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Species Richness and Distribution of Neotropical Rodents, with Conservation Implications

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Species Richness and Distribution of Neotropical Rodents, with Conservation Implications DOI 10.1515/mammalia-2012-0050 Mammalia 2013; 77(1): 1–19 Giovanni Amori *, Federica Chiozza , Bruce D. Patterson , Carlo Rondinini , Jan Schipper and Luca Luiselli Species richness and distribution of Neotropical rodents, with conservation implications Abstract: The correlates of species richness and conser- Carlo Rondinini: Department of Biology and Biotechnology ‘ Charles vation status of South American rodents were studied Darwin ’ , Viale dell ’ Universit à 32, 00185 Rome , Italy by analyzing the ranges of 791 species (belonging to 159 Jan Schipper: Big Island Invasive Species Committee , 23 East Kawili Street, Hilo, HI 96720 , USA genera and 16 families). The distribution data (size of Luca Luiselli: Centre of Environmental Studies Demetra s.r.l. , 2 each species ’ range in km ) and the relative quantity of Eni Spa Environmental Department, via Olona 7, 00198 Rome , Italy each macrohabitat type (in km 2 ) were obtained from the Global Mammal Assessment data bank of the Interna- tional Union for Conservation of Nature (IUCN), and the Global Land Cover 2000, respectively. We excluded mainly Introduction island species from analyses but included those species that occur on both islands and the mainland. Habitats Macroecological spatial diversity patterns are among were grouped according to seven categories (shrubland, the most intriguing issues in modern ecology and bio- forest, grassland, savannah, wetlands, desert, and artifi- geography theories (e.g., Lennon et al. 2001 , Koleff cial). Mean range sizes varied significantly among fami- et al. 2003a ). Hence, ecologists have spent considerable lies, with members of the family Cuniculidae having larger effort in distinguishing between different components ranges than the species belonging to the rest of the fami- of species diversity, including alpha or local diversity lies. Mean range size did not differ significantly between ( α ), beta diversity or differentiation ( β ), and gamma or endemic and non-endemic taxa. There was a significant regional diversity ( γ ) (e.g., Lennon et al. 2001 , Koleff positive relation between total species richness and the et al. 2003a,b ). The various components of species availability of habitat types. Specialized species (i.e., diversity have both biogeographic and ecological under- those linked to a single habitat type) were found espe- pinnings, with the biogeographic aspects explaining cially in forests, but shrublands and grasslands were also taxonomic distinctiveness and/or endemism rates and important. IUCN threatened species were distributed in a ecological aspects explaining the reasons behind counts scattered way, and essentially in forests, grasslands, and of the number of species in a given geographic area. It is shrublands. No region of the Neotropics housed more well demonstrated that areas rich in endemics are often than two to three threatened taxa, apart from a spot in also species rich, although patterns in species richness north-central Peru with five species. The richness of IUCN and endemism are not always positively related (Ceballos threatened species was higher in the montane forest eco- and Brown 1995 ). systems of the Andes, north-central Peru, than in other Several ecological and evolutionary hypotheses have areas of South America. There was a mismatch between been formulated during the last 200 years to explain geo- the hotspot maps for threatened and endemic species. The graphic patterns in richness, with many hypotheses being conservation implications of these patterns are discussed. conjectural or untestable. As a consequence, there is an increasing effort to reduce the number of hypotheses into Keywords: conservation; correlates of distribution; a minimum set of testable and plausible ones (see Jetz and macro ecology; Rodentia; South America. Rahbek 2001 , Mittelbach et al. 2007 , Terribile and Diniz - Filho 2009 ). Obviously, many factors may affect a species ’ *Corresponding author: Giovanni Amori, CNR , Institute of geographic distribution (Whittaker et al. 2001 , Anderson Ecosystem Studies, Viale dell ’ Universit à 32, 00185 Rome , Italy , et al. 2002a , Hawkins et al. 2003a ), and the extent of the e-mail: [email protected] main habitats suitable for a given species may play a con- Federica Chiozza: Department of Biology and Biotechnology ‘ Charles Darwin ’ , Viale dell ’ Universit à 32, 00185 Rome , Italy siderable role in determining the extent of its geographic Bruce D. Patterson: Department of Zoology , Field Museum of Natural range (e.g., Anderson et al. 2002b , Hawkins et al. 2003a,b , History, 1400 South Lake Shore Drive, Chicago, IL 60605 , USA Willig et al. 2003 , Hawkins 2004 ). 