A dated molecular phylogeny of the Proctolabinae (Orthoptera, Acrididae), especially the Lithoscirtae, and the evolution of their adaptive traits and present biogeography

Abstract

We present a phylogeny of the Proctolabinae derived from their 12S and 16S mitochondrial ribosomal gene sequences, using 15 genera and 24 species. Phylogenetic analysis was performed using 4 different methods embodying different assumptions (maximum parsimony, neighbor-joining, maximum likelihood and Bayesian probability methods), all of which result in closely similar trees. The results largely corroborate the relationships and classification previously suggested by morphology. A phylogenetic tree including members of the Oedipodinae, Proctolabinae and Melanoplinae, fulfills the criteria of a molecular clock, which we calibrate using the divergence of the Oedipodinae from the other acridid subfamilies (Gaunt & Miles 2002). The major “star-burst” radiation of acridid subfamilies, previously documented by the present authors on the basis of a different analysis, and here represented by the divergence of the Proctolabinae and Melanoplinae, is estimated to have occurred 60 Mya, at the K/T boundary. The modern tribes and subtribes of the Proctolabinae were established in the subsequent 10 My, and most of the current genera were established between 25 and 35 Mya. We examine the phylogenetic distribution of food-plant specialisation, and of the correlated traits of flightlessness and of endo- and epiphytic oviposition, primarily within the subtribe Lithoscirtae. The original specialisation of this group was apparently on the Solanaceae, soon after the origin of that family around 38 Mya, with later radiation onto the Asteraceae and other unrelated families. The spectrum of food plants used is not based on relationship but rather on ecological proximity. Oviposition in or on the food-plant is primitive for this subtribe, and has been developed in different ways in the various clades. The power of flight has been lost and/or regained and wing form modified independently in several different lineages throughout the subfamily. The modern and historical biogeography of the subfamily is discussed in the light of its apparent antiquity and of the current understanding of Central American plate tectonics.