What drives genetic and phenotypic divergence in the Red-crowned Ant tanager (Habia rubica, Aves: Cardinalidae), a polytypic species?

Sandra M Ramírez‐Barrera,Tania M Orozco‐Téllez,Julián A Velasco,Blanca E Hernández‐Baños,Alma M Vázquez‐López

doi:10.1002/ece3.5742

Sandra M Ramírez‐Barrera, Tania M Orozco‐Téllez + Show 3 more

Open Access

https://doi.org/10.1002/ece3.5742

Copy DOI

Abstract

AimThe effects of geographic and environmental variables on patterns of genetic and phenotypic differentiation have been thoroughly studied. Ecological speciation involves reproductive isolation due to divergent natural selection that can result in a positive correlation between genetic divergence and adaptive phenotypic divergence (isolation by adaptation, IBA). If the phenotypic target of selection is unknown or not easily measured, environmental variation can be used as a proxy, expecting positive correlation between genetic and environmental distances, independent of geographic distances (isolation by environment, IBE). The null model is that the amount of gene flow between populations decreases as the geographic distance between them increases, and genetic divergence is due simply to the neutral effects of genetic drift (isolation by distance, IBD). However, since phenotypic differentiation in natural populations may be autocorrelated with geographic distance, it is often difficult to distinguish IBA from the neutral expectation of IBD. In this work, we test hypotheses of IBA, IBE, and IBD in the Red‐crowned Ant tanager (Habia rubica).LocationMesoamerica (Mexico—Central America) and South America.Taxon Habia rubica (Aves: Cardinalidae).MethodsWe compiled genetic data, coloration, and morphometric data from specimens from collections in Mexico and the United States. We used the Multiple Matrix Regression with Randomization (MMRR) approach to evaluate the influence of geographic and environmental distances on genetic and phenotypic differentiation of H. rubica at both phylogroup and population levels.ResultsOur results provide strong evidence that geographic distance is the main driver of genetic variation in H. rubica. We did not find evidence that climate variation is driving population differentiation in this species across a widespread geographic region.Main conclusionsOur data point to geographic isolation as the main factor structuring genetic variation within populations of H. rubica and suggest that climate is not playing a major role in genetic differentiation within this species.

Highlights

Many animal species show considerable levels of intraspecific variation that reflect the effects of selective and/or neutral evo‐ lution (Lande, 1976; Morales et al, 2017; Nosil, 2012; Seeholzer & Brumfield, 2017; Zamudio‐Beltrán & Hernández‐Baños, 2015)
Isolation by adaptation (IBA; Rundle & Nosil, 2005) is defined as the effect of environmental gradients that results in divergent natural selection that can lead to adaptive phenotypic divergence between populations, resulting in a positive correlation between genetic divergence and adaptive phenotypic differentiation (Funk, 1998; Guayasamin et al, 2017)
Our results provide strong evidence that geographic distance is a major driver of genetic variation in H. rubica

Summary

| INTRODUCTION

Many animal species show considerable levels of intraspecific variation that reflect the effects of selective and/or neutral evo‐ lution (Lande, 1976; Morales et al, 2017; Nosil, 2012; Seeholzer & Brumfield, 2017; Zamudio‐Beltrán & Hernández‐Baños, 2015). Isolation by environment (IBE, Wang & Bradburd, 2014) is defined as the occupation of two populations in different points on the ecological gradient This process is observed when the phenotypic target of selection is unknown or is not eas‐ ily measured, and the environmental variation can be used as a proxy and a positive correlation between genetic divergence and environmental dissimilarity is expected. Several factors make the Red‐crowned Ant tanager (Habia rubica) a good model for performing tests of IBD and IBE It is a highly poly‐ typic species that is distributed from central Mexico to northeastern Argentina and southeastern Brazil (Figure 2a), and it has a continen‐ tal distribution that encompasses a variety of suitable environments. Robles environmental divergence under IBE, and/or geographic distance under IBD (Figure 1)

| MATERIALS AND METHODS

| DISCUSSION

Findings

CONFLICT OF INTEREST