THE HELICINA UMBONATA COMPLEX IN THE WEST INDIES (GASTROPODA, PROSOBRANCHIA, HELICINIDAE) FRED G. THOMPSONI ABSTRACT: The umbonata species group is placed in Helicina (s.s.) because 6f characteristics of the radula and embryonic shell sculpture, The group consists of five taxa: H. u. umbonata Shuttleworth, H. u. pitheca, new subspecies, H, tiobasis new species, H. dominicensis Pfeiffer, and H. rhips new species. The latter three species occur on Hispaniola, H. u. umbonata on Puerto Rico, and H. u. pitheca on Mona Island. Foraging specialization and habitat selection are discussed as the basis for evolution within the Helicinidae. SUMARIO: El grupo de especies umbonata es incluida en el genero Helicina (s. s,) por las caracteristicas de la adula y la escultura de la concha embri6nica, El grupo consiste de cinco taxa: H. u. umbonata Shuttlew6rth, H. u. pitheca n. sub sp., H. liobasis n. sp., H domini- ce Mis Pfeiffer y H. rhips n. sp., Las tres dltimas especies ocurren en la Isla Hispaniola, H. u. umbonata en Puerto Rico y H. u. pitheca en la Isla Mona. La especializaci6n de forage y la selecci6n de habitat son discutidas como bases para la evoluci6n dentro de la familia Helicinidae. TABLE OF CONTENTS PROLOGUE 2 ACKNOWLEDGEMENTS 2 INTRODUCTION 2 HISTORICAL ACCOUNT .,. 2 ADAFTIVE RADIATION WITHIN THE HELICINIDAE. 5 GENERIC RELATIONSHIPS OF THE UMBONATA SPECIES GROUP 5 Characters of the umbonata group 7 Comparisons with Helicina .. .. .. 9 Comparisons with Lucidella (s, s.) . 9 Comparisons with Lucidella (Poenia) . 9 Comparisons with Alcadia. 9 Generic relationships .. .. 10 ECOLOGICAL DEPLOYMENT OF THE UMBONATA SPECIES GROUP. 11 SPECIFIC RELATIONSHIPS .............,.....,...,. 11 SYSTEMATICS OF THE UMBONATA SPECIES GROUP 12 He/icina u. umbonata SHUTTLEWORTH 12 Helicina umbonata pitheca NEW SUBSPECIES 15 Helicina liobasis NEW SPECIES 17 Helicina dominicensis PFEIFFER . 19 Helicina rhips NEW SPECIES 21 LITERATURE CITED . 23 'The author is Associate Curator in Malacology, Florida State Museum, University of Florida, Gainesville, FL 32611. THOMPSON, FRED G. 1982. The Helicina umbonata complex in the West Indies. Bull. Florida State Mus., Biol. Sci. 28(1): 1-23. 2 BULLETIN FLORIDA STATE MUSEUM Vol. 28, No. 1 PROLOGUE In May 1974 Howard W. Campbell initiated a study to assess the potential environmental impact of proposed economic developments on Mona Island. A survey of the land snail fauna was made by Campbell and the author. The molluscan fauna had been summarized (Clench 1951), but some taxonomic problems remained to be resolved. One was the generic relationships of the helicinid land snail known as Lucidella um- bonata (Shuttleworth). The following year a similar trip was organized by Campbell to Saona Island and the adjacent mainland of Hispaniola. Another species of helicinid was discovered that is closely related to um- bonata. Additional field work in Puerto Rico and Hispaniola yielded critical material that resolves the systematics of umbonata and related species. This paper is dedicated to Dr. Howard W. Campbell, who was instrumental in much of my field work in Middle America and the United States. He.shall be remembered for his companionship on many field trips and the close friendship I enjoyed since we first met. ACKNOWLEDGEMENTS Field work relevant to this study on Puerto Rico and Mona Island was supported, in part, by contracts 14-16-0088-785 and 85911-1400-906-01 from the U.S. Fish and Wildlife Service. Field work on Hispaniola was supported, in part, by National Geographic Society Research Grant No. 1541. I am grateful to the officials of both organizations for the support they have rendered to me. Figures 8-29 were made on a HITACHI S-415-A Scanning Electron Micro- scope in the Department of Zoology, University of Florida. The following individuals assisted me