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Elements transferred from a mother to her eggs may strongly influence the phenotype of her offspring. Such maternal effects depend on the genotype of the mother, and while multiple ploidy levels occur naturally in some vertebrate species, studies evaluating the impact of maternal ploidy on offspring are scarce. This paper aimed to test whether maternal ploidy is responsible for the two reproductive phenotypes observed in the triploid fish Chrosomus eos × eos‐neogaeus. Indeed, these hybrids have two different maternal origins (diploid or triploid) and display two reproductive phenotypes, ameiotic and meiotic hybridogenesis, resulting in diploid and haploid eggs, respectively. To this end, we first conducted a genomic survey to identify epigenetic variations in triploid larvae reared under common garden conditions, concordantly with their maternal origin. The results revealed that the polymorphic epigenetic loci of the larvae clustered into two highly distinct groups consistently with the ploidy of their mother. Diagnostic epigenetic loci were then tested in triploid adult females whose reproductive pathways were already known, to infer their own maternal origin. Altogether, the results suggest that triploid larvae from diploid and triploid mothers will develop the ameiotic and meiotic hybridogenesis pathway, respectively. This confirms that the development of a given reproductive pathway in triploid females results from the ploidy of their mother. Overall, this study supports a strong maternal effect, introducing maternal ploidy and reproductive pathways as additional cause and effect of maternal effects, respectively. [ABSTRACT FROM AUTHOR]

Accurate identification of species and their geographic origins is crucial to assess the impacts of exotic species. This is particularly relevant when multiple introductions are suspected. Species complexes are therefore problematic, as different species can be treated as a single taxon. The highly diversified European complex Arion subfuscus (Draparnaud, 1805) s.l. is abundant throughout northeastern North America. However, surveys performed in the United States have reported a low mitochondrial diversity associated with a single species. To assess whether regions characterized by different human activities harbor different diversities, the taxonomic identities, distributions, and origins of the species of this complex in Quebec (Canada) were determined. The mitochondrial 16S rDNA gene was analyzed in 526 specimens from 69 locations. Both Arion fuscus (O.F. Muller, 1774) and Arion subfuscus (Draparnaud, 1805) s. str. (lineages S1 and S2) were detected. Arion fuscus was the most abundant species, contrasting withprevious studies conductedinNorth America.Anexplosive range expansion occurred during the last 50 years. Moreover, the presence of different haplotypes confirmed multiple introductions of these species. These results emphasize the importance of not considering an exotic species complex as a single taxon, especially in regions with different human activities. Key words: alien species, Arion fuscus, Arion subfuscus, dispersal, distribution expansion, exotic invasive species, gastropod, haplotypes, invasion, mitochondrial diversity, slug, species complex, 16S rDNA. La determination precise de l'identite des especes et de leurs origines geographiques est essentielle pour evaluer les impacts des especes exotiques. Ceci est particulierement important si des introductions multiples sont suspectees. Les complexes d'especes sont donc problematiques puisque differentes especes peuvent etre traitees comme etant un seul taxon. Le complexe europeen, tres diversifie, Arion subfuscus (Draparnaud, 1805) s.l. est abondant dans tout le nord-est de l'Amerique du Nord. Cependant, des inventaires realises aux Etats-Unis ont releve une diversite mitochondriale faible associee a une seule espece. Afin d'evaluer si des regions caracterisees par des activites humaines differentes presentent des diversites differentes, l'identite taxonomique, la repartition et les origines des especes du complexe au Quebec (Canada) ont ete determinees. Le gene mitochondrial de l'ADNr 16S a ete analyse pour 526 specimens en provenance de 69 sites. Les especes Arion fuscus (O.F. Muller, 1774) et Arion subfuscus (Draparnaud, 1805) s. str. (lignees S1 et S2) ont ete detectees. Cependant, A. fuscus est l'espece la plus abondante, ce qui contraste avec les etudes precedentes realisees en Amerique du Nord. Une expansion fulgurante de la repartition s'est produite au cours des 50 dernieres annees. De plus, la presence de divers haplotypes a permis de confirmer de multiples introductions de ces especes. Ces resultats soulignent l'importance de ne pas considerer un complexe d'especes exotiques comme un seul taxon, notamment dans des regions avec des activites humaines differentes. Mots-cles: Arion fuscus, Arion subfuscus, complexe d'especes, dispersion, diversite mitochondriale, espece exotique envahissante, expansion de la repartition, gasteropode, haplotypes, invasion, limace, ADNr 16S., Introduction Numerous studies have reported the impacts that exotic species have on their novel ecosystems by developing new biotic and abiotic interactions (e.g., Bohlen et al. 2004; Meirmans et al. [...]

