26 May 2016 Ants of Barbados (Hymenoptera, Formicidae)
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US ISSN 0006-9698 CAMBRIDGE,MASS. 26 MAY 2016 NUMBER 548 ANTS OF BARBADOS (HYMENOPTERA, FORMICIDAE) JAMES K. WETTERER,1 DAVID LUBERTAZZI,2 JIGNASHA D. RANA2 AND EDWARD O. WILSON2 ABSTRACT. The Caribbean region is considered a threatened biodiversity hotspot because of its high levels of biotic endemism and widespread habitat destruction. On Caribbean islands, as elsewhere in the world, ants are a critical component of virtually every terrestrial ecosystem. Nonetheless, the ants of most Caribbean islands remain poorly known. Here, we reviewed historical accounts, compiled published and unpublished ant records, and collected new specimens to document the diversity of ants on the Caribbean island of Barbados, including summary accounts for each species. We expected Barbados to have a relatively depauperate native ant fauna with few endemic species because of high isolation, young age, flat terrain, and high degree of habitat destruction. Furthermore, we expected to find many exotic ants, introduced throughout a long history of international commerce dating back to the 1600s. Our investigations increased the list of ant taxa knownfromBarbadosto69(46NewWorldand23OldWorld). Of these, 62 are represented among specimens we collected, and seven are New World species only known from earlier records. We found that Barbados has fewer New World ant species and more Old World ant species than are known for Grenada and St. Vincent, two neighboring Caribbean islands of similar size. Most of the New World ant species in Barbados are continuously distributed from South American and Trinidad, through the Lesser Antilles and are probably native (i.e., predating human arrival). Some New World species in Barbados, however, may be exotics introduced through human commerce, as are all Old World ant species present. Six previously recorded New World species that we did not find may now be extinct in Barbados. These include Atta cephalotes lutea and Crematogaster brevidentata, the only two ant taxa thought to be endemic to Barbados, each collected just once .110 years ago. KEY WORDS: ants; biogeography; exotic species; island biogeography; West Indies INTRODUCTION The Caribbean region is recognized as a threatened biodiversity hotspot because of 1 Wilkes Honors College, Florida Atlantic University, 5353 its high levels of biotic endemism (e.g., 58% Parkside Drive, Jupiter, Florida 33458, U.S.A.; e-mail: of terrestrial plant species and 51% of [email protected]. 2 Museum of Comparative Zoology, Harvard University, terrestrial vertebrate species) and widespread Cambridge, Massachusetts 02138, U.S.A. habitat destruction (only 10–15% intact E The President and Fellows of Harvard College 2016. 2 BREVIORA No. 548 Figure 1. Major islands (.50 km2) of the eastern Caribbean. Unshaded areas are now submerged but were dry land 15 kya when sea levels were , 150 m lower. native vegetation remaining) (Solo´rzanoet al., other islands of the Lesser Antilles of similar 2005). On Caribbean islands, as elsewhere in size, we expected Barbados to have a rela- the world, ants are critical components of tively depauperate native ant fauna based on virtually every terrestrial ecosystem (e.g., as several factors. First, Barbados is the most scavengers, predators of other arthropods, isolated island of the Lesser Antilles, far to seed dispersers, etc.) (Ho¨lldobler and Wilson, the east of all other islands (Fig. 1). Addi- 1990). Despite their importance, the native tionally, Barbados has never been connected ants of most Caribbean islands have remained to any other land mass, so all terrestrial largely unknown. Now, several destructive species that have colonized Barbados had to exotic ant species are spreading through cross the intervening ocean. Barbados is also the region threatening native biodiversity. one of the youngest islands of the Lesser Here, we have compiled published and un- Antilles, emerging only about 1 million years published ant records and collected new speci- ago. Finally, compared with other major mens to document the diversity of ants island in the Lesser Antilles, Barbados is from Barbados. flatter, more developed, and with less intact Barbados is the fourth largest island of the forest. Soon after European colonization in Lesser Antilles (Fig. 1). Compared with the 1600s, settlers quickly cleared most of the 2016 ANTS OF BARBADOS (HYMENOPTERA, FORMICIDAE) 3 forest for agriculture. In contrast, we ex- Barbados (presumably before 1893): Trigly- pected Barbados to be home to many exotic phothrix striatidens Emery (5 Tetramorium ant species, introduced throughout a long lanuginosum Mayr) and Camponotus sexgut- history of international commerce. Barbados tatus grenadensis Forel (5 Camponotus