Download Mating systems - WordPress.com

12.1 Sexual conflict and environmental
conditions affect the evolution of mating
systems
• Mating system – the social associations and
number of sexual partners an individual has
during one breeding season
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
The evolution of social mating
systems
• Emlen and Oring model is based on sexual conflict
and resource distribution
• Sexual conflict – differential selection on males and
females to maximize their fitness
– Female fitness is most often limited by access to
resources
– Male fitness is most often limited by the number of
mates
• Resource amount and distribution vary in different
environments
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
http://www.bbc.com/earth/bespoke/story/20
140908-twisted-world-of-sexualorgans/media/z3300303-weevil_penislr_1.jpg
Figure 1 Male Genitalia and Injury to Females The male genitalia of C. maculatus are armed with rigid spines that cause internal
injuries in females during copulation. The ventral spines are here pointing toward top right and the dorsal spines in the op...
Cosima Hotzy , Göran Arnqvist
Sperm Competition Favors Harmful Males in Seed Beetles
Current Biology, Volume 19, Issue 5, 2009, 404 - 407
http://dx.doi.org/10.1016/j.cub.2009.01.045
Figure 2 Covariation between Genital Spines and Sperm Competition Success The relationship between the average length of the
ventral spines of the genitalia and mean male fertilization success, here measured as the absolute proportion of eggs that are fer...
Cosima Hotzy , Göran Arnqvist
Sperm Competition Favors Harmful Males in Seed Beetles
Current Biology, Volume 19, Issue 5, 2009, 404 - 407
http://dx.doi.org/10.1016/j.cub.2009.01.045
Holland and Rice 1998
Holland and Rice 1998
Holland and Rice 1999
Holland and Rice 1999
The evolution of social mating
systems
• Female defense polygyny – males monopolize
aggregations of females directly
• Resource defense polygyny – males defend
territories rich in resources that are used by and
attract females
• Lek – a location where an aggregation of males
display to females
– Males often form a dominance hierarchy, and
dominant males obtain the most matings (male
dominance polygyny)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
The evolution of social mating systems
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Mating systems in reed warblers
• Research question 1: How does habitat quality
(amount of food resources) correlate with
mating system?
• Research question 2: How are habitat quality
and mating system related to the level of male
care? (Leisler, Winkler, & Wink 2002)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Mating systems in reed warblers
• Methods:
– Created a phylogeny of reed warblers
– Estimated habitat quality for each species as
“poor,” “medium,” or “good”
– Characterized the relative level of male care
provided to offspring (fully equal to or some
fraction less than the care provided by a female)
– Mapped these data onto the phylogeny
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Mating systems in reed warblers
• Results:
– Most species are
monogamous and
live in poor-quality
habitats
– Four species display
polygyny and live in
medium-quality
habitats
– One species displays
promiscuity and lives
in good-quality
habitat
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Mating systems in reed warblers
• Results:
– Most species show high
levels of parental care
– Reduced parental care
occurs in polygynous
species and in the
promiscuous species
• Conclusion:
– Habitat quality is
correlated with mating
system and level of
paternal care
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Phylogenetic analysis of the relationship between
paternal care and food supply of six species of
acrocephaline warblers. Paternal care data were squareroot-arcsine-transformed prior to analysis. The regression
through the origin was associated with a correlation of r =
−0.859, P < 0.0001
12.2 Monogamy often evolves when
biparental care is required to raise
offspring
• Monogamy
– One male associates and mates with one female,
often forming a pair-bond
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
California mouse monogamy
• Research question: How does male care affect
reproductive success in monogamous mice?
(Gubernick & Teferi 2000)
• Hypothesis: High levels of paternal care are
required to successfully raise offspring
• Prediction: Reproductive success will be low if
paternal care is absent
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
California mouse monogamy
• Methods:
– California mice (Peromyscus californicus)
– Experimentally removed the male from
monogamous pair
– Compared offspring number and success
(emergence from burrow) to control pairs that
contained a male
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
California mouse monogamy
• Results:
– Both groups produced a
similar number of young
– Families with fathers
removed had lower
offspring success
• Conclusion:
– Male care enhances
reproductive success in
monogamous mice
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Monogamy without biparental care:
snapping shrimp
• Monogamy occurs in some species without
biparental care
• Territorial cooperation hypothesis – two
individuals (one of each sex) can better defend
a critical resource needed for reproduction
• Mate-guarding hypothesis – a single male can
benefit by remaining close to a single female
during one or more reproductive cycles
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Monogamy without biparental care:
snapping shrimp
• Research question: Why are snapping shrimp
monogamous when males provide no care?
