Banks S C, Ward S J, Lindenmayer D B, Finlayson G R, Lawson S J, Taylor A C
Centre for Biodiversity: Analysis, Policy and Management, School of Biological Sciences, Monash University, Victoria, 3800, Australia.
Mol Ecol. 2005 May;14(6):1789-801. doi: 10.1111/j.1365-294X.2005.02535.x.
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.
栖息地破碎化是全球生物多样性丧失的主要原因之一。然而，对于其对斑块内种群过程（如社会结构和交配系统）的更直接影响，我们所知相对较少，而这些过程的改变可能在灭绝风险中发挥重要作用。我们研究了因建立外来针叶人工林导致的栖息地破碎化对澳大利亚有袋食肉动物敏捷狭足袋鼩的社会亲缘结构和繁殖系统的影响。在破碎化栖息地中，雄性的扩散受限导致各片段种群中潜在配偶之间的亲缘关系升高，这可能增加近亲繁殖的风险。敏捷狭足袋鼩在树洞中群居筑巢；这些巢穴是交配季节雌雄个体进行社会接触的重要场所。针对破碎化栖息地中潜在配偶之间亲缘关系升高的情况，敏捷狭足袋鼩在大片段区域显著避免与异性亲属共用巢穴（但在小片段区域并非如此，可能是由于巢穴位置有限且种群规模较小）。因为在未破碎化栖息地中，异性个体在亲缘关系方面随机共用巢穴，所以我们将破碎化栖息地中的这种现象解释为通过配偶选择避免近亲繁殖的先兆。尽管有证据表明处于高近亲繁殖风险的雌性敏捷狭足袋鼩选择了亲缘关系相对较远的配偶，但与未破碎化栖息地相比，破碎化栖息地中的雌性并没有整体上增加对亲缘关系较近配偶的回避。模拟结果表明，在任何一种栖息地环境中，只有扩散而非非随机交配有助于避免近亲繁殖。然而，栖息地破碎化确实影响了交配系统，由于种群规模和种群连通性的降低，多重父权的程度有所下降。这反过来又减少了繁殖季节中可供雌性选择的雄性数量。这表明，除了明显的招募减少、斑块重新定殖和遗传漂变增加的影响外，栖息地斑块中种群的隔离可能会导致繁殖行为的变化，从而加剧栖息地破碎化的负面影响。
