Eco-Evolutionary Dynamics and Rapid Evolution

Eco-Evolutionary Dynamics

  • Eco-evolutionary dynamics involve the feedback between evolution and ecology.

  • A study in British Columbia with three-spine sticklebacks demonstrated how recently diverged eco-morphs in freshwater lakes (benthic and limnetic/pelagic forms) stemming from a generalist marine ancestor can shape prey communities, primary production, and water spectral qualities.

  • The experiment used common garden setups with cattle tanks, comparing different treatments of eco-morphs (combined or individual) against the ancestral form.

  • Observed changes in ecosystem properties (e.g., dissolved oxygen, dissolved organic carbon) can further influence the evolution of these species.

Rapid Evolution

  • To observe eco-evolutionary dynamics, evolution needs to occur on timescales congruent with ecological processes.

  • Conditions for rapid evolution:

    • Colonization of new habitats leading to rapid adaptation by founder populations.

    • Local adaptations to heterogeneity within meta-populations, such as pesticide resistance due to human influences or melanistic moths adapting to industrial pollution.

  • Example: Melanistic moths became dominant during industrial pollution due to strong selection pressure, shifting back to white morphs as pollution attenuated.

Niche Construction

  • Organisms actively shape their environment, influencing their own niches, establishing a dialectical relationship.

  • Beavers are examples of organisms that strongly interact with their environment by creating new habitats.

  • Niche construction contrasts with the adaptationist view by highlighting organisms as active participants rather than passive recipients of environmental conditions.

  • Hutchinson's eco-evolutionary play analogy depicts ecology and evolution interacting in concert.

Cyclical Interaction

  • Evolution affects ecology and vice versa, creating a feedback loop.

  • Changes in ecological interactions drive evolutionary change in organismal traits, which in turn affect the form of ecological interactions.

  • Darwin's finches in the Galapagos exhibit adaptations to food resources, potentially changing plant distribution and affecting their own traits' evolution.

Requirements for Eco-Evolutionary Feedbacks

  • Strong effect of phenotype: Organisms strongly interact with and structure the environment (strong interactor).

  • Environmental selection: Changes in the environment affect the fitness landscape, leading to directional or disruptive selection.

  • Genetic diversity: Sufficient standing genetic diversity or capacity allows populations to evolve in response to environmental changes.

  • Measurable variations: Genetic and phenotypic variations need to be observable at the population level, using modern molecular tools like genomic sequencing.

  • Congruent time scales: Ecological and evolutionary responses must occur on similar time scales, necessitating rapid evolution.

Empirical Examples of Eco-Evolutionary Dynamics

  • Lab experiments using chemostats to study algal-rotifer interactions.

  • Alawi (North American diadromous fish) interactions with zooplankton prey.

  • Guppy evolution influenced by sexual selection and predation.

  • Darwin's finches on the Galapagos and tree examples from North America.

Chemostat Experiments: Algae and Rotifers

  • Chemostats provide highly controlled environments to study consumer-resource dynamics.

  • Chlorella (algae) serves as a resource for rotifers (small aquatic animals).

  • Experiments compare consumer-resource dynamics with diverse multiple algal clone treatments versus single-clone cultures.

  • Multiple clones: higher likelihood of evolution

  • Single clone: lower level of evolution.

  • With diverse algal clone you potentially see selection occurring: some morphs/clones become more prominent when they face the strong selection pressure by the rotifer (consumer).

  • The existence of a single clone results in limited scope of evolution.

  • Chemostats enable observation of processes over multiple generations under constant environmental conditions to study evolutionary and ecological dynamics.

  • Chemostat setup: Beaker is sealed, stirrer, constant temperature, nutrients going in, oxygenation, metabolic wastes are removed.

Results

  • Single clone treatment: Strong cycling between the rotifers and their consumers. Predator-prey cycling. High frequency cycling.

  • Multiple algal clone treatment: The dynamics are totally different. Longer cycle period. Rotifers prey on certain clones selectively/ on the more palatable clones. As a result, the clones that aren't hunted so much become more prominent.

  • Conclusion: predator prey cycling is delayed.

  • Strong selection pressure is present. Those cause directional selection pressure within the consumer population.

  • The ecological properties of the system + predator prey cycling are being altered.

  • Those researches used mathematical formula, which helped them predict different possible scenarios. They were able to make a mechanistic model in order to showcase what may be expected.

  • Trade off between competitive ability VS defense against consumption.

  • Single clone morphs: Lower competitive abilities, better defense against consumption.

  • Multiple clones assemblages: There are populations that are superior when it comes to competitive abilities. But they're also able to better defend themselves from the consumption. This makes the cycle phase of consumer resources' interactions being shifted.

Cycling Periods

  • Single clone algal cultures (lacking genetic variability)

    • Short cycle periods

    • Quarter period phase lags

  • Multiple clone assemblages (genetically variable)

    • Long cycles

    • Predator prey densities are almost out of phase

Interesting conclusion: the stabilizing effects of diversity

  • The presence of evolution changes the predator prey dynamics.

  • Long term data from lakes showcases stochastic numbers on phytoplankton species. This may happen due to rapid evolution. If we ignore evolution, we're missing an essential aspect of the system, which is needed to explain the dynamics.

  • Important conclusion: Anti predator defenses have an effect on the growth rates and the densities of rotifers.

  • Gene frequencies are impacted as well.

