Mating systems are diverse in animals, notably in crustaceans, but can be inferred from a limited set of parameters. Baeza and Thiel (2007) proposed a model predicting mating systems of symbiotic crustaceans with three host characteristics and the risk of predation. These authors proposed five mating systems, ranging from monogamy to polygynandry (where multiple mating occurs for both genders). Using microsatellite loci, we tested the putatively mating system of the ectoparasite crab Dissodactylus primitivus. We determined the mating frequencies of males and females, parentage assignment (COLONY & GERUD software) as well as the contents of female spermathecae. Our results are globally consistent with the model of Baeza and Thiel and showed, together with previous aquarium experiments, that this ectoparasite evolved a polygamous mating system where males and females move between hosts for mate search. Parentage analyses revealed that polyandry is frequent and concerns more than 60% of clutches, with clutches being fertilized by up to 6 different fathers. Polygyny is supported by the detection of eight males having sired two different broods. We also detected a significant paternity skew in 92% of the multipaternal broods. Moreover, this skew is probably higher than the estimation from the brood because additional alleles were detected in most of spermathecae. This high skew could be explained by several factors as sperm competition or cryptic female choice. Our genetic data, combined with previous anatomic analyses, provide consistent arguments to suggest sperm precedence in D. primitivus.

Aim Studying the changes in species ranges during the last glaciation event is an important step towards the understanding of the observed patterns of intra‐specific genetic variability. We focused on bumblebees, an interesting biological model to address these questions because cold‐adapted species are likely to have experienced different geographical range histories during the last glacial period compared to more commonly studied, strictly temperate, species. We investigated and compared historical hypotheses regarding the geographical range of five common and co‐distributed West Palaearctic bumblebee species. Location Europe, West Palaearctic. Methods For each species, we inferred present and past (Last Glacial Maximum) distributions from species occurrence records, and present and past climatic data, using the ecological niche modelling (ENM) approach implemented in Maxent. Based on genetic data previously obtained from the sequencing of three gene fragments (mitochondrial locus COI and two nuclear loci EF‐1α and PEPCK), we then compared global and local patterns of genetic variation using several summary statistics as well as a visual mapping of genetic variation. Finally, we used a spatially explicit model of DNA sequence coalescence to test and compare four evolutionary scenarios derived from ENM results and patterns of genetic diversity. Results Ecological niche modelling results based on climatic data clearly suggested a range continuum in Europe during the last glaciation. Yet, the related evolutionary scenario involving such continuum was less supported than alternative scenarios involving a more fragmented distribution. Indeed, for the three out of five species for which genetic data allowed discriminating among tested scenarios, the scenario that included a fragmented range during the last glaciation was identified as the most likely. Main conclusions Although ENM suggested that bumblebees would have maintained a range continuum across Europe during the last glaciation, coalescent simulations tended to refute the persistence of a large range continuum for these species during this period. This suggests that even for cold‐adapted species, the cooling periods have significantly shrunk and fragmented their respective ranges.

Insect species with a wide distribution offer a great opportunity to trace latitudinal variation in the photoperiodic regulation of traits important in reproduction and stress tolerances. We measured this variation in the photoperiodic time-measuring system underlying reproductive diapause in Drosophila montana, using a Nanda-Hamner (NH) protocol. None of the study strains showed diel rhythmicity in female diapause proportions under a constant day length (12 h) and varying night lengths in photoperiods ranging from 16 to 84 h at 16°C. In the northernmost strains (above 55°N), nearly all females entered diapause under all photoperiods and about half of them even in continuous darkness, while the females of the southern strains showed high diapause proportions only in the circadian 24 h photoperiod. Significant correlation between the strains’ mean diapause proportions in ≥ 24 h photoperiods and critical day length (CDL; half of the females enter diapause) suggests at least partial causal connection between the traits. Interestingly, females of the northern strains entered diapause even in ≤ 24 h photoperiods, where the night length was shorter than their critical night length (24 h - CDL), but where the females experienced a higher number of Light:Dark cycles than in 24 h photoperiods. NH experiments, performed on the control and selection lines in our previous selection experiment, and completed here, gave similar results and confirmed that selection for shorter, southern-type CDL decreases female diapausing rate in non-circadian photoperiods. Overall, our study shows that D. montana females measure night length quantitatively, that the photoperiodic counter may play a prominent but slightly different role in extra short and extra long photoperiods and that northern strains show high stability against perturbations in the photoperiod length and in the presence of LD cycles. These features are best explained by the quantitative versions of the damped external coincidence model.

