Abstract
The quantification of realized niche overlap and the integration of species distribution models (SDMs) with calibrated phylogenies to study niche evolution are becoming not only powerful tools to understand speciation events, but can also be used as proxies regarding the delimitation of cryptic species. We applied these techniques in order to unravel how the fundamental niche evolved during cladogenesis within the Tarentola mauritanica species-complex. Our results suggest that diversification within this complex, during the Miocene and Pleistocene, is associated with both niche divergence and niche conservatism, with a pattern that varies depending on whether the variables involved are related to the mean or seasonality of temperature and humidity. Moreover, climatic variables related to humidity and temperature seasonality were involved in the niche shift and genetic diversification of the European/North African clade during the Pleistocene and in its maintenance in a fundamental niche distinct from that of the remaining members of the group. This study further highlights the need for a taxonomic revision of the T. mauritanica species-complex.
Highlights
Speciation by natural selection occurs mainly through two distinct mechanisms; mutationorder and ecological speciation [1,2,3] (Fig 1)
The dimensionality of the 30 variables listed in S1 Table was reduced into four principal components, with the first two explaining 83.15% of the total variance (PC1 explaining 71% and PC2 12% of the total variance)
As for PC1, most of the variation along the axis was explained by 21 variables (|r| 0.8) pertaining to different temporal transformations of humidity (Middle Infra-Red), Land Surface Temperature, Normalised Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), while PC2 was mainly associated with seasonality (X4) and annual range (X7) of the Middle Infra-Red and by the seasonality of the Land Surface Temperature (X13)
Summary
Speciation by natural selection occurs mainly through two distinct mechanisms; mutationorder and ecological speciation [1,2,3] (Fig 1). Mutation-order speciation occurs when distinct advantageous or neutral mutations are fixed by chance between different populations/entities, while these are under similar ecological conditions or selective pressures [1,3] The fixation of such mutations by drift, reduces the fitness of hybrids over evolutionary time scales [4]. Ecological speciation refers to the evolution of reproductive isolation between species primarily by differential adaptation to distinct environmental or ecological conditions [5,6,7]. In this context, natural selection acts as a divergent mechanism driving to fixation.
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