Short-term dynamics and species' traits predict long term extinction risk in experimental forest fragments at Wog Wog

Background/Question/Methods

Global habitat loss continues at a furious and accelerating rate and accounts for most biodiversity loss. A critical consequence is that the only remnants of many ecosystems are small fragments of once continuous habitat, so the fate of global biodiversity depends on the survival of species in these fragments of habitat. Frequently researchers are able to record extinctions after they happen but are rarely in the position to follow a large group of species through the fragmentation event and beyond to determine which species are at risk of extinction, which species are not, and why. Large scale and long term fragmentation experiments provide this kind of unprecedented evidence of how extinction happens. We follow a diverse beetle community through 25 years of experimental forest fragmentation at Wog Wog in south eastern Australia. We ask: 1) Do the short-term responses of beetle species through 5 years post experimental fragmentation predict their long term responses 25 years post fragmentation? 2) Do species' short-term responses and life-history traits predict long-term responses to fragmentation better than short-term responses alone? And if yes, do traits of species that predicted short-term responses also predict long term responses?

Results/Conclusions

Species short-term responses did not predict their long-term responses 25 years after experimental fragmentation (~ 25 generations). However, species short-term responses plus the traits of species that predicted species’ declines five years after fragmentation predicted species’ responses 25 years after fragmentation. Trophic level, degree of isolation/specialization, and rarity were all predictors. One additional trait, body size, did not predict species responses at five years but did predict species responses at 25 years, post fragmentation. Species that were both naturally rare and large, or isolated predators, showed the largest declines toward extinction. This long-term, large-scale experimental evidence demonstrates that short-term responses to fragmentation combined with life-history traits can predict extinction risk. Further, life-history traits that ecologists have historically expected to place species at risk of extinction are indeed predictive of extinction risk (rarity, large body size, specialization, high trophic level). However, short term responses alone (~ five generations) may largely reflect transient dynamics that do not predict species long-term fates.