Ecological niche modelling as an exploratory tool for identifying species limits: an example based on Mexican muroid rodents

Niche conservatism theory suggests that recently diverged sister species share the same ecological niche. However, if the ecological niche evolves as part of the speciation process, the ecological pattern could be useful for recognizing cryptic species. In a broad sense systematists agree that the niche characters could be used for species differentiation. However, to date such characters have been ignored. We used the genetic algorithm for rule‐set production for modelling the ecological niche as a means of inferring ecological divergence in allopatric populations of muroid rodents for which taxonomic identity is uncertain. Our results show that niche differentiation is significant in most of the identified phylogroups. The differentiation is likely associated with natural evolutionary units, which can be identified by applying species concepts based on phylogenetic and ecological patterns (e.g. phylogenetic, cohesive, evolutionary). Even so, the role of the niche partition within phylogenetic reconstruction may be a limited one.     

Geographical variation in genet (Genetta genetta L.) diet: a literature review

The geographical variation in the Genet Genetta genetta L. diet was analysed from 12 locations covering its entire range. Data were obtained from the available literature on food studies in this species. We studied the general food spectrum of this species and compared the importance of different prey items in each area through PCA analysis. The possible influence of some large-scale environmental factors (latitude, altitude, Mediterraneity) on diet were studied by means of regression analysis and anova . The study assessed the frequency of occurrence of each prey group and diet diversity. Results show the existence of two ‘food’ groups: (i) Genets which feed on a wide food spectrum, especially arthropods and (ii) Genets which feed on small mammals at a high frequency, while the remaining prey items are scarce or absent. At the intraspecific level, Genets behave as generalist species, with the small mammals (especially, the Woodmouse) as the most outstanding prey item. However, when compared with the diet of other medium-sized Palaearctic carnivores, we can say that the Genet is intermediate between typical generalists (Martens Martes spp., Red Foxes Vulpes vulpes and Badgers Meles meles) and specialists (Otters Lutra lutra, Stoat Mustela erminea and Weasel Mustela nivalis). Finally, anova shows the existence of a relationship between diet diversity and Mediterraneity (associated with taxa such as arthropods, reptiles and amphibians), but no relationship was found for latitude or altitude. The importance of interspecific competition, based on island data, is discussed.     

Does GARP really fail miserably? A response to Stockman et al. (2006)

Stockman et al. (2006 ) found that ecological niche models built using DesktopGARP ‘failed miserably’ to predict trapdoor spider (genus Promyrmekiaphila) distributions in California. This apparent failure of GARP (Genetic Algorithm for Rule‐Set Production) was actually a failure of the authors’ methods, that is, attempting to build ecological niche models using single data points. In this paper, we present a re‐analysis of their original data using standard methods with the data appropriately partitioned into training/testing subsets. This re‐evaluation generated accurate distributional predictions that we contrast with theirs. We address the consequences of model‐building using single data points and the need for a foundational understanding of the principles of ecological niche modelling.     

Historical stability of diversity patterns in African estrildid finches (Aves: Estrildidae)?

Studying shifts in species diversity through time and space is an essential component of many aspects of biogeography and ecology. In this study, we predict the potential distribution of 61 species of African estrildid finches in order to assess current and past diversity patterns. Models were projected onto two climatic scenarios (Community Climate System Model, CCSM, and Model for Interdisciplinary Research on Climate, MIROC) representing past climate conditions, as might be expected during the Last Glacial Maximum 21 000 years BP. Subsequent overlays of the resulting potential distributions were conducted under different dispersal assumptions and compared with expert maps. Our results suggest highly similar current distribution patterns obtained by both methods. Projections onto Pleistocene scenarios showed similar patterns, with only small differences under limited and unlimited dispersal assumptions. Looking separately at diversity patterns predicted for forest and savannah species, diversity hot spots of forest species under MIROC conditions were consistent with suggested forest refugia, but were inconsistent under CCSM conditions. According to our models, savannah species were more widely distributed during the cooler and drier conditions of the Pleistocene. By using ecological niche models we show that current diversity patterns of a whole species group may have changed only slightly since the Pleistocene, suggesting a pattern of general spatial stability. However, we emphasize the importance of using different climatic scenarios as well as including the supposed dispersal of organisms in the modelling, as these factors influence results on a broad scale. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 455–470.     

Lineage diversification in a widespread species: roles for niche divergence and conservatism in the common kingsnake, Lampropeltis getula

Niche conservatism and niche divergence are both important ecological mechanisms associated with promoting allopatric speciation across geographical barriers. However, the potential for variable responses in widely distributed organisms has not been fully investigated. For allopatric sister lineages, three patterns for the interaction of ecological niche preference and geographical barriers are possible: (i) niche conservatism at a physical barrier; (ii) niche divergence at a physical barrier; and (iii) niche divergence in the absence of a physical barrier. We test for the presence of these patterns in a transcontinentally distributed snake species, the common kingsnake ( Lampropeltis getula ), to determine the relative frequency of niche conservatism or divergence in a single species complex inhabiting multiple distinct ecoregions. We infer the phylogeographic structure of the kingsnake using a range-wide data set sampled for the mitochondrial gene cytochrome b . We use coalescent simulation methods to test for the presence of structured lineage formation vs. fragmentation of a widespread ancestor. Finally, we use statistical techniques for creating and evaluating ecological niche models to test for conservatism of ecological niche preferences. Significant geographical structure is present in the kingsnake, for which coalescent tests indicate structured population division. Surprisingly, we find evidence for all three patterns of conservatism and divergence. This suggests that ecological niche preferences may be labile on recent phylogenetic timescales, and that lineage formation in widespread species can result from an interaction between inertial tendencies of niche conservatism and natural selection on populations in ecologically divergent habitats.