INSECTA MUNDI, Vol. 20, No. 3-4, September-December, 2006 165 The beetle fauna of Dominica, Lesser Antilles (Insecta: Coleoptera): Diversity and distribution Stewart B. Peck Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada stewart_peck@carleton. ca Abstract. The beetle fauna of the island of Dominica is summarized. It is presently known to contain 269 genera, and 361 species (in 42 families), of which 347 are named at a species level. Of these, 62 species are endemic to the island. The other naturally occurring species number 262, and another 23 species are of such wide distribution that they have probably been accidentally introduced and distributed, at least in part, by human activities. Undoubtedly, the actual numbers of species on Dominica are many times higher than now reported. This highlights the poor level of knowledge of the beetles of Dominica and the Lesser Antilles in general. Of the species known to occur elsewhere, the largest numbers are shared with neighboring Guadeloupe (201), and then with South America (126), Puerto Rico (113), Cuba (107), and Mexico-Central America (108). The Antillean island chain probably represents the main avenue of natural overwater dispersal via intermediate stepping-stone islands. The distributional patterns of the species shared with Dominica and elsewhere in the Caribbean suggest stages in a dynamic taxon cycle of species origin, range expansion, distribution contraction, and re-speciation. Introduction windward (eastern) side (with an average of 250 mm of rain annually). Rainfall is heavy and varies season- The islands of the West Indies are increasingly ally, with the dry season from mid-January to mid- recognized as a hotspot for species biodiversity June and the rainy season from mid-June to mid- (Myers et al. 2000, Myers 2003, Mittermeier et al. January. April is the driest month. The yearly aver- 2005). But this generalization is mostly based on a few age temperature is 26oC at the southwestern coastal better-known groups such as vascular plants, terres- capital city of Roseau, with an average maximum of trial vertebrates and perhaps butterflies (Ricklefs and 29oC and a minimum of 24oC. In the highland interior Lovette 1999). The terrestrial animal groups that are of the island the temperatures are markedly lower actually the most diverse are the insect orders Diptera (about 10oC lower at about 600 m). Large areas, (true flies), Lepidoptera (moths), Hymenoptera (bees, especially at higher elevations, are protected in Forest wasps and ants) and especially Coleoptera (beetles). Reserves and National Parks. Development has been Beetles alone are estimated to account for some 20% relatively minor in comparison to some other islands of all the worlds animal species known to science in the Lesser Antilles. The present national policy of (Wheeler 1990, Wilson 1992). The goal and purpose of Dominica is to promote ecotourism through conserva- this report is to provide a critical summary of knowl- tion practices for the generation of foreign exchange. edge of the diversity of the beetle fauna of Dominica, The geological age and origin of Dominica is and to provide a starting point for others to add to similar to that of most of the other high islands in the what is now known. mostly volcanic island arc of the Lesser Antilles. The The island. Dominica is in the Leeward Islands whole island arc lies to the west of the trench into group, near the middle of the of the Lesser Antilles which the Atlantic (North American) seafloor plate is chain of islands. It lies between 15º10' to 15º40' N being overridden by the Caribbean seafloor plate. latitude and 61º15' to 61º30' W longitude, and between Dominica is volcanic in origin and bedrock and may the French islands of Guadeloupe (45 km to the north) be, at most, only of mid-Tertiary age, and available for and Martinique (40 km to the south) (Fig. 1). It is 751 terrestrial colonization only since the Miocene. There km2 in area, with a maximum elevation of 1447 m and is no compelling evidence of continuous land connec- is roughly tear-drop in shape, with a length of 48 km tions between the major Lesser Antillean volcanic and a width of 24 km at its widest (in the southern islands from the Miocene onwards (Donnelly, 1988). half). It is a lush and comparatively undisturbed Thus, Dominica has probably always been an isolated island, with a drier leeward (western) side (with an oceanic island, never with a land bridge connection to average of 190 mm of rain annually), and a wetter other islands (Hedges 2001). The general biotic distri- 166 Volume 20, No. 3-4, September-December, 2006, INSECTA MUNDI Table 1. Early collectors of insects who provided beetle records for the island of Dominica with time of their activity (if known), based upon specimens