Abstract
BackgroundUnderstanding how phenotypic variation scales from individuals, through populations, up to species, and how it relates to genetic and environmental factors, is essential for deciphering the evolutionary mechanisms that drive biodiversity. We used two species of Podarcis wall lizards to test whether phenotypic diversity within and divergence across populations follow concordant patterns, and to examine how phenotypic variation responds to genetic and environmental variability across different hierarchical levels of biological organization, in an explicit geographic framework.ResultsWe found a general concordance of phenotypic variation across hierarchical levels (i.e. individuals and populations). However, we also found that within-population diversity does not exhibit a coherent geographic structure for most traits, while among-population divergence does, suggesting that different mechanisms may underlie the generation of diversity at these two levels. Furthermore, the association of phenotypic variation with genetic and environmental factors varied extensively between hierarchical levels and across traits, hampering the identification of simple rules to explain what yields diversity.ConclusionsOur results in some cases comply with general ecological and evolutionary predictions, but in others they are difficult to explain in the geographic framework used, suggesting that habitat characteristics and other regulatory mechanisms may have a more substantial contribution in shaping phenotypic diversity.
Highlights
Understanding how phenotypic variation scales from individuals, through populations, up to species, and how it relates to genetic and environmental factors, is essential for deciphering the evolutionary mechanisms that drive biodiversity
Using exactly the same set of individual specimens, we quantified a series of morphological traits and used genetic sampling to characterize recent population connectivity and diversity, and evolutionary history. Based on these individually-matched samples, we addressed the following questions: 1) Are patterns of morphological variation concordant at the within- and among-population levels? This is expected if phenotypic diversity responds to the same evolutionary influences – either stochastic or adaptive – at the individual and population levels
Patterns of morphological variation The examination of the principal components (PC) of morphological variation across individuals and across populations indicated that, the amount of variance captured differed between the two analyses, variation patterns were transversal to both hierarchical levels for all traits, except for head shape, in both species
Summary
Understanding how phenotypic variation scales from individuals, through populations, up to species, and how it relates to genetic and environmental factors, is essential for deciphering the evolutionary mechanisms that drive biodiversity. We used two species of Podarcis wall lizards to test whether phenotypic diversity within and divergence across populations follow concordant patterns, and to examine how phenotypic variation responds to genetic and environmental variability across different hierarchical levels of biological organization, in an explicit geographic framework. Greater degrees of (neutral) genetic divergence between populations are typically associated to lower connectivity between them, and the more differentiated these populations are predicted to be phenotypically, under the null hypothesis of random accumulation of variation. As the phenotypic optima are expected to be similar for individuals of the same species that inhabit similar environments, we frequently observe population-level responses to environmental variation, and it is not unusual for patterns of phenotypic divergence to correlate to environmental differences across populations [5, 12]
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