Many species have fragmented distribution with small isolated populations suffering inbreeding depression and/or reduced ability to evolve. Without gene flow from another population within the ...species (genetic rescue), these populations are likely to be extirpated. However, there have been only ~ 20 published cases of such outcrossing for conservation purposes, probably a very low proportion of populations that would potentially benefit. As one impediment to genetic rescues is the lack of an overview of the magnitude and consistency of genetic rescue effects in wild species, I carried out a meta‐analysis. Outcrossing of inbred populations resulted in beneficial effects in 92.9% of 156 cases screened as having a low risk of outbreeding depression. The median increase in composite fitness (combined fecundity and survival) following outcrossing was 148% in stressful environments and 45% in benign ones. Fitness benefits also increased significantly with maternal ΔF (reduction in inbreeding coefficient due to gene flow) and for naturally outbreeding versus inbreeding species. However, benefits did not differ significantly among invertebrates, vertebrates and plants. Evolutionary potential for fitness characters in inbred populations also benefited from gene flow. There are no scientific impediments to the widespread use of outcrossing to genetically rescue inbred populations of naturally outbreeding species, provided potential crosses have a low risk of outbreeding depression. I provide revised guidelines for the management of genetic rescue attempts.
See also the Perspective by Waller
Current rates of climate change require organisms to respond through migration, phenotypic plasticity, or genetic changes via adaptation. We focused on questions regarding species’ and populations’ ...ability to respond to climate change through adaptation. Specifically, the role adaptive introgression, movement of genetic material from the genome of 1 species into the genome of another through repeated interbreeding, may play in increasing species’ ability to respond to a changing climate. Such interspecific gene flow may mediate extinction risk or consequences of limited adaptive potential that result from standing genetic variation and mutation alone, enabling a quicker demographic recovery in response to changing environments. Despite the near dismissal of the potential benefits of hybridization by conservation practitioners, we examined a number of case studies across different taxa that suggest gene flow between sympatric or parapatric sister species or within species that exhibit strong ecotypic differentiation may represent an underutilized management option to conserve evolutionary potential in a changing environment. This will be particularly true where advanced‐generation hybrids exhibit adaptive traits outside the parental phenotypic range, a phenomenon known as transgressive segregation. The ideas presented in this essay are meant to provoke discussion regarding how we maintain evolutionary potential, the conservation value of natural hybrid zones, and consideration of their important role in adaptation to climate.
•Genetic factors remain inadequately addressed in conservation management.•Effective population size (Ne)=50 does not prevent inbreeding depression.•Ne⩾100 is required to limit inbreeding depression ...to 10% over 5 generations.•Ne=500 is too low for retaining evolutionary potential; Ne⩾1000 is required.•IUCN Red List Criterion C thresholds for population size require doubling.
Conservation managers typically need to make prompt decisions based on limited information and resources. Consequently, generalisations have essential roles in guiding interventions. Here, we (i) critique information on some widely accepted generalisations and variables affecting them, (ii) assess how adequately genetic factors are currently incorporated into population viability analysis (PVA) models used to estimate minimum viable population sizes, and (iii) relate the above to population size thresholds of the IUCN Red List criteria for threatened species that were derived from genetic considerations. Evidence accumulated since 1980 shows that genetically effective population size (Ne)=50 is inadequate for preventing inbreeding depression over five generations in the wild, with Ne⩾100 being required to limit loss in total fitness to ⩽10%. Further, even Ne=500 is too low for retaining evolutionary potential for fitness in perpetuity; a better approximation is Ne⩾1000. Extrapolation from census population size (N) to Ne depends on knowing the ratio of Ne/N, yet this information is unavailable for most wild populations. Ratio averages (∼0.1–0.2) from meta-analyses are sufficient, provided adjustments are made for dissimilar life histories. Most PVA-based risk assessments ignore or inadequately model genetic factors. PVA should routinely include realistic inbreeding depression, and genetic impacts on evolutionary potential should be incorporated where appropriate. Genetic generalisations used in conservation, the treatment of genetics in PVAs, and sections of the IUCN Red List criteria derived from genetic considerations, all require revision to be more effective conservation tools.
•We review plastic and evolutionary responses of Mediterranean plants to global change.•Plasticity differs among species and populations, among traits and environmental factors.•Little is known about ...whether genetic variation can drive a measurable evolutionary change.•Habitat fragmentation exacerbates the negative impacts of climate change.•Knowledge is particularly scant on the constraints to plasticity, its adaptive value and its transgenerational potential.