The ribosomal intergenic spacer (IGS), responsible for the rate of transcription of rRNA genes, is associated with the growth and fecundity of individuals. A previous study of IGS length variants in a yellow perch (Perca flavescens) population revealed the presence of two predominant alleles differing by 1 kb due to variation in the number of repeat units. This study aims to assess whether length variation of IGS is the result of selection in natural populations. Length variation of IGS and 11 neutral microsatellite loci were assessed in geographically distant yellow perch populations. Most populations displayed the very same IGS alleles; they did not differ in frequencies among populations and the [F.sub.ST] was not significantly different from zero. In contrast, diversity at microsatellite loci was high and differed among populations ([F.sub.ST] = 0.18). Selection test based on [F.sub.ST] identified IGS as a significant outlier from neutral expectations for population differentiation. Heterozygote excess was also detected in one specific cohort, suggesting temporal variation in the selection regime. While the exact mechanism remains to be specified, together the results of this study support the contention that balancing selection is acting to maintain two distinct IGS alleles in natural fish populations. Key words: balancing selection, ribosomal intergenic spacer (IGS), yellow perch (Perca flavescens), genotype. L'espaceur intergenique ribosomique (IGS) responsable du taux de transcription des genes codant pour les ARNr a ete associe a la croissance et a la fecondite des individus. Une etude precedente sur la variation en taille de l'IGS chez la perchaude (Perca flavescens) a revele la presence de deux alleles predominants qui different par 1 kb en raison de la variation du nombre de repetitions. L'objectif de cette etude est de determiner si la variation en taille de l'IGS provient de selection agissant sur les populations naturelles. La variation en taille de l'IGS et de 11 loci microsatellites neutres a ete determinee sur des populations de perchaudes geographiquement distantes. La plupart des populations ont demontre les memes alleles IGS; ils ne differaient pas en frequence entre les populations et le [F.sub.ST] n'etait pas significativement different de zero. Au contraire, la diversite des loci microsatellites etait elevee et differait entre les populations ([F.sub.ST] = 0.18). Le test de selection base sur le [F.sub.ST] a identifie l'IGS comme significativement different des valeurs attendues neutres pour la differentiation des populations. Un exces d'heterozygotes a egalement ete detecte dans une cohorte specifique suggerant une variation temporelle du regime de selection. Bien que le mecanisme exact reste a elucider, les resultats de cette etude supportent le fait que la selection balancee joue pour maintenir deux alleles distincts dans les populations naturelles de poissons. Mots-cles : selection balancee, espaceur intergenique ribosomique (IGS), perchaude (Perca flavescens), genotype., Introduction Balancing selection is a particular evolutionary process allowing the long-term persistence of different allelic lineage within population as well as among populations. Different situations such as heterozygous advantage, where [...]

