Speciation within Columnea section Angustiflora (Gesneriaceae): Islands, pollinators and climate

- Phylogenetic relationships of Columnea section Angustiflorae were resolved using DNA sequences from multiple loci.
- Geographic distributions identified allopatry as a mechanism for speciation in one sister species pair.
- Ancestral state reconstruction correlation with climate tolerances identified five additional forces driving speciation.
- Pollinator shifts are likely to have had the greatest effect on speciation in this clade.

Despite many advances in evolutionary biology, understanding the proximate mechanisms that lead to speciation for many taxonomic groups remains elusive. Phylogenetic analyses provide a means to generate well-supported estimates of species relationships. Understanding how genetic isolation (restricted gene flow) occurred in the past requires not only a well-supported molecular phylogenetic analysis, but also an understanding of when character states that define species may have changed. In this study, phylogenetic trees resolve species level relationships for fourteen of the fifteen species within Columnea section Angustiflorae (Gesneriaceae). The distributions of sister species pairs are compared and ancestral character states are reconstructed using Bayesian stochastic mapping. Climate variables were also assessed and shifts in ancestral climate conditions were mapped using SEEVA. The relationships between morphological character states and climate variables were assessed with correlation analyses. These results indicate that species in section Angustiflorae have likely diverged as a result of allopatric, parapatric, and sympatric speciation, with both biotic and abiotic forces driving morphological and phenological divergence.