Cryptic clades, fruit wall morphology and biology of Andira (Leguminosae: Papilionoideae)

Abstract

Andira comprises 29 species distributed throughout tropical America, with two subspecies in Africa. Its fruits are unusual for a papilionoid legume because they are drupes. The majority of species have fruits dispersed by bats, but eight species have larger fruits dispersed by rodents. Some fruits of both dispersal types are secondarily dispersed by water. Cladistic analysis of chloroplast DNA (cpDNA) restriction site characters discovered four well-supported clades of Andira species. None of these «cryptic» clades had been recognized by previous workers, because they are not apparently marked by any known morphological innovations. This prompted a search for new characters that might support these groupings. An anatomical study of fruit walls of 25 Andira species revealed the presence of three principal endocarp types, dominated by (1) parenchyma, (2) fibres, or (3) stone cells. These features are best coded as a single unordered multistate character. When incorporated into a simultaneous cladistic analysis of previously gathered molecular and morphological data, states of this endocarp character are shown to be apomorphies for two of the well-supported clades evident in the cpDNA restriction site data. The most likely plesiomorphic state for the endocarp is parenchyma-dominated. Thicker, stronger endocarps of fibres and stone cells may have evolved in response to the need to protect the seed from predators.