2 G. Amori et al.: South American rodent distributions Rodents are the most important group of mammals in terms of the number of species (Wilson and Reeder 2005 ), and they are widespread and very speciose in the Neo- tropics (Patterson 2000 ). A number of studies have exam- ined the determinants of the species distribution of some select groups of South American rodents (e.g., Arita et al. 1997 , Patterson 2000 , Anderson et al. 2002a,b , Anderson and Martinez -Meyer 2004 ), and there is also an all-taxon study on the environmental correlates of species richness in mammals of South America (Ruggiero and Kitzberger 2004 ). Focusing on rodent species, we analyze in this article the geographic patterns of species richness and Legend the richness of those species considered threatened by Cultivated the International Union for Conservation of Nature (IUCN Forest Grassland 2011 ) in South America and part of Central America also Shrubland in relation to the various major habitat types ( = vegetation Artificial zones), and discuss the conservation implications of our Bare results. 0 1000 2000 3000 4000 km Figure 1 Map of the Neotropical biogeographic region (modified Materials and methods from Udvardy 1975 ), including the main macrohabitat types that have been used for the present study. Data sources forest, renamed as ‘ flooded ’ ) in order to more deeply For this study, we included the Neotropical geographic evaluate the relative importance of the different types of region ( sensu Udvardy 1975 ), including also central and forest at the continental level. The total availability of the northern Mexico but excluding the Caribbean islands and various habitat categories across the study region (in km2 ) islets (Udvardy 1975 ; Figure 1 ). Northern Mexico, although was obtained from the GlobCover database (Table 1). not belonging to the Neotropical region, was included Distribution data for each species (size range in km2 ) for practical reasons, as there is no clear demarcation were obtained from the 2011 IUCN Red List (IUCN 2011 ). We between Neotropical and Nearctic Mexico in the distri- removed from analyses those species that were not classi- bution summaries of IUCN (2011) . The Caribbean islands fied to defined habitat categories (i.e., unknown, other) in were excluded because most of the rodents are endemic or the original IUCN (2011) table, or that had an incomplete extinct and their distributions have been grossly altered database. Thus, whereas for analyses of species richness by human settlement, both Amerindian and European we considered 791 species, for analyses of habitats we con- (Morgan and Woods 1986 , D á valos and Turvey 2012 ). This sidered only 701 species. It should be noted that the IUCN would have greatly confounded the understanding of the Red List is updated every year, and especially for Roden- main patterns relative to mainland South America. While tia it may be dated as new rodent species are continually we excluded strictly insular species from analyses, we nonetheless included those species that occur on both islands and the mainland. Habitat category Surface (km2 ) Overall, we collated range-size data for 791 species Cultivated 2,608,656 belonging to 159 genera and 16 families (following Forest (including flooded) 11,519,657 the taxonomy adopted by IUCN 2011 ). Habitats were Grassland (including savannahs) 1,675,596 grouped according to seven categories, mapped using the Shrubland 3,412,028 Artificial 14,344 GlobCover Land Cover v2 2008 database (2008): culti- Bare 531,286 vated, forest, grassland, shrubland, artificial, and bare = ( open areas) (Figure 1). However, for the conservation Table 1 Relative availability of the various habitat categories analyses, we split one category (forest) into two subcate- across the studied region. gories (dry forest, simply named as ‘ forest ’ and flooded Data from the Global Land Cover 2000 database. G. Amori et al.: South American rodent distributions 3 being described. Maps were generated using ArcGIS 10.0 (ESRI 2010 ). Statistical analyses All data were checked for normality and homoscedastic- ity before any tests. When data were normally distributed (either with or without log transformation), parametric tests were used. Otherwise, non-parametric tests were used (Zar 1984 ). Levene ’ s test was used to test for the para- metric distribution of variables (Zar 1984 ). Richness Differences in mean range size among rodent families 0–5 were tested by one-way univariate analyses of variance 5–10 (ANOVAs) followed by Tukey honest significance post hoc 10–20 tests. Welch ANOVA design was used when variances were 20–30 heterogeneous. To evaluate whether species occurring in >30 multiple habitat types had larger ranges than more spe- 0 1000 2000 3000 4000 cialized species, we ran a Spearman ’ s rank correlation km with the range extent of each species
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