Holocene southward expansion in seasonally dry tropical forests in South America: phylogeography of Ficus bonijesulapensis (Moraceae)

Abstract

We conducted a phylogeographical and niche modelling study of the tree Ficus bonijesulapensis, endemic to Brazilian seasonally dry tropical forests (SDTFs), in order to evaluate the effects of Quaternary climatic fluctuations on population dynamics. The trnQ–5′rps16 region of plastid DNA was sequenced from 15 populations. Three phylogeographical groups were identified by the median-joining algorithm network and spatial analysis of molecular variance (SAMOVA) (FCT = 0.591): a central-west, a central-east and a scattered group. The central groups had higher total haplotype and nucleotide diversities than the scattered group. Ecological niche modelling suggested that, since the Last Interglacial (130 kyr bp), the central and north regions have been relatively stable, whereas the southern region of the species distribution has been less stable. The phylogeographical groups showed concordance with the floristic units described for SDTFs. The low genetic diversity, unimodal mismatch distribution and unfavourable climatic conditions in the southern region suggest a recent southward expansion of the range of the species during the Holocene, supporting the hypothesis of the southward expansion of SDTFs during this period. The central and northern regions of the current distribution of F. bonijesulapensis, which are consistent with arboreal caatinga and rock outcrop floristic units, were potential refugia during Quaternary climatic fluctuations.