, C. Sargent 3 (holotype A!, isotype NY!) .

Thrinax ponceana Cook (1901: 536) . Type:— PUERTO RICO. West of Ponce, no date, O. Cook 1005 (holotype US!) .

Thrinax praeceps Cook (1901: 536) . Type:— PUERTO RICO. Utuado to Arrecibo , 13 July 1901, L. Underwood & R . Griggs 850 (holotype US!, isotypes BH!, NY!) .

Thrinax bahamensis Cook in Northrop (1902: 20). Type:— BAHAMAS. Andros Island, Big Cabbage Creek , June 1890, J. & A. Northrop 668 (holotype US!, isotype NY!) .

Thrinax drudei Beccari (1907: 269) . Lectotype (designated by Read 1975):— CUBA. No locality, 1860, C. Wright 3965 (lectotype A!, isolectotypes F n.v., F image!, FI!, GH!, K!, NY!, US!).

Thrinax punctulata Beccari (1907: 280) . Lectotype (designated by Read 1975):— CUBA. Pinar del Río, Guanajay, 10 December 1904, Baker & van Hermann 4245 (lectotype NY!, isolectotypes F n.v., F image!, FI!, HAC n.v., HAJB!, the holotype at B was destroyed).

Thrinax ekmanii Burret (1929: 27) . Type:— HAITI. Inter Cuba et Haiti, Ile la Navase , at the lighthouse, 23 October 1928, E. Ekman 10839 (holotype S n.v., S image!, isotypes EHH n.v., EHH image!, US!) .

Stems 2.0(0.5–6.0) m long and 10.3(5.0–14.0) cm diameter, solitary. Leaves more or less deciduous or only leaf bases persisting on stem; leaf sheaths split at the base; leaf sheath fibers 0.2(0.1–0.4) mm diameter, thin, flimsy, closely woven, forming ligules at the apices; petioles 11.3(4.6–25.2) mm diameter just below the apex; palmans 22.6(7.2– 49.5) cm long, relatively long, without prominent adaxial veins; interfold filaments absent; leaf blades not wedge-shaped; segments 44(21–89) per leaf, the middle ones 59.1(28.5–99.0) cm long and 3.2(1.7–5.2) cm wide; segments not pendulous at the apices, giving the leaf a flat appearance; middle leaf segments relatively long and narrow without a shoulder distal to the palman, tapering gradually towards the apex, widest at palman apex; middle leaf segment apices attenuate; leaf segments not waxy or sometimes with a deciduous, thin layer of wax adaxially, without indumentum abaxially, with close rows of small, whitish dots between the veins on the abaxial surface, together with fewer, larger, scattered brownish or greenish scales, with well-developed transverse veinlets. Inflorescences erect, at least initially, amongst or above the leaves, with numerous partial inflorescences; rachis bracts tubular, closely sheathing, membranous, brown tomentose; partial inflorescences 12(8–18); proximalmost rachillae straight, 8.3(3.3–17.7) cm long and 0.8(0.5–1.1) mm diameter in fruit; rachillae glabrous at or near anthesis; flowers spirally arranged; stamens 6, elongate, spreading irregularly at anthesis, the anthers latrorse; fruit pedicels 0.3(0.1–0.8) mm long; fruits 4.7(3.7–5.7) mm long and 4.6(3.5–5.8) mm diameter, white, whitish, whitish-green, or gray; fruit surfaces smooth or sometimes with projecting fibers; seed surfaces smooth; seeds in longitudinal section intruded by the hilum from base to about half way, the apex of the intrusion rounded, rarely intruded by the hilum more than half way.

Distribution and habitat:— USA (Florida), Bahamas, Turks and Caicos Islands, Cuba, Hispaniola, Puerto Rico, British Virgin Islands, Anguilla, and Barbuda ( Fig. 21 ) in woodlands, scrublands, sand dunes, or beaches, or on mogotes or limestone cliffs, at 103(1–275) m elevation.

Taxonomic notes:— In the protologue, Wendland cited two specimens, the first collected by Morris and the second by Nicholls. Read (1975) designated the Nicholls specimen as lectotype, supposedly at K but not seen by him. Moya (2019) designated the Morris specimen as lectotype .