(Mathews 2002a; Mathews 2002b; Mathews
2003)
• Hypothesis: Territorial cooperation or mate
guarding favor monogamy
• Prediction: Pairs will better defend resources
or males will most often guard females that
are close to sexual receptivity
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Monogamy without biparental care:
snapping shrimp
• Methods:
– Snapping shrimp (Alpheus angulatus)
– Resident shrimp constructed a burrow used for
nesting
– Four treatments differed in the type of residents
(male or female, single or in a pair) and a single
intruder (male or female)
– Recorded percent of contests won by the resident
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Monogamy without biparental care:
snapping shrimp
• Results:
– Females in pairs won more contests than solitary
females
– Males in pairs won more contests than solitary
males
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Monogamy without biparental care:
snapping shrimp
• Methods:
– Presented a male with
water from two arms of a
Y-maze
– One arm contained water
from a tank with snapping
shrimp (either a male or
a female; females at
different time to sexual
receptivity)
– Recorded the behavior of
test shrimp
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Monogamy without biparental care:
snapping shrimp
• Results:
– Males only responded to water that contained
females close to sexual receptivity
• Conclusion:
– Territorial cooperation and mate guarding have
favored monogamy in snapping shrimp
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
12.3 Polygyny and polyandry evolve when
one sex can defend multiple mates or the
resources they seek
• Female defense polygyny
– Males defend and mate with multiple females
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Female defense polygyny in horses
• Research question: Do male horses defend
females directly or the resources they seek?
(Linklater et al. 1999; Linklater et al. 2000)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Female defense polygyny in horses
• Methods:
– Wild horses (Equus caballus)
– Live in social groups called bands
– Bands typically contain one male and multiple
females
– Recorded the movement behavior of several
bands
– Plotted the home range used by each band
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Female defense polygyny in horses
• Results:
– Males defended their
females from other males
– All bands used the same
geographic areas over
time
• Conclusion:
– Males defend females
directly
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Resource defense polygyny in blackbirds
• Polygyny threshold
model – Females should
mate polygynously only
when the benefits of
doing so (extra
resources) exceed the
costs (sharing resources
with other females)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Resource defense polygyny in blackbirds
• Research question: Why do some blackbirds
mate monogamously while others mate
polygynously? (Pribil & Searcy 2001)
• Hypothesis: The polygyny threshold model
explains variation in polygyny
• Prediction: Polygyny should only be observed
on high-quality territories
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Resource defense polygyny in
blackbirds
• Methods:
– Red-winged blackbirds (Agelaius phoeniceus)
– Selected adjacent territories of males (dyads)
– Added nesting platforms over water (high-quality territory)
for one male
– Added nesting platforms over land (low-quality territory)
for other male and removed his female
– Newly arriving females had two options: mate polygynously
on a high-quality territory or mate monogamously on a
low-quality territory
– Recorded behavior of newly arriving females
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Resource defense polygyny in
blackbirds
• Results:
– In 12 of the 14 male dyads, newly arriving females settled
on the high-quality territory and mated polygynously
– These females had high reproductive success; the two
females that mated monogamously had low reproductive
success
• Conclusion:
– Territory quality affects observed mating system in redwinged blackbirds as predicted by the polygyny
threshold model
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Resource defense polygyny in
carrion beetles
• Research question: What is the mating system
of carrion beetles? (Suzuki, Nagano, &
Kobayashi 2006)
• Hypothesis: Observed male-male aggression
over carrion suggests resource defense
polygyny
• Prediction: Multiple females will mate with
males that win fights over resources that
attract females (carrion)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Resource defense polygyny in
carrion beetles
• Methods:
– Carrion beetles (Ptomascopus
morio)
– Placed four virgins (two males,
two females) in area with a
piece of meat
– Recorded mating success of all
individuals using DNA
fingerprinting of offspring and
adults
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Resource defense polygyny in
carrion beetles
• Results:
– The two females had similar
reproductive success
– The large male had higher
reproductive success than
the small male
• Conclusion:
– Resource defense polygyny
appears to be the mating
system in this species
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Male dominance polygyny: the evolution
of leks – hotspots or hotshots?
• Hotspot hypothesis – males can benefit by
aggregating on leks near a location in the
environment where they are likely to
encounter females
• Hotshot hypothesis – males can benefit by
aggregating on leks near high-quality males that
attract females
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Lekking behavior in the great snipe
• Research
question: Why
do male great
snipe (Gallinago
media) aggregate
on leks?
(Höglund &
Robertson 1990)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Lekking behavior in the great snipe
• Methods:
– Great snipe (Gallinago media)
– Observed male interactions on leks to
determine dominance relationships
– Removed individual males for one night
– Recorded behavior of remaining males
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Lekking behavior in the great snipe
• Results:
– When dominants were removed, their territory
remained unoccupied and subordinates moved
away
– When subordinates were removed, other
subordinates added the vacant space to their
territories
• Conclusion:
– These results support the hotshot hypothesis
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Peafowl leks
• Research question:
Why do male peafowl
aggregate on leks?
