L3 local adaptation 3 Flashcards
What is local adaptation?
The process by which populations evolve traits that increase fitness in their specific environmental conditions despite ongoing gene flow.
Why was local adaptation historically thought to be limited in marine systems?
Because extensive gene flow in open water was assumed to homogenize populations and dilute local selective pressures.
What recent findings challenge the traditional view of marine local adaptation?
Empirical studies show nuanced mechanisms—like limited dispersal and environmental heterogeneity—that allow selection to overcome gene flow.
How can microbes mediate local adaptation?
Microbial interactions with hosts can influence selection pressures, linking host‐parasite dynamics to local evolutionary responses.
Which broader evolutionary processes are linked to microbial mediation of local adaptation?
Host-parasite coevolution, the Red Queen hypothesis, the evolution of sex, and ecosystem-scale dynamics.
What is the Red Queen hypothesis?
The idea that species must continuously evolve to maintain fitness relative to interacting species, such as parasites.
What challenge does rapid environmental change pose for local adaptation?
Populations may lag behind shifting conditions (e.g., climate change), leading to maladaptation.
How might understanding local adaptation trends help mitigate climate change effects?
By identifying mismatches between environmental shifts and species’ responses to guide conservation or management strategies.
Which simple population-genetic models illustrate the tension between selection and gene flow?
The island model and the two-patch model.
What is the conceptual expectation of gene flow in marine systems?
Long-distance dispersal that homogenizes genetic variation across populations.
Give an example of a marine temperature gradient that drives local adaptation.
Off California’s coast, sea surface temperatures range from ~8 °C to ~24 °C, similar to temperature differences between Copenhagen and warmer regions.
How do upwelling and topography contribute to local adaptation?
They create long-term stable environmental contrasts (e.g., nutrient and temperature gradients) that act as selective forces.
Besides dispersal, what abiotic factors influence local adaptation?
Temperature stability, chemical concentrations, and other environmental heterogeneities.
How does environmental heterogeneity interact with gene flow to enable local adaptation?
Small-scale abiotic differences can create strong localized selection that outpaces homogenizing gene flow.
What range of dispersal distances has been measured in marine organisms?
From as little as ~2 m (e.g., some snails) up to 50–200 km in other species.
How do limited dispersal distances affect the potential for local adaptation?
They reduce gene homogenization and allow populations to respond to local selective pressures.
What are reciprocal transplant experiments?
Experiments that swap individuals between environments to test for genetic differences in fitness across sites.
Name two experimental approaches used to study local adaptation.
Reciprocal transplant experiments and kamikaze experiments to assess dispersal and adaptive differentiation.
What is balance polymorphism?
Genetic differentiation arising from repeated within-generation selection under low selection gradients and high dispersal.
Why is within-generation selection sometimes debated as true adaptation?
Because it may be transient and not reliably transmitted to subsequent generations.
What is microbially mediated local adaptation (MMLA)?
The process by which local microbial communities interact with host genotypes to modulate host fitness and drive adaptation.
How does the revised model of local adaptation incorporate the microbiome?
It treats the microbiome as an additional source of fitness effects that interacts reciprocally with host genes under environmental pressures.
What is microbial mediated adaptive plasticity (MMAP)?
When hosts gain enhanced performance by associating with their locally adapted microbial communities.
What three factors are systematically varied in factorial designs testing MMLA?
Environment, host phenotype (genotype), and microbial community.
What experimental result provides key evidence for microbial mediation?
Higher host fitness when paired with local microbes versus sterilized or non-local microbes, indicating a host × microbe × environment interaction.
Describe the soil transplantation experiment setup.
Soil and seeds from two habitats are planted in plots with either native microbes intact or sterilized; cross‐transplants test local versus non‐local microbe effects.
What outcome in soil experiments highlights context-dependency?
Sometimes local seeds perform worse with native microbes, showing that microbial benefits vary by context.
How do local microbial communities directly affect host fitness?
By supplying nutrients, producing growth‐modulating compounds, or protecting against pathogens in a site-specific manner.
