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Species invading non‐native habitats can cause irreversible environmental damage and economic harm. Yet, how introduced species become widespread invaders remains poorly understood. Adaptation within native‐range habitats and rapid adaptation to new environments may both influence invasion success. Here, we examine these hypotheses using 7058 SNPs from 36 native, 40 introduced and 19 farmed populations of tench, a fish native to Eurasia. We examined genetic structure among these populations and accounted for long‐term evolutionary history within the native range to assess whether introduced populations exhibited lower genetic diversity than native populations. Subsequent to infer genotype–environment correlations within native‐range habitats, we assessed whether adaptation to native environments may have shaped the success of some introduced populations. At the broad scale, two glacial refugia contributed to the ancestry and genomic diversity of tench. However, native, introduced and farmed populations of admixed origin exhibited up to 10‐fold more genetic diversity (i.e., observed heterozygosity, expected heterozygosity and allelic richness) compared to populations with predominantly single‐source ancestry. The effects of introduction to a new location were also apparent as introduced populations exhibited fewer private alleles (mean = 9.9 and 18.9 private alleles in introduced and native populations, respectively) and higher population‐specific Fst compared to native populations, highlighting their distinctiveness relative to the pool of allelic frequencies across tench populations. Finally, introduced populations with varying levels of genetic variation and similar genetic compositions have become established and persisted under strikingly different climatic and ecological conditions. Our results suggest that lack of prior adaptation and low genetic variation may not consistently hinder the success of introduced populations for species with a demonstrated ability to expand their native range. [ABSTRACT FROM AUTHOR]

Environmental sex determination implies that sex is defined by environmental factors influencing the maternal organism and/or oocytes. It provides population sex ratios that will maximise the sustainability of the population under incipient environmental conditions. Environmental factors responsible for sex determination include temperature, photoperiod, food availability, and population density. These cues stimulate the release of chemical signalling molecules (i.e. hormones) that determine the sex of newborns.We have analysed the responses of three Daphnia pulex clones (I, K, and S), isolated from different natural populations, to juvenile hormone methyl farnesoate (MF) in terms of survivorship, fecundity, production of males and ephippia, and expression of genes involved in sex determination (dsx1) and hormonal regulation (JHAMT, Met, RXR). Clonal individuals were exposed to: (1) high MF concentration (0.8 µM) combined with stressful conditions; (2) low MF concentration (0.15 µM) combined with optimal conditions of population density and food availability in two subsequent generations.The genetically different clones of D. pulex differed in the propensity for male and ephippia production and in the sensitivity to the stimuli that lead to the switch from parthenogenetic to sexual reproduction.A significant induction of male production was observed in all three clones when exposed to MF. In conditions mimicking crowding, only clone S produced male offspring even in absence of MF and showed higher expression levels of JHAMT and dsx1 genes. This response suggests that clone S has a high propensity to produce males probably due to a high sensitivity of receptors to environmental stimuli activating the endogenous biosynthesis of MF. However, clone S exposed to high MF concentration produced fewer males than clones I and K, which generally have a low natural propensity to produce males. High MF concentration coupled with conditions mimicking crowding, probably activated a feedback mechanism in clone S via the differential modulation of genes involved in the synthesis as well in the degradation of MF.Exposure to low MF concentration for two subsequent generations resulted in a reduction of male progeny production from the first (G1) to the second (G2) generation. All analysed genes were up‐regulated in both generations treated with MF, but with lower expression in G2. The reduced up‐regulation of the dsx1 gene matched with the lower male production. Based on our results and literature data, we hypothesised that the maternal dsx1 mRNA probably plays some role early in oocyte development, and causes the eggs that receive the dsx1 signal to develop into males.Exposure to MF for two generations significantly increased ephippia production. These results suggest that the induction of male and ephippia might have a common root in the MF pathway. The effect of MF on life‐history traits (delay in the age at maturity and fecundity reduction), sex ratio, and ephippia production suggests a direct impact of the juvenile hormone on the level of population growth. Thus, as a consequence of the switch from parthenogenetic to sexual reproduction, MF influences Daphnia population metrics and in this way probably maximises the sustainability of the population under variable environmental conditions. [ABSTRACT FROM AUTHOR]

Current species distributions at high latitudes are the product of expansion from glacial refugia into previously uninhabitable areas at the end of the last glaciation. The traditional view of postglacial colonization is that southern populations expanded their ranges into unoccupied northern territories. Recent findings on mitochondrial DNA (mtDNA) of British small mammals have challenged this simple colonization scenario by demonstrating a more complex genetic turnover in Britain during the Pleistocene--Holocene transition where one mtDNA clade of each species was replaced by another mtDNA clade of the same species. Here, we provide evidence from one of those small mammals, the bank vole (Clethrionomys glareolus), that the replacement was genome-wide. Using more than 10 000 autosomal SNPs we found that similar to mtDNA, bank vole genomes in Britain form two (north and south) clusters which admix. Therefore, the genome of the original postglacial colonists (the northern cluster) was probably replaced by another wave of migration from a different continental European population (the southern cluster), and we gained support for this by modelling with approximate Bayesian computation. This finding emphasizes the importance of analysis of genome-wide diversity within species under changing climate in creating opportunities for sophisticated testing of population history scenarios. [ABSTRACT FROM AUTHOR]

The article focuses on the observation of fighting behavior in Eleutherodactylus marnockii frogs in a roadside habitat in Texas, shedding light on a poorly documented aspect of the species' behavior.

