GULF OF GUINEA CONSERVATION GROUP

GULF OF GUINEA ISLANDS' BIODIVERSITY NETWORK


VARIATION IN THE FREQUENCY OF THE ECHOLOCATION CALLS OF Hipposideros ruber IN THE GULF OF GUINEA: AN EXPLORATION OF THE ADAPTIVE MEANING OF THE CONSTANT FREQUENCY VALUE IN RHINOLOPHOID CF BATS

ANTONIO GUILLÉN1, 2, JAVIER JUSTE B. 2, 3 AND CARLOS IBÁÑEZ 2

1Department of Biology, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121-4499, USA
2 Estación Biológica de Doñana, CSIC, Apartado 1056, 41080 Sevilla, Spain
3 Departamento de Bioquímica y Biología Molecular IV, Universidad Complutense de Madrid, Facultad de Veterinaria, 28040 Madrid, Spain

RUNNING TITLE:  Variation in echolocation of Hipposideros ruber

Abstract

This study describes variation patterns in the constant frequency (CF) segment of echolocation calls of the bat Hipposideros ruber within and among populations across the region of the Gulf of Guinea. Correlations of variation in CF with variation in body size, body condition, environmental humidity, and presence of ecologically similar species are studied in an attempt to identify the forces driving the evolution of CF. We found that bats may adapt the frequency to humidity, and that CF may evolve under interspecific interactions, either of ecological or social nature. The results support an adaptive value for the high values of CF, and challenge the 'Allotonic Frequency Hypothesis'.  We found correlation of frequency with a body condition index, what might trigger social selection processes
in this species sexually dimorphic in CF. Combined social and environmental selection on CF could trigger diversification of bats along ecotones separating habitats with contrasting air humidity.

Keywords: adaptation, constant frequency,  Chiroptera, Echolocation, geographic variation, Hipposideros ruber, humidity, speciation