Effects of Forest Fragmentation on Invertebrate Diversity in Southeastern Massachusetts
In areas with dense human populations, such as the northeastern U.S., patches of relatively undisturbed habitat tend to become fragmented, or separated into relatively small, disconnected parcels. Loss of habitat should have negative consequences for most species (Fahrig 2003). For example, a reduction in habitat area generally leads to reduced population abundance and genetic diversity (Hanski et al. 1996, Gibbs 2001), thereby increasing the risk of local extinction (i.e., the disappearance of a species from a particular patch of habitat). Extinction risk increases further if individuals of a species cannot readily move between habitat patches to replace a population that has gone locally extinct (the “rescue effect”; Hanski 1982).
Although habitat fragmentation is generally considered to have negative effects on biodiversity, empirical studies have produced contradictory evidence, with some studies even demonstrating an increase in species richness with increased fragmentation (Fahrig 2003, Ewers and Didham 2006). One explanation is that some species traits mediate susceptibility to habitat loss or fragmentation. For example, habitat specialists and rare species are more strongly affected by fragmentation than are abundant generalists (Henle et al. 2004). In addition, factors such as mixing of species at habitat boundaries (i.e., edge effects) can confound a study of the effects of fragmentation (Ewers and Didham 2006).
In Summer 2012, while funded by a Summer Grant from CARS, I conducted sampling to supplement data collected with my students in Fall 2011, established tentative identifications, and conducted preliminary analyses to evaluate patterns of biodiversity in response to urbanization and fragmentation, especially with respect to edge effects. Although additional analyses are ongoing, these preliminary results are presented here.
Bloch, Christopher P. (2012). Effects of Forest Fragmentation on Invertebrate Diversity in Southeastern Massachusetts. CARS Summer Grants. Item 143.