Habitat destruction has driven many once-contiguous animal populations into remnant patches of varying size and isolation. The underlying framework for the conservation of fragmented populations is founded on the principles of island biogeography, wherein the probability of species occurrence in habitat patches varies as a function of patch size and isolation. Despite decades of research, the general importance of patch area and isolation as predictors of species occupancy in fragmented terrestrial systems remains unknown because of a lack of quantitative synthesis. Here, we compile occupancy data from 1,015 bird, mammal, reptile, amphibian, and invertebrate population networks on 6 continents and show that patch area and isolation are surprisingly poor predictors of occupancy for most species. We examine factors such as improper scaling and biases in species representation as explanations and find that the type of land cover separating patches most strongly affects the sensitivity of species to patch area and isolation. Our results indicate that patch area and isolation are indeed important factors affecting the occupancy of many species, but properties of the intervening matrix should not be ignored. Improving matrix quality may lead to higher conservation returns than manipulating the size and configuration of remnant patches for many of the species that persist in the aftermath of habitat destruction.incidence function ͉ island biogeography ͉ logistic regression ͉ metaanalysis ͉ occupancy H abitat loss and fragmentation are major threats to terrestrial biodiversity (1). Globally, Ϸ40% of land has been converted for agricultural use (2), and regions as diverse as the eastern United States, the Philippines, and Ghana have lost Ͼ90% of their natural habitat (3, 4). Conservation theory and practice are founded on the principle that large habitat patches have more species than small ones and connected patches have more species than isolated ones (5). Although few would dispute this basic premise, we still do not know the general value of patch area and isolation as predictors of species occupancy in fragmented terrestrial systems. Despite hundreds of patch occupancy studies over Ͼ4 decades, there has been no quantitative synthesis of these findings. Several syntheses have examined species-area and diversity relationships (6, 7), but the species occupancy patterns that underlie diversity patterns in fragmented landscapes have been overlooked (8). How important is patch isolation relative to patch size in determining where species occur, and how consistent are these effects across diverse taxonomic groups? These are foundational, yet unanswered, questions for ecology and conservation biology.We synthesized patch occupancy data from 89 studies of terrestrial fauna on 6 continents (Table S1) to determine how patch area and isolation affect species' occurrence patterns. Collectively, these studies recorded the occurrence of 785 animal species (Table 1) in 1,015 population networks surveyed in 12,370 discrete habitat p...

Aim Elucidating patterns in species responses to habitat fragmentation is an important focus of ecology and conservation, but studies are often geographically restricted, taxonomically narrow or use indirect measures of species vulnerability. We investigated predictors of species presence after fragmentation using data from studies around the world that included all four terrestrial vertebrate classes, thus allowing direct inter-taxonomic comparison.Location World-wide.Methods We used generalized linear mixed-effect models in an information theoretic framework to assess the factors that explained species presence in remnant habitat patches (3342 patches; 1559 species, mostly birds; and 65,695 records of patch-specific presence-absence). We developed a novel metric of fragmentation sensitivity, defined as the maximum rate of change in probability of presence with changing patch size ('Peak Change'), to distinguish between general rarity on the landscape and sensitivity to fragmentation per se.Results Size of remnant habitat patches was the most important driver of species presence. Across all classes, habitat specialists, carnivores and larger species had a lower probability of presence, and those effects were substantially modified by interactions. Sensitivity to fragmentation (measured by Peak Change) was influenced primarily by habitat type and specialization, but also by fecundity, life span and body mass. Reptiles were more sensitive than other classes. Grassland species had a lower probability of presence, though sample size was relatively small, but forest and shrubland species were more sensitive.Main conclusions Habitat relationships were more important than lifehistory characteristics in predicting the effects of fragmentation. Habitat specialization increased sensitivity to fragmentation and interacted with class and habitat type; forest specialists and habitat-specific reptiles were particularly sensitive to fragmentation. Our results suggest that when conservationists are faced with disturbances that could fragment habitat they should pay particular attention to specialists, particularly reptiles. Further, our results highlight that the probability of presence in fragmented landscapes and true sensitivity to fragmentation are predicted by different factors.

We counted fecal pellets of snowshoe hares (Lepus americanus) once a year in 10 areas in the southwestern Yukon from 1987 to 1996. Pellets in eighty 0.155-m 2 quadrats were counted and cleared each June on all areas, and we correlated these counts with estimates of absolute hare density obtained by intensive mark-recapture methods in the same areas. There is a strong relationship between pellet counts and population density (r = 0.76), and we present a predictive log-log regression to quantify this relationship, which improves on our previously published 1987 regression, particularly at low hare densities. The precision of density estimates can be improved most easily by increasing the number of sets of quadrats in an area (one set = 80 plots), rather than increasing the number of plots counted within one set. The most important question remaining concerns the generality of this relationship for snowshoe hares living in other habitats in the eastern and southern portions of their geographic range.Résumé : Nous avons compté les boulettes fécales de Lièvres d'Amérique (Lepus americanus) une fois l'an en 10 zones du sud-ouest du Yukon, de 1987 à 1996. Les boulettes ont été comptées chaque juin, puis retirées, dans quatre-vingt quadrats de 0,155 m 2 dans chacune des zones; par la suite, ces nombres ont été mis en corrélation avec des estimations de la densité absolue des lièvres obtenues par des méthodes intensives de capture-recapture dans les mêmes zones. Il y a une forte corrélation entre le nombre de boulettes et la densité de la population (r = 0,76) et nous présentons ici une régression log-log prédictive pour quantifier cette relation, ce qui rend plus robuste la régression que nous avons publiée en 1987, particulièrement lorsque la densité des lièvres est faible. La précision des estimations de la densité peut être raffinée davantage en augmentant le nombre d'ensembles de quadrats dans une région (1 ensemble = 80 parcelles), plutôt que le nombre de parcelles dans chaque ensemble. Il reste à déterminer à quel point cette relation est gé-néralisée chez les lièvres qui vivent dans d'autres habitats dans les portions est et sud de leur répartition.[Traduit par la Rédaction] 4Krebs et al.