Beta diversity and community structure of a Neotropical anuran assemblage (Pacaya-Samiria Reserve, Peru)

Background/Question/Methods

Many communities are thought to follow assembly rules, such that nonrandom co-occurrence patterns indicate competitive interactions among species. The richness of these local communities is influenced by richness at broader spatial scales. Here we use null models to quantify relationships among co-existing species of Anurans at multiple scales along the Samiria River in the Peruvian Amazon. We hypothesized that species would co-occur less often than expected by chance. We also hypothesized alpha (α) diversity would be lower than expected by chance, while beta (β) diversity would be higher. We surveyed during both daytime and nighttime within two habitat types: 8 seasonally-flooded forest sites, and 2 riverine sites with aquatic vegetation. Upon detection of a specimen we identified it to species. We partitioned diversity among sites within a habitat type (β­­₁), and among habitat types (β­­₂).

Results/Conclusions

We recorded 24 observed species of Anurans between June and August, 2012. The calculated c-score indicated species co-occurred less than expected by chance (c_obs,exp = 1.26, 1.17, p = 0.01), suggesting that competition could be structuring the community. We found that α diversity was much lower than expected (α_obs,exp = 8.67, 14.89), and conversely that the β­­₁ and β­­₂ components were higher than expected (β­­_1(obs,exp) = 7.83, 5.72, β­­_2(obs,exp) = 7.5, 3.39). Our data suggest that the diversity of the Anuran assemblage is highly structured regionally, with interspecific competition structuring communities locally.