Interactions in the evolution of dispersal distance and emigration propensity

transcript

Interactions in the evolution of dispersaldistance and emigration propensity

Andreas Gros

29 October 2008

Interactions in the evolution of dispersal distance and emi grationpropensity

Andreas Gros 29.10.2008

1. Introduction

• Thesis overview• Important factors

2. Detailed view on

(a) Local adaptations(b) Sex-biased dispersal

Introduction

Introduction - Dispersal

Why study dispersal?

Image: c©User eco-photography CC-License: CC-BY-NC-ND 2006 via Flickr

Image: c©User Imbaker CC-License: CC-BY-NC-SA 2007 via Flickr

Image: c©User crustmania CC-License: CC-BY-NC-ND 2006 via Flickr

Introduction - Work overview

Work overview:

• With Thomas Hovestadt and Hans Joachim Poethke (Uni Wurzburg)

• Evolution of

• local adaptations in dispersal strategies• dispersal under distance dependent costs• sex-biased dispersal under sex-specific dispersal costs• sex-biased dispersal under asymmetric competition

• With Ulf Dieckmann (IIASA, Laxenburg)

• Evolution of dispersal kernels

• With Martin Wegmann (Uni Wurzburg)

• Analysis of patch irreplacibility

Work overview:

• Evolution of

Work overview:

• Evolution of

Work overview:

• Evolution of

Work overview:

• Evolution of

Work overview:

• Evolution of

Work overview:

• Evolution of

Actively moving organisms “Dispersal is thepermanent movement an individual makes from itsbirth site to the place where it reproduces or wouldhave reproduced had it survived and found a mate.”(Howard,1960)

Sessile organisms “Dispersal includes all mechanismsleading to the displacement of offspring away fromthe position of the mother.” (Hovestadt, 2005)

Introduction - Costs and benefits of dispersal

Image: c©User spinedoc18 CC-License: CC-BY-NC 2007 via Flickr

• Costs:

• Dispersal mortality• Investment in

dispersal mechanisminstead of fertility

• Time spent ondispersal

Introduction - Costs and benefits of dispersal

• Costs:

• Dispersal mortality• Investment in

dispersal mechanisminstead fertility

• Time spent ondispersal

• Benefits:

• Avoidance of(kin-)competition

• Avoidance ofinbreeding depression

• Avoidance of badconditions

Introduction - Driving factor

Kin-competition

• Dispersal pays be-cause of demographicbenefits

Kin-competition

• Does dispersal stillpay?

Kin-competition

• Dispersal pays

• because you cancompete withnon-siblings

Kin-competition

• Dispersal pays

• because you cancompete withnon-siblings

• and your relativeshave the chance torear more offspring

Thesis chapters

Detailed view on two chapters of my thesis:

• Evolution of

• local adaptations in dispersal strategies (Gros et. al, 2006)1

• sex-biased dispersal under sex-specific dispersal costs (Gros et.al, 2008) 2

1Gros, A., Poehtke, H.J., Hovestadt, T., 2006. Oikos 114: 544-552

2Gros, A., Hovestadt, T., Poehtke, H.J., 2008. Ecological Modelling 219: 226-233

Local adaptations

Evolution of local adaptations in dispersal strategies

• Evolution of local adaptations in dispersal strategies

Image: c©User Aaron Escobar 2008 CC-BY via Flickr

4 factors play a role:

• increase in costs towards the border

• increase in costs towards the border• decrease in competition towards the border

• dispersal destroys local adaptation

• dispersal destroys local adaptation• kin-competition drives dispersal

The questions:

• Do we find local adaptation?• If yes, under which conditions can local adaptation evolve?

• The system: annual clonal plants on an island

• How far to disperse one’s offspring on an island?

• How do the corresponding phenotypes look like?

Image: c©User Roger Smith 2006 CC-BY-NC-ND via Flickr

• How do the corresponding phenotypes look like?

0 1 2 3 4 5

dispersal kernel

distance

mean distance = 1mean distance = 2

• Resulting seed density

• The system: plants on an island

• The model:

A4A3A2A1

• The system: plants on an island Different dispersal functions:

kernel prob. density traits

Global (G) Gp

Nearest Neighbour (NN) Gp

Neg. Exp. (NE) Gd

Neg. Exp.+ (NE+) Gd, Gp

Skewed (S) Gd

Skewed+ (S+) Gd, Gp

Results

area number

A1 A2 A3 A4center rim

A4A3A2A1

Results

area number

small patch (radius 25)

A4A3A2A1

Results

area number

big patch (radius 150)small patch (radius 25)

A4A3A2A1

Results

area number

A4A3A2A1

island (patch) size is most important determinant fordispersal distance

Results

area number

A4A3A2A1

minimum patch size necessary for local adaptation

Summary

• Island size strongly influences dispersal distances• Local adaptations evolve only above a certain habitat size• Below that size the cost-benefit profile of dispersal is too weak

and local adaptation is completely destroyed by dispersal

Summary

Sex-biased dispersal

Evolution of sex-biased dispersal: the role of sex-specificdispersal costs, demographic stochasticity, and inbreedi ng

• Sex-biased dispersal

1. female-biased (often in birds)2. male-biased (often in mammals)

Image: c©User nkenji 2007 CC-BY-NC-ND via Flickr

Image: c©User mecocrus 2006 CC-BY-NC-SA via Flickr

It is unclear

• under which circumstances sex-biased dispersalevolves, and

• which factors determine exactly which gender becomesmore dispersive 3

3Kokko, H. & Jennions, M. D., 2008. Parental investment, sexual selection and sex ratios. J. Evol. Biol. 21, 919-948.