in the field: Steven R Christman, Ronald I. Crombie, Richard Franz, Roy W. MeDiarmid, and, of course, Howard W. Campbell. INTRODUCTION HISTORICAL AccouNT This paper concerns a group of moderate-sized operculate land snails of the family Helicinidae that occurs on Puerto Rico, Hispaniola (Fig. 7), and small islands in between. Two are known species. Two others and a subspecies are described as new. Over the years the known species have been shuffled among various genera on the basis of limited data on the shell and operculum. The discovery of the new taxa on Hispaniola and Mona Island requires a reexamination of the others in order to resolve questions about systematic relationships. New data based on embryonic shell sculpture and the radula demonstrate the close relationships among the species and that their generic affinities are different thah previously thought. The two known species are Helicina umbonata Shuttleworth and Helicina dominicensis Pfeiffer 1851. Both were described on the basis of shell and opercular characteristics. Details of the embryonic shell sculp- ture were not noted, because such data were not utilized in helicinid sys- tematics until now. The radula of neither species had been described. 1982 THOMPSON: HELECINA UMBONATA COMPLEX 3 e LRn·.y- .wr M, Fb '& - 1/1 2 3 i *S, 2 - ' :Be C -- Sf 5 4 , 4 5 6 I 3 1-2,4-6 FIGURES 1-6. - Opercula of Helicina, 1 - H. u. umbonata Sh, (UF 23139); 2 -H. u, pitheca n, ssp. (UF 24064); 3-H. rhips n. sp., paratype (UF 23234); 4-H. dominicensts Pfr. (UF 23549); 5 - H. liobasis n. sp., paratype (UF 25264),6 -H. liobasis n. sp. (UF 25266). Scales equal 2 mm. H. umbonata is a common Puerto Rican snail that has long been familiar to malacologists. Its shell was figured twice (Wagner 1911, van , der Schalie 1948), and it is well represented in museum collections. On no 8 occasion has it been misidentified in the literature, nor has any other species been mistaken for it. Wagner (1911:355), in his monograph of the Helicinidae, placed umbonata in Lucidella because of similar shape and postembryonic shell sculpture to the Jamaican L. aureola (Ferrusac), the type species of Lucidella. Most subsequent authors followed Wagner. Baker (1962:17) placed umbonata in LucideUa, subgenus Poenia without comment. The present study demonstrates the close relationship of um- bonata to Helicina (s. s.) and not to Lucidella (s. 1.). H. dominicends is less well known. It was mentioned only thrice since its original description. Wagner (1911:340) placed dominicensis in Alcadia on the basis of its operculum. This study demonstrates that dominicensis is not related to Alcadia but to Helicina (s. s.). ATLANTIC OCEAN pes (UF 35169). samples encompass the variation usually encountered, except for occa- sional gerontic specimens. MESIC (UF 35169) XERIC (UF 24964) Shell width 5.5-6.5 (6.3) 5.1-5.8 Shell height 4.0-5.0 (4.8) 3.8-4.3 Aperture width 2.0-2.4 (2.7) 2.0-2.3 Aperture height 2.3-2.9 (2.2) 2.1-2.5 Whorls 5.3-5.7 (5.7) 5.2-5.5 TYPE LOCALITY. - MONA ISLAND, Sardinero. HOLOTYPE: (UF 35168); collected 21 May 1974 by Howard W. Campbell and Fred G. Thompson. PARATYPES: UF 35169(89); same data as the holotype. DISTRIBUTION. - Endemic on Mona Island (UF collections, 17 stations) and nearby Monito Island (Thompson, 1976; UF 35158). They appear to be ubiquitous on Mona Island. Live snails usually are found on plants within a few meters of the ground. The snail aestivates on trees, shrubs, and herbaceous plants. The specimens from Monito Island are somewhat intermediate in character between umbonata and pitheca. They have typical pitheca sculpture, color, and descent of the aperture. REMARKS -This is a well-differentiated subspecies that is readily dis- tinguished from H. u. umbonata by its color, sculpture, and shape. All 1982 THOMPSON : HELECINA UMBONATA