Global change poses new challenges for plant species, including novel and complex combinations of environmental conditions to which plants should adjust and adapt. Mediterranean ecosystems are recognized biodiversity hotspots but are also global change hotspots due to the concerted action of multiple environmental drivers. In the face of these changes, Mediterranean plants can migrate to more suitable habitats, adapt through natural selection, adjust via phenotypic plasticity or go extinct. In this paper, we review responses of Mediterranean plants to global change, specifically focusing on plastic and microevolutionary responses to climate change, and common factors that affect and limit such responses, such as habitat fragmentation.
The available evidence suggests that Mediterranean species can respond plastically to environmental change, but plasticity differs not only among species and populations but also among traits and environmental factors to which the plants are responding. Dry Mediterranean climates could limit the expression of plasticity in still uncertain ways. Although there is evidence for significant within-population evolutionary potential for functionally important traits in several Mediterranean species, little is known about whether this variation drives measurable evolutionary change. Habitat fragmentation exacerbates the negative impacts of climate change because it limits both the expression of plasticity and the evolutionary potential of plants. Invasive species, typically initiated as small populations in novel environments, provide important ecological and evolutionary insights on responses to global change that can foster specific research on Mediterranean plants. Our revision revealed that knowledge for Mediterranean plants is particularly scant on the constraints to plasticity, its adaptive value and its transgenerational potential, as well as on the fine-tuning of genetic change to environmental change.
Abstract
Parasitic life-strategies in the phylum Nematoda (roundworms) are remarkably diverse and intricate in terms of evolution and taxonomy. By analysing novel rDNA data obtained on rare ...host-associated groups with unusual biology, we reveal paraphyly of the last major taxon with uncertain higher-rank classification that united solely parasitic nematodes (Marimermithida) to show that primarily marine parasitism only emerged independently and repeatedly in a few free-living lineages. We report secondary seaward ingression of land-based parasites (Mermithida) via invading hosts in the subtidal zone to illustrate the host-borne scenario of oceanic fish and mammal colonization by primarily terrestrial parasites (Spiruria). We also present the first molecular data on marine nematodes from unicellular hosts (foraminiferan protozoans) to demonstrate the independent origins of exploitative nematode associations at a microscopic scale. We argue that, in contrast with primarily intestinal associations arising from saprotrophy and commensalism, non-intestinal host capture (colonization of host body cavity or internal organs) is likely to be a primary route of transition to truly exploitative parasitism in roundworms. Predispositions to host capture in nematode morphology, ecology and life cycles imply its evolution as part of innate pre-adaptations to crossing environmental boundaries to enable multiple successful transitions to parasitism in the phylum history.
Understanding and predicting how adaptation will contribute to species' resilience to climate change will be paramount to successfully managing biodiversity for conservation, agriculture, and human ...health‐related purposes. Making predictions that capture how species will respond to climate change requires an understanding of how key traits and environmental drivers interact to shape fitness in a changing world. Current trait‐based models suggest that low‐ to mid‐latitude populations will be most at risk, although these models focus on upper thermal limits, which may not be the most important trait driving species' distributions and fitness under climate change. In this review, we discuss how different traits (stress, fitness and phenology) might contribute and interact to shape insect responses to climate change. We examine the potential for adaptive genetic and plastic responses in these key traits and show that, although there is evidence of range shifts and trait changes, explicit consideration of what underpins these changes, be that genetic or plastic responses, is largely missing. Despite little empirical evidence for adaptive shifts, incorporating adaptation into models of climate change resilience is essential for predicting how species will respond under climate change. We are making some headway, although more data are needed, especially from taxonomic groups outside of Drosophila, and across diverse geographical regions. Climate change responses are likely to be complex, and such complexity will be difficult to capture in laboratory experiments. Moving towards well designed field experiments would allow us to not only capture this complexity, but also study more diverse species.
Making predictions that capture how and which insect species will respond adaptively to climate change requires an understanding of which key traits and environmental drivers interact to shape fitness in a changing world.
We explore how stress resistance, fitness and phenology shape current distributions and future responses to climate, as well as the evidence for adaptive genetic and plastic responses in these traits.
Although there is evidence of range shifts and trait changes, few studies disentangle genetic and plastic responses. More data from taxonomically diverse groups, capturing field complexity are required.
Evolution in an acidifying ocean Sunday, Jennifer M.; Calosi, Piero; Dupont, Sam ...
