Effects of habitat fragmentation and isolation on species richness: evidence from biogeographic patterns

Abstract

Habitat subdivision by geography or human activity may be an important determinant of regional species richness. Cumulative species-area relationships for vertebrates, land plants, and insects on island archipelagoes show that collections of small islands generally harbor more species than comparable areas composed of one or a few large islands. The effect of the degree of habitat subdivision in increasing species richness appears to increase with the distance from potential sources of colonists. Mountaintop biotas show no clear differences between species richness on large alpine areas and collections of smaller peaks. National park faunas generally have more species in collections of small parks than in the larger parks. In all cases where a consistent effect of subdivision is observed, the more subdivided collection of islands or isolates contains more species. To the degree that these data provide guidance for establishing nature reserves, they suggest that increasing the numbers of reserves may be an important component of conservation strategies.

Short-term effects of drawing water for connectivity of rivers and lakes on zooplankton community structure

“…However, increasing connectivity led to a decrease in regional diversity, but an increase in the percent similarity of local communities within regions. These data supported the concept that the connection among local patches may decrease regional diversity when patches were previously heterogeneous, and this has been proved from empirical surveys of connected and unconnected habitats (Harrison, 1997(Harrison, , 1999Quinn and Harrison, 1988), as well as theoretical modeling (Hastings and Gavrilets, 1999;Amarasekare, 2000;Mouquet and Loreau, 2002). Research has also shown no relation between the local species richness and three connectivity variables and that the connectivity only acts secondarily by increasing the general species richness within a pond through dispersal from ponds with different environmental conditions (Cottenie and De Meester, 2003).…”

How Should Beta-Diversity Inform Biodiversity Conservation?

“…In landscapes with high species turnover along spatial or environmental gradients, protected area networks must successfully capture this variation or risk losing species [84]. Thus, turnover might favour multiple spatially 285 disjunct reserves over single large parks [22,85,86]. On the other hand, high neutral beta diversity or nestedness (richness differences along spatial gradients) imply that conservation could better focus on diverse sites at the expense of species-poor areas.…”

Large and least isolated fragments preserve habitat specialist spiders best in dry sandy grasslands in Hungary

“…Habitat reduction and alteration negatively influence the 33 distribution, abundance and diversity of characteristic plant and animal species of natural 34 habitats (Quinn and Harrison 1988; Baur and Erhardt 1995; Gilbert et al 1998) and have 35 been regarded as the main threats to compositional and structural biodiversity (Noss 1991;36 Didham et al 1996). Therefore, disturbance sensitive species may disappear from natural 37 and semi-natural habitats.…”