COMPLEX 17 samples of H. u. pitheca are dominated by specimens with a distinct supraperipheral orange band. Some specimens have a spiral series of spots or lack markings on the last whorl. H. u. umbonata has a poorly defined color pattern that seldom forms a peripheral band, although the blotches and. spots tend to be spirally arranged. In H. u. umbonata the spiral lira- tions are quite heavy and obscure the suture, whereas H. u. pitheca has weaker spirallirations that do not obscure the suture. The H. u. umbonata lirations are stronger along the periphery, accentuating the peripheral angle, and the sculpture continues undiminished to the aperture. H. u. pitheca has a more inflated body whorl with a rounded periphery and a weakly inflated base, and the aperture descends slightly below the periphery. In H. u. umbonata the aperture descends farther along the last 1/10 whorl (Figs. 21, 43). ETYMoLOGY. -From the Greek pithekos, meaning monkey, in this case a patronym for Mona Island; mona, from modern Spanish, meaning monkey. Helicina liobasis NEW SPECIES SHELL (FIGS. 44-49). - Medium-sized, about 5 mm in width. Dome- shaped, about 0.78-0.90 times as high as wide; spire convex, raised, about 0.42-0.53 times height of shell. Whorls 4.6-5.1 (5.1 in holotype). Last whorl rounded, descending to aperture below peripheral band. Proto- conch with 1.1 whorls; sculptured with fine pits arranged in spiral series (Fig. 17). Subsequent whorls sculptured with about 3-6 low, wide spiral cords that lie above the periphery; cords crossed by variable axial stria- tions which become obsolete on the periphery. Base smooth, or nearly so (Figs. 22,45); some specimens have occasional faint spiral and axial stria- tions. Whorls inflated; last 1/4 whorl descending below periphery to aper- ture. Umbilical callus blue-gray in live specimens, finely granular. Color pattern consisting of rust-colored spiral bands on a cream-white back- ground. Lower band distinct, lying along periphery. Upper band poorly ~ defined, lying along middle of shoulder and corresponding part of earlier whorls; separated from suture by a narrow white zone. In some specimens upper band is broken into several narrow bands that lie in grooves be- tween spiral cords. Frequently upper band has superimposed rusty blotches that extend to suture. Protoconch yellow. Lip and columella white. Interior of aperture light orange. Aperture half-moon shaped, oblique and sigmoid in lateral profile; about 0.47-0.58 times height of shell and 0.42-0.46 times width of shell. Lip sharp-edged; internally thickened above and increasingly tllicker to base. Outer lip very slightly reflected, bordered behind by a very shallow groove. Columella oblique and curved forward, ending in a very weak basal denticle that is con- nected to posterior edge of umbilical callus by a weak buttress. 18 BULLETIN FLORIDA STATE MUSEUM Vol. 28, No. 1 44 45 ** 47 48 FIGURES 44 -49 . - Helicina liobasiy n . sp . 44-46 - Holotype (UF 25263): 47-49 - Paratypes (UF 25264). OPERCULUM (FIGS. 5-6). - Calcareous plate widest at middle; base bluntly rounded. Apex pointed, strongly hooked to left. Columellar ridge sharp, narrow, highest near base, not reflected laterally. Measurements in mm of 19 specimens from the type lot are as follow (holotype in parentheses): shell width 4.8-5.4 (5.2), shell height 3.8-4.7 (4.3), aperture width 1.9-2.4 (2.4), aperture height 2.0-2.5 (2.4). The shell of H. liobasis shows little variation aside from size and relative height. The type lot nearly encompasses the full range of varia- tion found in other populations. The series from 4 km SE Punta Cana con- tains a gerontic shell 6.6 mm in diameter. The series from Punta Palmillos has a preponderance of relatively depressed shells, but the total variation within this series is within the variation of