INTRODUCTION

The West Indies harbors a diverse fauna and flora with high levels of endemism (Myers et al., 2000; Hedges, 2001; Willig et al., 2009; Acevedo-Rodríguez and Strong, 2012; Dávalos and Turvey, 2012). Of the 53 extant bat species currently known from the West Indies, nearly half are endemic to the region (Dávalos and Turvey, 2012). There are 18 species of bats today living on the island of Hispaniola (Dávalos and Turvey, 2012; Nuñez Novas and León, 2011; Tejedor et al., 2005) and the sparse fossil record provides little evidence as to how this assemblage of species evolved (Griffiths and Klingener, 1988; McFarlane et al., 2000). Hispaniola has lost much of its mammalian diversity in the last 100,000 years, but the chronology of these extinctions is poorly documented (McFarlane et al., 2000). Understanding the timing of these extinctions is essential to understanding the evolution of the contemporary fauna of Hispaniola. Fossil bats have been recorded from superficial deposits and fossilized owl pellets from the Dominican Republic (Miller, 1929b, 1930; Morgan, 2001) and Haiti (Koopman, 1955; Miller, 1918, 1929a, 1930; Silva Taboada, 1952). New fossil faunas recovered from two sinkhole caves in the Dominican Republic represent the biggest chiropteran fossil collection recorded from eastern Hispaniola (figs. 1–2). Here we describe these new collections in an effort to evaluate the taxonomic diversity of the fossil bat fauna of the island, and to provide context for understanding the bat diversity found in the Caribbean region today.

FIGURE 2.

Map showing the localities where fossil bats have been recorded in Hispaniola. Circles indicate localities reported by other studies. Squares indicate localities presented by this study. Haiti: (1) Diquini, (2) Gonâve Island, (3) Port-de-Paix, (4) Saint-Michel-de-l'Atalaye, and (5) La Selle. Dominican Republic: (6) Cueva de Lily, (7) Oleg's Bat Cave, (8) Cerro de San Francisco, (9) Constanza, and (10) San Gabriel.

MATERIALS AND METHODS

The fossil collections described in this paper were recovered from two sinkhole caves on the eastern coastline of Hispaniola: Cueva de Lily (19°33′51.19″ N, 69°54′27.32″ W) in the Maria Trinidad Sánchez province, and Oleg's Bat Cave (10 km West of Bavaro, precise locality information can be provided upon request) in the La Altagracia province (fig. 2). Specimens in both caves were collected as part of a joint project involving Brooklyn College and the Museo del Hombre Dominicano, focusing on the recovery of primate and other vertebrate remains from underwater caves. They were retrieved from the cave floors by a team of scuba divers. The Dominican Republic Speleological Society worked on behalf of the Museo del Hombre Dominicano.

Cueva de Lily is approximately a 900 m long system of fully freshwater-flooded passages and caverns, with a maximum depth of 21 m. The bat fossils were collected from two areas within the cave: one approximately 100 m from a secondary cave entrance, and the other further in at 180 m. The depth of the cave in both cases was between 3–8 m. The size of the tunnel at both collection sites was approximately 5 m wide by 5–6 m high, large enough to support a bat colony if dry. In the dry part at the second entrance of Cueva de Lily, there is currently a small bat colony.

Table 1.

Diversity of extant, fossil, and subfossil remains of bats from Hispaniola reported by this study,^a Morgan (2001),^b Miller (1930),^c Miller (1929b),^d Miller (1929a),^e Silva Taboada (1952),^f Koopman (1955),^g and Miller (1918).^h The records presented here include extant records (e) and remains from three different sources: fossils (x), fossilized owl pellets (xx), and superficial deposits (yy).

continued

FIGURE 3.

Mormoopidae skulls: dorsal, lateral, and ventral views. A. Mormoops blainvillei, B. Pteronotus macleayii, C. Pteronotus parnellii, D. Pteronotus quadridens. Scale bar = 5 mm.

FIGURE 4.

