Out breeding Depression in Plants: Implications for the conservation of critically endangered tree species.

Processes at various hierarchical scales determine the survival probabilities of tropical trees in fragmented landscapes. In small, isolated populations the local persistence may be affected by loss of genetic diversity and inbreeding depression. These effects can be alleviated by gene flow, i.e. exchange of pollen and seeds between populations. On the other hand, gene flow may disrupt locally adaptive gene complexes that have evolved in isolated populations resulting in outbreeding depression. Outbreeding depression in progeny fitness may arise from disruption of local adaptation, disruption of allelic co adaptation, or a combination of these “environmental” and “physiological” mechanisms. The minimum spatial scale over which outbreeding depression arises would depend on the spatial scale of gene dispersal. Characterizing outbreeding depression on the shortest spatial scales over which it is expressed, as well as its variation and causes, is worthwhile because it has important implications for the evolution and conservation of tropical forest trees. In this study, an attempt was made to understand the genetic basis of outbreeding depression in a model system Momordica tuberosa. Specifically the study examined the influence of outbreeding depression on fruit set, seed number, and seed weight and on germination. The studies shed light on outbreeding depression and its possible impacts on the isolated populations in the fragmented landscapes and offer strategies to mitigate the effects during species recovery.