Evolutionary Ecology and Macroevolution

exam 3

speciation

• can only happen with a barrier to gene flow

• populations become evolutionary independent, eventually diverging and reproductively incomplete

evolutionary ecology

• a field within both ecology and evolution that examines how interactions between and within species evolve, and the interactions between species and
  their environment

• It explicitly considers the evolutionary effects of competitors, mutualists, predators, prey, and pathogens

Can we see “trends” in evolution

• If resources are limited, then competition is inevitable

• Species Interactions are everywhere in nature and human health

All species face

• predators

• competition

• limited resources

Thomas Malthus

• One of the first to think about the human demography (study of population structure)

• Used mathematics to describe population dynamics

• Realized the remarkable numerical power of unchecked population growth

• Viewed this intrinsic property of populations a source of great human suffering
  

No evolutionary trend

• body size is as likely to increase as to decrease

Passive trend

• no directional tendency to change, but the precursor starts at a minimum size beyond which evolution cannot take subsequent lineages

Active trend

• each lineage tend to increase in a body size

What are the mechanisms behind an active evolutionary trend?

scenario 1:

• A trait gives lineages/species a HIGHER chance of speciation

• All species have the same change of extinction

scenario 2:

• A trait gives lineages/species a LOWER chance of extinction

• All species have the same change of speciation

ex: limb complexity trend in crustaceans

Fitness filters

• environment

  • ex: excess O₂

• resources

  • lush vegetation

• competition

  • reduce fitness

  • Species with less competition will have higher fitness

• predation

  • Limiting similarity

• disease

Species interations

• pathogen virulence, behavioral manipulation by parasites, genetic variation in immune system genes, insect vectors of plant pathogens, farming, fishing...

Evolution of ecological niches

• A single plant species can be a resource that is partitioned by multiple species, some closely related

• will aim to minimize species trait
  overlap (similarity) and thus, to maximize phenotypical differences
  between coexisting species

• expected to create specialization (narrower)

Limiting similarity

• is expected to be stronger at
  the tips of a phylogenies (Or in cases of convergent evolution)

• at larger phylogenetic scales, these effects level off

• Species have diverge and
  do not overlap ecologically
  or have moved to a new location

• Thus, competition takes a secondary role

• Predation and environmental adaptation become key players

Niche partitioning (adaptive zones)

• A way to reduce competition and other negative species interactions

• will maximize differences between species

The specialization paradox

• the conflict between organisms evolving to fit specific niches (specialists) and the need to adapt to changing environments

• questioning how extreme specialization doesn't always lead to extinction

• not all groups of organisms are equally diverse (species rich)

Why are not all species specialized?

• can range from diffuse to
  specialized one-to-one relationships

ex: Diffuse pollinator network in urban ecosystems in England

Why are so many herbivores generalist if they have so much competition?

• because plants and predators are also evolving

ex: protium (tree) and Leafhoppers

Green World Hypothesis

• aka why is the world green

• Predators and plants are such a strong selective force on herbivores that keep herbivores populations at bay

• in turn, reduces the role of competition in herbivore evolution...

ex: Forest tent caterpillar

Why animals and insects do not eat ALL plants?

• due to a long-standing evolutionary battle where plants developed a wide array of physical and chemical defenses to protect themselves from being eaten

ex: insects and other herbivores adapt to these defense

what can a plant do if it gets attacked?

• physical defenses (like thorns and waxy coatings), chemical defenses (producing toxins or deterrents), and cellular responses that activate its immune system, reprogram cells to fight invaders, or even signal to nearby plants through root networks

Evolutionary arms race

• Coevolving species have to constantly “improve” to meet each new adaptation with a “better” adaptation of their own

Escalation

• Co-adaptations become increasingly powerful

Red Queen Hypothesis

• species must constantly evolve ("run") simply to maintain their fitness in a changing environment, as other species are also evolving

co-speciation

• The relationship is so close that when two populations of the first species break gene flow...

• the populations of the interacting species also break gene flow

• is not a _____ when the two phylogenies do not match, indicating that the two species' evolutionary paths have not been tightly linked over time

ex: plants and butterflies

ant, fungal cultures, and pathogens

Mutualistic Relationship

• partnerships where different species cooperate, and both benefit through a process of co-evolution

ex: figs and wasps