The river zonation hypothesis predicts that abiotic and biotic conditions along riparian gradients drive variation in animal communities. Glass frogs are a diverse group of Neotropical anurans that use riparian habitats exclusively for oviposition and larval development, but little is known about how glass frog communities are distributed across riparian gradients. Here, we measured glass frog community assembly across a gradient of riparian habitats from first- to fifth-order streams at La Selva Biological Station, Costa Rica. We performed repeated nocturnal frog calling surveys and built occupancy and N-mixture abundance models to test for varying patterns of species occupancy, community assembly, species richness (α-diversity) and species turnover (ß-diversity). We observed significant differences in patterns of species occupancy and community assembly across a stream-order gradient: occupancy of two species increased with stream order (Teratohyla pulverata, Hyalinobatrachium fleischmanni), one species decreased (Teratohyla spinosa), and one species did not vary (Espadarana prosoblepon). We evaluated four a priori hypotheses describing how α- and ß-diversity of centrolenids are shaped across the riparian gradient; our data were most consistent with a pattern of nested assemblages and increasing species richness along the riparian gradient. Species-specific patterns of occupancy and abundance resulted in assemblage-level differences consistent with theoretical predictions for highly aquatic organisms along riparian gradients.

Amphibians are one of the most threatened animal groups. In the Family Centrolenidae c. 50% of the species are declining and threatened with extinction. One of these is the glassfrog Cochranella mache, endemic to seasonal evergreen forests of the West Ecuadorian region and restricted to highly fragmented forest of < 100 km2 in the Cordillera Mache-Chindul, north-western coastal Ecuador, at 100–640 m. We surveyed this region to elucidate the distribution and conservation status of C. mache. We located it in three new localities and also found a museum specimen from a further new locality. We recommend that the species should be categorized as Critically Endangered because of the continuous and progressive destruction of its increasingly fragmented habitat. Recent surveys of glassfrog species sympatric with C. mache showed low relative abundances compared to surveys in the 1970s and 1980s. Because of the relationship between forest and local climate we suggest that gradual declines of lowland glassfrog populations may be caused by local climate changes produced by forest destruction. In situ conservation is required to halt and mitigate these impacts. Further research on the effects of habitat loss, fragmentation, and associated climate changes on Neotropical amphibians is required.