Elisabet Weingartner

Towards a better understanding of the higher systematics of Nymphalidae (Lepidoptera: Papilionoidea).

Research on the molecular systematics of higher taxa in the butterfly family Nymphalidae (Lepidoptera) is only just beginning. Outgroup selection is difficult at the moment due to the lack of consensus on the basal relationships of the major groups in Nymphalidae. We identify four major clades in the Nymphalidae based on a cladistic analysis of one mitochondrial gene sequence (COI, 1450 bp) and two nuclear gene sequences (EF-1alpha, 1064 bp, and wingless, 412-415 bp) from 54 exemplar species sampled from all currently recognized subfamilies. The COI data set was found to be highly incongruent with the nuclear data sets and a Partitioned Bremer Support analysis shows that the COI data set largely undermines support for most clades. Transitions at the third codon positions of the COI data set were highly saturated, but analyzing the combined data set with the COI third positions removed did not change the results. The major clades we found are termed the danaine clade (including Danainae), the satyrine clade (including Charaxinae, Satyrinae, Calinaginae, and Morphinae), the heliconiine clade (including Heliconiinae and Limenitidinae excluding Biblidini, Cyrestini, Pseudergolini, and Coeini) and the nymphaline clade (including Nymphalinae, Apaturinae, and Coeini, Cyrestini, Pseudergolini, and Biblidini from Limenitidinae). The heliconiine and nymphaline clades are sister groups, while the most parsimonious explanation for the combined data set places the danaine clade as the most basal large group of Nymphalidae. Our results give one of the strongest hypotheses for the subfamilial relationships within Nymphalidae. We were able to resolve the polyphyletic nature of Limenitidinae, which we recommend to be split into three subfamilies: Limenitidinae, Biblidinae, and Cyrestinae. The tribe Coeini belongs in Nymphalinae.

Dynamics of host plant use and species diversity in Polygonia butterflies (Nymphalidae).

The ability of insects to utilize different host plants has been suggested to be a dynamic and transient phase. During or after this phase, species can shift to novel host plants or respecialize on ancestral ones. Expanding the range of host plants might also be a factor leading to higher levels of net speciation rates. In this paper, we have studied the possible importance of host plant range for diversification in the genus Polygonia (Nymphalidae, Nymphalini). We have compared species richness between sistergroups in order to find out if there are any differences in number of species between clades including species that utilize only the ancestral host plants (‘urticalean rosids’) and their sisterclades with a broader (or in some cases potentially broader) host plant repertoire. Four comparisons could be made, and although these are not all phylogenetically or statistically independent, all showed clades including butterfly species using other or additional host plants than the urticalean rosids to be more species‐rich than their sisterclade restricted to the ancestral host plants. These results are consistent with the theory that expansions in host plant range are involved in the process of diversification in butterflies and other phytophagous insects, in line with the general theory that plasticity may drive speciation.

Speciation in Pararge (Satyrinae: Nymphalidae) butterflies – North Africa is the source of ancestral populations of all Pararge species

Abstract The genus Pararge comprises three species: P. aegeria, distributed in Europe and North Africa; P. xiphia, endemic to Madeira; and P. xiphioides, endemic to the Canary Islands. Two subspecies are recognized in P. aegeria, P. a. tircis and P. a. aegeria, distributed in northern and southern Europe, respectively. In the 1970s, P. aegeria appeared on Madeira. However, despite the status of P. aegeria as a model species in ecological studies, the evolutionary history of Pararge remains unknown. We studied the phylogenetic relationships of the three Pararge species, using the mitochondrial gene cytochrome oxidase subunit I and the nuclear gene wingless to infer modes and times of speciation. On the basis of our analyses, Pararge forms a strongly supported monophyletic group, with the DNA haplotypes of the three species also forming well‐supported monophyletic groups. We found that P. xiphia diverged first from the common ancestor a maximum of five million years ago, with P. xiphioides and P. aegeria being sister species that diverged a maximum of three million years ago. The two subspecies, P. a. tircis and P. a. aegeria, were not distinguishable on the basis of DNA haplotypes; instead, our data clearly distinguished between European specimens and those from North Africa. Madeiran P. aegeria has North African haplotypes and thus originated from there rather than from Europe. We hypothesize that the Mediterranean Sea forms a strong barrier to dispersal for Pararge butterflies, and has done so for approximately the past one million years.

Timing major conflict between mitochondrial and nuclear genes in species relationships of Polygonia butterflies (Nymphalidae: Nymphalini).

BackgroundMajor conflict between mitochondrial and nuclear genes in estimating species relationships is an increasingly common finding in animals. Usually this is attributed to incomplete lineage sorting, but recently the possibility has been raised that hybridization is important in generating such phylogenetic patterns. Just how widespread ancient and/or recent hybridization is in animals and how it affects estimates of species relationships is still not well-known.ResultsWe investigate the species relationships and their evolutionary history over time in the genus Polygonia using DNA sequences from two mitochondrial gene regions (COI and ND1, total 1931 bp) and four nuclear gene regions (EF-1α, wingless, GAPDH and RpS5, total 2948 bp). We found clear, strongly supported conflict between mitochondrial and nuclear DNA sequences in estimating species relationships in the genus Polygonia. Nodes at which there was no conflict tended to have diverged at the same time when analyzed separately, while nodes at which conflict was present diverged at different times. We find that two species create most of the conflict, and attribute the conflict found in Polygonia satyrus to ancient hybridization and conflict found in Polygonia oreas to recent or ongoing hybridization. In both examples, the nuclear gene regions tended to give the phylogenetic relationships of the species supported by morphology and biology.ConclusionStudies inferring species-level relationships using molecular data should never be based on a single locus. Here we show that the phylogenetic hypothesis generated using mitochondrial DNA gives a very different interpretation of the evolutionary history of Polygonia species compared to that generated from nuclear DNA. We show that possible cases of hybridization in Polygonia are not limited to sister species, but may be inferred further back in time. Furthermore, we provide more evidence that Haldanes effect might not be as strong a process in preventing hybridization in butterflies as has been previously thought.

