ASSEMBLY MECHANISMS OF NEOTROPICAL BUTTERFLY COMMUNITIES ALONG AN ENVIRONMENTAL GRADIENT

Our goal was to test the hypothesis that assembly processes that limit species similarity (i.e., competition) predominantly occur in more stable abiotic environments, whereas habitat filtering (i.e., habitat characteristics) is a major driver of community composition within more variable environments at regional (e.g., aseasonal vs seasonal forests) and local scales (e.g., understory vs. canopy). A combined approach of phylogenetic- and functional trait-based analyses using forewing length and aspect ratio as traits, were used to this hypothesis.\n\nA 3-year survey was carried out at three sites (i.e., wet, transition and dry forests) across a climatic gradient in western Ecuador. Transition and dry forests were considered as seasonal, whereas wet forest were considered aseasonal. Butterflies were sampled using traps baited with rotting banana and prawn every two months from Nov 2010 to Sep 2013. Traps were set up at two heights, in the understory and canopy. DNA was extracted to sequence the barcode section of the mitochondrial gene cytochrome oxidase 1 (COI) for phylogenetic analyses. Measurements of morphological traits, forewing length and aspect ratio were done using digital photographs of specimens.\n\nA total of 6466 specimens representing 142 species of Nymphalidae were recorded. Based on phylogenetic- and trait-based 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 at regional (i.e., aseasonal forest vs seasonal forests) and local scales (i.e., understory vs. canopy). My study of assembly mechanisms revealed the opposite pattern, with stronger evidence for the action of ecological filters in the assembly of butterfly communities from the wet aseasonal forests, and competition likely to be a major assembly process within dry seasonal forests. The present study therefore provided new insights into community assembly mechanisms in one of the richest butterfly faunas worldwide.