Search

Removal of non-native fish populations can be crucial to the conservation of native species, but often presents a complex challenge for managers. The goal of Trojan Y chromosome (TYC) programs is to skew the non-native sex ratio until only males remain, leading to eradication. We present results from a simulation model used to explore effects of alternative management approaches on an in-progress mechanical removal and TYC program to eradicate non-native brook trout (Salvelinus fontinalis). Simulation results indicated that stocking fingerling YY males (~137 mm) was more effective than stocking catchable- sized YY males (~230 mm), although questions about intercohort competition warrant further investigation. Increasing the proportion of mature fingerling YY males reduced treatment time by increasing the number of YY male spawners and increasing density- dependent mortality on young, mature wild brook trout. Maximizing the spatial distribution of YY male releases may be crucial to program success but is also dependent upon immediate dispersal movements. Principles derived from our results can be broadly applied to the management of other aquatic invaded systems using TYC programs to eradicate non-native species. Si le retrait de populations de poissons non indigenes peut s'averer crucial pour la conservation d'especes indigenes, il constitue souvent un defi complexe pour les gestionnaires. L'objectif des programmes bases sur un chromosome Y << cheval de Troie >> (CYCT) est de modifier le rapport de masculinite d'especes non indigenes jusqu'a ce que seuls des males demeurent, menant a leur eradication. Nous presentons les resultats d'un modele de simulation utilise pour explorer les effets de differentes approches de gestion sur un programme en cours de retrait mecanique et base sur les CYCT visant l'eradication d'ombles de fontaine (Salvelinus fontinalis) non indigenes. Les resultats de simulations indiquent que l'ensemencement d'alevins males YY d'un an (~137 mm) est plus efficace que l'ensemencement de males YY de taille exploitable (~230 mm), bien que des questions concernant la concurrence entre cohortes necessitent un examen plus pousse. Une plus grande proportion d'alevins males YY matures reduit la duree du traitement en rehaussant le nombre de geniteurs males YY et la mortalite dependante de la densite des jeunes ombles de fontaine sauvages matures. La maximisation de la repartition spatiale des lachers de males YY pourrait constituer un element cle du succes de tels programmes, mais depend aussi des deplacements de dispersion immediats. Les principes derives de nos resultats peuvent s'appliquer plus largement a la gestion d'autres systemes aquatiques envahis par le recours a des programmes bases sur les CYCT pour eradiquer des especes non indigenes. [Traduit par la Redaction], Introduction The establishment and spread of non-native fish species present substantial challenges for the conservation and management of natural resources (Havel et al. 2015). One approach to the removal of [...]

Gray fox (Urocyon cinereoargenteus (Schreber, 1775)) populations in portions of the eastern United States have experienced declines whose trajectories differ from those of other mesocarnivore populations. One hypothesis is that gray fox declines may result from interspecific interactions, particularly competition with abundant coyotes (Corns latrans Say, 1823). Alternatively, gray foxes may respond negatively to increased urbanization and reduced forest cover. To evaluate these hypotheses, we used single-species occupancy models of camera trap data to test the effects of habitat covariates, such as the amount of urbanization and forest, on coyote and gray fox occupancy. Additionally, we test the effect of an index based on an N-mixture model of the number of coyotes at each camera trap site on gray fox occupancy. Results indicate that occupancy probabilities of coyote and gray fox relate positively to the amount of forest, but they provided no evidence urban cover impacts gray foxes. Additionally, gray fox occupancy was negatively related to the index of the number of coyotes at each site. Our models support the idea that interactions with coyotes impact gray fox occupancy across the eastern United States. These results illustrate how large-scale studies can relate mechanisms identified within specific landscapes to phenomena observed at larger scales. Key words: Cams latrans, coyote, competition, gray fox, interspecific, mesopredator release, occupancy, Urocyon cinereoargenteus. Les populations de renards gris (Urocyon cinereoargenteus (Schreber, 1775)) dans certaines parties de l'est des Etats-Unis ont connu des baisses dont les trajectoires different de celles des populations d'autres mesocarnivores. Une hypothese pour expliquer ce phenomene veut que les declins de renards gris pourraient decouler d'interactions entre especes, plus particulierement la concurrence d'abondants coyotes (Canis latrans Say, 1823). II se pourrait par contre que les renards gris reagissent negativement a l'urbanisation accrue et a la diminution du couvert forestier. Afin d'evaluer ces hypotheses, nous avons utilise des modeles d'occupation d'espece unique appliques a des donnees de pieges photographiques pour examiner les effets de covariables associees a l'habitat, telles que la quantite d'espaces urbanises et de foret, sur l'occupation des coyotes et des renards gris. Nous avons egalement verifie l'effet d'un indice base sur un modele N-melange du nombre de coyotes a chaque site de piege photographique sur l'occupation par les renards gris. Les resultats indiquent que les probability d'occupation par des coyotes et des renards gris sont positivement reliees a la quantite de couvert forestier, mais ne revelent aucun signe d'une influence de la couverture urbaine sur les renards gris. L'occupation des renards gris est en outre negativement reliee a l'indice du nombre de coyotes dans chaque site. Nos modeles appuient l'idee selon laquelle les interactions avec les coyotes auraient une incidence sur l'occupation des renards gris dans l'est des Etats-Unis. Ces resultats illustrent comment des etudes a grande echelle peuvent permettre de relier des mecanismes observes dans des paysages precis a des phenomenes observes a plus grande echelle. [Traduit par la Redaction] Mots-cles : Canis latrans, coyote, concurrence, renard gris, interspecifique, liberation de mesopredateurs, occupation, Urocyon cinereoargenteus., Introduction Medium-sized carnivores, or mesocarnivores, may benefit from the extirpation of top predators and from being able to exploit modified landscapes (Prugh et al. 2009; Bateman and Fleming 2012). The [...]

