Ficus insipida subsp. insipida (Moraceae) reveals the role of ecology in the phylogeography of widespread Neotropical rain forest tree species

Aim: To examine the phylogeography of Ficus insipida subsp. insipida in order to investigate patterns of spatial genetic structure across the Neotropics and within Amazonia.

Location: Neotropics.

Methods: Plastid DNA (trnH-psbA; 410 individuals from 54 populations) and nuclear ribosomal internal transcribed spacer (ITS; 85 individuals from 27 populations) sequences were sampled from Mexico to Bolivia, representing the full extent of the taxon's distribution. Divergence of plastid lineages was dated using a Bayesian coalescent approach. Genetic diversity was assessed with indices of haplotype and nucleotide diversities, and genetic structure was examined using spatial analysis of molecular variance (SAMOVA) and haplotype networks. Population expansion within Amazonia was tested using neutrality and mismatch distribution tests.

Results: trnH-psbA sequences yielded 19 haplotypes restricted to either Mesoamerica or Amazonia; six haplotypes were found among ITS sequences. Diversification of the plastid DNA haplotypes began c. 14.6 Ma. Haplotype diversity for trnH-psbA was higher in Amazonia. Seven genetically differentiated SAMOVA groups were described for trnH-psbA, of which two were also supported by the presence of unique ITS sequences. Population expansion was suggested for both markers for the SAMOVA group that contains most Amazonian populations.

Main conclusions: Our results show marked population genetic structure in F. insipida between Mesoamerica and Amazonia, implying that the Andes and seasonally dry areas of northern South America are eco-climatic barriers to its migration. This pattern is shared with other widespread pioneer species affiliated to wet habitats, indicating that the ecological characteristics of species may impact upon large-scale phylogeography. Ficus insipida also shows genetic structure in north-western Amazonia potentially related to pre-Pleistocene historical events. In contrast, evident population expansion elsewhere in Amazonia, in particular the presence of genetically uniform populations across the south-west, indicate recent colonization. Our findings are consistent with palaeoecological data that suggest recent post-glacial expansion of Amazonian forests in the south.