The intergenic spacer (IGS) is located between ribosomal RNA (rRNA) gene copies. Within the IGS, regulatory elements for rRNA gene transcription are found, as well as a varying number of other repetitive elements that are at the root of IGS length heterogeneity. This heterogeneity has been shown to have a functional significance through its effect on growth rate. Here, we present the structural organization of yellow perch (Perca flavescens) IGS based on its entire sequence, as well as the IGS length variation within a natural population. Yellow perch IGS structure has four discrete regions containing tandem repeat elements. For three of these regions, no specific length class was detected as allele size was seemingly normally distributed. However, for one repeat region, PCR amplification uncovered the presence of two distinctive IGS variants representing a length difference of 1116 bp. This repeat region was also devoid of any CpG sites despite a high GC content. Balanced selection may be holding the alleles in the population and would account for the high diversity of length variants observed for adjacent regions. Our study is an important precursor for further work aiming to assess the role of IGS length variation in influencing growth rate in fish. Keywords: IGS, spacer length variants, rRNA genes, repetitive elements, Perca flavescens. L'espaceur intergenique (IGS) est situe entre chaque copie des genes de l'ADN ribosomique (ADNr). Le nombre d'elements regulateurs de la transcription des genes ADNr ainsi qu'un nombre variable d'autres elements repetes sont a la base de la variation en taille de l'IGS. Il a ete demontre que cette heterogeneite a un role fonctionnel de par son effet sur le taux de croissance. Dans cette etude, nous presentons l'organisation de l'IGS de la perchaude (Perca flavescens) a partir de la sequence complete ainsi que la variation en taille de l'IGS dans une population naturelle. L'IGS de la perchaude contient quatre regions differentes contenant des elements repetes en tandem. Pour trois de ces regions, il n'y a pas de categories distinctives et la taille des alleles est normalement distribuee. Cependant, pour la region restante, les amplifications par PCR revelent la presence de deux alleles distinctifs, presentant une difference de 1116 pb. Cette region repetee est egalement depourvue de CpG malgre un fort contenu en GC. La selection balancee pourrait maintenir ces deux alleles depuis longtemps dans la population et expliquer la diversite elevee d'alleles de tailles differentes observee dans les regions adjacentes. Cette etude est un important precurseur aux futurs travaux portant sur le role de la variation en taille des IGS et de son influence sur la croissance des poissons. Mots-cles : IGS, variants de longueur de l'espaceur, genes d'ARNr, elements repetes, Perca flavescens., Introduction The multicopy genes encoding ribosomal RNA (rRNA) are arranged as tandem head-to-tail repeats in ribosomal DNA (rDNA). Each copy is composed of three coding genes (18S, 5.8S, and 28S) [...]

We evaluated the effects of temporal variation of fish density estimates on the explanatory power of habitat use models. Fish density estimates were obtained using visual surveys (10 visits) in eighteen 100 m reaches over a 7-week period. Physical attributes of reaches were estimated. Field data were used to develop a simulation domain (10 000 reaches) that reflected the spatio-temporal variability of fish density estimates and physical attributes. Simulations indicated that for a sampling effort of approximately 200 surveys, the number of reaches surveyed (25 to 200) and the number of surveys per reach (1 to 8) affected the adjusted [R.sup.2] of models by 5% to 42%. The established practice of sampling a maximized number of reaches once did not appear necessarily optimal for developing habitat use models. Analysis of temporal coefficients of variation suggests that species within the same family may require a similar survey design. Hence, for salmonids, it may be more appropriate to sample more reaches once, and for cyprinids, it may be more optimal to repeatedly sample fewer reaches. Nous avons evalue l'effet de variations temporelles de la densite de poissons sur le pouvoir explicatif de modeles d'utilisation de l'habitat et les variables explicatives incluses dans ces modeles. Les densites d'especes de poissons ont ete estimees 10 fois dans dix-huit troncons de 100 m durant 7 semaines de l'ete 2007. Les caracteristiques physiques ont ete documentees. Les donnees de terrain ont ete utilisees pour developper un domaine de simulations (10 000 troncons) refletant la variabilite spatiale et temporelle des estimes de densites de poissons et la variabilite spatiale des caracteristiques des habitats. Des simulations ont indique que, pour un effort constant d'approximativement 200 inventaires, le nombre de troncons echantillonnes (25 a 200) et le nombre d'inventaires par troncon (1 a 8) ont affecte le [R.sup.2] ajuste des modeles par 5 a 42 %. Nos resultats suggerent que la strategie d'echantillonnage optimale differe selon la famille d'appartenance de l'espece. Pour certaines (salmonides), il semble optimal d'echantillonner une seule fois un nombre maximal de sites. Pour d'autres (cyprinides), il serait preferable d'echantillonner de facon repetee un nombre diminue de sites., Introduction Habitat loss has been recognized as a major threat to the survival of fish populations (Evans et al. 1996; Richter et al. 1997; Reed and Czech 2005). One objective [...]

