Ecological Phenotypic Plasticity Quiz

Key Questions on the Role of Phenotypic Plasticity in Eco-Evolutionary Dynamics

• Phenotypic plasticity is the ability of an organism to change its phenotype in response to environmental changes, which can be influenced by genetics, phenotypic plasticity, or both
• Plasticity can be adaptive, maladaptive, or neutral. Costs and limits of plasticity vary considerably, often being weak and difficult to detect.
• Variable environments often favor the evolution of increased plasticity, which in turn can buffer fitness and support colonization of new habitats.
• Phenotypic plasticity can sometimes aid or hinder ecological speciation, though more empirical studies are needed.

How to Infer Plasticity

• Common approach involves experimental manipulations under controlled conditions, measuring the reaction norm (relationship between genotype and phenotype in different environments).
• In species lacking inbred lines or clones, plasticity is estimated using related individuals (e.g., siblings) randomly sampled from different groups.
• Different groups can display similar or different reaction norms, reflecting either inherent genetic differences or plasticity in response to environmental factors.

Evidence From Nature

• Plasticity can be adaptive, maladaptive, or neutral, often posing a more nuanced question about the conditions promoting this most adaptive plasticity.
• Whether plasticity has inherent costs or limits is often debated; results from meta-analyses reveal weak and variable costs.
• Specific environmental (spatial variation, dispersal, etc.) and organismal (plasticity costs/limits, etc.) characteristics can impact the evolution of plasticity.

To What Extent Does Plasticity Aid Colonization and Responses to Environmental Change?

• Phenotypic rescue, achieved through plasticity or genetic change, can help organisms persist and colonize new environments during environmental stressors.
• The Baldwin Effect highlights how adaptive plasticity can direct subsequent genetic change in a similar direction, a phenomenon also known as genetic assimilation
• Empirical evidence for plasticity’s importance in responding to environmental change is seen in some species exhibiting phenological shifts (e.g., breeding times) in response to climate warming.
• Plasticity may sometimes be key for colonization and responses to environmental change, but may not always be necessary.

Does Plasticity Promote or Constrain Genetic Evolution?

• Plasticity can potentially shield genotypes from selection, potentially slowing adaptive genetic change.
• Conversely, plasticity can facilitate colonization/persistence in extreme environments, potentially increasing selection on other traits or exposing cryptic genetic variation.
• Plasticity may influence genetic architecture so as to increase the production of adaptive phenotypes.
• Counter-gradient variation, wherein genetic and plastic effects have opposing directions, implies that maladaptive plasticity can promote compensatory genetic change.

Does Plasticity Help or Hinder Ecological Speciation?

• Plasticity can potentially promote speciation when similar in direction to genetic differences between species.
• Polyphenism (generating different phenotypes in response to different environments) can facilitate character displacement and sharpen reproductive barriers.
• Species that form more species may also show greater plasticity. However, plasticity can also potentially constrain speciation by shielding genotypes.
• Imprinting on parents, conspecifics, environments, or resources can lead to assortative mating, thereby generating reproductive isolation, influenced, in part, by plasticity.

How Fast Does Plasticity Evolve?

• Reaction norms can evolve over decades, exemplified by studies on Daphnia phototaxis in response to changing predation pressures.
• Some species (e.g., Polygonum cespitosum, Hemigrapsus sanguineus) show evolved plasticity related to changing habitats, confirming the potential for rapid plasticity evolution.
• Meta-analyses are crucial for establishing broader evolutionary plasticity rates.

How Might Plasticity Have Community/Ecosystem Effects?

• Plasticity in organismal traits (e.g., foraging in fishes, biological stoichiometry in animals and plants) can influence community and ecosystem dynamics.
• Plastic changes often have cascading effects on other communities and ecosystems, as seen in shifts of foraging traits or phenology.
• Formal studies linking plasticity to community/ecosystem dynamics are currently rare, but this area warrants further investigation.