The Contribution of Cultivated and Semi-Natural Patches to the Beta Diversity of Nocturnal Lepidoptera within an Organic Century-Old Olive Grove in a Fragmented Landscape

Abstract

The simplification of agricultural landscapes that has occurred in recent decades has led to a consequent decline in biodiversity. The aim of this study was to investigate the role of cultivated and semi-natural areas to sustain the beta diversity of nocturnal Lepidoptera. A dataset available for an organic century-old olive farm was analysed. Sampling was carried out from July 2018 to June 2019 within eight sites. The beta diversity was explored using the Bray–Curtis quantitative similarity index. To assess the main process driving community composition, two measures of nestedness were calculated. The analyses showed that most species were more abundant in semi-natural sites, although some species were found to be barycentric or exclusive to the olive groves. The nestedness at farm and site scales confirmed that the main process driving the composition of the moth community was species impoverishment, but this process was not found to be significant when comparisons involved herbaceous semi-natural habitats and cultivated sites. We found out that the contribution of olive groves to the farm beta diversity was small but non-negligible. To improve the sustainable management of an olive grove, it is preferable to promote the presence of tree-covered areas since semi-natural herbaceous cover can be represented within the farm by low-input olive groves.