Dispersal of freshwater mussels occurs when the larvae parasitize fishes. In northeastern North America, distributions of floater mussels (Pyganodon spp.) are allopatric and arranged in an east-west pattern that corresponds poorly with the biogeographic patterns of the regional fish fauna. This study aims at determining whether associations with distinct fish species can explain the distribution of floaters. Here, we devised a framework based on a series of novel distributional null models to elucidate dispersal of species that are dependent on host species. The distributional patterns of floaters were tested by controlling for associations with fishes, while host-parasite associations were assessed with null models based on cooccurrence patterns. The disjoint distribution of the giant floater (Pyganodon grandis) and the eastern floater (Pyganodon cataracta) could not be explained by their association with distinct host fish and is likely the result of associations with distinct host populations rather than distinct species. In contrast, the distribution of the Newfoundland floater (Pyganodon fragilis) could be explained by its association with euryhaline fishes. Such associations may have also promoted differentiation with its sister taxa, the eastern floater. This study demonstrated the effects of positive biological associations on distributional patterns and the utility of a null model framework to uncover them. La dispersion des moules d'eau douce survient lorsque des larves parasitent des poissons. Dans le nord-est de l'Amerique du Nord, les anodontes (Pyganodon spp.) presentent des repartitions allopatriques dans un patron est-ouest dont la correspondance aux patron biogeographiques observes pour les communautes de poissons dans la region est faible. Cette etude vise a determiner si des associations avec des especes distinctes de poissons peuvent expliquer les repartitions des especes d' anodontes. Nous avons donc developpe une serie de modeles nuls concus pour elucider la dispersion des especes dont la repartition est liee a celles d'especes hotes. Les patrons de repartition des anodontes ont ete testes en controlant les associations hote-parasite, alors que ces associations ont ete determinees a partir de modeles nuls bases sur les patrons de co occurence. Les repartitions disjointes de l' anodnote geante (Pyganodon grandis)etdel' anodonte de l' Est (Pyganodon cataracta) ne peuvent etre expliquees par leurs associations avec des poissons hotes distincts et resultent probablement d'associations avec des populations distinctes plutot que des especes distinctes. En revanche, les associations distinctes de l'anodonte de Terre-Neuve (Pyganodon fragilis) avec des especes de poissons euryhalins permettent d'expliquer sa repartition. Ces associations distinctes ont egalement pu favoriser la differenciation avec son taxon soeur, l'anodonte de l'Est. Cette etude a demontre les effets des associations biologiques positives sur les patrons de repartition et le grand potentiel des modeles nuls pour detecter de telles associations., Introduction Dispersal is an important factor determining the distribution of species (e.g., Belyea and Lancaster 1999). However, a large number of organisms rely on other species for their dispersal (Vaughn [...]

