Explaining biogeographical range size and measuring its effect on species diversification in bark beetles

AIM: To test whether geographical range size is influenced by ecological factors and whether species diversification increases with range sizes in bark beetles. LOCATION: Global METHODS: Here, we (1) evaluate how several predictors – namely mode of reproduction, symbiotic associations with fungi, host‐plant type, utilization of specific host‐plant clades, and level of host‐plant specialization – influence geographical range size, and (2) explicitly test whether range size is associated with species diversification. Analyses were performed with a dataset of 109 genera using Ornstein‐Uhlenbeck adaptation models which control for phylogenetic constraints. RESULTS: We found regular inbreeding by sibling mating to predict an increase in geographical range size, whereas angiosperm hosts type predicted smaller geographical ranges compared to gymnosperm associated lineages. Variation in range size was also associated with utilization of specific host‐plant clades, with conifers being the strongest predictor. Furthermore, the number of utilized host‐plant clades showed a positive association with genera level range size. Our analyses also found fungus farming to predict a reduction in geographical range size, but with a smaller effect size than for inbreeding and host‐type. Lastly, we found a strong positive association between biogeographical range size and species diversification rates. MAIN CONCLUSIONS: We conclude that allopatric speciation is an important contributor to the distribution of species richness in bark beetles. Our study supports the idea that range expansion and speciation are intrinsically linked, and that reproductive behaviour and host‐type preference – through their influence on biogeographical dispersal ability – are ultimately determining factors of species diversification in bark beetles.