the type lot. DISTRIBUTION (FIG. 7). - Found along the extreme eastern tip of Hispaniola and offshore islands in Departamento ( = Dpto.) de Altagracia, Dominican Republic. It appears to be restricted to a narrow zone along the coast. Numerous field collections were made at localities inland from 1982 THOMPSON: HELECINA UMBONATA COMPLEX 19 El Macao, Punta Cana, and Boca de Yuma. No specimens were found ex- cept at coastal localities. H. liobasis, like H. umbonata, is arboreal. Live specimens were col- lected on Saona Island, Punta Palmillos, and south of El Macao crawling on coconut palms and shrubs. Other live specimens were found aestivating on tree trunks and shrub stems. TYPE LOCALITY. - DOMINICAN REPUBLIC, ALTAGRACIA Dpro., north coast of Isla Saona opposite Isla Catalinita. The area consists of a low submesic open forest on a limestone terrain with occasional small clearings. The lower vegetation was heavily browsed by goats. Snail shells occurred under limestone slabs in forest floor litter. Occasional live specimens were found on tree trunks. HOLOTYPE: UF 25265; collected 18 February 1975 by Howard W. Campbell and Fred G. Thompson. PARATYPES: UF 25264 (59), UF 25247 (3), UF 25254 (1); same data as the holotype. OTHER LOCALITIES. - DOMINICAN REPUBLIC: ALTAGRACIA DPTO,: 1 km SW El Macao (UF 25268, 8); Punta Cana (UF 25276, 1); 4 km SE Punta Cana (UF 25269, 2); Punta Palmillas (UF 25266, 23); Isla Catalinita (UF 25267,7). REMARKS. - Helicina liobasis is similar to H. dominicensis and H. rhips in its dome-shaped shell, its narrow pointed operculum, and its color pat- tern. It differi from H. umbonata in these as well as other characteristics, which are discussed under that species. H. liobasis differs from the His- paniolan species by its weaker columella denticle, its sculpture, and its peristome. The sculpture of H. liobasis consists of much wider spiral cords and lacks the axial threads that give a matted pattern to the shells of H. dominicensis and H. rhips. The outer peristome of H. liobasis is hardly reflected. What little reflection occurs is accentuated by a weak postlabial groove. In other Hispaniolan species, the outer and basal lips are con- spicuously reflected. ETYMoLOGY . - Liobasis , from the Greek, leios meaning smooth and basis, meaning base, alluding to the lack of sculpture on the base of the shell. Helicina dominicensis PFEIFFER Helicina dominicensis Pfeiffer 1851; Proc. Zool. Soc. (London): 149. - 1852; Monogr. Pneumon. Viv. 1:352. - Crosse 1891; Jour. de Con- chyl. 39:185. Alcadia (Analcadia) dominicensis (Pfeiffer) Wagner 1911; in Martini and Chemnitz, Syst. Conchyl. Cab., Helicinidae: 355; pl. 68, figs. 1-3. SHELL (FIGS. 50-53). - Medium-sized, about 5-6 mm wide; conico- 20 BULLETIN FLORIDA STATE MUSEUM Vol. 28, No. 1 *401 -1 50 51 52 53 FIGURES 50-53.- Helicina dominirensis Pfr. (UF 23183). globose, about 0.85-0.92 times as high as wide. Spire raised, straight- sided, forming an obtuse cone with a blunt apex. Body whorl rotund, uniformly rounded. Suture deeply impressed. Whorls 5.0-5.3. Protoconch with about 1.3 whorls, typically sculptured for group. Whorls regularly increasing in size, shouldered along suture, regularly descending: last 1/10 whorl descending slightly below periphery to aperture. Whorls sculptured with numerous low spiral cords that are crossed by finer. lower radial threads forming a matted surface: spiral cords slightly finer on base of shell than above. Umbilical callus small, about 1/6 diameter of shell, white, granular, with a weak indentation at base of columella. Ground color yellowish-white with a broad spiral dull yellow zone around periphery and on spire. Protoconch light yellow. Interior of aperture light orange. Peristome white. Aperture half-moon shaped: about as high as wide; about 0.49-0.52 times height of shell. Outer