β-Diversity partitioning of moth communities within and between different forest types

The partitioning of β-diversity is a recurrent practice in biogeographic and ecological studies that can provide key insights for land management, such as identification of biodiversity hot-spots. In this study, we used Baselga's metrics to measure the contribution of spatial turnover (β_sim) and nestedness-resultant dissimilarity (β_nes) to overall β-diversity (β_sor) within- and between-forest types. We analyzed a presence/absence dataset concerning 593 species of nocturnal Lepidoptera sampled within chestnut, silver fir, beech, and black pine forests of southern Italy. Ordination methods and analysis of similarities were used to assess the relative contribution of β_sim and β_nes to β_sor, and to assess their relationships with variables linked to the experimental design and known to be determinant for insect diversity and abundance. We found that β_sor was mostly due to turnover, around 98.5% in β-diversity assessment of the whole sample, and around 91% in β-diversity assessment of individual forests. Using ordination analyses based on β_sim, stands were grouped according to forest type, while β_nes alone was used to ordinate stands coherently with their species richness. Nevertheless, the addition of β_nes to β_sim produced a more ecologically coherent grouping of stands within individual forest types, and β_nes alone was able to recognize patterns determined by human disturbance. In conclusion, we demonstrate that β-diversity partitioning can help to detect differences in magnitude and role of processes determining the composition of forest moth communities as in different forests the same pattern can be due to opposite processes, providing strong ecological insights into managing forest biodiversity.