Abstract for presentation at Biodiversity Extinction Crisis Conference - A Pacific Response

Many species are now restricted to small and isolated populations and it has been suggested that promoting inter-population movements or connectivity could partly counteract the negative effects of habitat fragmentation on population dynamics and genetics, and ultimately reduce extinction risk. However, the efficiency and suitability of such conservation measures have been highly questioned. Here, we review the current literature to determine whether we can and whether we should promote connectivity. First, we document the ability of different management strategies, and especially corridors, to increase movement rate in fragmented landscapes. Then, considering the population genetics approach, we recall that to ensure metapopulation persistence, genetic diversity should be adequately distributed within, and among populations, to prevent inbreeding and allele fixation within populations, while still maintaining enough genetic divergence among populations to allow local adaptation. While the appropriate level of gene flow to reach such an optimum has been known for many years, we show that translating this value into an optimal dispersal rate is highly problematic. Third, we show that many of the positive effects of connectivity on population dynamics (e.g. colonisation facilitation, rescue effect) largely rely on a density dependent dispersal pattern that is only weakly supported by empirical evidence. We discuss the conditions under which dispersal may increase population synchrony and the associated risk of global extinction. We conclude that a joint approach of population genetics and dynamics would be very valuable. Finally, we suggest that considering the behavioural mechanisms underlying individual movements and reproductive success will make a significant contribution towards predicting dispersal patterns under different landscape configurations, and the effective gene flow in natural populations under selection.