Trends in ecology & evolution (Amsterdam),
02/2014, Letnik:
29, Številka:
2
Journal Article
Recenzirano
•We summarize tools for assessing evolutionary potential under ocean acidification.•We review studies of past adaptation, genetic variation, and experimental evolution.•We highlight progress and ...challenges and recommend future research directions.•Longer-term experiments that focus on fitness-related responses are recommended.
Ocean acidification poses a global threat to biodiversity, yet species might have the capacity to adapt through evolutionary change. Here we summarize tools available to determine species’ capacity for evolutionary adaptation to future ocean change and review the progress made to date with respect to ocean acidification. We focus on two key approaches: measuring standing genetic variation within populations and experimental evolution. We highlight benefits and challenges of each approach and recommend future research directions for understanding the modulating role of evolution in a changing ocean.
Abstract
Background and aims
Within-population genetic and phenotypic variation play a key role in the development of adaptive responses to environmental change. Between-population variation is also ...an essential element in assessing the evolutionary potential of species in response to changes in environmental conditions. In this context, common garden experiments are a useful tool to separate the genetic and environmental components of phenotypic variation. We aimed to assess within- and between-population phenotypic variation of Lupinus angustifolius L. in terms of its evolutionary potential to adapt to ongoing climate change.
Methods
We evaluated populations’ phenotypic variation of foliar, phenological and reproductive traits with a common garden experiment. Patterns of functional trait variation were assessed with (1) mixed model analyses and coefficients of variation (CVs) with confidence intervals, (2) principal component analyses (PCAs) and (3) correlations between pairs of traits. Analyses were performed at the population level (four populations) and at the latitude level (grouping pairs of populations located in two latitudinal ranges).
Key Results
Phenotypic variation had a significant genetic component associated with a latitudinal pattern. (1) Mixed models found lower specific leaf area, advanced flowering phenology and lower seed production of heavier seeds in southern populations, whereas CV analyses showed lower within-latitude variation especially in phenological and reproductive traits in southern populations. (2) PCAs showed a clearer differentiation of phenotypic variation between latitudes than between populations. (3) Correlation analyses showed a greater number of significant correlations between traits in southern populations (25 vs. 13).
Conclusions
Between-population phenotypic variation was determined by contrasting temperature and drought at different latitude and elevation. Southern populations had differential trait values compatible with adaptations to high temperatures and drought. Moreover, they had lower within-population variation and a greater number of trait correlations probably as a result of these limiting conditions, making them more vulnerable to climate change.
An increasing number of short‐term experimental studies show significant effects of projected ocean warming and ocean acidification on the performance on marine organisms. Yet, it remains unclear if ...we can reliably predict the impact of climate change on marine populations and ecosystems, because we lack sufficient understanding of the capacity for marine organisms to adapt to rapid climate change. In this review, we emphasise why an evolutionary perspective is crucial to understanding climate change impacts in the sea and examine the approaches that may be useful for addressing this challenge. We first consider what the geological record and present‐day analogues of future climate conditions can tell us about the potential for adaptation to climate change. We also examine evidence that phenotypic plasticity may assist marine species to persist in a rapidly changing climate. We then outline the various experimental approaches that can be used to estimate evolutionary potential, focusing on molecular tools, quantitative genetics, and experimental evolution, and we describe the benefits of combining different approaches to gain a deeper understanding of evolutionary potential. Our goal is to provide a platform for future research addressing the evolutionary potential for marine organisms to cope with climate change.
Although there are many examples of contemporary directional selection, evidence for responses to selection that match predictions are often missing in quantitative genetic studies of wild ...populations. This is despite the presence of genetic variation and selection pressures – theoretical prerequisites for the response to selection. This conundrum can be explained by statistical issues with accurate parameter estimation, and by biological mechanisms that interfere with the response to selection. These biological mechanisms can accelerate or constrain this response. These mechanisms are generally studied independently but might act simultaneously. We therefore integrated these mechanisms to explore their potential combined effect. This has implications for explaining the apparent evolutionary stasis of wild populations and the conservation of wildlife.
Recent discoveries at the intersection of quantitative genetics and evolutionary ecology are challenging our views on the potential of wild populations to respond to selection.
Multiple biological mechanisms can disconnect genetic variation from the response to selection in the wild. We highlight areas for future research.
We provide an integrative framework that can be used to qualitatively assess the combined influence of these mechanisms on the response to selection.
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