The conservation genetics of endangered 'Eucalyptus camaldulensis' Dehnh. subsp. 'camaldulensis' (River Red Gum) in an eastern Australian floodplain

Abstract

Of primary concern to conservation biologists is that the level of genetic variability remaining within fragmented remnant populations may be insufficient for maintaining reproductive and evolutionary processes. The consequences and contributions of genetic declivities on the persistence of remnant communities, however, are not consistent across species. Plant breeding systems, historical mating patterns and pollinator behaviour can impact upon the susceptibility of a species to genetic decline; while the extinction threat presented by environmental factors may render genetic concerns redundant, at least in the immediate future. Thus, to accurately assess the resilience of remnant communities, genetic diversity and the impact of genetic diversity on individual fitness should be considered within the context of environmental factors and a range of time scales. 'Eucalyptus camaldulensis' is a dominant species of tree in many riparian and floodplain ecosystems in Australia. In the Hunter Valley catchment region, the distribution of the species has been reduced to a series of disconnected remnants along small stretches of river and floodplain habitats. 'Eucalyptus camaldulensis' is a niche specialist in which several critical life-stages are water dependant. The species is also known to hybridize with closely related species and exhibits a complex breeding system that enables post-zygotic selection based on the fitness of zygotes and available resources. Hence, the ecological viability of remnants, the level of inherent genetic variability, the impact of genetic variability on progeny performance and the breeding response of individuals to altered mating opportunities are potentially complicated. This research investigated key genetic and non-genetic attributes in thirteen remnant communities to assess genetic resources and their contribution to population persistence.