Computer simulations of genetic data are increasingly used to investigate the impact of complex historical scenarios on patterns of genetic variation. Yet, in most empirical studies, relatively large portions of species ranges are often treated as panmictic populations, ignoring the underlying spatial context. In some cases, however, a more accurate spatial model is required. We use a spatially explicit model of coalescence (easily constructed by overlaying a two-dimensional grid on maps displaying an estimate of past and current species ranges) to evaluate the potential of several summary statistics to differentiate three typical phylogeographic scenarios. We first explore the variation of each summary statistic within the boundaries of each phylogeographic scenario, and identify those that appear most promising for a comparison of historical scenarios and/or to infer historical parameters. We then combine a selected set of summary statistics in a single chi-square statistic and evaluate whether it can be used to differentiate past geographic fragmentation or range expansion from a simple scenario of isolation by distance. We also investigate the benefits of using a spatially explicit model by comparing its performance to alternative models that are less spatially explicit (lower geographic resolution). The results identify conditions in which each summary statistic is useful to infer the evolution of a species range, and allow us to validate our spatially explicit model of coalescence and our procedure to compare simulated and observed sequence data. We also provide a detailed description of the spatially explicit model of coalescence used, which is currently lacking.

Past environmental changes have shaped the demographic history and genetic diversity of natural populations, yet the timescale and strength of these effects have not been investigated systematically and simultaneously for multiple phylogenetically distant species. We performed comparative population genomic analyses and demographic inference for seven ecologically contrasting European tree species sampled across their ranges. While patterns of genetic diversity and differentiation were species-specific and best explained jointly by each species' geographic range and dispersal ability, ancient population expansion events were shared and synchronous across species. Effective population sizes increased or remained stable over time, indicating that despite major changes in their geographic ranges, major forest tree species have been remarkably genetically resilient to the environmental challenges of repeated glacial cycles.

Mitochondrial genome heteroplasmy-the presence of more than one genomic variant in individuals-is considered only occasional in animals, and most often involves molecules differing only by a few recent mutations. Thanks to new sequencing technologies, a large number of DNA fragments from a single individual can now be sequenced and visualized separately, allowing new insights into intra-individual mitochondrial genome variation. Here, we report evidence from both (i) massive parallel sequencing (MPS) of genomic extracts and (ii) Sanger sequencing of PCR products, for the widespread co-occurrence of two distantly related (greater than 1% nucleotide divergence, excluding the control region) mitochondrial genomes in individuals of a natural population of the leaf beetle Sanger sequencing of PCR products using universal primers previously failed to identify heteroplasmy in this population. Its occurrence was detected with MPS data and may have important implications for evolutionary studies. It suggests the need to re-evaluate, using MPS techniques, the proportion of animal species displaying heteroplasmy.

Analysing genomic variation within and between sister species is a first step towards understanding species boundaries. We focused on two sister species of cold‐resistant leaf beetles, Gonioctena quinquepunctata and G. intermedia, whose ranges overlap in the Alps. A previous study of DNA sequence variation had revealed multiple instances of mitochondrial genome introgression in this region, suggesting recent hybridization between the two species. To evaluate the extent of gene exchange resulting from these hybridization events, we sampled individuals of both species inside and outside the hybrid zone and analysed genomic variation among them using RAD‐seq markers. Individual levels of introgression in the nuclear genome were estimated first by defining species‐specific SNPs (displaying a fixed difference between species) a priori and second by using model‐based methods. Both types of analyses indicated little gene exchange, if any, between species at the level of the nuclear genome. Whereas the first method suggested slightly more gene flow, we argue that it has likely overestimated introgression in the phylogeographic context of this study. We conclude that strong intrinsic barriers prevent genetic exchange at the level of the nuclear genome between the two species. The apparent discrepancy observed between introgression occurring in the nuclear and mitochondrial genomes could be explained by selection acting in favour of the latter. Also, these results have consequences for the phylogeographic study of each species, since we can assume that genetic diversity in the overlapping portion of their ranges is not the product of introgression.

Pinus sylvestris (Scots pine) is the most widespread coniferous tree in the boreal forests of Eurasia, with major economic and ecological importance. However, its large and repetitive genome presents a challenge for conducting genome-wide analyses such as association studies, genetic mapping and genomic selection. We present a new 50K single-nucleotide polymorphism (SNP) genotyping array for Scots pine research, breeding and other applications. To select the SNP set, we first genotyped 480 Scots pine samples on a 407 540 SNP screening array and identified 47 712 high-quality SNPs for the final array (called 'PiSy50k'). Here, we provide details of the design and testing, as well as allele frequency estimates from the discovery panel, functional annotation, tissuespecific expression patterns and expression level information for the SNPs or corresponding genes, when available. We validated the performance of the PiSy50k array using samples from Finland and Scotland. Overall, 39 678 (83.2%) SNPs showed low error rates (mean = 0.9%). Relatedness estimates based on array genotypes were consistent with the expected pedigrees, and the level of Mendelian error was negligible. In addition, array genotypes successfully discriminate between Scots pine populations of Finnish and Scottish origins. The PiSy50k SNP array will be a valuable tool for a wide variety of future genetic studies and forestry applications.