What's in a species? The multiple connotations of the question tend to lack simple answers, and not surprisingly so. For example, speciation is a gradual process. Can we say when exactly a child has become an adult? We have precocious youngsters and late bloomers, and often, adults are in some ways childish. There are many triggers for and routes to adolescence. All this holds for speciation, and delimiting species can therefore be a tricky task. Recently, the field of integrative taxonomy has emerged-species delimitation based on multiple sources of evidence. Given that we expect species to exhibit peculiarities in at least one or a few aspects, might it be their alleles of a gene, their morphology, chemistry, behaviour, ecology, reproductive compatibility, or whatever, investigating not just one but several of these aspects makes it more likely that we capture such peculiarities. If the same pattern is found multiply, we talk about agreement among disciplines, and species delimitation is easy. But what if different disciplines tell different stories? Such disagreement makes species delimitation more difficult but is also an opportunity for evolutionary biology (Schlick-Steiner et al. 2010). In this issue of Molecular Ecology, Andújar et al. (2014) present a comprehensive integrative-taxonomic case study of Mesocarabus ground beetles including nomenclatural consequences. They resolve extensive disagreement among disciplines by invoking evolutionary explanations, and the process of conflict resolution thus advances knowledge on species boundaries and evolutionary processes simultaneously.
Keywords: disagreement among disciplines; hybrid speciation; hybridization; integrative taxonomy; nomenclatural consequences; species delimitation.
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