Requirements for, Eco Evolutionary Dynamics

  • Strong interactor. The rotifer is able to influence the algae numbers.

  • The algae cells are responsive and they're changing as a response to the consumption.

  • There are measurable effects, that can be seen through the growth rates and the presence of different algal clones.

  • The dynamics grant with those ecological interactions.

Alawi and Zooplankton Prey

  • Alawi: North American fish (shad; similar to herring)

  • Anadromous: These fish need to go to the coast in order to complete their life cycle.

  • Anadermy: spawn in freshwater -> juvenile moves to the coast -> adulthood stage takes place -> adult returns from the ocean to complete the lifestyle.

  • Some populations are landlocked, meaning that they complete the lifestyle without going to the ocean.

  • It has a top down effect on prey, making it a strong interactor.

    • They consume zooplankton, which means the algae are being released from the consumption of the consumers.

Complex cycle

  • The migration behavior impacts the interaction between the alawi and the zooplankton.

  • Landlocked: They are stuck there. That means their interaction with the environment are different.

  • The black color shows the landlocked populations

  • There are functional trait differences, which showcase phenotypic variation between anadromous and landlocked.

Traits

  • Gait width: the dimension of the mouth opening. This influences the size of prey, which can be consumed.

  • The spacing of the gill raker is shorter. These instruments' purpose is to help the fish filter zooplankton.

  • Fish size difference: Landlocked fish force the zooplankton prey to be smaller. The population gets this trait because it needs to rely on hunting smaller prey.

  • Anadromous population is capable of getting wider spacing and the large bodied zooplankton prey is allowed to recover. Fish have a really strong top town effect on the zooplankton community.

  • The morphology divergence and the prey selection between the anadromous population compared to the landlocked population shapes the ecological role of fish in the lakes.

  • Lake's ecosystem properties are changed. Phytoplankton communities are altered, which has consequences on color/spectral qualities.

Guppies

  • These fish became an extremely useful model system to observe evolutionary change, that happen in population.

  • Guppies showcase that their evolution is not a slow process.

  • There may be errors and large scale issues by inferring and observing the rate of evolutionary change from recorded fossils.

  • Sexual selection and predation have an effect on guppy community: cryptic morphs can happen, which makes these morphs less likely to be hunted.

  • Populations can cycle rapidly. Approach in order to get multiple generations through the experimental phase in a short period of time.

  • Guppies can respond rapidly to the environmental selective pressures/ predatory fish.

Pike cichlid impact

  • This larger predatory fish poses strong selective pressure.

  • The predation causes the life history traits to diverge with significant differences.

  • The sites with lack of predators have a larger density compared to the sites with creditors.

  • Densities change the amount the fish interact with the environment.

  • When we have a high density setting with lacks of predators, the resource availability is altered which has consequences. When we encounter high densities, competition is more intense. Body sizes are also affected.

Question

  • Do the environments get affected in similar way when we have different populations of guppies under equal biomass?

  • High predation populations are comprised of smaller sized individuals. That means there are higher nutrient rates because there are higher metabolic demands. They consume more.

  • Low predation populations are comprised of larger individuals, which means their the opposite.

  • Nutrient fluxes were tested, this influenced the primary production and also ecosystem properties.

  • The nitrogen and phosphorus levels are impacted as a result of the difference of body size.

  • High predation population interacts strongly with their environment, because they excrete more nutrients. There is a change to the feeding. They consume greater quantities of algae and only a little invertabrates. Low predation guppies tend do act vice versa.

Other consequences

  • Competiton is being induced within the community.

  • Biomass of algae becomes higher which may change the populations' evolution in the future.

  • Consumption of algae can increase the quantities of specific pigment, which are required to produce the colorful traits for intersexual selection.

  • Trade off might exist. More research could be conducted to find a more significant conclusion.

  • At different levels of organization, there exist biotic factors produced by predators, which influence the evolution of a population.
    *Biotic factor, environment, predators are the drivers for evolutionary change.

Darwin's Finches

  • There are several types of finches, that showcase strong differences of phenotypic traits like size of the bill. These distinct traits determine what traits they can feed upon.

  • Seeds are limited and finches deplete the seed they favor. There is selective pressure to consume the seeds that are harder, bigger and tougher.

  • There is a feedback that influences the environment, due to the fact that finches tend to consume certain seeds first, reducing the viability of the plants, which are now less likely to reproduce.

  • During the heavy rainfall seasons, this mechanism stops affecting finches, which means climate is essential and a driver of this dynamic. Sometimes this is more apparent and sometimes less strong.

  • The point is that rainfall can drive evolution directly, by mediating the capacity of these fish in order to construct their niche.

Crossbill

  • Bird species from North America.

  • Uses its bill in order to exploit pine seeds and get access to the seeds.

  • Availability of seed most likely drove its evolution.

Poplars

  • Deciduous tree.

  • These trees have a strong with the environment due to 3 factors:

    • Creating shade

    • Decomposing leaves

    • During the winter, these leaves fall

  • High concentrations of leaf tannins impact the soil processes.

  • Tanins impact toxicity of organisms and affects soil functions.

  • A feedback in the system would alter availability of nutrient quantities within the soil.

  • A compensatory mechanism occurs where the trees produce find and deeper roots in order to acquire as much nutrients as possible.

  • Eco evolutionary feedbacks exists. This driving influences the soil process and affects the amount of nutrients the plants get.