Insights from ecological niche modeling on the taxonomic distinction and niche differentiation between the black-spotted and red-spotted tokay geckoes (Gekko gecko).

Yueyun Zhang,Yong Huang,Chongtao Chen,Weicai Chen,Li Li,Chengjian Zhao

doi:10.1002/ece3.1183

Abstract

The black-spotted tokay and the red-spotted tokay are morphologically distinct and have largely allopatric distributions. The black-spotted tokay is characterized by a small body size and dark skin with sundry spots, while the red-spotted tokay has a relatively large body size and red spots. Based on morphological, karyotypic, genetic, and distribution differences, recent studies suggested their species status; however, their classifications remain controversial, and additional data such as ecological niches are necessary to establish firm hypotheses regarding their taxonomic status. We reconstructed their ecological niches models using climatic and geographic data. We then performed niche similarity tests (niche identity and background tests) and point-based analyses to explore whether ecological differentiation has occurred, and whether such differences are sufficient to explain the maintenance of their separate segments of environmental ranges. We found that both niche models of the black- and the red-spotted tokay had a good fit and a robust performance, as indicated by the high area under the curve (AUC) values (“black” = 0.982, SD = ± 0.002, “red” = 0.966 ± 0.02). Significant ecological differentiation across the entire geographic range was found, indicating that the involvement of ecological differentiation is important for species differentiation. Divergence along the environmental axes is highly associated with climatic conditions, with isothermality being important for the “black” form, while temperature seasonality, precipitation of warmest quarter, and annual temperature range together being important for the “red” form. These factors are likely important factors in niche differentiation between the two forms, which result in morphological replacement. Overall, beside morphological and genetic differentiation information, our results contribute to additional insights into taxonomic distinction and niche differentiation between the black- and the red-spotted tokay.

Highlights

It is well known that many species can be difficult to diagnose and delimit, especially when using single operational criterion such as morphological characters or DNA markers (de Queiroz 2007)
Ecology and Evolution published by John Wiley & Sons Ltd
The divergence time of Gekko gecko was estimated at 65 million years ago (Gamble et al 2010), which is sufficiently long for ecological niche divergence

Summary

Introduction

It is well known that many species can be difficult to diagnose and delimit, especially when using single operational criterion such as morphological characters or DNA markers (de Queiroz 2007). More and more studies suggested that the addition of ecological niche modeling for taxa into phylogeographic surveys provides further insights into species taxonomy and distributions of organisms (Aneides flavipunctatus, Rissler and Apodaca 2007; Phelsuma, Raxworthy et al 2007; Phrynosoma, Leache et al, 2009; Calotes versicolor, Huang et al 2013). We performed background tests to evaluate whether the potential ecological niches of the “red” form and the “black” form are more different from one another than expected based on the differences in the environment they occurred (Warren et al 2008). The niche model for the focal species (e.g., the “red” form) is compared to a series of pseudoreplicate models generated by randomly sampling the “background” of its sister form (e.g., the “black” form; Warren et al 2008;). Schoener’s D and Hellinger’s-based I, which calculated from the observed niche overlap, were compared to a null distribution of 100 replicates pseudoreplicate models overlap values (Warren et al 2008)

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Discussion

Conclusion