Adaptive evolution of context-dependent style curvature in some species of the Malvaceae: a molecular phylogenetic approach

Abstract

The evolution of floral movement responding to pollination environments has long intrigued biologists. This has been mostly demonstrated in different species, but has as yet few explanations at the family level. Style curvature occurs in 23 species of eight genera among our observed and surveyed 52 species of 13 genera in the Malvaceae. To analyze the origin of style curvature in these species, we mapped this and correlated characters onto molecular phylogenetic trees that were constructed using the combination of the chloroplast DNA sequences of ndhF and the rpl16 intron. The results showed that style curvature evolved at least five times in species with herkogamous flowers. The occurrence of style curvature was associated with a shift to annual or perennial herbs with herkogamous flowers, which have similar ecological distributions with unpredictable pollinator environments. Style curvature appears to have evolved to facilitate delayed selfing if outcrossing fails under unpredictable pollination conditions.