The effects of habitat fragmentation on the social kin structure and mating system of the agile antechinus, Antechinus agilis

Abstract

Habitat fragmentation is one of the major contributors to the loss of biodiversity worldwide. However, relatively little is known about its more immediate impacts on within-patch population processes such as social structure and mating systems, whose alteration may play an important role in extinction risk. We investigated the impacts of habitat fragmentation due to the establishment of an exotic softwood plantation on the social kin structure and breeding system of the Australian marsupial carnivore, Antechinus agilis. Restricted dispersal by males in fragmented habitat resulted in elevated relatedness among potential mates in populations in fragments, potentially increasing the risk of inbreeding. Antechinus agilis nests communally in tree hollows; these nests are important points for social contact between males and females in the mating season. In response to elevated relatedness among potential mates in fragmented habitat, A. agilis significantly avoided sharing nests with opposite-sex relatives in large fragment sites (but not in small ones, possibly due to limited nest locations and small population sizes). Because opposite-sex individuals shared nests randomly with respect to relatedness in unfragmented habitat, we interpreted the phenomenon in fragmented habitat as a precursor to inbreeding avoidance via mate choice. Despite evidence that female A. agilis at high inbreeding risk selected relatively unrelated mates, there was no overall increased avoidance of related mates by females in fragmented habitats compared to unfragmented habitats. Simulations indicated that only dispersal, and not nonrandom mating, contributed to inbreeding avoidance in either habitat context. However, habitat fragmentation did influence the mating system in that the degree of multiple paternity was reduced due to the reduction in population sizes and population connectivity. This, in turn, reduced the number of males available to females in the breeding season. This suggests that in addition to the obvious impacts of reduced recruitment, patch recolonization and increased genetic drift, the isolation of populations in habitat patches may cause changes in breeding behaviour that contribute to the negative impacts of habitat fragmentation.

On some genetic consequences of social structure, mating systems, dispersal, and sampling

“…A number of ecological and conservation studies have argued that changes in habitat composition affect group size, mate availability, and mating behavior (9,87,88). Moreover, the increasingly reduced and fragmented landscapes (89) may limit dispersal, increase isolation, and promote high relatedness within groups.…”

Small mammals and retention islands: An experimental study of animal response to alternative logging practices

“…The spatial configuration of islands may be an additional or alternative reason for the unexpected lack of a difference in animal abundance between large and small islands. That is, connectivity between the three small islands may have been sufficient to avoid negative impacts of patch size and isolation (Banks et al, 2005).…”

Effects of landscape composition and configuration on northern flying squirrels in a forest mosaic

“…The negative response of northern flying squirrels to the amount of non-habitat matrix within 176 ha indicates the species responds strongly to landscape context. Habitat loss resulting in patch isolation may alter species distributions (Ficetola, 2004), social interactions (Banks et al, 2005), species richness (Estrada et al, 1994), breeding success (Cooper and Walters, 2002), colonization success (Berggren et al, 2001) and the probability of recolonization (Bé lisle et al, 2001). Habitat loss may change movement patterns due to decreased movement efficiency in areas without trees (Scheibe et al, 2006), behavioural changes relating to encountering patch edges (Desrochers et al, 2003), gap-crossing decisions (Bé lisle et al, 2001) and/or increased predation risk (Kurki et al, 1998).…”

“…Some species may respond consistently to landscape configuration despite varying landscape composition (landscape configuration hypothesis, Villard et al, 1999;Betts et al, 2006). Changes in landscape configuration may reduce the probability of population persistence if the dispersal ability of individuals is disrupted (Bé lisle et al, 2001;Banks et al, 2005) or through indirect mechanisms such as the spatial distribution of predators. Small patches may attract disproportionately fewer individuals than large patches for species using conspecifics in habitat selection (Fletcher, 2006).…”