Habitat specificity, host plants and areas of endemism for the genera-group Blepharida s.l. in the Afrotropical region (Coleoptera, Chrysomelidae, Galerucinae, Alticini)

Abstract

Knowledge of the processes that generate biodiversity is a core-issue of any conservation strategy because it allows predicting the effects of environmental changes in the number and distribution of target taxa. Some phytophagous insects can be good potential indicators of such processes, thanks to their wide distribution and their sensitivity to climate change, due to the association with specific environments and host plants. Unfortunately, this ecological information is often lacking. However, statistical tools allow reconstructing the ecological features of interest, based on the presence-absence data of the taxa, the climatic and vegetational features of their distributional areas, and the available data about their host plants. In this paper, we apply some geostatistical methods to identify processes and patterns of biodiversity at a continental scale, focusing on a group of phytophagous insects widespread in sub-Saharan Africa. The genus Calotheca Heyden (Chrysomelidae) is mainly distributed in the eastern and southern parts of sub-Saharan Africa, with some extensions northward, while Blepharidina Bechyné occurs in the intertropical zone of Africa, with two subgenera, Blepharidina s. str. and Blepharidina (Afroblepharida) Biondi and D’Alessandro. These genera show different ecological preferences. Through an up-to-date presence-absence dataset, in the light of the terrestrial ecoregions of sub-Saharan Africa and the distribution of their possible host plants, we interpreted the pattern of occurrence of these three supraspecific taxa, by geostatistical analyses in GIS and R environments. The separation of Blepharidina from Calotheca was probably driven by changes in climate as adaptation to more xeric and warm environments with a major occupancy of semidesert and savannah habitats, especially in the Afroblepharida species. Based on our data and analyses, Calotheca is mainly associated with Searsia (Anacardiaceae), and Blepharidina is likely associated with Commiphora (Burseraceae). This hypothesis is also corroborated by the widespread and even dominance of the Commiphora plants in the ecoregions where both Blepharidina s.str. and, above all, Afroblepharida, are more common. The main areas of endemism of the two genera are also differently located: Calotheca in the temperate zone; Blepharidina within the intertropical belt.