Lower effective sizes (Ne) than census sizes (N) are routinely documented in natural populations, but knowledge of how multiple factors interact to lower Ne/N ratios is often limited. We show how combined habitat and life-history influences drive a 2.4- to 6.1-fold difference in Ne/N ratios between two pristine brook trout (Salvelinus fontinalis) populations occupying streams separated by only 750 m. Local habitat features, particularly drainage area and stream depth, govern trout biomass produced in each stream. They also generate higher trout densities in the shallower stream by favoring smaller body size and earlier age-at-maturity. The combination of higher densities and reduced breeding site availability in the shallower stream likely leads to more competition among breeding trout, which results in greater variance in individual reproductive success and a greater reduction in Ne relative to N. A similar disparity between juvenile or adult densities and breeding habitat availability is reported for other species and hence may also result in divergent Ne/N ratios elsewhere. These divergent Ne/N ratios between adjacent populations are also an instructive reminder for species conservation programs that genetic and demographic parameters may differ dramatically within species.

Sands, D.P.A .. Scott, S.E. and Moff at, R., 1997. The threatened Richmond birdwing but terfly (Ornithoptera richmondia [Gray]): a community conservation project. Memoirs o_f1he Museum o_ .Destruction of coastal rainforests in south-eastern Queensland and north-eastern New South Wales has led to extinction of 0. richmondia fr om two-thirds of its original range and a sharp decline in surviving populations. The species is further threatened by depletion of t he butterfly's lowland food plant, Pararistolochia praevenosa, and by presence and spread of the Dutchman's Pipe vine, Aristolochia e/egans, which attracts oviposition but the leaves are toxic to larvae when they attempt to feed. Originally from South America, Dutchman's Pipe has spread from garden cultivation into national parks and reserves. Above 800 m on the Queensland/NSW Border Ranges, P. laheyana, also supports birdwing larvae. However, these populations are subject to periodic extinctions, probably due to climatic stress at the higher altitudes where re-colonisation is thought to be dependent on immigrants fr om low land populations. Community groups and state national parks authorities are participating in projects to conserve the Richmond birdwing butterfly. The CSIRO's Double Helix Sci ence Club is co-ordinating studies on P. praevenosa by students at more than 130 schools, where growth and phenology of 12 vines at each school are being monitored to understand the butterfly's host plant interactions. Aspects of biology of the butterfly and its food plants and strategies which have a bearing on its conservation are discussed.