Morphological diversity and community organization of desert anurans

Abstract

Morphological approaches have been used extensively to understand assembly rules (species interactions, environmental filtering, and neutral processes) that structure ecological communities. Desert anurans cope with limited water by either being restricted to permanent water or becoming more fossorial, which should be reflected in their morphology. We examined morphological diversity of 16 frog species across six habitat types within the Chihuahuan Desert to investigate the relationship between species richness and morphological space. We measured 13 morphological traits associated with locomotion, habitat use, and feeding. Principal components analysis separated species into three ecomorphological groups: fossorial, terrestrial, and semi-aquatic species. Morphological diversity was analyzed and compared against a null model and revealed nonrandom community structure. The total assemblage morphospace increased in relation to species richness, though this relationship was not significant. Species were significantly packed within the morphospace exhibiting high morphological similarity while being less evenly dispersed, with increasing species richness, indicative of a response to an environmental gradient. Given the highly xeric nature of the Chihuahuan Desert, our results support the assumption that environmental filtering, rather than interspecific interactions, shapes assemblages' structure by favoring species with similar traits to co-occur more often within a given habitat type than expected by chance.