Complex mitonuclear interactions and metabolic costs of mating in male seed beetles.

The lack of evolutionary response to selection on mitochondrial genes through males predicts the evolution of nuclear genetic influence on male-specific mitochondrial function, for example by gene duplication and evolution of sex-specific expression of paralogs involved in metabolic pathways. Intergenomic epistasis may therefore be a prevalent feature of the genetic architecture of male-specific organismal function. Here, we assess the role of mitonuclear genetic variation for male metabolic phenotypes [metabolic rate and respiratory quotient (RQ)] associated with ejaculate renewal, in the seed beetle Callosobruchus maculatus, by assaying lines with crossed combinations of distinct mitochondrial haplotypes and nuclear lineages. We found a significant increase in metabolic rate following mating relative to virgin males. Moreover, processes associated with ejaculate renewal showed variation in metabolic rate that was affected by mitonuclear interactions. Mitochondrial haplotype influenced mating-related changes in RQ, but this pattern varied over time. Mitonuclear genotype and the energy spent during ejaculate production affected the weight of the ejaculate, but the strength of this effect varied across mitochondrial haplotypes showing that the genetic architecture of male-specific reproductive function is complex. Our findings unveil hitherto underappreciated metabolic costs of mating and ejaculate renewal, and provide the first empirical demonstration of mitonuclear epistasis on male reproductive metabolic processes.

Transcontinental migratory connectivity predicts parasite prevalence in breeding populations of the European barn swallow.

Parasites exert a major impact on the eco-evolutionary dynamics of their hosts and the associated biotic environment. Migration constitutes an effective means for long-distance invasions of vector-borne parasites and promotes their rapid spread. Yet, ecological and spatial information on population-specific host-parasite connectivity is essentially lacking. Here, we address this question in a system consisting of a transcontinental migrant species, the European barn swallow (Hirundo rustica) which serves as a vector for avian endoparasites in the genera Plasmodium, Haemoproteus and Leucocytozoon. Using feather stable isotope ratios as geographically informative markers, we first assessed migratory connectivity in the host: Northern European breeding populations predominantly overwintered in dry, savannah-like habitats in Southern Africa, whereas Southern European populations were associated with wetland habitats in Western Central Africa. Wintering areas of swallows breeding in Central Europe indicated a migratory divide with both migratory programmes occurring within the same breeding population. Subsequent genetic screens of parasites in the breeding populations revealed a link between the host's migratory programme and its parasitic repertoire: controlling for effects of local breeding location, prevalence of Africa-transmitted Plasmodium lineages was significantly higher in individuals overwintering in the moist habitats of Western Central Africa, even among sympatrically breeding individuals with different overwintering locations. For the rarer Haemoproteus parasites, prevalence was best explained by breeding location alone, whereas no clear pattern emerged for the least abundant parasite Leucocytozoon. These results have implications for our understanding of spatio-temporal host-parasite dynamics in migratory species and the spread of avian borne diseases.

ESwab challenges influenza virus propagation in cell cultures.

Although the ESwab kit (Copan, Brescia, Italy) is intended for sampling bacteria for culture, this kit is increasingly also used for virus sampling. The effect of ESwab medium on influenza virus detection by real-time reverse transcription-polymerase chain reaction (RT-PCR) or virus propagation in Madin-Darby canine kidney (MDCK) cell culture was investigated. The ESwab medium was suitable for viral RNA detection but not for viral propagation due to cytotoxicity. Sampling influenza viruses with ESwab challenges influenza surveillance by strongly limiting the possibility of antigenic characterisation.

Isospora hypoleucae sp. n. (Apicomplexa: Eimeriidae), a new coccidian parasite found in the Pied Flycatcher (Ficedula hypoleuca).

