11.1 sexual selection favors characteristics that enhance reproductive success primary sexual...
Post on 21-Jan-2016
221 Views
Preview:
TRANSCRIPT
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
11.1 Sexual selection favors characteristics that enhance reproductive success
• Primary sexual characteristics– Genitalia and organs of reproduction
• Secondary sexual characteristics– Morphological differences between the sexes
that are not directly involved in reproduction
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Bateman’s hypothesis
• Bateman’s hypothesis:– Female
reproductive success is most strongly limited by the number and success of eggs that she can produce, whereas male reproductive success is limited by the number of mates
Figure 11-9
Figure 11-10
Figure 11-11
Figure 11-12
Figure 10.8 Differences between the sexes in sexual behavior may arise from fundamental differences in parental investment that affect the rate at which individuals can produce offspring
Antlers as weapons in red deer
• Research question: Are antlers weapons used in mate competition? (Kruuk et al. 2002)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Antlers as weapons in red deer
• Methods:– Red deer (Cervus
elaphas)– Collected and
weighed antlers shed
– Used blood samples to determine reproductive success (paternity)
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Antlers as weapons in red deer
• Results:– Males with larger
antlers had higher reproductive success
• Conclusion:– Sexual selection
has influenced antlers as an exaggerated trait in mate choice
Featured Research
Weapon size and mating success in dung beetles
• Research question: What is the role of the male’s horn-like projection? (Pomfret & Knell 2006)
• Hypothesis: Large horns provide an advantage in mate competition
• Prediction: Males with the larger horn will win most fights
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Weapon size and mating success in dung beetles
• Methods:– Dung beetles (Euoniticellus intermedius)– Staged fights between males matched
for body size but not horn length– Recorded outcome of interactions and
mating success
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Weapon size and mating success in dung beetles
• Results:– Males with larger
horns won more fights
• Conclusion:– The maintenance of
long horns can be explained by sexual selection driven by male-male competition
Featured Research
Ornaments and mate choice in peafowl
• Research question: Are peacock tails an ornament used in mate choice? (Loyau, Saint Jalme, & Sorci 2005)
• Males aggregate on leks, where they display to females
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Ornaments and mate choice in peafowl
• Methods:– Peacocks (Pavo cristatus)– Measured:
• Tail length and male body size• Number and duration of tail displays• Number of vocalizations and copulations
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Ornaments and mate choice in peafowl
• Results:– Larger males with
longer tails were most successful in defending a display site
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Ornaments and mate choice in peafowl
• Results:– Males performing the
most displays and with the greatest number of ocelli obtained the most copulations
• Conclusion:– Mate competition and
mate choice are important in evolution of peacock tail
Featured Research
The origin of sexually selected traits: the sensory bias hypothesis in guppies
• Research question: How does a male trait become selected in female mate preference? (Rodd et al. 2002)
• Hypothesis: Sensory bias hypothesis – female mating preferences are a byproduct of preexisting biases in a female’s sensory system
• Prediction: Males and females should be attracted to orange-colored objects because orange is associated with carotenoids
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
The origin of sexually selected traits: the sensory bias hypothesis in guppies
• Methods:– Guppies (Poecilia
reticulata)– Several populations– Placed small color
discs on leaf in water– Recorded all
approaches and pecks
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
The origin of sexually selected traits: the sensory bias hypothesis in guppies
• Results:– Males and females were
attracted to orange and red discs
• Conclusion:– Female mating
preference could be linked to preexisting preference for orange food objects
Featured Research
Jones and Hunter 1998
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
11.2 Females select males to obtain direct material benefits
• Direct material benefits– Material resources obtained by a female
from mating with a particular male
• Nuptial gift– A physical resource such as a food item
that a male provides to a female to enhance his mating success
Female choice and nuptial gifts in fireflies
• Research question: How does the variation in the duration of male flashes affect female choice and fitness? (Lewis, Cratsley, & Rooney 2004)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Female choice and nuptial gifts in fireflies
• Methods:– Fireflies (Photinus
