Globally, biodiversity is being lost rapidly through habitat loss and fragmentation. Around one-third of all forests have been cleared, and what remains is fragmented. Therefore, the persistence of unique forest ecosystems, communities and species depends on their persistence in fragmented landscapes. Two predictors of species persistence in fragmented landscapes over long time scales (10s of generations) are life-history traits that predict extinction risk, and population responses to fragmentation over short timescales. Here we test and contrast the ability of traits and short term responses to predict long-term responses of beetle species to experimental forest fragmentation at Wog Wog, NSW, Australia. The experiment has a dynamic matrix, a crop-plantation pine forest, composed of seedlings and young trees seven years after fragmentation and mature trees at 27 years. This means that we should expect landscape-scale drivers of species' responses (e.g. changes in solar radiation and water regimes) to combine with the predicted risks of small population size and isolation.
Results/Conclusions
Both short-term responses (seven years after fragmentation) and species' traits predicted the decline of beetle species 27 years after fragmentation. Traits that predicted declines in the short term continued to predict declines in the long term. Species that were isolated on fragments and naturally rare continued to decline, and isolated predators declined more than other trophic levels. The dynamic matrix also broadly determined species responses. Many beetle species that initially could not inhabit an open, seedling-filled matrix later colonized a mature pine plantation matrix, and vice versa, driving changes in species responses in fragments between the early and later years of the experiment (e.g. declines became increases and vice versa). For example, while in the short-term predators declined in abundance in fragments compared to controls, in the long term predators were unaffected by fragmentation. Thus, both landscape-scale impacts (e.g. abiotic) and the risks associated with small population size drove species declines, although the latter dominated.