Phyllostomidae skulls: dorsal, lateral, and ventral views. A. Brachyphylla nana, B. Erophylla bombifrons, C. Monophyllus redmani, D. Phyllonycteris poeyi. Scale bar = 5 mm.

Like Cueva de Lily, Oleg's Bat Cave is an approximately 900 m long system of fully freshwater-flooded passages and caverns, with a maximum depth of 11 m. The bat fossils were collected from the surface of a rocky area (fig. 1), located approximately 15 m away from the nearest entrance/exit. Although there was some silt present, the collecting process did not involve any excavation, only picking specimens off the substrate surface. The rocky plateau was at a depth of 8 m (fig. 1).

FIGURE 5.

Chiropteran mandibles. A. Mormoops blainvillei, B. Pteronotus macleayii, C. Pteronotus parnellii, D. Pteronotus quadridens, E. Brachyphylla nana, F. Erophylla bombifrons, G. Monophyllus redmani, H. Phyllonycteris poeyi. Scale bar = 5 mm.

All specimens were hand collected and removed from the caves in water-filled plastic containers. Specimens were placed on screens to dry and many were sprayed lightly with White Rain^® hairspray as a means of hardening them. After collection and drying, all specimens were subsequently processed and identified at Duke University and the American Museum of Natural History. Specimens were identified based on comparisons with skeletal material of the 18 extant chiropteran species of Hispaniola as well as closely related species from elsewhere in the Caribbean region, Central America, and South America. Extant specimens utilized in the comparative analysis (see appendix) were taken from the collections of the American Museum of Natural History, New York (AMNH), the Royal Ontario Museum, Toronto, Canada (ROM), and the National Museum of Natural History, Smithsonian Institution, Washington, DC (USNM). The fossil specimens described in this paper are housed in the AMNH Mammalogy collections and the Museo del Hombre Dominicano, Santo Domingo, Dominican Republic (MHD).

Table 2.

Measurements (mm) of the humeri of the three species of Mormoops.

RESULTS

A total of 497 skeletal elements were identified, 165 from Oleg's bat cave and 332 from Cueva de Lily. Eleven species from three families were identified from these collections (figs. 3–6). Many of these species inhabit Hispaniola today, including all five phyllostomids, the single natalid, and three of the five identified mormoopid species.

DISCUSSION

The flooded nature of both cave localities makes it impossible to determine the age of the fossils or the time span in which they were deposited. However, the presence of extinct (†Mormoops magna) and extirpated (Pteronotus macleayii) species along with other vertebrate taxa recovered from these caves that are currently under study (final identifications not yet available) suggests that these fossils may be from the Late Pleistocene. Extinct sloth remains have been recovered from Cueva de Lily. Among the more interesting remains from Oleg's Bat Cave, which is more complex geologically and may be more heterogeneous taphonomically, are sloths, extinct rodents, a solenodon, an extinct bird with Cuban affinities, and the extirpated Cuban crocodile, Crocodylus rhombifer.

Historically, 23 species of bats have been recorded from Hispaniola of which only 18 species are currently extant on the island (table 1). Of the five species that no longer occur on Hispaniola, two are extinct mormoopid species (†Mormoops magna and †Pteronotus sp.) and three are extant species that occur elsewhere in the Caribbean (Mormoops megalophylla, Pteronotus macleayii, and Lasiurus insularis). †Mormoops magna, apparently endemic to the islands of Cuba and Hispaniola, is known only from humeri remains from three localites. Similarly, †Pteronotus sp. is known only from a single mandible collected at Cerro de San Francisco (Morgan, 2001). The abundance of fossil bat remains in Oleg's Bat Cave and Cueva de Lily opens the possibility that future collecting expeditions may be able to collect additional material for these two species. Little is known about these extinct taxa other than that they occurred sympatrically with congeners, suggesting that diversity of sympatric mormoopid communities may have been even greater in the Pleistocene than it is today. A recently discovered correlation between loss of species and loss of island area due to rising sea levels since the last glacial maximum (LGM) suggests that climate change may have been one of the major drivers of extinction of Caribbean bats since the Pleistocene (Dávalos and Russell, 2012).

FIGURE 6.

