45 research outputs found
Pathways to global-change effects on biodiversity: new opportunities for dynamically forecasting demography and species interactions
In structured populations, persistence under environmental change may be particularly threatened when abiotic factors simultaneously negatively affect survival and reproduction of several life cycle stages, as opposed to a single stage. Such effects can then be exacerbated when species interactions generate reciprocal feedbacks between the demographic rates of the different species. Despite the importance of such demographic feedbacks, forecasts that account for them are limited as individual-based data on interacting species are perceived to be essential for such mechanistic forecasting-but are rarely available. Here, we first review the current shortcomings in assessing demographic feedbacks in population and community dynamics. We then present an overview of advances in statistical tools that provide an opportunity to leverage population-level data on abundances of multiple species to infer stage-specific demography. Lastly, we showcase a state-of-the-art Bayesian method to infer and project stage-specific survival and reproduction for several interacting species in a Mediterranean shrub community. This case study shows that climate change threatens populations most strongly by changing the interaction effects of conspecific and heterospecific neighbours on both juvenile and adult survival. Thus, the repurposing of multi-species abundance data for mechanistic forecasting can substantially improve our understanding of emerging threats on biodiversity.12 página
Environmental change, if unaccounted, prevents detection of cryptic evolution in a wild population
Detecting contemporary evolution requires demonstrating that genetic change has occurred. Mixed effects models allow estimation of quantitative genetic parameters and are widely used to study evolution in wild populations. However, predictions of evolution based on these parameters frequently fail to match observations. Here, we applied three commonly used quantitative genetic approaches to predict the evolution of size at maturity in a wild population of Trinidadian guppies. Crucially, we tested our predictions against evolutionary change observed in common-garden experiments performed on samples from the same population. We show that standard quantitative genetic models underestimated or failed to detect the cryptic evolution of this trait as demonstrated by the common-garden experiments. The models failed because (1) size at maturity and fitness both decreased with increases in population density, (2) offspring experienced higher population densities than their parents, and (3) selection on size was strongest at high densities. When we accounted for environmental change, predictions better matched observations in the common-garden experiments, although substantial uncertainty remained. Our results demonstrate that predictions of evolution are unreliable if environmental change is not appropriately captured in models
Simulating nutrient release from parental carcasses increases the growth, biomass and genetic diversity of juvenile Atlantic salmon
The net transport of nutrients by migratory fish from oceans to inland spawning areas has decreased due to population declines and migration barriers. Restoration of nutrients to increasingly oligotrophic upland streams (that were historically salmon spawning areas) have shown short‐term benefits for juvenile salmon, but the longer term consequences are little known.
Here we simulated the deposition of a small number of adult Atlantic salmon Salmo salar carcasses at the end of the spawning period in five Scottish upland streams (‘high parental nutrient’ treatment), while leaving five reference streams without carcasses (‘low parental nutrient’ treatment). All streams received exactly the same number of salmon eggs (n = 3,000) drawn in equal number from the same 30 wild‐origin families, thereby controlling for initial egg density and genetic composition. We then monitored the resulting juvenile salmon and their macroinvertebrate prey, repeating the carcass addition treatment in the next spawning season.
Macroinvertebrate biomass and abundance were five times higher in the high parental nutrient streams, even 1 year after the carcass addition, and led to faster growth of juvenile salmon over the next 2 years (but with no change in population density). This faster growth led to more fish exceeding the size threshold that would trigger emigration to sea at 2 rather than 3 years of age. There was also higher genetic diversity among surviving salmon in high parental nutrient streams; genotyping showed that these effects were not due to immigration but to differential survival.
Synthesis and applications. This 2‐year field experiment shows that adding nutrients that simulate the presence of small numbers of adult salmon carcasses can have long‐term effects on the growth rate of juvenile salmon, likely increasing the number that will migrate to sea early and also increasing their genetic diversity. However, the feasibility of adding nutrients to spawning streams as a management tool to boost salmon populations will depend on whether the benefits at this stage are maintained over the entire life cycle
Simulating nutrient release from parental carcasses increases the growth, biomass and genetic diversity of juvenile Atlantic salmon
The net transport of nutrients by migratory fish from oceans to inland spawning areas has decreased due to population declines and migration barriers. Restoration of nutrients to increasingly oligotrophic upland streams (that were historically salmon spawning areas) have shown short‐term benefits for juvenile salmon, but the longer term consequences are little known.
Here we simulated the deposition of a small number of adult Atlantic salmon Salmo salar carcasses at the end of the spawning period in five Scottish upland streams (‘high parental nutrient’ treatment), while leaving five reference streams without carcasses (‘low parental nutrient’ treatment). All streams received exactly the same number of salmon eggs (n = 3,000) drawn in equal number from the same 30 wild‐origin families, thereby controlling for initial egg density and genetic composition. We then monitored the resulting juvenile salmon and their macroinvertebrate prey, repeating the carcass addition treatment in the next spawning season.
