Adaptive significance and genetic basis of a
balanced colour-polymorphism
2 UK RAD meeting 31 of August 2010
Octávio S. Paulo & Sofia G. Seabra
Computational Biology and Population Genomics Group
Centro de Biologia Ambiental
Faculdade de Ciências da Universidade de Lisboa
1
Project & Team
Adaptive significance and genetic basis of a balanced
colour-polymorphism (2010-2013)
PI: Sofia Seabra (postdoc)
Technician: Sara Silva
Two PhD candidates: Ana Sofia e Bruno Vieira
Prof. A. Quartau (University of Lisbon)
Prof. Paulo Borges (University of Azores)
Consultants: Selcuk Yurtsever (University of Trakya,
Turkey)
Olli Halkka (University of Helsinki, Finland)
Chris Jiggins (University of Cambridge)
2
The spittlebug: Philaenus spumarius (Hemiptera, Cercopidae)
Nymphs form the
protective spittle mass
Xylem feeders
Anual life cycle
Adults – several morphotypes
3
Dorsal Colour Polymorphism
Non-melanic forms
Melanic forms
Stewart & Lees, 1996
4
Genetics of the dorsal colour polymorphism
Dominance and codominance relations
• 1 autossimic locus with 7 alleles
• The more frequent allele is the
recessive (morphotype TYP)
• Sex intercation
• Other regulating factores
5
In: Halkka, 1990
Differences in the frequency of the morphotypes among populations
Geographic clines - North–South in Europe and North
America and West-East in North America
In: Halkka, 1990
6
Differences in the frequency of the morphotypes among populations
Geographic clines and
also lowland/highland clines
Halkka et al. 1974, 1975
7
Differences in the frequency of the morphotypes among populations
Industrial melanism – Wales- Cynon Valley
Lees et al. 1983
8
Differences in the frequency of the morphotypes among populations
Habitat differences – frequency differences
Ex: A- open field, B-cool pinewood, C -warmer pinewood
Quartau & Borges 1997
9
Differences in the frequency of the morphotypes among populations
Constant habitat - constant frequency
Exchange habitats experiments
10
Specific hypotheses will be tested about adaptation related to the
balanced colour polymorphism of P. spumarius.
Do melanic and nonmelanic phenotypes have differential selective values?
Are there signatures of selection in the genome of P. spumarius, either
balancing or directional selection?
Are the markers showing these signatures in linkage disequilibrium,
pointing to a genome location under selection?
Are the loci showing variation within populations also divergent among
populations?
Are there genetic markers associated with the colour phenotypes?
Are these markers in linkage with each other, pointing to a genome
location responsible for the colour?
Can the associated loci be identified as candidate loci for the colour
polymorphism?
11
Project Spittlebug
The research will be divided in two main approaches:
1) to carry out an experimental study on the selective
advantage/disadvantage of melanic forms of Philaenus
spumarius.
2) to carry out a genome scan to study the balance between
gene flow and adaptation, to identify loci under selection and
to associate loci with colour phenotypes.
12
Experimental study
Three different colour phenotypes will be used in these
experiments: typicus (TYP), trilineatus (TRI) marginellus (MAR),
the most common melanic
1) The reproductive success and survival rates will be assessed from three
different crosses: 30 TYP male x TRI female, 30 TYP male x MAR female and 30
TYP male x TYP female
2) The humidity factor (resistance to desiccation) will be tested. Females of
different colour phenotypes (30 melanic and 60 non-melanic (30 TYP and 30
TRI)), captured as nymphs in the field in spring, will be put at two different
humidities (15 each in optimal and 15 each in low humidity) with the same
temperature and photoperiod regimes. Survival will be assessed, as well as
behavioural aspects (activity level, location in the plant, preference for
background colour).
3) The duration of egg maturation (time between copulation and oviposition)
will be examined. 30 melanic (MAR) and 60 non-melanic (30 TYP and 30 TRI)
females will be placed in the same temperature / humidity / photoperiod regimes
and will be mated to TYP males. The mated females will be placed in separate
cages and the number of days to oviposition will be counted for each female.
13
Populations to sample for RADS
14
Floragenex - Biota
Busack SD 1986 National Geographic Research 2(1):17-36
15
Floragenex - Biota
16
Next year
17
Hohenlohe et al. 2010
18
MPE paper update
19