Relaxed random walk model coupled with ecological niche modeling unravel the dispersal dynamics of a Neotropical savanna tree species in the deeper Quaternary.

Rosane G Collevatti,Matheus S Lima-Ribeiro,Suelen G Rabelo,Levi C Terribile

doi:10.3389/fpls.2015.00653

Abstract

Understanding the dispersal routes of Neotropical savanna tree species is an essential step to unravel the effects of past climate change on genetic patterns, species distribution and population demography. Here we reconstruct the demographic history and dispersal dynamics of the Neotropical savanna tree species Tabebuia aurea to understand the effects of Quaternary climate change on its current spatial patterns of genetic diversity. We sampled 285 individuals from 21 populations throughout Brazilian savannas and sequenced all individuals for three chloroplast intergenic spacers and ITS nrDNA. We analyzed data using a multi-model inference framework by coupling the relaxed random walk model (RRW), ecological niche modeling (ENM) and statistical phylogeography. The most recent common ancestor of T. aurea lineages dated from ~4.0 ± 2.5 Ma. T. aurea lineages cyclically dispersed from the West toward the Central-West Brazil, and from the Southeast toward the East and Northeast Brazil, following the paleodistribution dynamics shown by the ENMs through the last glacial cycle. A historical refugium through time may have allowed dispersal of lineages among populations of Central Brazil, overlapping with population expansion during interglacial periods and the diversification of new lineages. Range and population expansion through the Quaternary were, respectively, the most frequent prediction from ENMs and the most likely demographic scenario from coalescent simulations. Consistent phylogeographic patterns among multiple modeling inferences indicate a promising approach, allowing us to understand how cyclical climate changes through the Quaternary drove complex population dynamics and the current patterns of species distribution and genetic diversity.

Highlights

Spatial displacements in species distributions due to Quaternary climate changes have played an important role in shaping the genetic diversity of many species across space (e.g., Taberlet et al, 1998)
Investigating these aspects of paleodistribution dynamics has been a key point to understand the effects of past colonization and to unravel the role of Quaternary climate changes in shaping the current spatial pattern of genetic diversity worldwide (e.g., Petit et al, 2002)
The reconstruction of lineages dispersal inferred using the relaxed random walk model (RRW), the distribution dynamics retrieved by ecological niche modeling (ENM) and the coalescent simulation predicted similar demographic and dispersal dynamics for T. aurea through the Quaternary

Summary

Introduction

Spatial displacements in species distributions due to Quaternary climate changes have played an important role in shaping the genetic diversity of many species across space (e.g., Taberlet et al, 1998). Allele surfing, i.e., the spread and frequency increase of a low-frequency allele that migrates on the wave of advance of a population in expansion (Excoffier and Ray, 2008; Arenas et al, 2012), and density-dependent processes due to the fast colonization and founder events may cause patches and sectoring in genetic diversity (see Excoffier et al, 2009; Waters et al, 2013 for reviews) Investigating these aspects of paleodistribution dynamics has been a key point to understand the effects of past colonization and to unravel the role of Quaternary climate changes in shaping the current spatial pattern of genetic diversity worldwide (e.g., Petit et al, 2002). Together with ENM and coalescence modeling, we propose that a direct spatio-temporal reconstruction of lineage dispersal (Lemey et al, 2009, 2010) should integrate the context of multimodel inference to better understand the climate footprint on demographic history, shaping the spatial pattern in genetic diversity (see Collevatti et al, 2015)

Methods

Results

Conclusion