Diversity, Distribution, and Conservation of Endemic Island Rodents
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ARTICLE IN PRESS Quaternary International 182 (2008) 6–15 Diversity, distribution, and conservation of endemic island rodents Giovanni Amoria,Ã, Spartaco Gippolitib, Kristofer M. Helgenc,d aInstitute of Ecosystem Studies, CNR-Institute of Ecosystem Studies, Via A. Borelli 50, 00161 Rome, Italy bConservation Unit, Pistoia Zoological Garden, Italy cDivision of Mammals, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, USA dDepartment of Biological Sciences, Division of Environmental and Life Sciences, Macquarie University, Sydney, New South Wales 2109, Australia Available online 8 June 2007 Abstract Rodents on islands are usually thought of by conservationists mainly in reference to invasive pest species, which have wrought considerable ecological damage on islands around the globe. However, almost one in five of the world’s nearly 2300 rodent species is an island endemic, and insular rodents suffer from high rates of extinction and endangerment. Rates of Quaternary extinction and current threat are especially high in the West Indies and the species-rich archipelagos of Southeast Asia. Rodent endemism reaches its most striking levels on large or remote oceanic islands, such as Madagascar, the Caribbean, the Ryukyu Islands, the oceanic Philippines, Sulawesi, the Galapagos, and the Solomon Islands, as well as on very large land-bridge islands, especially New Guinea. While conservation efforts in the past and present have focused mainly on charismatic mammals (such as birds and large mammals), efforts specifically targeted toward less conspicuous animals (such as insular rodents) may be necessary to stem large numbers of extinctions in the near future. r 2007 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction factors (genetic and ecological) has produced the high rates of endemism normally observed in island systems. Conservation of biodiversity has been described as one Impacts from human activities have caused the degrada- of the principal environmental challenges for humanity tion of many habitats and the decline of many species, in (Wilson, 1992) and considerable scientific efforts are some cases leading to their extinction. Particularly vulner- devoted to this issue. However, a gap exists between able are mammal populations on islands. Among insular theory and practice in conservation activities. In reality, mammals, rodents deserve special attention because of considerable attention and funds are directed toward a few their relatively high degree of representation in insular species (or, more rarely, habitats) of high economic or faunas, high rates of endemism, general lack of informa- emotional interest (Amori and Gippoliti, 2000), while vast tion on insular rodent population status, and little portions of global biodiversity remain neglected or still attention paid hitherto to their conservation compared to unknown. birds, larger mammals, and some reptiles in insular Here our attention is focused on island rodents, chosen contexts. Ironically, rodent species in island ecosystems especially because the dynamics of insular faunas are of are often considered only in a negative context, because of high interest from an evolutionary and ecological stand- the well-known ecological damage wrought by a few widely point. Animal populations on different islands, especially introduced pest species (e.g. Rattus rattus, R. norvegicus, oceanic islands, are geographically and often genetically R. exulans, and Mus musculus), while the fate of endemic isolated, forming closed biological systems with reduced species is often overlooked. In fact, islands maintain an impacts from immigration. The combination of such enormous and largely irreplaceable heritage of rodent biological diversity (Ceballos and Brown, 1995), and the aim of this paper is to highlight the diversity of island ÃCorresponding author. Tel.: +39 06 49918013; fax: +39 06 4457516. endemic rodents and provide some remarks on conserva- E-mail address: [email protected] (G. Amori). tion priorities. 