Revista Chilena de Historia Natural 77 (3): 547-558, 2004
RESEARCH ARTICLE
Short-term effects of habitat fragmentation on the abundance and species richness of beetles
in experimental alfalfa microlandscapes
Habitat loss and fragmentation are considered as the main causes of biodiversity
depression. Habitat loss implies a reduction of suitable habitat for organisms, and habitat fragmentation is a change in the spatial
configuration of the landscape, with the remaining fragments resulting more or less isolated. Recent theory indicates that the effects of
habitat loss are more important than those of habitat fragmentation, however there are few experimental studies evaluating both
processes separately. To test the effects of habitat fragmentation per se on the abundance, species richness and diversity of epigeal
coleopterans, 15 (30 x 30 m) alfalfa microlandscapes, distributed in three blocks, were created. On twelve of them, 84 % of the habitat
was removed, leaving in each landscape four or 16 fragments separated by 2 or 6 m of bare ground. From December 2002 to April
2003, before and after fragmentation, coleopterans were sampled using pitfall traps. In total, 8,074 coleopterans of 75 species
belonging to 16 families were captured. Neither habitat fragmentation nor habitat loss affected the total abundance of coleopterans, with
the exception of Anthicidae that was more abundant in the microlandscapes composed by four fragments separated by 2 m. This
family was also more abundant in the matrix of fragmented microlandscapes, while most other beetle families were more abundant in
the fragments, significantly Carabidae and Lathridiidae. Species richness (per trap and per landscape) was higher in microlandscapes
with 16 fragments separated by 6 m. Contrary to what is described frequently in the literature, habitat fragmentation did not negatively
affect the abundance or the species richness of epigeal coleopterans. Rather, smaller and more isolated alfalfa fragments seem to
provide habitat to support greater biodiversity. These results agree with more recent findings where habitat fragmentation per se
seems not to have deleterious effects on the fauna, instead, it could favor the biota, at least at short time scales.
Key words:
habitat fragmentation,
habitat loss, microlandscapes, diversity of epigeal beetles
