Fragmentation reduces genetic and species diversity

It is widely recognized that the diversity of species that persist in forest fragments is likely to be a reduced subset of that in larger intact systems, but what of the genetic diversity of species holding on in fragments? In this June’s issue of Ecology Letters, Matt Struebig and colleagues report that there can be parallel declines in genetic diversity in small fragments, but not in all species.

Working in forest fragments embedded in oil palm and rubber plantations surrounding a large tract of primary forest in Peninsular Malaysia, the authors found the expected decline in species richness with fragment size, and that, as Struebig had previously reported, this relationship was driven by bats that not only forage in forests, but roost in foliage and tree hollows within them (“forest bats”). To look at the relationship between fragment size and genetic diversity (allelic richness) they focused on three species that are relatively common in the large primary forest (Krau Wildlife Reserve), but which were expected to differ in their response to fragmentation. The cave-roosting colonial Rhinolophus lepidus is highly vagile and from Matt’s earlier work, does not show an abundance response to fragmentation.   R. trifoliatus and Kerivoula papillosa both roost within the forest in vegetation (R. trifoliatus) or small tree hollows (K. papillosa) and have small home ranges, and were expected to show a reduction in genetic diversity. This is largely what the authors found; while the genetic diversity of R. lepidus captured in forest fragments didn’t differ from those in continous forest, there was a reduction in genetic diversity in fragments relative to continous forest in both R. trifoliatus and K. papillosa, and for the latter, this decline correlated significantly with fragment area.  

The article is currently available for download from Ecology letters here

Struebig, M. J., T. Kingston, E. J. Petit, A. Zubaid, A. Mohd.-Adnan, and S. J. Rossiter (2011). Parallel declines in species and genetic diversity in tropical forest fragments. Ecology Letters 14:  580-590.