Isolation and Lack of Potential Mates may Threaten an Endangered Arid-Zone Acacia

Le résumé fourni par la source

Clonality may provide reproductive assurance for many threatened plants while limiting sexual reproductive success either through energetic tradeoffs or because clones are self-incompatible. Most stands of the Australian arid-zone plant Acacia carneorum, flower annually but low seed set and an absence of sexual recruitment now suggest that this species and other, important arid-zone ecosystem engineers may have low genotypic diversity. Indeed, our recent landscape-scale genetic study revealed that stands are typically monoclonal, with genets usually separated by kilometers. An inability to set sexually produced seed or a lack of genetically diverse mates may explain almost system-wide reproductive failure. Here, using microsatellite markers, we genotyped 100 seeds from a rare fruiting stand (Middle-Camp), together with all adult plants within it and its 4 neighboring stands (up to 5 km distant). As expected, all stands surveyed were monoclonal. However, the Middle-Camp seeds were generated sexually. Comparing seed genotypes with the single Middle-Camp genotype and those of genets from neighboring and other regional stands (n = 26), revealed that 73 seeds were sired by the Middle-Camp genet. Within these Middle-Camp seeds we detected 19 genotypes in proportions consistent with self-fertilization of that genet. For the remaining 27 seeds, comprising 8 different genotypes, paternity was assigned to the nearest neighboring stands Mallee and Mallee-West, approximately 1 km distant. Ironically, given this species' vast geographic range, a small number of stands with reproductively compatible near neighbors may provide the only sources of novel genotypes.

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