(Loyau, Saint Jalme, &
Sorci 2007)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Peafowl leks
• Methods:
– Peafowl (Pavo cristatus)
– Recorded male-male interactions, male display
rates, female visitation rates, and mating success of
males on a lek near a feeding area
– Then removed each male for about two weeks
and recorded the effect on males and females
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Peafowl leks
• Results:
– Males closest to the feeding
site obtained the most matings
– New males quickly settled on
the sites of removed males
– The number of female visits to
a display site was similar
before and after a male was
removed
• Conclusion:
– These results support the
hotspot hypothesis; females
preferred to mate with males
close to the feeding site
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Polydandry and sex-role reversal
• Sex-role reversed species
– Females exhibit high levels of
territorial defense and
aggression while males
provide high levels of
parental care
• May be favored in resourcepoor environments or
where predation on
offspring is high
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
12.4 The presence of social associations
distinguishes polygynandry from
promiscuity
• Polygynandry (also called plural breeding)
– Social associations are formed between multiple
males and multiple females
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Polygynandry in European badgers
• Research question:
What is the mating
system of the European
badger? (Dugdale et al.
2007)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Polygynandry in European badgers
• Methods:
– European badger (Meles meles)
– Over a seven-year period, recorded social
associations of groups and collected blood
samples for DNA analysis to determine
parentage
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Polygynandry in European badgers
• Results:
– Social groups averaged six
adult males and six adult
females
– Within social groups, multiple
males and multiple females
reproduced within a single
breeding attempt
• Conclusion:
– Polygynandry is the mating
system in the populations
studied
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Promiscuity and scramble competition:
seaweed flies and red squirrels
• Promiscuity is characterized by scramble
competition: individuals compete with one
another to obtain copulations with multiple
mates
• For example, seaweed fly (Coelopa frigida) males
mount a female every eight minutes and a
female can mate with hundreds of males
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Promiscuity and scramble competition:
seaweed flies and red squirrels
• Research
question: What is
the mating
system of red
squirrels? (Lane
et al. 2008)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Promiscuity and scramble competition:
seaweed flies and red squirrels
• Methods:
– Red squirrels (Tamiasciurus hudsonicus)
– Marked individuals and collected blood
samples for DNA paternity analysis
– Followed females on their single day of sexual
receptivity and recorded “mating chases” and
copulations
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Promiscuity and scramble competition:
seaweed flies and red squirrels
• Results:
– Females copulated with an average of 5.8 males
– 82.5% of litters with more than one young were
sired by multiple males (mean of 2.3 sires per
litter)
• Conclusion:
– These data indicate a promiscuous mating system
with scramble competition
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
12.5 Social and genetic mating systems
differ when extra-pair mating occurs
• Social mating system
– Based on observations of social associations among the
sexes
• Genetic mating system
– Based on the actual number of sexual partners that
contribute to a set of offspring
• Extra-pair copulations
– Copulations that occur outside established social
associations (i.e., pair bonds)
• Genetic quality hypothesis
– Females that engage in multi-male matings can improve the
fitness of their offspring via genetic mechanisms
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Extra-pair mating in juncos
• Research question: Why do
female juncos engage in extrapair copulations? (Gerlach et al.
2012)
• Hypothesis: Females can
enhance the fitness of their
offspring
• Prediction: Offspring from
extra-pair matings will have
higher fitness than within-pair
offspring
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Extra-pair mating in juncos
• Methods:
– Dark-eyed juncos (Junco hyemalis)
– DNA analyses since 1990 allowed
determination of paternity
– Examined the number of secondgeneration offspring
(grandoffspring) produced by
males and females that were
produced from within-pair and
extra-pair matings
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Extra-pair mating in juncos
• Results:
– Extra-pair young
produced more
grandoffspring than
within-pair young
• Conclusion:
– The fitness of female
offspring from extra-pair
matings is higher than
that of within-pair young
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Marmot extra-pair mating
• Research question: Why do female marmots
engage in extra-pair copulations? (Cohas et al.
2007)
• Hypothesis: Females can enhance the fitness
of their offspring
• Prediction: Extra-pair young will have higher
fitness than within-pair young
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Marmot extra-pair mating
• Methods:
– Alpine marmots
(Marmota marmota)
– Marked individuals
and collected hair or tissue samples for DNA analysis
– Determined the social status of all individuals
(dominant or subordinate)
– Dominant males obtain most of the matings
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
Marmot extra-pair mating
• Results:
– Of 220 offspring, 45
resulted from extra-pair
matings
– Extra-pair offspring had
higher survivorship and a
greater probability of
becoming dominant than
within-pair young
• Conclusion:
– Females can improve their
fitness by seeking extra-pair
partners
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press