A conceptual framework for studying species composition in fragments, islands and other patchy ecosystems

Abstract

Aim I propose and develop a new classification system to explain diversity patterns in habitat fragments, equally applicable to islands and other inherently patchy ecosystems. My primary goal is to provide an inclusive model to improve the comparability of studies and enhance future efforts to synthesize their findings, yielding a generalized basis for understanding species composition in patchy ecosystems. Results Differentiating islands from fragments and incorporating patch age and patch: matrix contrast, eight classes of patch are distinguished, spanning a range of geographical features. To compare studies of diversity patterns among and between patch types, patch biota are divided into three categories based on their origin—relict species (present before fragmentation), matrix‐derived species and interpatch dispersers. Applying this novel scheme to existing data, the effects of insularization are synthesized. Direct comparisons among fragments revealed broad similarity in the long‐term effects of habitat fragmentation compared with highly divergent patterns in younger landscapes (<200 years). Holding patch: matrix contrast and age constant, fragments and islands were compared. Despite initial differences in community assembly, the biota of islands and fragments converge in several properties over time, as diversities stabilize and patch biotas become distinct from the surrounding matrix. Main conclusions Although necessarily broad, this framework provides an explicit context within which to test forty‐four specific predictions regarding the distribution of diversity in patchy landscapes and thereby gain a clearer understanding of the long‐term biological consequences of insularization. I propose that the fragments‐as‐islands analogy be revisited, potentially yielding valuable insight into the long‐term future awaiting anthropogenically altered ecosystems.

Positive relationship between genetic- and species diversity on limestone outcrops in the Carpathian Mountains

“…Local genetic and species diversity showed parallel patterns in this island-like system of outcrops in the Carpathian Mountains, which is an expected result in isolated mainland ecosystems (Michelangeli, 2000;Watson, 2002;Vellend, 2003;but see Puş caş et al, 2008;Sei et al, 2009). It also appears that the intra-and interspecific diversity patterns are shaped by similar mechanisms.…”

“…Although there is accumulating theoretical and empirical support for similarity between oceanic and mainland island systems (Vellend, 2003;Vellend and Geber, 2005;Wehenkel et al, 2006;Sei et al, 2009;Lamy et al, 2013), nonsignificant (Puş caş et al, 2008;Taberlet et al, 2012) and negative (Silvertown et al, 2009;Fady and Conord, 2010) correlations have also been reported. An important source of these contradictory results is the lack of a clear outline of the history of fragmentation and extent of habitat isolation, despite readily available frameworks (Watson, 2002). The older the fragmentation and the more pronounced the ecological contrast with the landscape matrix, the more likely the mainland habitat patches are to follow biogeographical processes typical of isolated oceanic island systems.…”

“…The older the fragmentation and the more pronounced the ecological contrast with the landscape matrix, the more likely the mainland habitat patches are to follow biogeographical processes typical of isolated oceanic island systems. Yet, few studies have investigated the mechanisms of coexistence of genotypes and species in such welldefined mainland island systems, despite an evident need for generalizations (Watson, 2002;Taberlet et al, 2012).…”

Consequences of impediments to animal movements at different scales: A conceptual framework and review

“…Several frameworks have previously been developed for conceptualizing the structural composition of landscapes (Fischer, Lindenmayer, & Fazey, 2004;Forman, 1995;McIntyre & Barrett, 1992;Watson, 2002;Wiens, Stenseth, Van Horne, & Ims, 1993). However, these frameworks were not extended to classify the mechanisms driving isolation effects on animal populations.…”

Biogeographic patterns of the East African coastal forest vertebrate fauna

“…However, the relative importance of these factors in determining species distribution throughout the fragmented habitat differs among taxa, depending on life history traits such as dispersal ability (birds vs. reptiles) and level of dependence on the forest resources (specialists vs. generalists) (Ricklefs and Lovette 1999;Gascon et al 1999;Watson 2002). Moreover, historical factors (e.g.…”