lip straight-edged above, weakly reflected laterally and below. Columella concave internally and arched forward below, forming a blunt denticle. OPERCULUM (FIG. 4). - Calcareous plate acutely pointed above and bluntly rounded below. Apex sharp, moderately hooked to left. Widest point of plate at middle. Columellar ridge thick and sharp-crested below, very low along apical half; ridge not projecting sideways beyond margin of basal plate. Measurements in mm based upon 11 adults are as follow: shell width 5.2-5.8, shell height 4.6-5.3, aperture width 2.4-2.7, aperture height 2.4-2.7. DISTRIBUTION (FIG. 7). - Endemic to Hispaniola where it has a moderate distribution in the Azua basin and occurs as far east as the area near Bani. I found it at only five localities. Its paucity in collections may be due to its apparent habitat preference. I found it only in clusters of the terrestrial bromeliad, Brometia pinguin, which grows in dense thickets on alluvium in xeric areas, and it was not found on limestone outcrops within 1982 THOMPSON: HELECINA UMBONATA COMPLEX 21 the same area. This habitat was infrequently searched for snails because relatively few species occur there compared to the much richer fauna associated with limestone. Subsequent search in the bromeliad habitat may show that the species is more widely distributed. TYPE LOCALITY. - Pfeiffer (1851: 149) described this species from specimens collected by August Sa116, and gave Haiti ( = Hispaniola) as the type locality. Crosse (1891:39) recorded it from Las Charcas, Dominican Republic, also from specimens collected by Sa116 who visited there in 1849. Apparently Sa116 did not collect it elsewhere, nor has it been reported from elsewhere. Therefore, the type locality is restricted herein to Las Charcas, Departamento de Azua, Dominican Republic. SPECIMENS EXAMINED. -DOMINICAN REPUBLIC; Azu~ Dpro: 1 km SE Peralto, 510 m (UF 23549.3); 1 km N Estebania, 170 m (UF 23547.1); 2 km N Las Charcas, 80 m (UF 28183.8); 6 km ESE Las Charcas (UF 23063.3). PERAVIA DFro: 6 km WNW Bani (UF 23548.2). REMARKS. - H. dominicensis is very similar to H. rhips in shape, color, and sculpture. The two differ in size, whorl count, and aspects of the operculum, as is discussed under the latter species. Helicina rhips NEW SPECIES SHELL (FIGS. 54-57). - Large, about 7-8 mm in diameter. Conico- globose, about 0.84-0.92 times as high as wide; spiral convex, raised about 0.45-0.50 height of shell. Whorls 5.5-5.9 in adults. Protoconch con- sisting of about 1.1 whorls that are sculptured uniformly with small pits arranged in spiral series (Fig. 18). Subsequent whorls with relatively strong spiral chords crossed by finer axial threads creating a latticed pat- tern; about 3-4 chords on second whorl; about 20-25 chords between suture and lip on last whorl. Chords uniform in size over last whorl. Um- bilical callus coarsely granular, about 1/5 diameter of base, light yellow. Color of shell dull cream white to light pink with diffuse light yellow to light orange bands on body whorl; upper band lying about 1/3 of distance from suture to lip insertion; lower band lying just above periphery and lip insertion. Bands coalescing on upper whorls forming a brighter yellow or orange apex. Peristome and columella white. Interior of aperture dark yellow to orange. Aperture semilunar, about as high as wide, about 0.50-0.55 times height of shell and about 0.44-0.48 times width of shell; descending slightly and inserting on body whorl just below periphery. Lip moderately reflected at periphery and along base, not reflected above. Lip oblique and sigmoid in lateral profile. Columella arched and curved forward, ending as a blunt denticle that is connected to posterior edge of umbilical callus by a narrow buttress. OPERCULUM (FIG. 3). -Calcareous plate acutely pointed above, bluntly 22 BULLETIN FLORIDA STATE MUSEUM Vol. 28, No. 1 *4®5 54 55 56 57 FIGURES 54-57.