What are reciprocal interactions in MMLA studies?
Co‐adaptation where both host genotype and local microbiome jointly determine performance, beyond additive effects.
How can microbial interactions facilitate ecological speciation?
Divergent microbiomes can create reproductive or fitness barriers between host populations in different environments.
How does host‐parasite coevolution relate to MMLA?
Parasite pressure can drive local host adaptations and select for microbial defenses, creating multi‐tiered adaptation.
Summarize the snail‐parasite case study.
Shoreline snails face high parasite infection and adapt by increasing sexual reproduction, whereas deep‐water snails have lower infection and reproduce asexually.
Why do snails closer to shore show higher sexual reproduction?
High parasite loads favor meiotic recombination to generate rare genotypes that resist local parasites.
How does the parasite’s life cycle influence snail adaptation?
It requires secondary hosts (ducks) present near shore; in deep water the parasite can’t complete its cycle, reducing selection on snails.
What is the Red Queen hypothesis in the context of snail‐parasite dynamics?
Continuous host‐parasite coevolution drives cyclic adaptation, with parasites adapting to common snail genotypes and hosts evolving new defenses.
What is an interaction plot and why is it useful in MMLA research?
A graph showing host fitness across combinations of host genotype, microbial presence, and environment to visualize three‐way interactions.
What makes temporal dynamics important in local adaptation studies?
Past, present, and future host‐microbe‐parasite interactions shape adaptive trajectories and may influence the persistence of specific adaptations.
Why are factorial experimental designs critical for understanding MMLA?
They isolate individual and interactive effects of hosts, microbes, and environment, revealing causal mechanisms behind adaptation.
Why are Trinidadian guppies considered a natural laboratory for local adaptation?
Their streams are naturally divided by waterfalls into high- and low-predation zones, creating distinct selection regimes.
How do downstream and upstream predation regimes differ for Trinidadian guppies?
Downstream pools have large predators (e.g., cichlids) preying on big guppies; upstream pools have small predators (e.g., killifish) targeting smaller guppies.
What life-history trait changes occur when guppies are transplanted downstream?
They evolve smaller body size and faster reproduction rates in response to higher predation risk.
How do guppy trait changes affect broader ecosystem dynamics?
Altered guppy diet and density shift algae and invertebrate populations, changing community biomass and species composition.
What is local maladaptation?
When populations show lower fitness in their native environment than when transplanted elsewhere.
How common is local maladaptation in experimental transplant studies?
About 79% of cases report locally adapted populations performing worse at home.
What are potential explanations for local maladaptation?
Recent environmental shifts, non-genetic factors, or temporal changes in adaptive peaks.
Why must we consider temporal fluctuations in local adaptation?
Adaptive optima can shift over time, so what was once advantageous may become maladaptive.
How does climate change create environmental mismatches for populations?
Rapid shifts in temperature or precipitation can outpace a population’s evolutionary response.
What short-term role can phenotypic plasticity play under climate change?
It buffers populations by allowing individuals to adjust traits without genetic change.
What is a drawback of relying on plasticity for adaptation?
It can mask underlying genetic variation needed for long-term evolutionary responses.
In the yellow warbler study, how was genomic local adaptation assessed?
By correlating pairwise genetic differentiation (F_ST) with geographic and multivariate environmental differences.
What did forecasts to 2050 reveal in the yellow warbler study?
Regions under stronger predicted climate change show higher genomic vulnerability and correlated population declines.
How did current population trends relate to predicted genomic vulnerability in warblers?
Declines were already occurring in areas with high forecasted genetic mismatch.
How might microbial transplants mitigate climate impacts on long-lived species?
By inoculating hosts (e.g., trees) with locally adapted microbes to boost stress resilience.
Why are microbial transplants especially useful for trees?
Trees have slow generation times and limited dispersal, so assisting them with beneficial microbes can speed adaptation.
What does ecological and evolutionary integration entail in local adaptation studies?
Linking organismal adaptations to community/ecosystem effects and speciation processes to capture full adaptive complexity.
