GULF OF GUINEA ISLANDS' BIODIVERSITY NETWORK

MORPHOLOGICAL AND ALLOZYME VARIATION OF Eidolon helvum (MAMMALIA: MEGACHIROPTERA) IN THE ISLANDS OF THE GULF OF GUINEA

JAVIER JUSTE B.1, 2, CARLOS IBÁÑEZ2 AND ANNIE MACHORDOM3

1. Departamento de Bioquímica y Biología Molecular IV. Facultad de
Veterinaria, Universidad Complutense de Madrid, Madrid 28040, Spain
2. Estación Biológica de Doñana, C.S.I.C, Apartado 1056, E-41080 Sevilla,
Spain
3. Museo Nacional de Ciencias Naturales (CSIC), José Gutiérrez Abascal 2,
28006 Madrid, Spain
 

Running title: Variation of Eidolon helvum in the Gulf of Guinea

Morphological and genetic variation is evaluated among populations of E. helvum in the islands of the Guinea Gulf (Central Africa). The populations from the islands of Bioko, Príncipe, and São Tomé do not show significant phenetic differentiation, although a trend is found towards a reduction of size in the oceanic islands. The low genetic distances between populations, as well as their values of Wright's fixation indexes, suggest that gene flow has hampered differentiation on these islands. In contrast, E. helvum bats from Annobón, the smallest and farthermost island, show remarkable morphological and genetic differentiation. E. helvum has unique migratory and dispersal behaviours in the mainland. Nonetheless, we did not find migratory behaviour in any of the island populations in the Gulf of Guinea. The combination of selective forces in harsher oceanic environments and restricted gene flow among populations has favoured the high degree of morphological differentiation of E. helvum on the most extreme island of the system. Due to a pronounced dry season in Annobón, an earlier achievement of sexual maturity -and consequently smaller size- may be advantageous in the absence of migration. The differentiation is more marked among females, which also suggests that selection may be linked to the reproductive pattern. The population of the island of Annobón is described as a new subespecies herein.