in the collections of the USNM or literature sources. Activity from 1964-1966 was during the Bredin- Archbold-Smithsonian Biological Survey. Anderson, D. M. 1965 Kislink & Cooley September, 1931 Angus, G. F. Godman and Salvin (1884); Druce (1884) Lutz, F. E. Leng and Mutchler (1922: 461) Ballou, H. A. Fisher (1932: 49) Matthews, E. 1964 Becher, E. F. 1908; Champion (1917: 230) Miner, R. W. Leng and Mutchler (1922: 461) Blackwelder, R. E.July, 1936; Blackwelder (1943) Nicholls, H. A. Leng and Mutchler (1922: 495) Busch, A. August, 1905 Porter, R. F. November 1917 Clarke, J. F. G. March, 1956; 1964 Ramage, G. A. Leng and Mutchler (1922: 488) Clarke, T. M. 1965 Robinson, H. 1964 Evans, H. E. 1965 Scott, H. 1912; AMNH Bull. (8) 10: 430 (1912) Fennah, R. G. July, 1941 Spilman, T. J. 1964 Flint, O. L. July, 1963; 1964 Splangler, P. J. 1964 Fook, H. W. 1913, Yale Expedition Stehle, H. April, 1946 Gagne, R. 1966 Steyskal, G. 1966 Hays April 15, 1930 Verrill, A. H. 1904-1905 Hespenheide, H. 1964 Wickham, H. F. Leng and Mutchler (1922: 496) Hubbard, H. G. March, 1894 Wirth, W. W. 1965 butional patterns are of overwater dispersal, not a Barbados, with 239 species of beetles. Peck et al. vicariant separation of prior continuous biotic distri- (2002) list a very incompletely known fauna of 672 butions existing on a land bridge as in the model species of beetles from the continental shelf island of proposed by Iturralde-Vinent and MacPhee (1999). Tobago, northeast of Trinidad. The beetle fauna. The beetles of the entire West The most important recent work on presenting Indies are still very poorly known. Blackwelder (1944- a multi-family overview of the beetles of a part of the 1957) summarized beetle data for the Neotropics, Lesser Antilles may be Fleutiaux et al. (1947) on the including the West Indies, as of the date of that French Antilles, because of its scope and thorough- publication. A recent summary of the Greater Anti- ness. This was projected to be a set of volumes, but I llean island of Cuba enumerates 2673 beetle species am aware of only one volume being published. This (Peck 2005). This compares to the 4675species known covers 25 families of Polyphaga, including 118 genera in the continental beetle fauna of Florida (Peck and and 207 species, with keys for generic and species Thomas 1998). The island of Hispaniola has 1466 identification, and many descriptions and fine illus- known beetle species (Perez-Gelabert 2005). Tiny trations. It estimates the entire beetle fauna of the Guana Island in the eastern-most part of the Greater French Antilles to be about 500-600 genera and about Antilles has received intensive attention by a variety 1500 species. of workers, and now has 405 documented beetle In the first summary compilation for Dominica, species (Valentine and Ivie 2005). 57 beetle species were reported by Leng and Mutchler Within the Lesser Antilles, Leng and Mutchler (1914, 1917) and then 123 species by Blackwelder (1914, 1917), listed 705 species of beetles for the (1944-1957) according to Spilman (1971). The first Guadeloupe island group from the work of Fleutiaux focused beetle survey of Dominica is that of Black- and Sallé (1890), Grouvelle (1902), and Grouvelle and welder (1943) as a part of his study of the Staphylin- Raffray (1908, 1912). The next best-known island may idae of the West Indies. He sampled in Dominica from be St. Vincent, which was collected by Mr. H. H. 18 May to 12 July, 1936, with 26 sample stations, and Smith in 1887-1889 as a part of a project of the British found 26 species of Staphylinidae, excluding Aleo- Association for the Advancement of Science on the charinae. Spilman (1971) inaugurated a series of insects of the islands of British West India (Holland modern reviews of the beetles of Dominica, but, 1919). The beetles were described by several workers unfortunately, only a few papers on the beetle fauna (e. g. Champion 1897), and Howard (1898) summa- have appeared since then (e. g., Cartwright and rized the results of the project up to that time. Later Chalumeau 1978). Chalumeau (1983a) and Chalumeau references are in Blackwelder (1944-1957). For the and Touroult (2005a) are summaries of their many islands of Grenada and the Grenadines, Woodruff et studies on Scarabaeoidea and Cerambycidae of the al. (1998) list 507 species of beetles (in 51 families). Lesser Antilles, with a focus on Guadeloupe, Domin- Bennett and Alam (1985) list the insect fauna of ica, and Martinique. INSECTA MUNDI, Vol. 20, No. 3-4, September-December, 2006 167 Figure 1. Principal islands of the eastern West Indies, showing the relative position of Dominica in the Lesser Antilles chain to other islands and continental lands (Florida, Nicaragua, and Colombia-Venezuela and continental shelf islands of northern South America).