An Intersite Comparison of Fruit Characteristics in Madagascar: Evidence for Selection Pressure Through Abiotic Constraints Rather Than Through Co-Evolution

Abstract

Fruit and seed characteristics are compared between a dry deciduous forest in the west and a humid littoral forest in the south-east of Madagascar to discriminate between the role of abiotic factors (humidity, climate, soil characteristics) and frugivorous vertebrates for the evolution of morphological and biochemical fruit characteristics. The sites differed in abiotic conditions but contain very similar communities of frugivorous vertebrates. Fruit selection by two lemur species (Eulemur fulvus and Cheirogaleus medius) that are important for seed dispersal and that are present at both study sites, was compared between sites to examine fixed selection criteria that could give rise to possible co-evolution between frugivores and their fruit species on the one hand or to dietary flexibility of the frugivores on the other hand. Our results show that most fruit characteristics differ significantly between study sites. Food selection by both lemur genera in relation to morphological and biochemical fruit characteristics co-varies closely with their representation at a given site. These results indicate that morphological and biochemical characteristics are more likely the result of abiotic conditions rather than of interactions between frugivorous lemurs and their food.