Natal site fidelity of the northern redbelly dace (Phoxinus eos), a common minnow in North America, was confirmed by combining ecological and genetic approaches. A 2-year mark-recapture experiment conducted at four sites separated by 50-450 m strongly supported the propensity of the dace to practice site fidelity during the reproductive period. Individuals recaptured at their marking sites were characterized with five microsatellite loci. Hardy-Weinberg equilibrium and allelic differentiation tests revealed that the fish from different sites significantly differed from a single panmictic and genetically uniform population, thus confirming the homing behaviour of the dace. The detection of a pattern of isolation by distance revealed that migration mostly occurred between nearby sites and decreased as distance from birth site increased. When considering the high population density of dace, their high swimming capability, the distribution of the spawning sites along the littoral zone, and the small size of the lake studied ( Un comportement de fidelite au site de naissance du ventre rouge du nord (Phoxinus eos), un cyprin commun d'Amerique du Nord, a ete confirme par la combinaison d'approches ecologique et genetique. Une experience de marquage et recaptures repetees pendant 2 annees sur quatre sites distants de 50 a 450 m supporte fortement la propension du cyprin au comportement de fidelite au site en periode de reproduction. Les individus recaptures a leur site de marquage ont ensuite ete caracterises avec cinq microsatellites. Les tests d'equilibre de Hardy-Weinberg et de differenciation allelique revelent que les poissons des differents sites different significativement d'une population panmictique et genetiquement uniforme, ce qui confirme le comportement de fidelite au site de naissance du cyprin. La detection d'un patron d'isolement par la distance revele que les echanges de migrants sont plus importants entre des sites rapproches et diminue avec une augmentation de la distance entre les sites de naissance et de ponte. En considerant la forte densite de cette population de cyprins, leur importante capacite natatoire, la distribution des sites de ponte le long de la zone littorale et la petite taille du lac etudie(, Introduction Natural populations are generally genetically structured, with a higher frequency of mating between individuals that are geographically close and (or) that reproduce during the same period. Spatially or temporally [...]

Abstract: Postglacial seas are expected to have had significant effects on the genetic structure of populations of obligate freshwater fishes. To assess this influence, mitochondrial DNA variability was evaluated in [...]

The factors affecting sex determination remain largely unknown for most bivalve species. Environmental factors, such as temperature, are known to influence sex determination in some species, and this has been hypothesized for the mussel Mytilus edulis , but not experimentally validated yet. Adult exposure to different environmental conditions during gametogenesis, which occurs seasonally, may also affect offspring phenotype, including sex determination. Intergenerational carryover effects have been reported in bivalves, but the impact of parental exposures on offspring sex determination has not been examined so far. To address these questions, artificial fertilizations were performed on individuals collected in three different years and their embryos were reared at three different temperatures to specifically test if the environment influences offspring sex ratio through effects on parental developing gametes and/or on developing embryos. The analysis of 1938 embryos from 25 crosses revealed a significant effect of both temperature treatments and sampling years on the proportion of females. However, the overall variation is mostly explained by the "temperature treatment × sampling years" interaction. Taken together, our results suggested that interannual environmental variations experienced by the parents (during gametogenesis) and embryo (during development) can influence the sex of the offspring in M. edulis. [ABSTRACT FROM AUTHOR]

Abstract Background While numerous studies revealed the major role of environmental changes of the Quaternary on the evolution of biodiversity, research on the influence of that period on current South-American fauna is scarce and have usually focused on lowland regions. In this study, the genetic structure of the pampas cat (Leopardus colocolo), a widely distributed felid, was determined and linked to ancient climate fluctuations on the Andean region. Results Using both mitochondrial sequences and nuclear microsatellites, we inferred the existence of at least four groups of populations in the central Andes, while other three localities, with little sample sizes (n = 3), presented differences in only one of these markers. The distribution of these groups is correlated to latitude, with a central area characterized by admixture of numerous mitochondrial clades. This suggests colonization from at least three glacial refuges and a contact zone between 20 degrees and 23 degrees S following a glaciation event. The similar coalescence times of the mitochondrial haplotypes indicated that the major clades split approximately one million years ago, likely during the Pre-Pastonian glacial period (0.80 – 1.30 MYA), followed by a demographic expansion in every clade during the Aftonian interglacial period (0.45 – 0.62 MYA). Interestingly, this structure roughly corresponds to the current recognised distribution of morphological subspecies. Conclusion The four groups of populations identified here must be considered different management units, and we propose the three localities showing differences in only mtDNA or ncDNA as provisional management units. The results revealed the influence of ancient climate fluctuations on the evolutionary history of this species. It is expected that the other species of land vertebrates with a smaller or similar mobility have been affected in the same manner by the glacial and interglacial periods in the central Andes