Beta diversity of Arctiinae moths (Lepidoptera: Erebidae) along a recovering tropical forest gradient.

Abstract

Amid widespread biodiversity loss and alarming rates of tropical deforestation, the potential of secondary forest succession in restoring β-diversity is still widely unexplored. To investigate β-diversity along naturally recovering forests, we collected the functionally diverse group of tiger moths (Erebidae: Arctiinae) with light traps in the Ecuadorian Chocó. Our plots ranged from active small-scale agricultural lands over natural regrowth stages (1-38 years) to old-growth forests. Along this gradient of increasing forest complexity, fundamental ecological theory predicts a rise in taxonomic (TBD), functional (FBD) and phylogenetic β-diversity (PBD). We also predicted an increase in body size, insect mimicry and aposematism, as well as a decrease of brightness and wing loading in assemblages along the gradient. To test these predictions, we calculated sample coverage-standardized TBD, FBD and PBD along Hill numbers. Community-weighted means (CWM) and standardized effect sizes of mean functional (ses.MFD) as well as phylogenetic distances (ses.MPD) were calculated to quantify functional and phylogenetic differences among species and communities. TBD and FBD showed non-linear responses with peaks in late recovery forests, with the effect restricted to rare species in FBD but evident for both rare and common species in TBD. In contrast, PBD declined linearly along the gradient only for rare species. While body size and aposematism responded as predicted, communities significantly decreased in mimicry and increased in wing loading along the gradient, contrary to our expectations. The decreasing ses.MFD along the gradient suggests increasing habitat filtering towards old-growth forests. Our study indicates that secondary forests can recover functional traits relatively quickly, while old-growth forests retain more stable and specialized communities, highlighting their continued importance for conservation.