Chiropteran humeri. A. Mormoops blainvillei (extant, ROM 89973), B. Mormoops megalophylla (extant, AMNH 25589), C. †Mormoops magna, D. †Mormoops magna (mirror image), E. Pteronotus macleayii (mirror image), F. Brachyphylla nana (mirror image), G. Erophylla bombifrons (mirror image), H. Monophyllus redmani (mirror image), I. Phyllonycteris poeyi. Scale bar = 10 mm.

Mormoops megalophylla, Pteronotus macleayii, and Lasiurus insularis are species that have been recorded in Hispaniola only as fossils. Extant populations of Pteronotus macleayii are currently found on the adjacent islands of Cuba and Jamaica, with Pleistocene records from Cuba, Hispaniola, and the Bahamas (New Providence). P. macleayii is considered an obligate cavedwelling species (Silva Taboada, 1979; McFarlane, 1986; Rodríguez-Durán and Kunz, 2001; Genoways et al., 2005). The slightly larger Pleistocene range of this taxon suggests that it was extirpated relatively recently from the more northern and eastern parts of its range, perhaps as a result of flooding of roost caves due to rising sea levels and climate change (Morgan, 2001).

Extant populations of Mormoops megalophylla have a wide range in mainland Central and South America but a very restricted distribution in the Caribbean, apparently limited to Aruba, Curaçao, and Bonaire (Netherlands Antilles), Trinidad, and Margarita Island (Simmons, 2005). In the West Indies, Pleistocene remains of M. megalophylla had been found in the Bahamas (Andros, Great Abaco), Cuba, Hispaniola, Jamaica, and Tobago, indicating that this taxon was once widespread in the Caribbean (Morgan, 2001; Rojas Martin, 2006). In the case of Lasiurus insularis, extant populations occur today only in Cuba, but fossils of this species are known from both Cuba and Hispaniola (Morales and Bickham, 1995; Morgan, 2001; Simmons, 2005; Dávalos and Turvey, 2012; Nuñez Novas and León, 2011). Reasons for the local or regional extinctions of these taxa could have included a variety of factors including competition with other bat species (Koopman and Williams, 1951; Williams, 1952), natural habitat changes (e.g., increased xerification; Pregill and Olson, 1981), deforestation (Gannon et al., 2005), flooding of roost caves due to sea-level changes (Morgan, 2001; Dávalos and Turvey, 2012), or more complex ecological factors associated with reduced island areas after the LGM (Dávalos and Russell, 2012). In the case of Lasiurus insularis, a tree-roosting species (Silva Taboada, 1979), anthropogenic deforestation and stochastic events such as hurricanes might have played a significant role; in the case of Mormoops and Pteronotus species, which rely on caves for roosts, rising sea levels and cave flooding seem more likely.

Only two of the extant species currently distributed in Hispaniola are thus far completely absent from the fossil record of the Island—Noctilio leporinus and Molossus molossus. Both species share a widespread distribution that extends from Mexico southward to Argentina and the West Indies. In the Caribbean region their fossil record is sparse, with the former species reported as fossils only from Barbuda, Cuba, and Puerto Rico, while the latter is known from fossils only from Antigua and possibly jamaica⁷ (Morgan, 2001; Olson and Nieves-Rivera, 2010). This may at least in part reflect the roosting habits of these taxa, both of which in natural situations prefer roosts in hollow trees to those in caves (Hood and Jones, 1984; Morgan, 2001; Genoways et al., 2005). Caves, which offer many opportunities for fossilization of vertebrates trapped or deposited within them, are by far the greatest source of fossil bats in the Caribbean region (Morgan, 1989, 1994, 2001). It is perhaps ironic that the flooding of these caves as a result of postglacial climate change may have significantly contributed to the extirpation and extinction of multiple populations of bats on Hispaniola and other Caribbean islands (Morgan, 2001; Dávalos and Turvey, 2012; Dávalos and Russell, 2012). However, in the case of Oleg's Bat Cave and Cueva de Lily, flooding has helped to preserve ancient records of bat diversity that provide new insights into the fauna of Hispaniola.