ignitus)– Measured male flash
duration and spermatophore size
– Created flashes of different lengths and measured female response
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Female choice and nuptial gifts in fireflies
• Results:– Males with
longer flash duration had larger spermatophores
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Female choice and nuptial gifts in fireflies
• Results:– Females responded more
to longer flashes
• Conclusion:– Females prefer to mate
with males with the longest flash duration and thus the largest spermatophores, which should increase fitness
Featured Research
Female choice and territory quality in lizards
• Research question: How does territory quality affect female choice and fitness? (Calsbeek & Sinervo 2002)
• Territory quality is based on rockiness (microclimates)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Female choice and territory quality in lizards
• Methods:– Side-blotched lizards (Uta stansburiana)– Larger males have territories with more
rocks – Manipulated territory quality
• Added rocks to small males’ territories• Removed rocks from large males’ territories
– Observed female mate choice– Measured egg-laying date and egg mass
of females
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Female choice and territory quality in lizards
• Results:– Females preferred improved
territories– Females on improved territories
laid eggs sooner and produced larger egg masses
• Conclusion:– Females select males based on
territory quality and derive a significant fitness gain by doing so
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
11.3 Female mate choice can evolve via indirect benefits to offspring
• Indirect genetic benefits– Genetic benefits females can obtain for
their offspring by mating with males that have high genetic quality
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Fisherian runaway and good genes
• Runaway process– An evolutionary process in which a male
trait co-evolves with a female preference for it and becomes increasingly exaggerated
• Handicap principle– Well-developed secondary sexual
characteristics are costly to survival but reliable signals of fitness
• Good genes– The alleles of high-quality individuals
Figure 11-32
Figure 16-14
Figure 16-15b
Sexual dimorphism
And behavior!
Long-tailed widowbird (male on left)
Mate choice for good genes in frogs
• Research question: How do females assess male quality? (Jacquiéry et al. 2009)
• Hypothesis: Females select males for genetic benefits based on their vocalizations
• Prediction: The most attractive males provide the best gene alleles (fitness) to offspring
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate choice for good genes in frogs
• Methods:– European tree frogs (Hyla arborea)– Captured and identified males
from four ponds– Observed number of matings– Collected egg masses and reared
in lab– Measured tadpole growth rate and
survival– Genotyped tadpoles to determine
parentage
Featured Research
SONG video
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate choice for good genes in frogs
• Results:– Only 10 of 15 males
sired offspring– Males that sired more
offspring produced tadpoles with higher growth rates
• Conclusion:– Females select males
for genetic benefits
Featured Research
Good genes and immune system function in birds
• Research question: How does parasite load affect mate choice? (Zuk et al. 1990)
• Hypothesis: Hamilton-Zuk hypothesis– Parasites and pathogens play an important role in
sexual selection when secondary sexual traits are costly and condition-dependent
• Predictions:1. Females should prefer to mate with males that have
the greatest expression of secondary sexual traits2. High parasite loads will reduce that expression in
males
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Good genes and immune system function in birds
• Methods:– Red jungle fowl (Gallus
gallus)– Infected half the males with
intestinal nematode– Measured size and color
intensity of comb – Conducted mate choice trials
with infected and controls (uninfected) males
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Good genes and immune system function in birds
• Results:– Parasitized males had
smaller, duller combs than controls
– Females preferred control males
• Conclusion:– Support for Hamilton-Zuk
hypothesis
Featured Research
Mate choice fitness benefits in spiders
• Research question: What is the importance of pheromones as signals of male quality in mate choice? (Koh et al. 2009)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate choice fitness benefits in spiders
• Methods:– Spitting spider (Scytodes sp.)– Mate choice experiment in Y
test chamber• Phase 1: Two males at end of
arms (chemical cues only)• Phase 2: Pheromones of males
only at end of arms (on filter paper)
– Mating experiment• Half of females mated with
preferred male, half with nonpreferred male
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate choice fitness benefits in spiders
• Results:– In Phase 2, almost
all females chose the pheromone of the male they chose in Phase 1
