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SUMMARY The primary objectives of this study were to determine (1) whether rapid cold-hardening (RCH) preserves reproductive behaviors during modest cooling,(2) whether increased mating success at a lower temperature comes at the cost of decreased performance at a higher temperature and (3) whether RCH is associated with an elevated metabolic rate. Drosophila melanogaster(Diptera: Drosphilidae) were rapidly cold-hardened by a 2-h exposure to 16°C prior to experiments. A temperature decrease of only 7°C(23°C to 16°C) prevented half (11/22) of the control pairs of D. melanogaster from engaging in any courtship activity. By contrast, most RCH pairs courted (17/20). Additionally, the 7°C transfer prevented mating in every pair of control flies, whereas more than half (11/20) of the RCH pairs mated. There was no evidence of impaired courtship or mating performance when RCH pairs were tested at 23°C. Finally, RCH is apparently not an energy-demanding process because no increase in the metabolic rate was detected during its induction. Overall, these data demonstrate that RCH serves to constantly fine-tune an insect's physiological state to match slight changes in environmental temperature. Furthermore, the RCH response is not restricted to cryoprotection and survival in the cold but also preserves more subtle behaviors, such as courtship, at moderate to high temperatures throughout the year.

BackgroundRepeated adaptive radiations are evident when phenotypic divergence occurs within lineages, but this divergence into different forms is convergent when compared across lineages. Classic examples of such repeated adaptive divergence occur in island (for example, Caribbean Anolis lizards) and lake systems (for example, African cichlids). Host-parasite systems in many respects are analogous to island systems, where host species represent isolated islands for parasites whose life cycle is highly tied to that of their hosts. Thus, host-parasite systems might exhibit interesting cases of repeated adaptive divergence as seen in island and lake systems.The feather lice of birds spend their entire life cycle on the body of the host and occupy distinct microhabitats on the host: head, wing, body and generalist. These microhabitat specialists show pronounced morphological differences corresponding to how they escape from host preening. We tested whether these different microhabitat specialists were a case of repeated adaptive divergence by constructing both morphological and molecular phylogenies for a diversity of avian feather lice, including many examples of head, wing, body and generalist forms.ResultsMorphological and molecular based phylogenies were highly incongruent, which could be explained by rampant convergence in morphology related to microhabitat specialization on the host. In many cases lice from different microhabitat specializations, but from the same group of birds, were sister taxa.ConclusionsThis pattern indicates a process of repeated adaptive divergence of these parasites within host group, but convergence when comparing parasites across host groups. These results suggest that host-parasite systems might be another case in which repeated adaptive radiations could be relatively common, but potentially overlooked, because morphological convergence can obscure evolutionary relationships.

Asexual reproduction is commonly thought to be associated with low genetic diversity in animals. Echmepteryx hageni (Insecta: 'Psocoptera') is one of several psocopteran species that are primarily parthenogenetic, but also exists in small, isolated sexual populations. We used mitochondrial DNA sequences to investigate the population history and genealogical relationships between the sexual and asexual forms of this species. The asexual population of E. hageni exhibits extremely high mitochondrial haplotype diversity (H=0.98), whereas the sexual forms had significantly lower haplotypic diversity (H=0.25, after correcting for sample size). This diversity in asexuals represents one the greatest genetic diversities reported for asexual animals in the literature. Nucleotide diversities were also higher in asexual compared to sexual populations (π=0.0071 vs. 0.00027). Compared to other reported estimates of π in insects, asexual nucleotide diversity is high, but not remarkably elevated. Three hypotheses might explain the elevated genetic diversity of asexual populations: (i) larger effective population size, (ii) greater mutation rate or (iii) possible recent origin of sexuals. In addition, phylogeographic analysis revealed little geographic structure among asexual E. hageni, although specimens from the upper Midwest form a single clade and are genetically differentiated. The mismatch distribution and neutrality tests indicate a historical population size increase, possibly associated with expansion from glacial refugia.

Data is presented in support of a phylogenetic reconstruction of one of the largest, and most poorly understood, groups of lice: the Brueelia-complex (Bush et al., 2015[1]). Presented data include the voucher information and molecular data (GenBank accession numbers) of 333 ingroup taxa within the Brueelia-complex and 30 outgroup taxa selected from across the order Phthiraptera. Also included are phylogenetic reconstructions based on Bayesian inference analyses of combined COI and EF-1α sequences for Brueelia-complex species and outgroup taxa.