A large historical refugium explains spatial patterns of genetic diversity in a Neotropical savanna tree species.
The relative role of Pleistocene climate changes in driving the geographic distribution and genetic diversity of South American species is not well known, especially from open biomes such as the Cerrado, the most diverse tropical savanna, encompassing high levels of endemism. Here the effects of Quaternary climatic changes on demographic history, distribution dynamics and genetic diversity of Dimorphandra mollis, an endemic tree species widely distributed in the Cerrado, were investigated.



A total of 38 populations covering most of the distribution of D. mollis were analysed using internal transcribed spacer (ITS) sequences and nuclear microsatellite variation [simple sequence repeats (SSRs)]. The framework incorporated statistical phylogeography, coalescent analyses and ecological niche modelling (ENM).



Different signatures of Quaternary climatic changes were found for ITS sequences and SSRs corresponding to different time slices. Coalescent analyses revealed large and constant effective population sizes, with high historical connectivity among the populations for ITS sequences and low effective population sizes and gene flow with recent population retraction for SSRs. ENMs indicated a slight geographical range retraction during the Last Glacial Maximum. A large historical refugium across central Brazil was predicted. Spatially explicit analyses showed a spatial cline pattern in genetic diversity related to the paleodistribution of D. mollis and to the centre of its historical refugium.



The complex genetic patterns found in D. mollis are the result of a slight geographical range retraction during the Last Glacial Maximum followed by population expansion to the east and south from a large refugium in the central part of the Cerrado. This historical refugium is coincident with an area predicted to be climatically stable under future climate scenarios. The identified refugium should be given high priority in conservation polices to safeguard the evolutionary potential of the species under predicted future climatic changes.
Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Caixa Postal 486, 31270-901 Belo Horizonte, MG, Brazil.
Helena Augusta Viana E
HA
Souza
Laboratório de Genética & Biodiversidade, ICB, Universidade Federal de Goiás, Caixa Postal 131, 74001-970 Goiânia, GO, Brazil.
Rosane Garcia
RG
Collevatti
Laboratório de Macroecologia, Universidade Federal de Goiás, Campus Jataí, 75801-615 Jataí, GO, Brazil.
Matheus S
MS
Lima-Ribeiro
Departamento de Botânica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Caixa Postal 486, 31270-901 Belo Horizonte, MG, Brazil.
José Pires de
JP
Lemos-Filho
Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Caixa Postal 486, 31270-901 Belo Horizonte, MG, Brazil lovatomb@icb.ufmg.br.
Maria Bernadete
MB
Lovato
D005075:Biological Evolution; D014644:Genetic Variation / Q000235:genetics*; D065948:Grassland; D010802:Phylogeny; D000068236:Refugium; D014197:Trees / Q000145:classification / Q000235:genetics*
Cerrado; Dimorphandra mollis; Neotropical savanna; climatic changes; coalescent analysis; demographic history; ecological niche modelling; genetic diversity; phylogeography; refugium