Abstract
Goals of this study were to: (1) develop distributional maps of modern rodent genera throughout the countries of South Africa, Lesotho, and Swaziland by georeferencing museum specimens; (2) assess habitat preferences for genera by cross-referencing locality position with South African vegetation; and (3) identify mean annual precipitation and temperature range where the genera are located. Conterminous South Africa including the countries of Lesotho and Swaziland Digital databases of rodent museum specimens housed in the Ditsong National Museum of Natural History, South Africa (DM), and the Division of Mammals, National Museum of Natural History, Smithsonian Institution, United States (NMNH), were acquired and then sorted into a subset of specimens with associated coordinate data. The coordinate data were then used to develop distributional maps for the rodent genera present within the study area. Percent habitat occupation and descriptive statistics for six climatic variables were then determined for each genus by cross-referencing locality positions with vegetation and climatic maps. This report presents a series of maps illustrating the distribution of 35 rodent genera based on 19,471 geo-referenced specimens obtained from two major collections. Inferred habitat use by taxon is provided for both locality and specimen percent occurrence at three hierarchical habitat levels: biome, bioregion, and vegetation unit. Descriptive statistics for six climatic variables are also provided for each genus based on locality and specimen percent incidence. As rodent faunas are commonly used in paleoenvironmental reconstructions, an accurate assessment of rodent environmental tolerance ranges is necessary before confidence can be placed in an actualistic model. While the data presented here represent only a subset of the modern geographic distributions for many of the taxa examined, a wide range of environmental regimes are observed, suggesting that more research is necessary in order to accurately reconstruct an environmental signature when these taxa are found in the fossil record.
Highlights
Rodent fossils are found in many Plio-Pleistocene fossilbearing localities within southern Africa (Winkler et al 2010), and are often used for reconstructing past environments (e.g., Avery 1984, 1987, 1992a,b, 1995, 2001; Cartmill 1967; De Graaff 1960; Matthews et al 2005, 2009; Thackeray 1987; Thackeray and Avery 1990)
South African Rodent Distributions based on the principle of actualism, which assumes that environmental tolerances of extant taxa are similar to the fossil taxa they morphologically resemble (Evans et al 1981; Wesselman 1984, 1995; Patnaik 2003 Stoetzel et al 2007, 2011; Wesselman et al 2009)
By quantifying rodent genus-level distributions along with climate data and vegetation types for South Africa, Lesotho, and Swaziland, this study provides a conservative baseline from which actualistic models of past environments may be developed
Summary
Rodent fossils are found in many Plio-Pleistocene fossilbearing localities within southern Africa (Winkler et al 2010), and are often used for reconstructing past environments (e.g., Avery 1984, 1987, 1992a,b, 1995, 2001; Cartmill 1967; De Graaff 1960; Matthews et al 2005, 2009; Thackeray 1987; Thackeray and Avery 1990). To accurately reconstruct past environments and avoid distorted paleoenvironmental signatures, comprehensive neontological data must be collected in order to accurately ascertain a taxon’s fundamental niche, defined as the set of all ecological factors forming an n-dimensional hypervolume in which a taxon is potentially able to exist indefinitely (Hutchinson 1957) It follows that over the course of a taxon’s survivorship, conditions controlling a taxon’s biogeographic distribution may change and current factors influencing modern distributions may not be analogous to those of the past (Van Couvering 1980; Wesselman 1984, 1995; Andrews 1990; Aguilar et al 1999; Patnaik 2003; Wesselman et al 2009). Various biotic and abiotic factors serve to limit a taxon to a smaller realized niche (Hutchinson 1957; Lomolino et al 2006), without a detailed understanding of a taxon’s modern ecological tolerances, paleoenvironmental reconstructions using modern faunas as proxies must be viewed with caution
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