Disentangling the roles of structural landscape factors and animal movement behaviour can present challenges for practitioners managing landscapes to maintain functional connectivity and achieve conservation goals. We used a landscape genetics approach to combine robust demographic, behavioural and genetic datasets with spatially explicit simulations to evaluate the effects of anthropogenic barriers (dams, culverts) and natural landscape resistance (gradient, elevation) affecting dispersal behaviour, genetic connectivity and genetic structure in a resident population of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi). Analyses based on 10 years of sampling effort revealed a pattern of restricted dispersal, and population genetics identified discrete population clusters between distal tributaries and the mainstem stream and no structure within the mainstem stream. Demogenetic simulations demonstrated that, for this population, the effects of existing anthropogenic barriers on population structure are redundant with effects of restricted dispersal associated with the underlying environmental resistance. Our approach provides an example of how extensive field sampling combined with landscape genetics can be incorporated into spatially explicit simulation modelling to explore how, together, movement ecology and landscape resistance can be used to inform decisions around restoration and connectivity. [ABSTRACT FROM AUTHOR]

Diet of the northern river otter (Lontra canadensis (Schreber, 1777)) has been examined throughout much of its range and across many habitat types. Few studies have examined prey selection based on prey abundance estimates, however, and prey selection results have been inconsistent. We determined composition, seasonal variation, and prey selection of otter diet in northern Utah comprising multiple habitat types and prey communities. We evaluated the hypothesis that otters take prey according to availability and in inverse proportion to swimming ability. Fish was the primary class of prey taken by otters (96.5%), followed by crustaceans (16.9%). Among families, otter diet was composed primarily of Salmonidae and Cottidae, the two families that dominated the fish community of the main-channel habitat. Otter diet varied seasonally for nearly all classes ([G.sub.[24]] = 127.8, P < 0.001) and families ([G.sub.[18]] = 13 2.94, P < 0.001) of prey. In particular, fish occurrence was lower during summer than during other seasons (P ≤ 0.05), whereas crustacean (i.e., crayfish (Astacoidea)) occurrence was higher ([G.sub.[3]] = 711, P < 0.001). At the family level, occurrence of Salmonidae was greatest during fall ([G.sub.[3]] = 11.7, P < 0.01). Within one of our habitat types, we found otters to select for prey in proportion to abundance and in inverse proportion to swimming ability, with otters selecting for Catostomidae and Cyprinidae, against Salmonidae, and Cottidae according to its abundance. We conclude that habitat type may be the initial driver of prey selection, while factors such as abundance, agility, and life history of prey may be secondary drivers. Key words: diet, feeding ecology, food habits, habitat, Lontra canadensis, prey selection, river otter, seasonal variation. Le regime alimentaire de la loutre de riviere (lontra canadensis (Schreber, 1777)) a ete etudid dans la majeure partie de son aire de repartition et dans de nombreux types d'habitats. Peu d'etudes se sont toutefois penchdes sur la sdlection de proies a la lumiere d'estimations de l'abondance des proies, et les resultats touchant a la selection de proies se sont avdrds peu cohdrents. Nous avons ddtermind la composition, les variations saisonnieres et la selection de proies de I'alimentation de la loutre dans le nord de l'Utah, une region qui comprend de nombreux types d'habitats et communautes de proies. Nous avons evalue l'hypothese voulant que les loutres choisissent leurs proies selon leur disponibilitd et de maniere inversement proportionnelle a leur capacite natatoire. Les poissons constituaient la principale classe de proies prises par les loutres (96,5 %), suivis des crustaces (16,9 %). En ce qui concerne les families, le regime des loutres dtait principalement compose de salmonides et de cottides, les deux families dominantes de la communautd de poissons de l'habitat de chenal principal. Le regime alimentaire des loutres variait selon la saison pour presque toutes les classes ([G.sub.[24]] = 127,8, P < 0,001) et families ([G.sub.[18]] = 132,94, P < 0,001) de proies. En particulier, la presence de poissons etait plus faible durant l'dtd que durant d'autres saisons (P ≤ 0,05), alors que la presence de crustaces (c.-a-d. ecrevisses (Astacoidea)) dtait plus dlevde ([G.sub.[3]] = 71,1, P < 0,001). Au niveau de la famille, la presence de salmonides etait la plus elevee a l'automne ([G.sub.[3]] = 11,7, P < 0,01). Dans un de nos types d'habitats, nous avons note que les loutres choisissaient leurs proies a des frequences proportionnelles a leur abondance et inversement proportionnelles a leur capacite natatoire, les loutres selectionnant des meuniers et cyprinidds plutot que des salmonidds, et des cottides selon leur abondance. Nous concluons que le type d'habitat pourrait etre le facteur initial de sdlection de proies, alors que des facteurs comme l'abondance, l'agilite et le cycle biologique des proies pourraient etre des facteurs secondaires. [Traduit par la Redaction] Mots-cles: regime alimentaire, dcologie de l'alimentation, habitudes alimentaires, habitat, Lontra canadensis, selection des proies, loutre de riviere, variations saisonnidres., Introduction Animals select resources that maximize fitness (e.g., Charnov 1976; Cowie 1977; Pyke 1978). How resources are selected influences other factors including habitat use, risk of predation, and social behavior. [...]