Explanations for sex-biased dispersal:

• avoidance of inbreeding depression

• avoidance of inbreeding depression• differences in competition about reproductive resources

• avoidance of inbreeding depression• differences in competition about reproductive resources• differences in dispersal payoff

• avoidance of inbreeding depression• differences in competition about reproductive resources• differences in dispersal payoff ... or costs

Differences in dispersal costs are an obvious reason forbiased dispersal, but can they explain big sex-biases indispersal propensity – especially when the cost differencesare small?

The model

• patch-matrix world

The model

• patch-matrix world• N breeding territories per

patch• annual, sexually reproducing

species• monogamous pairs• pairs with territory get an

equal number of offspring• individuals have two loci:

dm, df

The model

• patch-matrix world• N breeding territories per

patch• annual, sexually reproducing

species• monogamous pairs• pairs with territory get an

equal number of offspring• individuals have two loci:

dm, df

• dispersal mortality c

• disperser pick patchrandomly

Given the costs c, how many sib-lings should disperse?

Image: c©User Andrew Pescod CC-BY-NC-SA 2006 via Flickr

• Kin-selection theory states:

Rb > c

⇒ d∗ =

R−cR−c2

if R > c

0 if R ≤ c

Rb > c

⇒ d∗ =

R−cR−c2

if R > c

0 if R ≤ c

0.0 0.2 0.4 0.6 0.8 1.0

relatedness R

c = 0.4

How does it look like for sex-specific costs?

d∗f =

{R−cf

R−c2f

if R > cf

0 if R ≤ cf

d∗m =

R−cm

R−c2mif R > cm

0 if R ≤ cm

How does a difference in dispersal mortality influence dispersal?

Results from the numerical model

0.0 0.2 0.4 0.6 0.8 1.0

difference = 2 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 5 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 10 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 2 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 5 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 10 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 2 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 5 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 10 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 2 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 5 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 10 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 2 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 5 %

0.0 0.2 0.4 0.6 0.8 1.0

difference = 10 %

cSmall differences in dispersal mortality can cause bigdifferences in evolving dispersal propensities.

How does the evolutionary outcome depend on inbreeding-depression?

0.0 0.2 0.4 0.6 0.8 1.0

female dispersal

high inbreeding > c, no difference

0.0 0.2 0.4 0.6 0.8 1.0

female dispersal

male dispersal > female dispersal

female dispersal > male dispersal

0.0 0.2 0.4 0.6 0.8 1.0

female dispersal

male dispersal > female dispersal

female dispersal > male dispersal

0.0 0.2 0.4 0.6 0.8 1.0

female dispersal

inbreeding = 0.6, c = 0.4, difference = 10 %

0.0 0.2 0.4 0.6 0.8 1.0

female dispersal

inbreeding = c = 0.4, difference = 10 %

0.0 0.2 0.4 0.6 0.8 1.0

female dispersal

0.0 0.2 0.4 0.6 0.8 1.0

female dispersal

Small cost differences in dispersal can explain big biasesin dispersal propensity, especially in combination withinbreeding depression

Summary

• Small cost differences in dispersal can explain big biases in dispersalpropensity.

Summary

• In combination with inbreeding depression the dispersal biasincreases.

Summary

• In combination with inbreeding depression the dispersal biasincreases.

• Local adaptations to habitat conditions are only possible, if the habitatis big enough.

Outlook

Questions for future research

Outlook

• There’s now not only heterogeneity in space, butincreasingly also in time.

Outlook

• What are the rates of change of habitat conditions in spaceand time that species can adapt to?

• What are the predictions for changes in dispersal strategies?• Do we need to develop dedicated protection strategies for

genders?

Thank you to

• Thomas Hovestadt and Hans Joachim Poethke

Thank you to

• Thomas Hovestadt and Hans Joachim Poethke• all people from the Field Station

Thank you to

• Thomas Hovestadt and Hans Joachim Poethke• all people from the Field Station• my partner Pleuni Pennings

Thank you to

• Thomas Hovestadt and Hans Joachim Poethke• all people from the Field Station• my partner Pleuni Pennings• all family members

Thank you to

• Thomas Hovestadt and Hans Joachim Poethke• all people from the Field Station• my partner Pleuni Pennings• all family members• all the people that I forgot to mention

Thank you to

• Thomas Hovestadt and Hans Joachim Poethke• all people from the Field Station• my partner Pleuni Pennings• all family members• all the people that I forgot to mention• the DFG for financial support (DFG PO 244/3-1)

Thank you

Thank you for your attention!

Questions?

Interactions in the evolution of dispersal distance and emigration propensity

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