Coevolutionary interactions are thought to have spurred the evolution of key innovations and driven the diversification of much of life on Earth. However, the genetic and evolutionary basis of the innovations that facilitate such interactions remains poorly understood. We examined the coevolutionary interactions between plants (Brassicales) and butterflies (Pieridae), and uncovered evidence for an escalating evolutionary arms-race. Although gradual changes in trait complexity appear to have been facilitated by allelic turnover, key innovations are associated with gene and genome duplications. Furthermore, we show that the origins of both chemical defenses and of molecular counter adaptations were associated with shifts in diversification rates during the arms-race. These findings provide an important connection between the origins of biodiversity, coevolution, and the role of gene and genome duplications as a substrate for novel traits.ver half a century ago, Ehrlich and Raven (1) coined the term 'coevolution' and proposed that coevolutionary interactions between species with close ecological relationships generated much of the eukaryotic biodiversity on Earth. One of their primary examples of coevolution was the chemically mediated interactions between butterflies of the subfamily Pierinae (Pieridae, Lepidoptera) and their angiosperm host-plants in the order Brassicales. Members of the plant order Brassicales are united by their production of secondary metabolites called glucosinolates (i.e., mustard oils). Upon tissue damage, glucosinolates are modified into toxins long studied for their defensive properties and flavor (e.g., mustard and horseradish) (2). In the Arabidopsis thaliana (thale cress) genome, at least 52 genes are involved in glucosinolate biosynthesis (3, 4) and some exhibit strong evidence of adaptive evolution that is attributed to herbivore mediated selection (5, 6). Pierinae caterpillars detoxify the glucosinolates of their Brassicales host-plants by redirecting these otherwise toxic breakdown products to inert metabolites using a gene that encodes a nitrile-specifier protein (7). The key innovation of the Brassicales, defensive glucosinolates, evolved roughly 90 million years ago (Ma); within 10 million years, Pierinae responded with their own key innovation, the nitrilespecifier protein, and colonized the Brassicales. Subsequently, Pierinae net diversification rates increased compared with that of their sister clade Coliadinae, whose members did not colonize Brassicales (8).Although these studies provide "perhaps the most convincing example" that the evolution of a key innovation resulted in an increased net diversification rate (9), much remains unknown about the origins and subsequent evolutionary dynamics of the key innovations that have had macroevolutionary consequences. To address this gap in the literature, here we further investigate these key innovations in the aforementioned plant and butterfly lineages by (i) assessing if these innovations increased in complexity over time and are...

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Mitonuclear discordance across taxa is increasingly recognized as posing a major challenge to species delimitation based on DNA sequence data. Integrative taxonomy has been proposed as a promising framework to help address this problem. However, we still lack compelling empirical evidence scrutinizing the efficacy of integrative taxonomy in relation to, for instance, complex introgression scenarios involving many species. Here, we report remarkably widespread mitonuclear discordance between about 15 mitochondrial and 4 nuclear Brachionus calyciflorus groups identified using different species delimitation approaches. Using coalescent-, Bayesian admixture-, and allele sharing-based methods with DNA sequence or microsatellite data, we provide strong evidence in support of hybridization as a driver of the observed discordance. We then describe our combined molecular, morphological, and ecological approaches to resolving phylogenetic conflict and inferring species boundaries. Species delimitations based on the ITS1 and 28S nuclear DNA markers proved a more reliable predictor of morphological variation than delimitations using the mitochondrial COI gene. A short-term competition experiment further revealed systematic differences in the competitive ability between two of the nuclear-delimited species under six different growth conditions, independent of COI delimitations; hybrids were also observed. In light of these findings, we discuss the failure of the COI marker to estimate morphological stasis and morphological plasticity in the B. calyciflorus complex. By using B. calyciflorus as a representative case, we demonstrate the potential of integrative taxonomy to guide species delimitation in the presence of mitonuclear phylogenetic conflicts.

Within the insect order Lepidoptera (moths and butterflies), the so-called nonditrysian superfamilies are mostly species-poor but highly divergent, offering numerous synapomorphies and strong morphological evidence for deep divergences. Uncertainties remain, however, and tests of the widely accepted morphological framework using other evidence are desirable. The goal of this paper is to test previous hypotheses of nonditrysian phylogeny against a data set consisting of 61 nonditrysian species plus 20 representative Ditrysia and eight outgroups (Trichoptera), nearly all sequenced for 19 nuclear genes (up to 14 700 bp total). We compare our results in detail with those from previous studies of nonditrysians, and review the morphological evidence for and against each grouping The major conclusions are as follows. (i) There is very strong support for Lepidoptera minus Micropterigidae and Agathiphagidae, here termed Angiospermivora, but no definitive resolution of the position of Agathiphagidae, although support is strongest for alliance with Micropterigidae, consistent with another recent molecular study. (ii) There is very strong support for Glossata, which excludes Heterobathmiidae, but weak support for relationships among major homoneurous clades. Eriocraniidae diverge first, corroborating the morphological clade Coelolepida, but the morphological clades Myoglossata and Neolepidoptera are never monophyletic in the molecular trees; both are contradicted by strong support for Lophocoronoidea + Hepialoidea, the latter here including Correspondence: Charles Mitter, †Deceased 6 December 2014. No conflicts of interest were discovered. © 2015 The Royal Entomological Society 671 672 J. C. Regier et al.Mnesarchaeoidea syn.n. (iii) The surprising grouping of Acanthopteroctetidae + Neopseustidae, although weakly supported here, is consistent with another recent molecular study. (iv) Heteroneura is very strongly supported, as is a basal split of this clade into Nepticuloidea + Eulepidoptera. Relationships within Nepticuloidea accord closely with recent studies based on fewer genes but many more taxa. (v) Eulepidoptera are split into a very strongly supported clade consisting of Tischeriidae + Palaephatidae + Ditrysia, here termed Euheteroneura, and a moderately supported clade uniting Andesianidae with Adeloidea. (vi) Relationships within Adeloidea are strongly resolved and Tridentaformidae fam.n. is described for the heretofore problematic genus Tridentaforma Davis, which is strongly supported in an isolated position within the clade. (vii) Within Euheteroneura, the molecular evidence is conflicting with respect to the sister group to Ditrysia, but strongly supports paraphyly of Palaephatidae. We decline to change the classification, however, because of strong morphological evidence supporting palaephatid monophyly. (viii) We review the life histories and larval feeding habits of all nonditrysian families and assess the implications of our results for hypotheses about early lepidopteran phytophagy. The first host record for ...