the ecology of adaptive radiation. quick think of the first adaptive radiation that comes to mind
TRANSCRIPT
Ecological Opportunity
“loosely defined as a wealth of evolutionarily accessible resources little used by competing taxa” (Schluter 2000, p.69).
1985 1990 1995 2000 2005 2010 20150
20
40
60
80
100
120
140
160
180
200
use of "ecological opportunity" according to Google Scholar
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?
“Evolutionary divergence of members of a single phylogenetic lineageinto a variety of different adaptive forms.” Futuyma, Evolutionary Biology, 1998
Adaptive Radiation
AR Definitional IssuesIs pace of diversification part of the definition? In particular, does it have to be explosive?How are ARs distinguished from non-ARs?
AR Definitional IssuesIs 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 IssuesIs 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?
What Prompts AR?
Classic idea (Simpson, Major Features of Evolution, 1954)—AR requires:Geographical Access colonizationPhysical Access
mass extinction, appearance of new resource
Evolutionary Accesskey innovation
“The evolution of a trait that allows a species to interact with the environment in an entirely new way”
Key Innovation
“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
“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 AR2. KI refers to ecological diversity, not
number of species
What Is the Evidence that Ecological Opportunity Prompts
AR?Biogeography: AR on islandsPaleontology: AR after mass extinctionEvolution: AR associated with KIPhylogeny: Decline in diversification
as radiation progresses
What is the Evidence that Ecological Opportunity Prompts
AR?Biogeography: AR on islandsPaleontology: AR after mass extinctionEvolution: AR associated with KIPhylogeny: Decline in diversification
as radiation progressesExperimental evolution in lab
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?
Resourceavailability
Resource Spectrum
1. A species finds itself in a resource-rich environment
(seed size)
Resourceavailability
Resource Spectrum
4. Species partition resources to minimize interactions
(seed size)
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 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?
Resourceavailability
Resource Spectrum
2. Speciation occursResourceavailability
Resource Spectrum
1. A species finds itself in a resource-rich environment
Resourceavailability
Resource Spectrum
4. Species partition resources to minimize interactions
Speciation
AdaptiveDifferentiation
2 Steps
Resourceavailability
Resource Spectrum
1. A species finds itself in a resource-rich environment
Resourceavailability
Resource Spectrum
4. Species partition resources to minimize interactions
AdaptiveDifferentiation
Speciation +
1 StepResourceavailability
Resource Spectrum
2. Speciation occurs
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
Strong—in the presence of gene flow (sympatric/parapatric speciation)Weak—divergence driven by natural selection regardless of geographic context
Resourceavailability
Resource Spectrum
1. A species finds itself in a resource-rich environment
Resourceavailability
Resource Spectrum
4. Species partition resources to minimize interactions
AdaptiveDifferentiation
Speciation +
1 StepResourceavailability
Resource Spectrum
2. Speciation occurs
Strong Flavor:Speciation in presence of gene flow
Resourceavailability
Resource Spectrum
1. A species finds itself in a resource-rich environment
Resourceavailability
Resource Spectrum
3. Resources become scarce
Resourceavailability
Resource Spectrum
4. Species partition resources to minimize interactions
Speciation in allopatry
AdaptiveDifferentiation2-Step Models:
Does adaptive differentiation occur in allopatry or sympatry?
43
Nat Sel may be involved in speciation (weak ES);
Competition not important
Nat sel not part of speciation
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
Apparent competition/Competition for predator-free space (predation)
Apparent Competition
In Habitat A, Predator 1 preys on Prey 1More Prey 1 more Predator 1Predator 1 also opportunistically eats Prey 2More Predator 1 fewer Prey 2Hence, more Prey 1 fewer Prey 2“Apparent” competitionPromotes habitat divergence by Prey 2 to escape Prey 1’s predators
Other Processes That Could Promote AR
Apparent competition/Competition for predator-free space (predation)Parasitism/Herbivory ecologically the same as aboveMutualism/Coevolution
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
A Clade Outcompetes the Incumbent Clade and Replaces ItA Radiating Clade Creates Its own DiversityThe More Species in a Clade, the Greater the Resources to Exploit
Alternatives to Ecological Opportunity
A Clade Outcompetes the Incumbent Clade and Replaces ItA Radiating Clade Creates Its own DiversityThe 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 Opportunity
A Clade Outcompetes the Incumbent Clade and Replaces ItA Radiating Clade Creates Its own DiversityA Radiating Clade Creates New Niches: Ecosystem Engineers
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?
Galápagosmockingbird
Hawaiianthrush
How Do We Explain Clades That Experience Ecological Opportunity
and Don’t Radiate?
Mistake: No OpportunityInability to Utilize Resources—Lack of
EvolvabilityInability to Speciate
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?
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?
Estimating Adaptive Landscape Based on Distribution of Resources (seeds)
Schluter, D. and P. R. Grant. 1984. Determinants of morphological patterns in communitiesof Darwin’s finches. American Naturalist 123:175–196.
Critiques:LaboriousHighly ad hocIgnores Interspecific InteractionsEnvironmental Snapshot of Resource Availability
Body Size of Lesser Antillean Anolis
1-speciesIslands: Medium
2-speciesIslands:Large and Small
Schoener, Amer. Nat., 1970