sex- has traditionally depended heavily on im- guttatus Fabricius). ports from abroad, notably lumber and other On his way to Colombia in 1896, Forel building material (Peterson, 1973). himself made a short stop in Barbados and collected ants. In several subsequent publica- Published ant records from Barbados tions, Forel (1897, 1901, 1902, 1912a,c,d, Early reports on the natural history of 1913) reported 13 currently valid ant taxa Barbados mentioned several types of ants from Barbados: Brachymyrmex cordemoyi (Clark, 1670; Hughes, 1750; Coke, 1808–11; Forel, C. sexguttatus, C. sexguttatus grena- Schomburgk, 1848; see Appendix 1). These densis (5C. sexguttatus), Cardiocondyla accounts all appear to concern well-known emeryi Forel, Crematogaster brevispinosus pest species: a leaf-cutting ant (Atta sp.), brevidentata Forel (5Crematogaster breviden- a large carpenter ant [Camponotus atriceps tata Forel), Crematogaster steinheili Forel, (Smith)], the African big-headed ant [Pheidole Monomorium floricola (Jerdon), Odontoma- megacephala (Fabricius)], the tropical fire ant chus haematoda insularis Gue´rin (5Odonto- [Solenopsis geminata (Fabricius)], the ghost machus insularis Gue´rin), Prenolepis vividula ant [Tapinoma melanocephalum (Fabricius)], antillana Forel [5Nylanderia vividula antil- and the little fire ant [Wasmannia auropunc- lana (Forel)], Pheidole fallax jelskii antillensis tata (Roger)]. Unfortunately, no specimens Forel (5Pheidole jelskii Mayr), Pheidole exist to confirm these early reports, so the subarmata elongatula Forel (5Pheidole sub- species identities in these earliest reports armata Mayr), Platythyrea punctata pruinosa remain uncertain (see Appendix 1). There- Mayr [5Platythyrea punctata (Smith)], fore, despite anecdotal evidence on the S. geminata,andW. auropunctata. importance of these six pest ants in the early Crawley (1921) described Rhizomyrma history of Barbados, we did not include these marshalli Crawley (5 Acropyga goeldii Forel) early reports in our analyses. from Barbados. Wheeler (1923) compiled In the oldest published ant records with a list of ant taxa known from Barbados based extant voucher specimens, Smith (1877) de- on published records of Forel, plus new scribed Pseudomyrma pilosula Smith and material collected by Stoner (in 1918), Wheel- Pseudomyrma variabilis Smith [both 5 Pseu- er (in 1920), and Ballou (in 1922). Wheeler’s domyrmex gracilis (Fabricius)] from Barbados (1923) list included five previously unreported (date and collector unknown). Additionally, species: Brachymyrmex heeri obscurior Forel Ward (1989) reported that a specimen of (5Brachymyrmex obscurior Forel), Cremato- Pseudomyrmex maculatus (Smith) was on gaster carinata Mayr, Crematogaster brevis- the same pin as Smith’s P. variabilis type pinosa minutior Forel (5Crematogaster cri- specimen and presumably came from the nosa Mayr), Monomorium minutum Mayr (5 same source. Monomorium monomorium Bolton), and Pre- Forel (1893) described Atta lutea Forel (5 nolepis longicornis Latreille [5Paratrechina Atta cephalotes lutea Forel) based on speci- longicornis (Latreille)]. In total, Wheeler mens that W. G. Jeffreys collected in (1923) listed 21 valid taxa from Barbados Barbados. Wheeler (1923) reported addition- but omitted published records of Smith (1877; al ant specimens that Jeffreys collected in P. gracilis) and Crawley (1921; A. goeldii). 4 BREVIORA No. 548 Tucker (1953) cataloged all insects known Institute. We also pinned and identified from Barbados, including a very incomplete Barbados ant specimens collected by Jo- list of ant taxa as follows: Rhizomyrma sp. hanna P. E. C. Darlington in March 1987. (5Acropyga sp.), R. marshalli (5A. goeldii), Stefan P. Cover (SPC) and one of us (EOW) Brachymyrmex spp., C. sexguttatus, C. collected ants in Barbados 17–20 March 1998. sexguttatus grenadensis (5C. sexguttatus), Another author (JKW) collected ants in Crematogaster brevispinosa Mayr, C. brevis- Barbados 25–29 November 2003, 16–22 June pinosa brevidentata (5C. brevidentata), 2006, and 2–14 May 2014 (see Appendix 2 for Monomorium destructor Jerdon (5Tricho- site details). We conducted much of our myrmex destructor), Monomorium carbonar- sampling in the remaining intact forest, ium ebeninum (5Monomorium ebeninum), notably in Hackleton’s Cliff and Turner’s P. longicornis, S. geminata,andSolenopsis Hall Woods, and in small forest patches that corticalis Forel. Of these, C. brevispinosa, remain in deep gullies formed from collapsed S. corticalis, and M. destructor were new caves (e.g., Jack-in-the-Box gully). records, although the first two are most likely We collected ants following standard misidentifications; we therefore excluded methods used in numerous earlier ant faunal these records. surveys (e.g., Wetterer and Wetterer, 2004; Kempf (1972), in his catalog of Neotropical