Life history, population viability, and the potential for local adaptation in isolated trout populations

Habitat loss and fragmentation have caused population decline across taxa through impacts on life history diversity, dispersal patterns, and gene flow. Yet, intentional isolation of native fish populations is a frequently used management strategy to protect against negative interactions with invasive fish species. We evaluated the population viability and genetic diversity of 12 isolated populations of Oncorhynchus clarkii lewisi located on the Flathead Indian Reservation in Montana, USA. Length-structured integral projection models (IPMs) were used to project population growth rate (lambda) and its sensitivity to underlying vital rates and parameters. We examined relationships between lambda, genetic diversity, and habitat size and quality. Lambda ranged from 0.68 to 1.1 with 10 of 12 populations projected to be in decline. A sensitivity analysis of lambda with respect to projection matrix elements indicated that lambda was generally sensitive to changes in early life history stages (survival/growth), but patterns differed among populations. Another sensitivity analysis with respect to underlying model parameters showed highly consistent pattern across populations, with lambda being most sensitive to the slope of probability of maturity (estimated from published literature), generally followed by adult survival, and the slope of somatic growth rate (directly measured from each population). Lambda was not correlated with genetic diversity. For populations residing in small isolated streams (≤5 km of occupied habitat), lambda significantly increased with base flow discharge (r2=0.50, p<0.02). Our results highlight the potential importance of local adaptation for persistence of small, isolated populations. Specifically we saw evidence for higher probability of maturity at smaller sizes in the smallest, coldest isolated systems, increasing probability of persistence for these populations. Climate change threatens to further fragment populations of aquatic organisms and reduce summertime base flows in much of western North America. Insights from studies such as ours will inform management strategies for long-term persistence of species facing these challenges

Sammenheng mellom dødelighet hos brunørret og fysisk-kjemiske årstidsvariasjoner i en sur aluminiumsrik innsjø. (Relations between mortality on brown trout and seasonal variation in physical-chemical parameters in an acidic Al-rich lake)

Uorganisk aluminium (Ali) er uten tvil hovedårsaken til at fisk som brunørret (Salmo trutta L.) ikke er tilstede i Nepptjern. Konsentrasjonene av Al, kunne derimot ikke forklare sesongvariasjonene i giftighet. Det ble faktisk påvist en negativ korrelasjon mellom Al, og mortalitet. Basert på ulike statistiske analyser (PCA-analyser og overlevelseanalyser), er vannets temperatur, ionstyrke og O2-innhold, samt Al-polymerisering og fikselengde (alder) de faktorene som best forklarer de store sesongvariasjonene i giftighet. At det også ble påvist en negativ korrelasjon mellom (H*) og mortalitet, og tilsvarende positiv korrelasjon med ANC, er sterke indikasjoner på at Al-polymerisering er en viktig faktor for mortalitetsvariasjoner i innsjøen. Det ble også påvist at de lengste (eldste) fiskene gjennomgående var mest sensitive, men under tidlig snøsmelting på våren var mortaliteten høyest blant de minste fiskene. I rapporten antas at disse variasjonene kan skyldes ulik primære dødsårsak. I tilfeller hvor Al-akkumulering på fiskegjellene dominerende, antas det at de største/lengste fiskene har lavest forhold mellom gjelle-areal og kroppsvekt slik at disse vil dø først, med hypoksi som antatt viktigste dødsårsak. Med bakgrunn i samme teori, antas det at når de minste fiskene dør først, er hovedårsaken forstyrrelser i ionreguleringen over gjellene, slik at fisk med høyst gjelle-areal/kroppsvekt forholdet, raskest vil tape plasmaioner. Undersøkelsen har ingen fysiologiske resultater som direkte kan dokumentere disse ulike mekanismene, men rapporten antyder at hvis disse antakelsen er riktige, synes ionreguleringsvikt å være mindre akutt enn hypoksi i forbindelse med omfattende Al-polymerisering/akkumulering. Også fysisk/kjemiske sesongvariasjoner i innsjøen, både i tid og rom, er omhandlet i rapporten

Within-species variation in the gut microbiome of fish is driven by the interaction of light intensity and genetic background

Gut microbiome diversity and functions are jointly shaped by the host’s genetic background and environmental conditions, but the consequences of this interaction are still unclear. Unravelling the effect of the interaction between evolution and environment on the gut microbiome is particularly relevant considering the unprecedented level of human-driven disruption on the ecological and evolutionary trajectories of species. Here, we aimed to evaluate whether size-selective mortality influences the gut microbiome of medaka (Oryzias latipes), how environment conditions modulate the effect of the genetic background of medaka on their microbiota, and the association between microbiome diversity and medaka fitness. To do so, we studied two lineages of medaka that were raised under antagonistic size-selective regimes for 10 generations (i.e. the largest or the smallest breeders were removed to mimic fishing-like or natural mortality). In pond mesocosms, the two lineages were subjected to contrasting population density and light intensity (i.e. used as a proxy of primary production, hence resource availability). We observed significant differences in the gut microbiome composition and richness between the two lines, and this effect was mediated by light intensity. Indeed, the bacterial richness of fishing-like medaka (small-breeder line) was reduced by 34% under low-light conditions compared to high-light conditions, while it remained unchanged in natural mortality-selected medaka (large-breeder line). However, the observed changes in bacterial richness did not correlate with changes in growth rate or body condition, possibly due to functional redundancy among the microbial taxa residing in the gut. Given the growing evidence about the gut microbiomes importance to host health, more in-depth studies are required to fully understand the role of the microbiome in size-selected organisms and the possible ecosystem-level consequences

The EASIN Editorial Board: Quality assurance, exchange and sharing of alien species information in Europe

The European Alien Species Information Network (EASIN) aims to facilitate the exploration of alien species information in Europe, and is recognized as the information system supporting European Union Member States in the implementation of the recently published Invasive Alien Species Regulation. In this paper, we present the role and activities of the EASIN Editorial Board (EB), which is responsible for the quality assurance, safeguarding and constant improvement of EASIN. The EB is supported by a web platform that facilitates online discussions about alien species. This platform creates a virtual community by providing a forum-like interface that is moderated by the EB Members but is freely accessible to the scientific community and the general public. It allows all registered users to make comments, raise questions and share experience and expertise on alien species in Europe. Moreover, it provides a means for exchanging opinions and solving disputes in a transparent way. The overall EB activity is commonly agreed upon procedures and standards. © 2016 The Author(s)