Interactions in the evolution of dispersal distance and emigration propensity

Interactions in the evolution of dispersal
distance and emigration propensity

Andreas Gros

29 October 2008

Interactions in the evolution of dispersal distance and emigration
propensity

1. Introduction
• Thesis overview
• Important factors
2. Detailed view on
(a) Local adaptations
(b) Sex-biased dispersal

Andreas Gros 29.10.2008

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



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



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

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


Introduction - Costs and beneﬁts of dispersal

• Costs:
• Dispersal mortality
• Investment in
dispersal mechanism
instead of fertility
• Time spent on
dispersal

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


Introduction - Costs and beneﬁts of dispersal

• Costs: • Beneﬁts:
• Dispersal mortality • Avoidance of
• Investment in (kin-)competition
dispersal mechanism • Avoidance of
instead fertility inbreeding depression
• Time spent on • Avoidance of bad
dispersal conditions


Introduction - Driving factor

Kin-competition



Kin-competition

• Dispersal pays be-
cause of demographic
beneﬁts



Kin-competition

• Does dispersal still
pay?



Kin-competition

• Dispersal pays
• because you can
compete with
non-siblings



Kin-competition

• Dispersal pays
• because you can
compete with
non-siblings
• and your relatives
have the chance to
rear 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

1
Gros, A., Poehtke, H.J., Hovestadt, T., 2006. Oikos 114: 544-552
2
Gros, A., Hovestadt, T., Poehtke, H.J., 2008. Ecological Modelling 219: 226-233


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





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

X



• 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?
dispersal kernel

1.0
mean distance = 1
mean distance = 2
0.8
probability density

0.6
0.4
0.2
0.0

0 1 2 3 4 5

distance



• Resulting seed density



• The system: plants on an island

• The model:

A1 A2 A3 A4



• 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+) G d , Gp

Skewed (S) Gd

Skewed+ (S+) G d , Gp



Results

6
mean dispersal distance

5
A1 A2 A3 A4

4
3
2
1

A1 A2 A3 A4
center rim
area number



Results

6
small patch (radius 25)


5
A1 A2 A3 A4

4
3
2
1

A1 A2 A3 A4
center rim
area number



Results

6
big patch (radius 150)

5
A1 A2 A3 A4

4
3
2
1

A1 A2 A3 A4
center rim
area number



Results

6

5
A1 A2 A3 A4

4

island (patch) size is most important determinant for
dispersal distance
3
2
1

A1 A2 A3 A4
center rim
area number



Results

6

5
A1 A2 A3 A4

4

minimum patch size necessary for local adaptation
3
2
1

A1 A2 A3 A4
center rim
area number



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


Evolution of sex-biased dispersal: the role of sex-speciﬁc
dispersal costs, demographic stochasticity, and inbreeding

• 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 dispersal
evolves, and
• which factors determine exactly which gender becomes
more dispersive 3

3 Image: c User mecocrus 2006 CC-BY-NC-SA via Flickr
Kokko, 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



• differences in competition about reproductive resources



• differences in dispersal payoff



• differences in dispersal payoff ... or costs



• differences in dispersal payoff ... or costs

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



The model



The model

• patch-matrix world



The model

• N breeding territories per
patch
• annual, sexually reproducing
species
• monogamous pairs
• pairs with territory get an N=10
equal number of offspring
• individuals have two loci:
dm , df



The model

• N breeding territories per
patch
• annual, sexually reproducing
species
• monogamous pairs c c
• pairs with territory get an N=10
equal number of offspring
• individuals have two loci: c c
dm , df
• dispersal mortality c
• disperser pick patch
randomly



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





Rb > c

R−c
∗ R−c2
if R > c
⇒d =
0 if R ≤ c





1.0
c = 0.4
Rb > c

0.8
dispersal probability d

0.6
R−c
∗ R−c2
if R > c
⇒d =

0.4
0 if R ≤ c

0.2
0.0
0.0 0.2 0.4 0.6 0.8 1.0

relatedness R



How does it look like for sex-
speciﬁc costs?




How does it look like for sex-
speciﬁc costs?
R−cf
R−c2
if R > cf
d∗
f = f

0 if R ≤ cf

R−cm
R−c2
if R > cm
d∗
m = m
0 if R ≤ cm




How does a difference in dispersal mortality inﬂuence dispersal?




Results from the numerical model

difference = 2 % difference = 5 % difference = 10 %
0.5

0.5

0.5
a b c
0.4

0.4

0.4
0.3

0.3

0.3

N = 10
df , dm
0.2

0.2

0.2
0.1

0.1

0.1
0.0

0.0

0.0
0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0
c c c




Results from the numerical model

difference = 2 % difference = 5 % difference = 10 %
0.5

0.5

0.5
Small differences in dispersal mortality can cause big
a b c

differences in evolving dispersal propensities.
0.4

0.4

0.4
0.3

0.3

0.3

N = 10
df , dm
0.2

0.2

0.2
0.1

0.1

0.1
0.0

0.0

0.0
0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0
c c c



How does the evolutionary outcome depend on inbreeding-depression?




high inbreeding > c, no difference

1.0
0.8
male dispersal
0.6
0.4
0.2
0.0

0.0 0.2 0.4 0.6 0.8 1.0
female dispersal



high inbreeding > c, no difference

1.0
0.8 male dispersal > female dispersal
male dispersal
0.6
0.4
0.2

female dispersal > male dispersal
0.0

0.0 0.2 0.4 0.6 0.8 1.0
female dispersal



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

1.0
0.8
male dispersal
0.6
0.4
0.2
0.0

0.0 0.2 0.4 0.6 0.8 1.0
female dispersal



inbreeding = c = 0.4, difference = 10 %

1.0
0.8
male dispersal
0.6
0.4
0.2
0.0

0.0 0.2 0.4 0.6 0.8 1.0
female dispersal



inbreeding = c = 0.4, difference = 10 %

1.0
0.8

Small cost differences in dispersal can explain big biases
in dispersal propensity, especially in combination with
male dispersal
0.6

inbreeding depression
0.4
0.2
0.0

0.0 0.2 0.4 0.6 0.8 1.0
female dispersal

Summary


Summary

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


Summary

propensity.
• In combination with inbreeding depression the dispersal bias
increases.


Summary

propensity.
• In combination with inbreeding depression the dispersal bias
increases.
• Local adaptations to habitat conditions are only possible, if the habitat
is big enough.


Outlook

Questions for future research


Outlook

Image: c User Ron Layters CC-License: CC-BY-NC-SA 2008 via Flickr

Outlook

Image: c User Kevin Saff CC-License: CC-BY-SA 2005 via Flickr


Outlook

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

Image: c User Kevin Saff CC-License: CC-BY-SA 2005 via Flickr


Outlook

• What are the rates of change of habitat conditions in space
and 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?

Image: c User cliff1066 CC-License: CC-BY 2008 via Flickr


Thank you to

Image: c User TerenceKearns.com CC-License: CC-BY-NC-SA 2007 via Flickr


Thank you to

• Thomas Hovestadt and Hans Joachim Poethke



Thank you to

• all people from the Field Station



Thank you to

• my partner Pleuni Pennings



Thank you to

• all family members



Thank you to

• all the people that I forgot to mention



Thank you to

• 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!

Image: c User Elron6900 CC-License: CC-BY-NC 2007 via Flickr


Questions?


Questions?

Questions?


Interactions in the evolution of dispersal distance and emigration propensity

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