Differences in dispersal patterns between two populations of Black and Gold howler monkeys in Argentina.

OKLANDER, L. I., KOWALEWSKI, M. M.

Bello Horizonte, Minas Gerais, Brasil

Congreso; XII Congresso Brasileiro de Primatologia; 2007

Associação Brasileira de Primatologia

Demographic factors such as group size, group density, and male and female dispersal patterns affect the genetic structure of primate populations. In addition, habitat fragmentation may isolate populations and limit dispersal opportunities. We studied adults individuals in 7 groups of black and gold howlers (Alouatta caraya) inhabiting continuous forest (CF) on Isla Brasilera (27º 20´ S, 58º 40´ W) and 11 groups of black and gold howlers inhabiting a fragmented forest (FF) in Corrientes (27º 30’ S, 58º 41’ W) in northern Argentina. On the island, several groups overlap home ranges whereas in FF each group is restricted to a forest fragment. We analyzed the genetic variability of these groups using thirteen polymorphic microsatellites: (AC14, AC17, AC45, TGMS1, TGMS2, D5S117, D8S165, D17S804, LL1110, LL1118, LL157, AB12, and AB17). Our results indicated that Fst values between-sexes in the CF showed no differences (Females FST=0.042, Males FST=0.045, p=0.951) and kinship relationships between adults of the same sex were similar and relatively low for both sexes (Females r =0.082; Males r =0.085, p=0.983). However in the FF we found genetic differences between sexes (Females FST=0.246, Males FST=0.090, p=0.022) and differences in kinship relations between adults of the same sex (Females r =0.492; Males r =0.187, p=0.025). These results suggest that habitat fragmentation modifies the dispersion patterns of black and gold howler monkeys. In the CF both males and females disperse. As a result, groups are composed of adults individuals that are not close relatives. In contrast, in the FF, males disperse more than females (females are the philopatric sex) and groups are composed of adult females that are close relatives (mother/daughter or siblings). These two populations also differ in social organization and pattern of births seasonality. These results indicate that the species show a variety of responses to cope with fragmentation and can be one of the advantages that howlers possess to colonize different types of forests. However, the limits of A. caraya’s ecological plasticity remain unknown.