- Helicina rhips n. sp 54-56-Holotype (UF 23064): 57-Paratype (UF 23234). rounded below, and widest at midpoint. Apex more strongly hooked to left than in H. dominicensiL Columellar ridge sharp -edged , and project- ing sideways beyond margin of basal plate. Measurements in mm based on 25 mature specimens are as follow (holotype in parenthesis): shell width 7.0-8.4 (8.2), shell height 6.2-7.5 (7.0), aperture width 3.3-4.0 (3.7), aperture height 3.3-3.8 (3.7). DISTRIBUTION (FIG. 7), - Endemic to Hispaniola where it is known only from a low limestone mountain ridge that extends from Bani north- ward for about 8 km. The ridge is covered with a dense submesic thorn forest. The snail was not found in adjacent areas where numerous collec- tions were made. No live specimens were found. Dead shells were always associated with Agave cf. americana. TYPE LOCALITY. - DOMINICAN REPUBLIC: PERAVIA Dp'ro., 6 km north of Bani, 100 m elevation. The type locality is along the east side of a limestone mountain ridge about 0.5 km west of the Rio Bani. The area at the base of the ridge consists of a tallus slope of huge limestone slabs and boulders. Specimens were found only along the base of the rock wall forming the ridge, not on the tallus slope. HOLOTYPE: UF 23064, col- lected 23 January 1980 by Fred G. Thompson. PARATYPES: UF 23234 (23), same data as the holotype; UF 25246 (14), 2 km NE Bani, 100 m; UF 23190 (2), 1 km N Bani, 75 m. REMARKS. -Helicina rhips is closely related to U. dominicensis and ap- pears to be a giant replica of the latter. The two species differ in size, whorl-count, and the structure of the opercula. They are considered species for the following reasons. In other species of helicinids such size discrepancies do not occur, even over large geographic areas. In addition to its larger size, U. rhips has about a half whorl more than does U. dominicensig. Usually in helicinids subspecies differences in size are not accompanied by such differences in whorl count. The reflected col- umellar ridge on the operculum is unique within the tintbonata species group, and is a degree of differentiation not commonly found among closelv-related species. Finally, no trends toward intergradation occur. 1982 THOMPSON: HELECINA UMBONATA COMPLEX 23 H. dominicensis occupies a relatively large geographic area within the Azua basin and is monomorphic in size, whorl-count, and opercular structure throughout the area. ETYMoLOGY. - Rhips, from the Greek rhips, a wickerwork, net, or screen in allusion to the sculpture of the shell. LITERATURE CITED Baker, H. B. 1922. Notes on the radula of the Helicinidae. Proc. Acad. Nat, Sci, Philadelphia 76: 29-67; pls. 3-7. . 1925. Anatomy of Hendersonia (Helicina occulta): A primitive land snail. Proc. Acad. Nat. Sci. Philadelphia 77: 273-303; pls. 7-10. . 1926. Anatomical notes on American Helicinidae, Proc. Acad. Nat. Sci. Phila- delphia 78: 35-56; pl. 4-8. . 1962. Puerto Rican land operculates. Nautilus 76: 16-22. Caen, A. J. 1964. The perfection of animals. In J. E. Carthy and E. L. Duddington (eds.). Viewpoints in Biology (3): 36-63; Butterworths, London. Clench, Wm. J. 1951. Land shells of Mona Island, Puerto Rico. Jour. de Conchyl. 90: 269-276. Thompson, F. G. 1978. Ceochasma, a remarkable new land snail from Colima, Mexico (Gastropo(la, Prosobranchia, Helicinidae). Proc. Biol. Soc. Washington 81: 45-52. . 1980. Proserpinoid land snails and their relationships within the Archeogastro- poda. Malacologia 20: 1-33. Van der Schalie, H. 1948. The land and freshwater mollusks of Puerto Rico. Misc. Pub. Mus. Zool. Univ. Michigan (70): 1-134; pls. 1-14. Wagner, A. 1911. Die Familie der Helicinidae: In Martini und Chemnitz, Syst. Conchyl.- Cab., Nurnberg: 1-391; pls. 1-70.