HABITAT FRAGMENTATION: IMPLICATIONS FOR IN SITU CONSERVATION

Abstract

Ecosystem fragmentation is one of the crucial conservation problems in Brasil. A sample of 393 conservation units occupy 433.239 km², 5.08% of the country's area average area being 1.102km². Area-population size equilibrium analysis, using allometry of density for herbivore and carnivore­-onmivore focal mammals encompassing four orders of magnitude in body mass, indicates that large mammals would have a small number of effective viable populations, small totals for the species, relatively high endogamy levels and accentuated heterozigosity loss after 100 generations. Simulations of small populations subjected to environmental and demographic stochasticity suggest that extinction probability would be positively correlated to the spatial coefficient of variation in population size. Fragmentation simulations of future in situ conservation scenarios, involving increases in number and/or area of conservation units, suggest that real patterns of creation and fragmentation of units could induce complex behaviour in indices of temporal persistence, such as size and number of viable populations and total number of individuals of the species. The relationship between the magnitude of the extinction probability and population size is more important than either size or number of insularized fragments per se on the extinction probability. It is suggested that metapopulation theory might play a relevant role in conservation decisions regarding the national network of conservation units.