Macroinvertebrate biomass and abundance were five times higher in the high parental nutrient streams, even 1 year after the carcass addition, and led to faster growth of juvenile salmon over the next 2 years (but with no change in population density). This faster growth led to more fish exceeding the size threshold that would trigger emigration to sea at 2 rather than 3 years of age. There was also higher genetic diversity among surviving salmon in high parental nutrient streams; genotyping showed that these effects were not due to immigration but to differential survival.
Synthesis and applications. This 2‐year field experiment shows that adding nutrients that simulate the presence of small numbers of adult salmon carcasses can have long‐term effects on the growth rate of juvenile salmon, likely increasing the number that will migrate to sea early and also increasing their genetic diversity. However, the feasibility of adding nutrients to spawning streams as a management tool to boost salmon populations will depend on whether the benefits at this stage are maintained over the entire life cycle
Data from: Competitive asymmetry and local adaptation in Trinidadian guppies
1. The outcome of competition between individuals often depends on body-size. These competitive asymmetries can drive variation in demographic rates, influencing the ecology and evolution of life-histories. The magnitude and direction of such asymmetries differ among taxa, yet little is known empirically about how adaptation to resource limitation alters competitive asymmetries.
2. Here, we investigate the relationship between size-dependent competitive ability and adaptation to resource limitation.
3. We examined size-dependent competition in two ecotypes of Trinidadian guppy, adapted to high or low levels of resource competition. Using aquaria-based competition experiments, we describe how the size and ecotype of competitors influence somatic growth rate, whilst controlling for the confounding effect of niche differentiation. We replicated our study across two independent evolutionary origins of the 'competitive' ecotype.
4. The two 'competitive' ecotypes differed markedly in size-dependent asymmetry, indicating that adaptation to resource limitation alone is insufficient to explain changes in size-dependent competitive asymmetry. For one origin, the ecotype adapted to resource limitation was a superior competitor over a wide range of size pairings.
5. The equivalence of competitors varied over five-fold, dependent on size and ecotype; in three of four populations, larger individuals had a competitive advantage.
6. Our results demonstrate that competitive asymmetry has strong effects on somatic growth. Because somatic growth contributes to demographic parameters, intraspecific trait variation is likely to play a key role in regulating demographic rates. Our findings imply that the evolution of size-dependent asymmetries under conditions of intense competition is likely to be constrained by niche availability, although further research is needed to verify this
Data from: Life history evolution in guppies VIII: the demographics of density regulation in guppies (Poecilia reticulata)
In prior research, we found the way guppy life histories evolve in response to living in environments with a high or low risk of predation is consistent with life history theory that assumes no density-dependence. We later found that guppies from high predation environments experience higher mortality rates than those from low predation environments, but the increased risk was evenly distributed across all age/size classes. Life history theory that assumes density-independent population growth predicts that life histories will not evolve under such circumstances, yet we have shown with field introduction experiments that they do evolve. However, theory that incorporates density regulation predicts this pattern of mortality can result in the patterns of life history evolution we had observed. Here we report on density manipulation experiments performed in populations of guppies from low predation environments to ask whether natural populations normally experience density regulation and, if so, to characterize the short term demographic changes that underlie density regulation. Our experiments reveal that these populations are density regulated. Decreased density resulted in higher juvenile growth, decreased juvenile mortality rates and increased reproductive investment by adult females. Increased density causes reduced offspring size, increased fat storage by adult females and increased adult mortality
Anforderungsprofil fuer Schutzkleidung der Feuerwehr fuer die Brandbekaempfung - Grundschutz der Einsatzkraefte beim gesamten Einsatzspektrum
Available from TIB Hannover: RA 2039(99) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEArbeitsgemeinschaft der Innenministerien der Bundeslaender (Germany). Arbeitskreis 5 - Unterausschuss FeuerwehrangelegenheitenDEGerman
Data from: The evolution of coexistence: reciprocal adaptation promotes the assembly of a simple community
Species coexistence may result by chance when co-occurring species do not strongly interact or it may be an evolutionary outcome of strongly interacting species adapting to each other. While patterns like character displacement indicate that coexistence has often been an evolutionary outcome, it is unclear how often the evolution of coexistence represents adaptation in only one species or reciprocal adaptation among all interacting species. Here we demonstrate a strong role for evolution in the coexistence of guppies and killifish in Trinidadian streams. We experimentally recreated the temporal stages in the invasion and establishment of guppies into communities that previously contained only killifish. We combined demographic responses of guppies and killifish with a size-based integral projection model to calculate the fitness of the phenotypes of each species in each of the stages of community assembly. We show that guppies from locally adapted populations that are sympatric with killifish have higher fitness when paired with killifish than guppies from allopatric populations. This elevated fitness involves effects traceable to both guppy and killifish evolution. We discuss the implications of our results to the study of species coexistence and how it may be mediated through eco-evolutionary feedbacks