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The Ecology of Adaptive Radiation. QUICK. Think of the First Adaptive Radiation That Comes to Mind. Hawaiian Silverswords. Malagasy Vangids. Andean Espeletia. Ecological Opportunity.

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quick
QUICK

Think of the First Adaptive Radiation That Comes to Mind

slide6

Malagasy

Vangids

slide7

Andean

Espeletia

ecological opportunity
Ecological Opportunity

“loosely defined as a wealth of evolutionarily accessible resources little used by competing taxa” (Schluter 2000, p.69).

ecological opportunity1
Ecological Opportunity
  • Does it promote AR?
  • If so, how?
  • Is it required for AR?
  • Is it an operationally useful concept, or just a useful heuristic?
slide11

“Evolutionary divergence of members of a single phylogenetic lineageinto a variety of different adaptive forms.” Futuyma, Evolutionary Biology, 1998

Adaptive Radiation

ar definitional issues
AR Definitional Issues
  • Is pace of diversification part of the definition? In particular, does it have to be explosive?
  • How are ARs distinguished from non-ARs?
ar definitional issues1
AR Definitional Issues
  • Is pace of diversification part of the definition? In particular, does it have to be explosive?
  • How are ARs distinguished from non-ARs?
  • Does it make sense to categorize a continuously distributed characteristic?
ar definitional issues2
AR Definitional Issues
  • Is pace of diversification part of the definition? In particular, does it have to be explosive?
  • How are ARs distinguished from non-ARs?
  • Does it make sense to categorize a continuously distributed characteristic?
  • Is the number of species the appropriate metric?
slide18

AR

Non-Adaptive

Non-Radiation

Non-Adaptive

Radiation

what prompts ar
What Prompts AR?
  • Classic idea (Simpson, Major Features of Evolution, 1954)—AR requires:
  • Geographical Access
  • colonization
  • Physical Access
  • mass extinction, appearance of new resource
  • Evolutionary Access
  • key innovation
slide20
“The evolution of a trait that allows a species to interact with the environment in an entirely new way”

Key Innovation

slide21
“The evolution of a trait that allows a species to interact with the environment in an entirely new way”

Key Innovation

Note:

1. KI does not necessarily cause AR

slide22
“The evolution of a trait that allows a species to interact with the environment in an entirely new way”

Key Innovation

Note:

1. KI does not necessarily cause AR

2. KI refers to ecological diversity, not number of species

slide23

What Is the Evidence that Ecological Opportunity Prompts AR?

  • Biogeography: AR on islands
  • Paleontology: AR after mass extinction
  • Evolution: AR associated with KI
  • Phylogeny: Decline in diversification as radiation progresses
slide25

What is the Evidence that Ecological Opportunity Prompts AR?

  • Biogeography: AR on islands
  • Paleontology: AR after mass extinction
  • Evolution: AR associated with KI
  • Phylogeny: Decline in diversification as radiation progresses
  • Experimental evolution in lab
ecological opportunity2
Ecological Opportunity
  • Does it promote AR?
  • If so, how?
  • Is it required for AR?
  • Is it an operational useful concept, or just a useful heuristic?
adaptive radiation requires
Adaptive Radiation Requires:
  • Adaptive Diversification
  • Speciation
two questions
Two Questions:
  • Is interspecific competition the only ecological interaction that can lead to AR?
  • Is speciation+diversification a one-step process or a two-step process?
two questions1
Two Questions:
  • Is interspecific competition the only ecological interaction that can lead to AR?
  • Is speciation+diversification a one-step process or a two-step process?
slide36

Speciation

Adaptive

Differentiation

2 Steps

slide37

Speciation +

Adaptive

Differentiation

1 Step

ecological speciation
Ecological Speciation

Andrew P. Hendry. 2009. Ecological speciation! Or the lack thereof? Canadian Journal of Fisheries and Aquatic Sciences 66: 1383-1398.

two flavors of ecological speciation
Two Flavors of Ecological Speciation
  • Strong—in the presence of gene flow (sympatric/parapatric speciation)
  • Weak—divergence driven by natural selection regardless of geographic context
slide40

Strong Flavor:

Speciation in presence of gene flow

Speciation +

Adaptive

Differentiation

1 Step

slide41

Speciation in allopatry

Adaptive

Differentiation

  • 2-Step Models:
  • Does adaptive differentiation occur in allopatry or sympatry?
slide43

Nat Sel may be involved in speciation (weak ES);