Subspecific variation:—There is a gap in the distribution of L. morrisii centered on Hispaniola ( Fig. 21 ). Specimens from the western Caribbean ( Bahamas, Cuba, and the Florida Keys) differ significantly from specimens from the eastern Caribbean (Hispaniola, Puerto Rico, and islands to the east) in eight variables (petiole width, palman length, number of segments, segment length, segment width, rachillae length, rachillae width, pedicel length), with specimens from the western Caribbean having higher values for all variables except for pedicel length (t- test, P <0.05). However, there are numerous distinct populations within these two areas, and subspecies are not recognized for the same reasons discussed under Coccothrinax argentata —too few specimens from most of the smaller islands to test for differences in quantitative variables, dozens of populations and thus a potentially unwieldly number of subspecies, and evidence of dispersal and hybridization.

In the western Caribbean, L. morrisii occurs on numerous islands (including an isolated occurrence on Navassa Island). In Florida it occurs on the Keys, from Key Largo in the northeast to the Marquesas in the southwest. There is a gap in the distribution in the Keys, possibly related to substrate. The Lower Keys are oolitic limestone, while the Upper Keys are coral rock overlaid with sand (S. Zona pers. comm.). Plants from the Keys have a mean stem length of 1.9 m and occur at low elevations in wooded areas on sandy soils near the sea. On No Name Key and Big Pine Key, where L. morrisii overlaps with Coccothrinax argentata , putative hybrids are formed ( Nauman 1989, 1990). Nauman (1990) reported that putative hybrids were known from 22 locations on Big Pine Key and occurred only in mixed populations of the parents, although the hybrids were apparently sterile. Several specimens of L. morrisii examined in this study from No Name Key and Big Pine Key have the same dense indumentum as C. argentata and may be hybrids.

Leucothrinax morrisii occurs throughout the Bahamas ( Fig. 22 ) and Turks and Caicos Islands, with similar stem lengths (mean 1.9 m) and similar habitats to those of the Florida Keys. The specimens appear similar to those from the Florida Keys and there are no quantitative differences between the two populations. Some specimens (e.g. Wilson 8347) from Nassau occurring with Coccothrinax argentata , appear similar to the putative hybrids from the Florida Keys.

In Cuba there are two populations, one from western mogotes and the other from low elevations near the sea, mostly from eastern Cuba. The western mogote population occurs up to 275 m elevation, often growing in dense stands on sheer cliffs. Specimens from the western mogote population in Cuba differ from those from the Florida Keys and Bahamas in six variables (number of segments, segment length, rachillae length, rachillae width, fruit length, fruit diameter) with specimens from the western mogote population having higher values for the first three variables, and lower for the second three (t- test, P <0.05).

In the eastern Caribbean, L. morrisii occurs on Mona Island, to the east of Hispaniola. On Hispaniola itself it is known from only two, small areas in the extreme eastern part of the Dominican Republic. It then occurs on Puerto Rico and a few islands to the east (Vieques, the British Virgin Islands, Anguilla, and Barbuda).

There are three distinct populations in Puerto Rico. Along the northern part of the island, specimens have a mean stem length of 2.7 m and occur hills or cliffs on “moist/wet northern limestone” ( Helmer et al. 2002). In the southern part of the island specimens have a mean stem length of 1.6 m ( Fig. 22 ) and are mostly from hills on “dry-volcanic limestone” ( Helmer et al. 2002). This population includes the specimens from extreme southwest and extreme northeast Puerto Rico. Quantitatively, northern specimens differ from southern specimens in five variables (palman length, number of segments, segment length, segment width, rachilla length) (t -test, P <0.05), with northern specimens having higher values for all variables. Cook (1901) discussed the habitat of the southern plants (as Thrinax ponceana ). He noted that stunted plants of apparently great age grew in narrow fissures in the rocks, and that much larger plants occurred where conditions were more favorable.

The third population, also from southern Puerto Rico, comprises specimens from the Susúa State Forest that are said to occur in dry forest on serpentine soils. These specimens are also small like those from southern Puerto Rico. Quantitatively, Susúa State Forest specimens differ from southern Puerto Rico specimens in only two variables (rachilla length, pedicel length) (t -test, P <0.05), with Susúa State Forest specimens having higher values for both.

Figures

FIGURE 21. Distribution of Leucothrinax morrisii.

FIGURE 22. Leucothrinax morrisii cultivated at Montgomery Botanical Center, Miami. The plant on the right was grown from seeds from the Bahamas, the one on the left from seeds from southern Puerto Rico.