What to save, the host or the pest? The spatial distribution of xylophage insects within the Mediterranean oak woodlands of Southwestern Spain

Abstract

The Mediterranean oak forests are currently in severe decline. Although the oak decline has been mainly related to Phytophthora sp. and extreme climatic conditions, there are other biotic factors - such as the beetle Cerambyx “complex” - which are also implicated. The future climate change scenarios might aggravate this situation but also might enhance the dispersal and establishment of new beetle populations. We used the Andalusian forest health monitoring network (SEDA Network) to assess the current distribution of the beetles, using the Kernel Density Estimation approach, and the current and future distributions using ensemble Species Distribution Models. Model predictions revealed that dasometric (normal diameter and frequency of oak trees) and climatic (number of days with mean temperature above 30°C) variables were important to estimate the distribution of the Cerambyx “complex”.The model performance was analyzed by K, TSS, and AUC, which gave accurate (K>0.56; TSS>0.59 & AUC>0.87) to very accurate (K>0.63; TSS>0.64 & AUC>0.89) results for the models developed only with dasometric variables and with the combination of climatic and dasometric variables, respectively. We found four main regions where the xylophage beetles occur in Andalusia and a larger area which satisfies the environmental requirements of these beetles. The current potential habitat suitability of the xylophage beetles might increase under future climate scenarios, which might enhance the dispersal, colonization, and establishment of new populations of xylophage beetles in Andalusia.