Competition not important

Nat selnot part of speciation

slide44

Character Displacement

Assumption: Body size correlates with resource use

slide45

Nat Selpart of speciation;

Competition not important

Nat selnot part of speciation

slide46

Nat Selpart of speciation;

Competition not important

Nat selnot part of speciation

two questions2
Two Questions?
  • Is interspecific competition the only ecological interaction that can lead to AR?
  • Is speciation-diversification a one-step process or a two-step process?
other processes that could promote ar
Other Processes That Could Promote AR
  • Apparent competition/Competition for predator-free space (predation)
apparent competition
Apparent Competition
  • In Habitat A, Predator 1 preys on Prey 1
  • More Prey 1  more Predator 1
  • Predator 1 also opportunistically eats Prey 2
  • More Predator 1  fewer Prey 2
  • Hence, more Prey 1  fewer Prey 2
  • “Apparent” competition
  • Promotes habitat divergence by Prey 2 to escape Prey 1’s predators
other processes that could promote ar1
Other Processes That Could Promote AR
  • Apparent competition/Competition for predator-free space (predation)
  • Parasitism/Herbivory ecologically the same as above
  • Mutualism/Coevolution
ecological opportunity3
Ecological Opportunity
  • Does it promote AR?
  • If so, how?
  • Is it required for AR?
  • Is it an operationally useful concept, or just a useful heuristic?
alternatives to ecological opportunity
Alternatives to Ecological Opportunity
  • A Clade Outcompetes the Incumbent Clade and Replaces It
alternatives to ecological opportunity1
Alternatives to Ecological Opportunity
  • A Clade Outcompetes the Incumbent Clade and Replaces It
  • A Radiating Clade Creates Its own Diversity
    • The More Species in a Clade, the Greater the Resources to Exploit
intra clade predation
Intra-cladepredation

Scale-eating cichlid

Anolis

alternatives to ecological opportunity2
Alternatives to Ecological Opportunity
  • A Clade Outcompetes the Incumbent Clade and Replaces It
  • A Radiating Clade Creates Its own Diversity
    • The More Species in a Clade, the Greater the Resources to Exploit
    • Coevolution: More Species on one Side of a Coevolutionary Relationship May Spur More on the Other
alternatives to ecological opportunity3
Alternatives to Ecological Opportunity
  • A Clade Outcompetes the Incumbent Clade and Replaces It
  • A Radiating Clade Creates Its own Diversity
  • A Radiating Clade Creates New Niches: Ecosystem Engineers
ecological opportunity4
Ecological Opportunity
  • Does it promote AR?
  • If so, how?
  • Is it required for AR?
  • Is it an operationally useful concept, or just a useful heuristic?
  • How do we identify EO, much less quantify it?
how do we explain clades that experience ecological opportunity and don t radiate
How Do We Explain Clades That Experience Ecological Opportunity and Don’t Radiate?

Galápagos

mockingbird

Hawaiian

thrush

how do we explain clades that experience ecological opportunity and don t radiate1
How Do We Explain Clades That Experience Ecological Opportunity and Don’t Radiate?
  • Mistake: No Opportunity
  • Inability to Utilize Resources—Lack of Evolvability
  • Inability to Speciate
slide62

How Do We Identify Ecological Opportunity Other Than Retrospectively To Explain An Adaptive Radiation That Has Occurred?Can We Actually Quantify Opportunity Other Than Recognizing It After The Fact When A Clade Has Radiated?

slide63

How Do We Identify Ecological Opportunity Other Than Retrospectively To Explain An Adaptive Radiation That Has Occurred?Can We Actually Quantify Opportunity Other Than Recognizing It After The Fact When A Clade Has Radiated?

slide65

Estimating Adaptive Landscape Based on Distribution of Resources (seeds)

Schluter, D. and P. R. Grant. 1984. Determinants of morphological patterns in communities

of Darwin’s finches. American Naturalist 123:175–196.

slide66

Critiques:

  • Laborious
  • Highly ad hoc
  • Ignores Interspecific Interactions
  • Environmental Snapshot of Resource Availability
body size of lesser antillean anolis
Body Size of Lesser Antillean Anolis

1-species

Islands: Medium

2-species

Islands:

Large and Small

Schoener, Amer. Nat., 1970

adaptive peak for one species
Adaptive Peak for One Species

Resource (Insect) Availability

adaptive peaks for two species
Adaptive Peaks for Two Species

Resource (Insect) Availability