Preliminary evaluation of the effects of habitat fragmentation on habitat use and genetic diversity of pygmy marmosets in Ecuador

We evaluated the effects of habitat fragmentation on group size, home range size, and genetic variability of pygmy marmosets Callithrix pygmaea, from May 2008 through February 2010, in three wild groups in the San Pablo population in Ecuadorian Amazonia. Forest remnants in this area are surrounded by pasture and fields of plantain, corn, and manioc, and have been considerably reduced in the past decade. We used scan samples to record data on group size and home range size. We collected fecal samples from the groups to analyze n-DNA. The increase in habitat fragmentation in San Pablo did not appear to affect group size; the mean group size recorded during the study was similar to that obtained in previous years. A "nomadic" behavior not previously reported in any of our studied populations or elsewhere for this species was seen in the study groups. This behavior was characterized by the short-term use of small core areas and a continuous movement among them. The results of the genetic analyses suggest that nonrandom mating may be occurring in some groups. Genetic distances between groups appeared to be related to the linear distances between core areas. Overall, our results suggest that population responses to fragmentation are more complex than we initially expected.