1040-6182/$ - see front matter r 2007 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2007.05.014 ARTICLE IN PRESS G. Amori et al. / Quaternary International 182 (2008) 6–15 7 2. Insular rodents: how many, and where? Table 1 A basic summary of extant rodent genera endemic to islands For the purposes of this review, we compiled selected n species Genus Family Zoogeographical summary statistics on insular rodents worldwide. Rodents region from all islands are included, with New Guinea considered as the largest island. Islands are grouped according to the 2 Capromys Capromyidae Neotropical major zoogeographical regions. Taxonomic judgements 2 Geocapromys Capromyidae Neotropical 5 Mesocapromys Capromyidae Neotropical and distributional data are derived from Wilson and 3 Mysateles Capromyidae Neotropical Reeder (2005), in many cases supplemented with informa- 1 Plagiodontia Capromyidae Neotropical tion from newer publications on endemic island species 2 Nesoryzomys Cricetidae Neotropical (e.g. Goodman et al., 2005; Helgen, 2005a, b; Rickart et al., 1 Glirurus Gliridae Palaearctic 2005; Cucchi et al., 2006). We include in our compilation 1 Abeomelomys Muridae Australian 1 Anisomys Muridae Australian only those species that are extant or that we regard as 2 Baiyankamys Muridae Australian highly likely to be extant, and exclude those species that are 3 Chiruromys Muridae Australian well-established as extinct or that we regard as highly likely 2 Coccymys Muridae Australian to be extinct (see below). Judgements regarding species 1 Crossomys Muridae Australian extinctions rely largely on MacPhee and Fleming (1999), 2 Hyomys Muridae Australian 1 Leporillus Muridae Australian Amori and Clout (2003),andWilson and Reeder (2005). 3 Leptomys Muridae Australian Threatened genera were identified according to the criteria 1 Lorentzimys Muridae Australian by Amori and Gippoliti (2001, 2003). We level a special 2 Macruromys Muridae Australian focus on the genus rank in regional and other comparisons 4 Mallomys Muridae Australian of rodents. When applied consistently and in a phyloge- 2 Mammelomys Muridae Australian 2 Microhydromys Muridae Australian netic framework, as we feel is generally done appropriately 1 Parahydromys Muridae Australian across Rodentia, the genus represents a convenient means 2 Paraleptomys Muridae Australian for measuring biodiversity (Williams and Gaston, 1994), 9 Paramelomys Muridae Australian and can be very useful in conservation planning aimed at 2 Pogonomelomys Muridae Australian establishing the most pressing priorities (Russell et al., 5 Pogonomys Muridae Australian 1 Protochromys Muridae Australian 1998). Moreover, this taxonomic rank is useful in broad- 5 Pseudohydromys Muridae Australian scale comparisons because, though always dynamic (e.g. 4 Solomys Muridae Australian Weksler et al., 2006), it is usually more stable than 1 Xenuromys Muridae Australian taxonomy at the species level, especially for such a speciose 1 Abditomys Muridae Oriental group as Rodentia (Helgen, 2003a). 1 Anonymomys Muridae Oriental 10 Apomys Muridae Oriental Rodent species restricted to islands include at least 388 2 Archboldomys Muridae Oriental extant species (17.5% of all extant rodent species), 4 Batomys Muridae Oriental classified in 127 genera and 10 families. Species of Muridae 3 Bullimus Muridae Oriental (258 species) and Sciuridae (54 species) are most wide- 6 Bunomys Muridae Oriental spread on islands. There are 83 currently recognized rodent 2 Carpomys Muridae Oriental 5 Chrotomys Muridae Oriental genera entirely endemic to islands (corresponding to 197 4 Crateromys Muridae Oriental species in total), representing 17% of all rodent genera 4 Crunomys Muridae Oriental (Table 1). Only one rodent family, Capromyidae (the 1 Diplothrix Muridae Oriental hutias), is found only on islands, being endemic to the 2 Echiothrix Muridae Oriental Caribbean region. 1 Eropeplus Muridae Oriental 3 Haeromys Muridae Oriental It is well known that species richness typically scales 1 Kadarsanomys Muridae Oriental according to island size (MacArthur and Wilson, 1967). 1 Komodomys Muridae Oriental Degree of endemism, on the other hand, is less closely 1 Lenomys Muridae Oriental linked to an island’s size (Myers and De Grave, 2000; 2 Limnomys Muridae Oriental Fattorini, 2006) but rather to its remoteness and the 3 Margaretamys Muridae Oriental 1 Melasmothrix Muridae Oriental duration of its isolation, and thus to its geological history. 1 Nesoromys Muridae Oriental For example, Madagascar, isolated from all other land- 1 Palawanomys Muridae Oriental masses for the last 85 million years, shows an index of 1 Papagomys Muridae Oriental 100% endemism in its native rodent fauna (owing 1 Paruromys Muridae Oriental apparently to the infrequency of dispersal to and from 1 Paulamys Muridae Oriental 2 Phloeomys Muridae Oriental the island). Meanwhile, Borneo, which has been periodi- 1 Pithecheirops Muridae Oriental cally connected during times of lowered sea levels in the 2 Rhynchomys Muridae Oriental late Quaternary with other land areas on the Sunda Shelf 1 Sommeromys Muridae Oriental (including mainland Asia, Sumatra, and Java), has an 1 Srilankamys Muridae Oriental index of only 12%. Islands or archipelagos with highest 7 Taeromys Muridae Oriental ARTICLE IN PRESS 8 G. Amori et al. / Quaternary International 182 (2008) 6–15 Table 1 (continued ) oceanic islands have an endemism index of 465%, while all land-bridge islands have an endemism index