Testing the impact of effective population size on speciation rates – a negative correlation or lack thereof in lichenized fungi

The effect of microevolutionary processes on macroevolutionary patterns, and vice versa, is an important but under-investigated question. Here we present an integrative population genetic and phylogenetic study using molecular sequence data from three lichen-forming fungal lineages to empirically test the potential correlation between effective population size – approximated by the parameter θ – and estimated speciation rates using a phylogenetic tree (λ). A negative association between θ and λ was supported in one lineage of lichen-forming fungi, Melanelixia (Parmeliaceae), while no significant relationships was found for two other genera within the same family, Melanohalea and Xanthoparmelia. We discuss the significance of our results and the importance of considering microevolutionary processes when studying macroevolutionary patterns.