– Females who mated with preferred males had larger egg sacs, more and heavier eggs, and a higher hatch rate
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate choice fitness benefits in spiders
• Conclusion:– Male pheromones may function to
convey information about male quality
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
11.4 Sexual selection can also occur after mating
• Mate guarding– When a male follows his mate to prevent
her from mating with rivals – beetle video; fly video
• Extra-pair young– Offspring of a pair-bonded female
produced outside the pair bond by a third-party male
Mate guarding in warblers
• Research question: How effective is mate guarding? (Chuang-Dobbs, Webster, & Holmes 2001)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate guarding in warblers
• Methods:– Black-throated blue
warblers (Dendroica caerulescens)
– Observations:• Followed focal males and
measured distance between them and their mates
– Experiment:• Removed some males for
one hour during female’s fertile period
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate guarding in warblers
• Results:– Males who spent more time
mate guarding had fewer extra-pair offspring
– Experimentally removed males had more extra-pair offspring
• Conclusion:– Mate guarding can be an
effective strategy for increasing paternity assurance
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Sexual selection after mating
• Sperm competition– Competition between sperm of different
males to fertilize eggs
• Cryptic female choice– When female influences the fertilization
success of sperm from one male over that of others
• Inbreeding depression– A reduction in fitness as a result of mating
with close relatives
Sperm competition in tree swallows
• Research question: How can males increase paternity assurance? (Crowe et al. 2009)
• Hypothesis: Paternity assurance can be enhanced through frequent copulations
• Prediction: An increase in copulation rate should result in an increase in paternity for a male
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Sperm competition in tree swallows
• Methods:– Tree swallows
(Tachycineta bicolor)– Uniquely marked birds
and collected blood samples for genetic analysis
– Observed focal pairs for three hours per day for two weeks
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Sperm competition in tree swallows
• Results:– Increases in copulation
rate resulted in decrease of extra- pair offspring
• Conclusion:– Males can reduce
paternity loss from sperm competition by increasing their copulation frequency
Featured Research
Inbreeding avoidance via cryptic female choice in spiders
• Research question: Do females avoid inbreeding depression by cryptic female choice? (Welke & Schneider 2009)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Inbreeding avoidance via cryptic female choice in spiders
• Methods:– Orb spiders (Argiope lobata)– Experiment 1– Mating trials in which a
female mated sequentially with:• 1) Two sibling males (SS)• 2) Two nonsibling males (NN)• 3) Sibling and nonsibling male (SN or NS)
– Experiment 2 – Mating trials• One male of pair was made sterile
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Inbreeding avoidance via cryptic female choice in spiders
• Results:– For second male:
• Females stored more sperm from nonsibling than from sibling
• More eggs fertilized
• Conclusion:– Females display cryptic female
choice in regard to matings with siblings, which should reduce inbreeding depression
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
11.5 Mate choice by females favors alternative reproductive tactics in males
• Alternative mating tactics– Multiple behavioral mating phenotypes in a population
• Satellite male– Alternative, parasitic mating tactic in which a male
remains near a bourgeois male to intercept females that are attracted to the bourgeois male
• Sneaker male– Alternative, parasitic mating tactic in which a male
attempts to avoid detection so that he can quickly enter a bourgeois territory to fertilize eggs being deposited in a nest
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Evolution of alternative reproductive tactics
• Conditional strategy– Use of a particular strategy based on an
individual’s condition
• Evolutionary stable strategy (ESS)– A strategy that, if adopted by individuals
in a population, cannot be trumped by another strategy because it yields the highest fitness
Conditional satellite males in tree frogs
• Research question: Does male tree frog mating behavior represent a conditional reproductive strategy? (Humfeld 2008)
• Hypothesis: Males will adopt reproductive strategies based on their condition
• Predictions:1. Males differ in attractiveness to females;
unattractive males will be satellites2. Satellite males should have the same call
preferences as females (lower-frequency calls)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Conditional satellite males in tree frogs
• Methods:– Green tree frogs (Hyla
cinerea)– Recorded calls of bourgeois
and satellite males– