Climatic niche evolution in the viviparous Sceloporus torquatus group (Squamata: Phrynosomatidae).

Abstract

The cold-climate hypothesis is the main and most supported explanation of the evolution of viviparity among reptiles. This hypothesis sustains that viviparity arose as a means to save eggs from an increased mortality in nests linked with low temperatures. In this sense, some authors have stated that viviparity could constitute an evolutionary constraint.However, the link between evolutionary constraints and the evolution of ecological niches has not been well studied. Here, we study the climatic niche evolution of a group of viviparous lizards from North America to test whether the diversification of the group is linked with Phylogenetic Niche Conservatism (PNC). We evaluated phylogenetic signals and trait evolution, besides a reconstruction of ancestral climate tolerances, and did not find PNC in the ecological niche of the species in the group. Surprisingly, we did not find conservatism in any bioclimatic variables associated with temperature; we only had evidence of conservatism in Precipitation Seasonality (Bio15) and Precipitation of Coldest Quarter (Bio19). Analysis of relative disparity through time (DTT) indicates high divergence around 4.0 MYA and 0.65 MYA that coincides with orogenic and glacial periods. There is no evidence that climatic niche differentiation was the main factor in the diversification of the studied group. Orogenic and glacial periods probably promote cycles of the availability of new territories and isolation, which could promote the rapid accumulation of ecological differences between the species of the group. (Sexton et al. 2009;Nyári & Reddy, 2013). We refer to the niche or ecological niche of the 6 species to be those biotic and abiotic variables that allow the persistence of populations 7 (Hutchinson, 1957). At the same time, ecological components are important for speciation 8 process, as reproductive isolation could appear by the evolution of barriers to gene flow due to 9 divergent natural selection (Mayr, 1947;Pavey et al., 2010;Nosil, 2012). This kind of speciation 10 implies changes in the ecological niche, but ecological niches are multidimensional, and it is 11 unlikely that every dimension evolves in the same way (Schluter, 1996;Ackerly, 2003; Duran et 12 al., 2013). There are other cases where the reproductive isolation is conditioned by a 13 combination of ecological constraints and a vicariance process (e.g. geographic barriers), where 14 species could retain some ancestral requirements that limit the adaptation to the climatic 15 conditions imposed by the barrier (Wiens & Graham, 2005). The tendency of related species to 16 retain their ancestral requirements or niches through time is described as Phylogenetic Niche 17 Conservatism (PNC) (Boucher et al., 2014), and has been commonly studied by measuring the 18 Phylogenetic Signal (PS). PS is the tendency for related species to resemble each other more 19 than they resemble species drawn at random from the phylogenetic tree (Blomberg & Garland 20 2002), and for some authors, this is enough to verify PNC (Wiens e...

The role of climate and maternal manipulation in determining and maintaining reproductive mode in Liolaemus lizards

“…About 1500 of reptiles are viviparous, making them an interesting model to examine hypotheses on the origins of this evolutionary shift (Blackburn, 2006). Notably, most of these transitions are associated with cold climates, which are correlated with high elevations and latitudes (Blackburn, 1982, 1985; Esquerré et al., 2019; Hodges, 2004; Lambert & Wiens, 2013; Martínez‐Méndez et al., 2019; Pincheira‐Donoso et al., 2013, 2017; Pyron & Burbrink, 2014; Qualls et al., 1995; Schulte et al., 2000; Shine, 1985; Tinkle & Gibbons, 1977; Watson et al., 2014). The hypothesis most commonly put forward to explain how viviparity may have evolved is the “Cold Climate Hypothesis” (Shine, 1985; Tinkle & Gibbons, 1977).…”