A new Coccidia species is reported from the natural population of Pied Flycatcher (Ficedula hypoleuca) in northern Germany. Sporulated oocysts were found in faeces from 6 of 8 sampled adults. The spherical oocysts of the new Isospora species have a brownish, smooth, bi-layered wall. Average size of sporulated oocysts was 19.4 x 19.3 microm (17.5-22.8 microm x 17.5-22.8 microm ) with a shape index (length/width) of 1.0. The sporulated oocysts have no micropyle or residuum, but enclose several small polar granules that often cluster into 2-3 dumbbell-shaped formations. Sporocysts are slightly elongated, rounded at the end opposite the Stieda body, 15.3 microm x 9.2 microm in size (13.8-16.1 microm x 8.5-10.3 microm ), and have a shape index of 1.7 (1.6-1.8). The Stieda body has a prominent knob-like cap, whereas the substieda body is absent. Sporocysts contain a small compact sporocyst residuum and 4 sporozoites. COI haplotypes identical to those isolated from faecal oocysts were PCR amplified from the blood of 13-day-old nestlings, suggesting that the newly described species has extra-intestinal stages in blood. This represents the first description of a new avian Isospora species supported by molecular sequence data from the same oocysts that are described morphologically.

Correlated evolution between male ejaculate allocation and female remating behaviour in seed beetles (Bruchidae).

Sperm competition theory suggests that female remating rate determines the selective regime that dictates the evolution of male ejaculate allocation. To test for correlated evolution between female remating behaviour and male ejaculate traits, we subjected detailed experimental data on female and male reproductive traits in seven-seed beetle species to phylogenetic comparative analyses. The evolution of a larger first ejaculate was positively correlated with the evolution of a more rapid decline in ejaculate size over successive matings. Further, as predicted by theory, an increase in female remating rate correlated with the evolution of larger male testes but smaller ejaculates. However, an increase in female remating was associated with the evolution of a less even allocation of ejaculate resources over successive matings, contrary to classic sperm competition theory. We failed to find any evidence for coevolution between the pattern of male ejaculate allocation and variation in female quality and we conclude that some patterns of correlated evolution are congruent with current theory, whereas some are not. We suggest that this may reflect the fact that much sperm competition theory does not fully incorporate other factors that may affect the evolution of male and female traits, such as trade-offs between ejaculate expenditure and other competing demands and the evolution of resource acquisition.

Interspecific variation in ejaculate allocation and associated effects on female fitness in seed beetles.

When ejaculates are costly to produce, males are expected to allocate their ejaculate resources over successive matings in a manner that optimizes their reproductive success and this may have important consequences for their mates. In seed beetles (Coleoptera; Bruchidae), ejaculates vary in size across species from weighing less than 1%, up to as much as 8%, of male body weight. Ejaculates contain not only sperm but also a range of additional substances and females in some species gain benefits from receiving large ejaculates. Male ejaculate allocation may thus affect female fitness. Here, we first characterized the pattern of male ejaculate allocation over successive matings in seven-seed beetle species. We then assessed how this allocation affected female fitness in each species. Although females generally benefited from receiving large ejaculates, the interspecific variation observed both in ejaculate allocation patterns and in their effects on female fitness was remarkably large considering that the species studied are closely related. Our analyses suggest that variation in ejaculate composition is the key, both within and across species. We discuss possible causes for this variation and conclude that coevolution between male ejaculates and female utilization of ejaculate substances has apparently been rapid in this clade.

Evolutionary diversification of the bean beetle genus Callosobruchus (Coleoptera: Bruchidae): traits associated with stored-product pest status.

Despite the fact that many plant-feeding insects are pests, little effort has been made to identify key evolutionary trait transitions that allow taxa to acquire or lose pest status. A large proportion of species in the genus Callosobruchus are economically important pests of stored, dry postharvest beans of the tribe Phaseoleae. However, the evolution of this feeding habit is poorly understood. Here, we present a reconstruction of the phylogeny of the Asian and African Callosobruchus based on three mitochondrial genes, and assess which traits have been associated with the evolutionary origin or loss of ability to reproduce on dry beans. Our phylogenetic analysis showed that species group into the chinensis and the maculatus clades, which are also supported by genital morphology, and an additional paraphyletic group. Ancestral ability to use dry beans has been lost in the chinensis clade but acquired again in C. chinensis. Dry-bean use and host-plant use were both phylogenetically constrained and transitions in the two were significantly correlated. Host shifts from the subtribe Phaseolinae to Cajaninae were more common than the reverse and were more likely in species using young beans. The ability to use dry beans was more likely gained when using Phaseolinae hosts and promoted habitat shifts from tropical to temperate regions. Adaptation to arid climate was also associated with the ability to reproduce on dry beans and on Phaseolinae. Thus, our analysis suggests that physiological adaptations to an arid climate and to Phaseolinae hosts both render beetles predisposed to become pests of cultivated beans.