Species reintroductions are successful when established populations maintain both demographic stability and genetic diversity. Such a result may be obtained by ensuring both structural habitat connectivity and genetic connectivity among reintroduced and remnant populations. Nevertheless, prezygotic barriers such as assortative mating can prevent the flow of genetic material between populations, even when migration between populations is high. Limited gene flow may be particularly relevant for reintroductions that were sourced either from captive-bred populations or from disparate locations in the wild. American martens (Martes americana) have been reintroduced repeatedly in the Upper Midwestern United States in an effort to establish self-sustaining populations. We quantified levels of genetic diversity within and spatial genetic variance among four marten populations during two time periods separated by 10 years. Spatially informed and naïve discriminant analysis of principal components were used to assign individuals to populations. Results indicate that heterozygosity declined and inbreeding coefficients increased between the two collection periods, while genetic structure among populations also increased. Data are consistent with assortative mating contributing to reapportioning of genetic variation. Population assignment tests show that migration among populations is apparent, but admixture (based on cluster membership probabilities) is low and declined over time. Specifically, martens may be successfully dispersing between populations but a lack of admixture indicates a lack of reproductive contributions to genetic diversity by migrants. Because marten reintroductions in this region are well-documented and well-monitored, lessons can be derived from results to inform future reintroductions. We encourage a careful balance of supplementing genetic diversity via augmentation while avoiding translocation of animals from disparate populations that may result in reproductive isolation of migrants. In combination with the maintenance of a functionally connected landscape, this strategy would maximize the likelihood of a successful reintroduction in terms both of demography and genetics. [ABSTRACT FROM AUTHOR]

We implemented multilocus selection in a spatially‐explicit, individual‐based framework that enables multivariate environmental gradients to drive selection in many loci as a new module for the landscape genetics programs, CDPOP and CDMetaPOP. Our module simulates multilocus selection using a linear additive model, providing a flexible platform to evaluate a wide range of genotype‐environment associations. Importantly, the module allows simulation of selection in any number of loci under the influence of any number of environmental variables. We validated the module with individual‐based selection simulations under Wright‐Fisher assumptions. We then evaluated results for simulations under a simple landscape selection model. Next, we simulated individual‐based multilocus selection across a complex selection landscape with three loci linked to three different environmental variables. Finally, we demonstrated how the program can be used to simulate multilocus selection under varying selection strengths across different levels of gene flow in a landscape genetics framework. This new module provides a valuable addition to the study of landscape genetics, allowing for explicit evaluation of the contributions and interactions between gene flow and selection‐driven processes across complex, multivariate environmental and landscape conditions. [ABSTRACT FROM AUTHOR]

Combining landscape demographic and genetics models offers powerful methods for addressing questions for eco-evolutionary applications., Using two illustrative examples, we present Cost-Distance Meta-POPulation, a program to simulate changes in neutral and/or selection-driven genotypes through time as a function of individual-based movement, complex spatial population dynamics, and multiple and changing landscape drivers., Cost-Distance Meta-POPulation provides a novel tool for questions in landscape genetics by incorporating population viability analysis, while linking directly to conservation applications. [ABSTRACT FROM AUTHOR]