title: Life-history specialization was not an evolutionary dead-end in Pyrenean cave beetles.
abstract: Research on subterranean organisms has focused on the colonization process and some of the associated phenotypic changes, but little is known on the long-term evolutionary dynamics of subterranean lineages and the origin of some highly specialized complex characters. One of the most extreme modifications is the reduction of the number of larval instars in some Leptodirini beetles from the ancestral 3 to 2 and ultimately a single instar. This reduction is usually assumed to have occurred independently multiple times within the same lineage and geographical area, but its evolution has never been studied in a phylogenetic framework. Using a comprehensive molecular phylogeny, we found a low number of independent origins of the reduction in the number of instars, with a single transition, dated to the Oligocene-Miocene, from 3 to 2 and then 1 instar in the Pyrenees, the best-studied area. In the Pyrenees, the 1-instar lineage had a diversification rate (0.22 diversification events per lineage per million years) significantly higher than that of 3- or 2-instar lineages (0.10), and similar to that seen in other Coleopteran radiations. Far from being evolutionary dead-ends, ancient lineages fully adapted to subterranean life seem able to persist and diversify over long evolutionary periods.
authors.affiliation: Museo Nacional de Ciencias Naturales (MNCN, CSIC), José Gutiérrez Abascal 2, 28006 Madrid, Spain, Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), Passeig Maritim de la Barceloneta 37-49, 08003 Barcelona, Spain, Museu de Ciències Naturals (Zoologia), Passeig Picasso, 08003 Barcelona, Spain.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Cieslak
authors.forename: Javier
authors.initials: J
authors.lastname: Fresneda
authors.forename: Ignacio
authors.initials: I
authors.lastname: Ribera
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D005075:Biological Evolution; D059552:Caves; D001517:Coleoptera / Q000502:physiology*; D005602:France; D008018:Life Cycle Stages / Q000502:physiology*; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D013030:Spain
keywords: diversification; larval development; life cycle; speciation; subterranean environment