RESUMO
Many studies suggest that global warming is driving species ranges poleward and toward higher elevations at temperate latitudes, but evidence for range shifts is scarce for the tropics, where the shallow latitudinal temperature gradient makes upslope shifts more likely than poleward shifts. Based on new data for plants and insects on an elevational transect in Costa Rica, we assess the potential for lowland biotic attrition, range-shift gaps, and mountaintop extinctions under projected warming. We conclude that tropical lowland biotas may face a level of net lowland biotic attrition without parallel at higher latitudes (where range shifts may be compensated for by species from lower latitudes) and that a high proportion of tropical species soon faces gaps between current and projected elevational ranges.
Assuntos
Altitude , Biodiversidade , Ecossistema , Efeito Estufa , Insetos , Plantas , Clima Tropical , Aclimatação , Migração Animal , Animais , Formigas , Costa Rica , Demografia , Geografia , Mariposas , Dinâmica Populacional , Rubiaceae , TemperaturaRESUMO
Tropical ferns are characterized by a high diversity of plant life forms, yet there have been few large-scale studies on the functional ecology of these different forms. We examined epiphytic, hemiepiphytic, and terrestrial ferns, and asked whether there are differences in the mineral nutrition and water relations across different growth forms of a diverse assemblage of species. We measured specific leaf area, leaf nitrogen concentrations, and natural abundance of the stable isotopes delta(15)N and delta(13)C of 48 fern species from 36 genera across a wide range of habitats at La Selva Biological Station in Costa Rica. We found that epiphytes were significantly different in all measured variables from hemiepiphytic and terrestrial species, and that terrestrial and soil-rooted hemiepiphytes were indistinguishable in all variables excluding SLW. A multivariate analysis revealed that aspects of N nutrition were the most reliable at separating epiphytic species from other life forms. Our study demonstrates that the natural abundance of both C and N as well as N relations and leaf morphology are useful when segregating different plant life forms, and that the N cycle of epiphytic and terrestrial habitats function independently from each other.