María F. Checa (Museo QCAZ, Quito, Ecuador)

The stability hypothesis posits that stable environments provide species with enough resources to persist, opening space for limiting similarity (e.g., competition) mechanisms to determine community composition. Instead, harsh environments are expected to filter  species with traits adapted to these environments (i.e., habitat filtering). In the tropics, a continuum of environmental conditions, from aseasonal to seasonal forests can potentially determine species composition. A combined approach of phylogenetic- and  functional trait-based (forewing length and aspect ratio) analyses were used to test the hypothesis that seasonality affect the assembly processes that drive community composition within more stable environments (aseasonal forest) showing greater signatures  of competition, whereas habitat filtering dominating as an assembly mechanism in seasonal forests. A 3-year survey was carried out at three sites across a climatic gradient in western Ecuador. Canopy butterflies were sampled using traps baited with rotting  banana and shrimp every two months from Nov 2010 to Sep 2013. Measurements of morphological traits, forewing length and aspect ratio were done using digital photographs of specimens. A total of 6864 specimens representing 134 species of Nymphalidae and Hesperiidae  were included in the analyses. We rejected the hypothesis that assembly processes that limit species similarity (i.e., competition) are likely to predominantly occur in more ‘stable’ abiotic environments, whereas habitat filtering can be a major driver of  community composition within more variable environments. We found strong evidence that both assembly mechanisms, namely habitat filtering and competition, are shaping butterfly communities in seasonal and aseasonal forests. In general, we found significant

 levels of habitat filtering with phylogeny-based analyses. Trait based analyses however, showed that within a context of habitat filtering, competition is shaping the distribution of traits within communities. The present study therefore provided new insights  into assembly mechanisms of canopy communities in one of the richest butterfly faunas worldwide.