Shallow water bodies dominate the areal extent of continental waters and host a proportion of biodiversity higher than the percentage of Earth's surface they cover. Daphnia is a key component of small aquatic ecosystems food webs. Here we present the result of a survey in 24 ponds located in the core of Po river Basin, to assess the actual spreading of Daphnia species in one of the most productive areas of the Northern hemisphere. By using diagnostic genetic markers (12S rRNA and ND5 genes) we identified five Daphnia species: D. ambigua, D. curvirostris, D. longispina, D. obtusa and D. pulex in fourteen ponds. Additional analyses of two nuclear genes (LdhA and Rab4) revealed that D. pulex in the study area is native European strain. In opposite, D. ambigua shared haplotype with the North-Eastern American lineage that was introduced to Europe by long-distance dispersal. In the Po river Basin we identified a highly divergent lineage of D. longispina group that formed a clade with individuals from northern European Russia and might represent a new Daphnia species. Daphnia species in the Cremona province have European origin, except for D. ambigua which is a North American species spreading across Europe. Future attention will require monitoring of invasive species, particularly D. ambigua and the North American invasive clone of D. pulex that is already present in Northern Italy. [ABSTRACT FROM AUTHOR]

Background: Although posttranscriptional modification of mitochondrial (mt) transcripts plays key roles in completion of the coding information and in the expression of mtDNA-encoded genes, there is little experimental evidence on the polyadenylation status and the location of mt gene poly(A) sites for non-human mammals. Results: Poly(A)-enriched RNA-Seq reads collected for two wild-caught bank voles (Clethrionomys glareolus) were mapped to the complete mitochondrial genome of that species. Transcript polyadenylation was detected as unmapped adenine residues at the ends of the mapped reads. Where the tRNA punctuation model applied, there was the expected polyadenylation, except for the nad5 transcript, whose polyadenylated 3' end is at an intergenic sequence/cytochrome b boundary. As in human, two pairs of bank vole genes, nad4l/nad4 and atp8/atp6, are expressed from bicistronic transcripts. TAA stop codons of four bank vole protein-coding genes (nad1, atp6, cox3 and nad4) are incompletely encoded in the DNA and are completed by polyadenylation. This is three genes (nad2, nad3 and cob) less than in human. The bank vole nad2 gene encodes a full stop codon (TAA in one vole and TAG in the other), which is followed by a 2 bp UTR and the gene conforms to the tRNA punctuation model. In contrast, the annotations of the reference mouse and some other rodent mt genomes in GenBank include complete TAG stop codons in both nad1 and nad2, which overlap downstream trnI and trnW, respectively. Thus the RNA-Seq data of bank voles provides a model for stop codons of mt-encoded genes in mammals comparable to humans, but at odds with some of the interpretation based purely on genomic data in mouse and other rodents. Conclusions: This work demonstrates how RNA-Seq data were useful to recover mtDNA transcriptome data in a non-model rodent and to shed more light on mammalian mtDNA transcriptome and post-transcriptional modification. Even though gene content and organisation of mtDNA are strongly conserved among mammals, annotations that neglect the transcriptome may be prone to errors in relation to the stop codons. [ABSTRACT FROM AUTHOR]

We present the first complete sequence of the bank vole (Clethrionomys glareolus) mitochondrial genome (GenBank accession no. KF918859). The bank vole mitogenome is 16,353 base pairs long and shows the gene content, genome architecture and gene strand asymmetry typical for mammals. The sequence provides an important new genomic resource for the bank vole, which is a popular study species in ecological and evolutionary research. [ABSTRACT FROM AUTHOR]

The North American ecological species Daphnia pulicaria and Daphnia pulex are thought to have diverged from a common ancestor by adaptation to sympatric but ecologically distinct lake and pond habitats respectively. Based on mtDNA relationships, European D. pulicaria is considered a different species only distantly related to its North American counterpart, but both species share a lactate dehydrogenase (Ldh) allele F supposedly involved in lake adaptation in North America, and the same allele is also carried by the related Holarctic Daphnia tenebrosa. The correct inference of the species’ ancestral relationships is therefore critical for understanding the origin of their adaptive divergence. Our species tree inferred from unlinked nuclear loci for D. pulicaria and D. pulex resolved the European and North American D. pulicaria as sister clades, and we argue that the discordant mtDNA gene tree is best explained by capture of D. pulex mtDNA by D. pulicaria in North America. The Ldh gene tree shows that F-class alleles in D. pulicaria and D. tenebrosa are due to common descent (as opposed to introgression), with D. tenebrosa alleles paraphyletic with respect to D. pulicaria alleles. That D. tenebrosa still segregates the ancestral and derived amino acids at the two sites distinguishing the pond and lake alleles suggests that D. pulicaria inherited the derived states from the D. tenebrosa ancestry. Our results suggest that some adaptations restricting the gene flow between D. pulicaria and D. pulex might have evolved in response to selection in ancestral environments rather than in the species’ current sympatric habitats. The Arctic (D. tenebrosa) populations are likely to provide important clues about these issues. [ABSTRACT FROM AUTHOR]