BIOL 105: Lecture 13 Species Interactions

Vocabulary flashcards on species interactions and coevolution based on lecture notes.

Coevolution

Reciprocal genetic change in interacting species; evolution in one species causes adaptive change in another and vice versa.

• can occur in any intimate species interactions

Resources

Species that are eaten or used for habitat by a focal species.

Competitors

Species competing for food, space, or habitat with a focal species.

Enemies

Predators, parasites, etc. that interact with a focal species.

Mutualists

Species that provide fitness benefits to a focal species.

Symbioses

Intimate species interactions.

Buchnera

Bacterial symbionts in aphids, providing the insect with the amino acid Tryptophan.

Vertical Transmission

When mother aphids pass on their Buchnera symbionts to their offspring.

Mimicry

Close resemblance of an organism to a different organism, benefiting from the mistaken identity.

Batesian Mimicry

An unprotected species evolves to look like a protected species.

Müllerian Mimicry

A chemically protected species evolves to look like another protected species.

Red Queen Hypothesis

Predicts that species are constantly being reshaped by interactions with other species.

• Each species has to run (i.e., evolve) as fast as possible just to stay in the same place (survive) because interacting species also continue to evolve

Virulence

Reduction in the survival and reproduction of hosts by a pathogen.

• How much fitness cost in a parasite imposing on the species it is protecting

• Virulence, infectiousness, and host resistance are traits that evolve just like other phenotypes

Mutualisms

Interactions between species that benefit individuals of both species.

Ecological Character Displacement

Divergence in response to competition between species.

What did the observation of Angraecum sesquipedale by Darwin indicate?

He predicted the presence of a pollinator with an extremely long proboscis

• the long-tonged Sphinx Moth was later discovered

• An example of mutualism

Concordant

phylogenies ‘match’ reflecting divergence/speciation events that are shared between the coevolving partners.

What characteristic do the Aphid and Buchner phylogenies reflect?

Phylogenies are concordant

• Aphids have a bacteria symbiont Buchner that provides the insect with amino acid Tryptophan

• They have evolved together

Interactions between enemies and victims?

predators and prey, parasites and hosts, and herbivores and host plants

Stability of enemies and victims interactions

Interactions are often unstable

• enemies can cause extinction of each other’s populations

Arm’s race

each species adapts in response to the other and leads to

extreme traits

• Predators, parasites, and herbivores evolve extraordinary adaptations to capture prey, infect hosts, and consume plants

• Prey, hosts, and plants have elaborate counteradaptations.

net-casting spider adaptation

holds an expandable web that it uses to quickly envelope slowly flying insects that pass by

extraordinary adaptation of parasitic trematode

migrates to the eyestalk of its host, a land snail, and turns it a bright color to make the snail more visible to the next host in the parasite’s life cycle, a snail-eating bird such as a thrush

Katydids adaptations

have an extraordinary resemblance to leaves, including what looks like leaf venation and damage by herbivores

Arm’s race between Newts and snakes?

The rough-skinned newts are highly often toxic to protect from predation by the garter snake

• garter snake exhibits resistance to TTX toxicity that varies to near zero to extreme high resistance

  • highly toxic newt populations are often paired with highly resistant garter snakes

  • trait matching

  • pattern supports the hypothesis that newt and snake traits are evolving reciprocally

  • not always perfectly matched

Trait matching in cuckoo eggs

• Brood parasites (cuckoos) lay their eggs in the nests of other birds

• Some host species can recognize and reject the parasitic eggs

• cuckoos have evolved to match their host eggs

Brooke & Davies experiments (1988)

traced the fate of artificial cuckoo eggs placed in the nests of
different bird species.

• Host species that are never
  parasitized do not reject
  experimentally placed eggs.

• Host populations with a history of
  parasitism have evolved different mechanisms to reject experimentally placed eggs: pushing
  them out of the nest, abandoning
  the nest, or building over them

Cuckoo mimicry and host discrimination have each

coevolved with each other

Decaestecker ‘resurrection study’

pulling Daphnia and Pasteuria (bacteria) parasites from different sediment layers & tested hosts and parasites against each other

• Hypothesis: Pasteuria evolve to optimize infectivity on Daphnia and parasites evolve to increase virulence over time

Graph shows that hosts were more frequently infected by contemporary than by past or future bacteria, indicating that hosts and bacteria were evolving in concert

• satisfies coevolution that there is a temporal match between parasite and host

Looked at the fitness of parasite and host and noticed that the average virulence of the parasite increased over time

reciprocal exploitation

each species obtains something from the other

• mutualisms between species do not show altruism, but these characters

• not always stable over evolutionary time: many species cheat

Leads to coevolution

Why did the orchid’s nectar tube and the moth’s proboscis become so long?

Natural selection favors:

• Insects with a proboscis long enough to reach the nectar

• Flowers with spur lengths that force insects to press their head deep into flowers and pick up and deposit pollen

Outcomes of interspecific competition

• One species is driven to extinction.

• Competition imposes selection on one or both species leading to divergence in resource use