Bayesian species delimitation reveals generalist and specialist parasitic wasps on Galerucella beetles (Chrysomelidae): sorting by herbivore or plant host

BackgroundTo understand the ecological and evolutionary consequences of species interactions in food webs necessitates that interactions are properly identified. Genetic analyses suggest that many supposedly generalist parasitoid species should rather be defined as multiple species with a more narrow diet, reducing the probability that such species may mediate indirect interactions such as apparent competition among hosts. Recent studies showed that the parasitoid Asecodes lucens mediate apparent competition between two hosts, Galerucella tenella and G. calmariensis, affecting both interaction strengths and evolutionary feedbacks. The same parasitoid was also recorded from other species in the genus Galerucella, suggesting that similar indirect effects may also occur for other species pairs.MethodsTo explore the possibility of such interactions, we sequenced mitochondrial and nuclear genetic markers to resolve the phylogeny of both host and parasitoid and to test the number of parasitoid species involved. We thus collected 139 Galerucella larvae from 8 host plant species and sequenced 31 adult beetle and 108 parasitoid individuals.ResultsThe analysis of the Galerucella data, that also included sequences from previous studies, verified the five species previously documented as reciprocally monophyletic, but the Bayesian species delimitation for A. lucens suggested 3–4 cryptic taxa with a more specialised host use than previously suggested. The gene data analyzed under the multispecies coalescent model allowed us to reconstruct the species tree phylogeny for both host and parasitoid and we found a fully congruent coevolutionary pattern suggesting that parasitoid speciation followed upon host speciation.ConclusionUsing multilocus sequence data in a Bayesian species delimitation analysis we propose that hymenopteran parasitoids of the genus Asecodes that infest Galerucella larvae constitute at least three species with narrow diet breath. The evolution of parasitoid Asecodes and host Galerucella show a fully congruent coevolutionary pattern. This finding strengthens the hypothesis that the parasitoid in host search uses cues of the host rather than more general cues of both host and plant.

Population structure in relation to host-plant ecology and Wolbachia infestation in the comma butterfly

Experimental work on Polygonia c‐album, a temperate polyphagous butterfly species, has shown that Swedish, Belgian, Norwegian and Estonian females are generalists with respect to host‐plant preference, whereas females from UK and Spain are specialized on Urticaceae. Female preference is known to have a strong genetic component. We test whether the specialist and generalist populations form respective genetic clusters using data from mitochondrial sequences and 10 microsatellite loci. Results do not support this hypothesis, suggesting that the specialist and generalist traits have evolved more than once independently. Mitochondrial DNA variation suggests a rapid expansion scenario, with a single widespread haplotype occurring in high frequency, whereas microsatellite data indicate strong differentiation of the Moroccan population. Based on a comparison of polymorphism in the mitochondrial data and sequences from a nuclear gene, we show that the diversity in the former is significantly less than that expected under neutral evolution. Furthermore, we found that almost all butterfly samples were infected with a single strain of Wolbachia, a maternally inherited bacterium. We reason that indirect selection on the mitochondrial genome mediated by a recent sweep of Wolbachia infection has depleted variability in the mitochondrial sequences. We also surmise that P. c‐album could have expanded out of a single glacial refugium and colonized Morocco recently.

Investigating Concordance among Genetic Data, Subspecies Circumscriptions and Hostplant Use in the Nymphalid Butterfly Polygonia faunus

Subspecies are commonly used taxonomic units to formally describe intraspecific geographic variation in morphological traits. However, the concept of subspecies is not clearly defined, and there is little agreement about what they represent in terms of evolutionary units, and whether they can be used as reliably useful units in conservation, evolutionary theory and taxonomy. We here investigate whether the morphologically well-characterized subspecies in the North American butterfly Polygonia faunus are supported by genetic data from mitochondrial sequences and eight microsatellite loci. We also investigate the phylogeographic structure of P. faunus and test whether similarities in host-plant use among populations are related to genetic similarity. Neither the nuclear nor the mitochondrial data corroborated subspecies groupings. We found three well defined genetic clusters corresponding to California, Arizona and (New Mexico+Colorado). There was little structuring among the remaining populations, probably due to gene flow across populations. We found no support for the hypothesis that similarities in host use are related to genetic proximity. The results indicate that the species underwent a recent rapid expansion, probably from two glacial refugia in western North America. The mitochondrial haplotype network indicates at least two independent expansion phases into eastern North America. Our results clearly demonstrate that subspecies in P. faunus do not conform to the structuring of genetic variation. More studies on insects and other invertebrates are needed to better understand the scope of this phenomenon. The results of this study will be crucial in designing further experiments to understand the evolution of hostplant utilization in this species.