A large historical refugium explains spatial patterns of genetic diversity in a Neotropical savanna tree species

Abstract

Background and Aims 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.Methods 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).Key Results 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.Conclusions 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.

Phylogeographic Studies Depict the Role of Space and Time Scales of Plant Speciation in a Highly Diverse Neotropical Region

“…Additionally, a single species presented only a slight range retraction, with a large stable area maintained since the LGM (Souza et al, 2016). Higher genetic diversity in the core distribution of diverse plants has also been reported by these phylogeographic studies (Ramos et al, 2007;Novaes et al, 2010Novaes et al, , 2013Ribeiro et al, 2016;Souza et al, 2016).…”

“…Nevertheless, retraction with population subdivision in multiple refugia during the LGM has been recorded for a savanna tree species from central Brazil (Collevatti et al, 2012a) and a palm species restricted to wetlands (Lima et al, 2014). Additionally, a single species presented only a slight range retraction, with a large stable area maintained since the LGM (Souza et al, 2016). Higher genetic diversity in the core distribution of diverse plants has also been reported by these phylogeographic studies (Ramos et al, 2007;Novaes et al, 2010Novaes et al, , 2013Ribeiro et al, 2016;Souza et al, 2016).…”

“…Despite these contrasting patterns, studies of the flora of Cerrado have commonly reported a high level of population genetic differentiation (Collevatti et al, 2003;Ramos et al, 2007;Collevatti et al, 2012a, Novaes et al, 2013Bonatelli et al, 2014). A notable exception is the widely distributed tree species, Dimorphandra mollis, which has lower levels of genetic diversity and genetic differentiation (Souza et al, 2016). Additionally, an eastwest split in genetic structure was observed in both widely distributed tree species (Collevatti et al, 2003;Ramos et al, 2007Ramos et al, , 2009Novaes et al, 2010Novaes et al, , 2013Ribeiro et al, 2016) and plants from rocky fields (Collevati et al, 2009;Bonatelli et al, 2014).…”

Evolving in isolation: Genetic tests reject recent connections of Amazonian savannas with the central Cerrado

“…For example, our study revealed an unexpected cryptic species in B. coccolobifolia from the central and northern areas of the CC, an area reportedly of high species richness (Ratter et al., ). Other phylogeographic studies on Cerrado trees suggest the highest genetic diversity occurs in central areas of the Cerrado as well (e.g., Collevatti, Castro, Lima, & Telles, ; Novaes, Lemos‐Filho, Ribeiro, & Lovato, ; Souza, Collevatti, Lima‐Ribeiro, Lemos‐Filho, & Lovato, ); however, many of these have limited sampling of northern areas. Our results, as those with more extensive sampling (Collevatti, Terribile, Diniz, & Lima‐Ribeiro, ; Ribeiro, Lemos, Buzatti, Lovato, & Heuertz, ) have revealed high genetic diversity in north‐eastern plant populations, highlighting the importance of these areas to conservation efforts of the Cerrado, especially since these areas are part of an expanding agricultural frontier.…”

Caracterização e história biogeográfica dos ecossistemas secos neotropicais

“…A área climaticamente estável para a região central do Cerrado -área core -ao longo do tempo (UMG, presente e futuro) é reconhecida e identificada por modelagem de nicho ecológico para diversas espécies de plantas desse ecossistema (Terribile et al 2012;Bueno et al 2017). Os trabalhos filogeográficos acoplados à modelagem para plantas de Cerrado são concordantes em identificar tal região como climaticamente de maior adequabilidade no UMG e, detentora de maior diversidade genética atual (Collevatti et al 2012a;Collevatti et al 2012b;Collevatti et al 2014;De Lima et al 2014;Collevatti et al 2015;Souza et al 2017).…”