Comments on the Biogeography of the Genus 20 Acknowledgments 21 Literature Cited 22 Appendix 23 2. Rhagomys longilingua specimens 4 3. Detail of the manus of Rhagomys longilingua, new species 5 4. Detail of the pes of Rhagomys longi-from Southeastern Peru: With Comments on the Affinities of Rhagomys rufescens (Thomas, 1886
BackgroundThe extent of phenotypic differentiation in response to local environmental conditions is a key component of species adaptation and persistence. Understanding the structuring of phenotypic diversity in response to local environmental pressures can provide important insights into species evolutionary dynamics and responses to environmental change. This work examines the influence of steep environmental gradients on intraspecific phenotypic variation and tests two hypotheses about how the tropical soft grass mouse, Akodon mollis (Cricetidae, Rodentia), contends with the disparate environmental conditions encompassed by its broad distribution. Specifically, we test if the species expresses a geographically unstructured, or generalist, phenotype throughout its range or if it shows geographically localized morphological differentiation across disparate environments.ResultsUsing geometric morphometric and ecomorphological analyses of skull shape variation we found that despite distinct environmental conditions, geographically structured morphological variation is limited, with the notable exception of a distinct morphological disjunction at the high-elevation forest-grassland transition in the southern portion of A. mollis distribution. Based on genetic analyses, geographic isolation alone does not explain this localized phenotype, given that similar levels of genetic differentiation were also observed among individuals inhabiting other ecosystems that are nonetheless not distinct morphologically.ConclusionsInstead of phenotypic specialization across environments in these tropical mountains, there was limited differentiation of skull shape and size across the broad range of A. mollis, with the exception of individuals from the puna, the highest-elevation ecosystem. The high morphological variance among individuals, together with a weak association with local environmental conditions, not only highlights the flexibility of A. mollis’ skull, but also highlights the need for further study to understand what maintains the observed morphological patterns. The work also indicates that mechanisms other than processes linked to local ecological specialization as a driver of diversification may contribute to the high diversity of this tropical region.
Wilson and Reeder (2005) are denoted by carets. Records documented during recent NSF-funded surveys of the reserve are in boldface, first listing those with museum vouchers, while sight, sound, or sign records appear in parentheses. Locality codes and their locations are listed in the Gazetteer and shown in Figure 4. Minimum and maximum
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