L3 local adaptation 3

Question 1

What is local adaptation?

Answer 1

The process by which populations evolve traits that increase fitness in their specific environmental conditions despite ongoing gene flow.

Question 2

Why was local adaptation historically thought to be limited in marine systems?

Answer 2

Because extensive gene flow in open water was assumed to homogenize populations and dilute local selective pressures.

Question 3

What recent findings challenge the traditional view of marine local adaptation?

Answer 3

Empirical studies show nuanced mechanisms—like limited dispersal and environmental heterogeneity—that allow selection to overcome gene flow.

Question 4

How can microbes mediate local adaptation?

Answer 4

Microbial interactions with hosts can influence selection pressures, linking host‐parasite dynamics to local evolutionary responses.

Question 5

Which broader evolutionary processes are linked to microbial mediation of local adaptation?

Answer 5

Host-parasite coevolution, the Red Queen hypothesis, the evolution of sex, and ecosystem-scale dynamics.

Question 6

What is the Red Queen hypothesis?

Answer 6

The idea that species must continuously evolve to maintain fitness relative to interacting species, such as parasites.

Question 7

What challenge does rapid environmental change pose for local adaptation?

Answer 7

Populations may lag behind shifting conditions (e.g., climate change), leading to maladaptation.

Question 8

How might understanding local adaptation trends help mitigate climate change effects?

Answer 8

By identifying mismatches between environmental shifts and species’ responses to guide conservation or management strategies.

Question 9

Which simple population-genetic models illustrate the tension between selection and gene flow?

Answer 9

The island model and the two-patch model.

Question 10

What is the conceptual expectation of gene flow in marine systems?

Answer 10

Long-distance dispersal that homogenizes genetic variation across populations.

Question 11

Give an example of a marine temperature gradient that drives local adaptation.

Answer 11

Off California’s coast, sea surface temperatures range from ~8 °C to ~24 °C, similar to temperature differences between Copenhagen and warmer regions.

Question 12

How do upwelling and topography contribute to local adaptation?

Answer 12

They create long-term stable environmental contrasts (e.g., nutrient and temperature gradients) that act as selective forces.

Question 13

Besides dispersal, what abiotic factors influence local adaptation?

Answer 13

Temperature stability, chemical concentrations, and other environmental heterogeneities.

Question 14

How does environmental heterogeneity interact with gene flow to enable local adaptation?

Answer 14

Small-scale abiotic differences can create strong localized selection that outpaces homogenizing gene flow.

Question 15

What range of dispersal distances has been measured in marine organisms?

Answer 15

From as little as ~2 m (e.g., some snails) up to 50–200 km in other species.

Question 16

How do limited dispersal distances affect the potential for local adaptation?

Answer 16

They reduce gene homogenization and allow populations to respond to local selective pressures.

Question 17

What are reciprocal transplant experiments?

Answer 17

Experiments that swap individuals between environments to test for genetic differences in fitness across sites.

Question 18

Name two experimental approaches used to study local adaptation.

Answer 18

Reciprocal transplant experiments and kamikaze experiments to assess dispersal and adaptive differentiation.

Question 19

What is balance polymorphism?

Answer 19

Genetic differentiation arising from repeated within-generation selection under low selection gradients and high dispersal.

Question 20

Why is within-generation selection sometimes debated as true adaptation?

Answer 20

Because it may be transient and not reliably transmitted to subsequent generations.

Question 21

What is microbially mediated local adaptation (MMLA)?

Answer 21

The process by which local microbial communities interact with host genotypes to modulate host fitness and drive adaptation.

Question 22

How does the revised model of local adaptation incorporate the microbiome?

Answer 22

It treats the microbiome as an additional source of fitness effects that interacts reciprocally with host genes under environmental pressures.

Question 23

What is microbial mediated adaptive plasticity (MMAP)?

Answer 23

When hosts gain enhanced performance by associating with their locally adapted microbial communities.

Question 24

What three factors are systematically varied in factorial designs testing MMLA?

Answer 24

Environment, host phenotype (genotype), and microbial community.

Question 25

What experimental result provides key evidence for microbial mediation?

Answer 25

Higher host fitness when paired with local microbes versus sterilized or non-local microbes, indicating a host × microbe × environment interaction.

Question 26

Describe the soil transplantation experiment setup.

Answer 26

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.

Question 27

What outcome in soil experiments highlights context-dependency?

Answer 27

Sometimes local seeds perform worse with native microbes, showing that microbial benefits vary by context.

Question 28

How do local microbial communities directly affect host fitness?

Answer 28

By supplying nutrients, producing growth‐modulating compounds, or protecting against pathogens in a site-specific manner.

Question 29

What are reciprocal interactions in MMLA studies?

Answer 29

Co‐adaptation where both host genotype and local microbiome jointly determine performance, beyond additive effects.

Question 30

How can microbial interactions facilitate ecological speciation?

Answer 30

Divergent microbiomes can create reproductive or fitness barriers between host populations in different environments.

Question 31

How does host‐parasite coevolution relate to MMLA?

Answer 31

Parasite pressure can drive local host adaptations and select for microbial defenses, creating multi‐tiered adaptation.

Question 32

Summarize the snail‐parasite case study.

Answer 32

Shoreline snails face high parasite infection and adapt by increasing sexual reproduction, whereas deep‐water snails have lower infection and reproduce asexually.

Question 33

Why do snails closer to shore show higher sexual reproduction?

Answer 33

High parasite loads favor meiotic recombination to generate rare genotypes that resist local parasites.

Question 34

How does the parasite’s life cycle influence snail adaptation?

Answer 34

It requires secondary hosts (ducks) present near shore; in deep water the parasite can’t complete its cycle, reducing selection on snails.

Question 35

What is the Red Queen hypothesis in the context of snail‐parasite dynamics?

Answer 35

Continuous host‐parasite coevolution drives cyclic adaptation, with parasites adapting to common snail genotypes and hosts evolving new defenses.

Question 36

What is an interaction plot and why is it useful in MMLA research?

Answer 36

A graph showing host fitness across combinations of host genotype, microbial presence, and environment to visualize three‐way interactions.

Question 37

What makes temporal dynamics important in local adaptation studies?

Answer 37

Past, present, and future host‐microbe‐parasite interactions shape adaptive trajectories and may influence the persistence of specific adaptations.

Question 38

Why are factorial experimental designs critical for understanding MMLA?

Answer 38

They isolate individual and interactive effects of hosts, microbes, and environment, revealing causal mechanisms behind adaptation.

Question 39

Why are Trinidadian guppies considered a natural laboratory for local adaptation?

Answer 39

Their streams are naturally divided by waterfalls into high- and low-predation zones, creating distinct selection regimes.

Question 40

How do downstream and upstream predation regimes differ for Trinidadian guppies?

Answer 40

Downstream pools have large predators (e.g., cichlids) preying on big guppies; upstream pools have small predators (e.g., killifish) targeting smaller guppies.

Question 41

What life-history trait changes occur when guppies are transplanted downstream?

Answer 41

They evolve smaller body size and faster reproduction rates in response to higher predation risk.

Question 42

How do guppy trait changes affect broader ecosystem dynamics?

Answer 42

Altered guppy diet and density shift algae and invertebrate populations, changing community biomass and species composition.

Question 43

What is local maladaptation?

Answer 43

When populations show lower fitness in their native environment than when transplanted elsewhere.

Question 44

How common is local maladaptation in experimental transplant studies?

Answer 44

About 79% of cases report locally adapted populations performing worse at home.

Question 45

What are potential explanations for local maladaptation?

Answer 45

Recent environmental shifts, non-genetic factors, or temporal changes in adaptive peaks.

Question 46

Why must we consider temporal fluctuations in local adaptation?

Answer 46

Adaptive optima can shift over time, so what was once advantageous may become maladaptive.

Question 47

How does climate change create environmental mismatches for populations?

Answer 47

Rapid shifts in temperature or precipitation can outpace a population’s evolutionary response.

Question 48

What short-term role can phenotypic plasticity play under climate change?

Answer 48

It buffers populations by allowing individuals to adjust traits without genetic change.

Question 49

What is a drawback of relying on plasticity for adaptation?

Answer 49

It can mask underlying genetic variation needed for long-term evolutionary responses.

Question 50

In the yellow warbler study, how was genomic local adaptation assessed?

Answer 50

By correlating pairwise genetic differentiation (F_ST) with geographic and multivariate environmental differences.

Question 51

What did forecasts to 2050 reveal in the yellow warbler study?

Answer 51

Regions under stronger predicted climate change show higher genomic vulnerability and correlated population declines.

Question 52

How did current population trends relate to predicted genomic vulnerability in warblers?

Answer 52

Declines were already occurring in areas with high forecasted genetic mismatch.

Question 53

How might microbial transplants mitigate climate impacts on long-lived species?

Answer 53

By inoculating hosts (e.g., trees) with locally adapted microbes to boost stress resilience.

Question 54

Why are microbial transplants especially useful for trees?

Answer 54

Trees have slow generation times and limited dispersal, so assisting them with beneficial microbes can speed adaptation.

Question 55

What does ecological and evolutionary integration entail in local adaptation studies?

Answer 55

Linking organismal adaptations to community/ecosystem effects and speciation processes to capture full adaptive complexity.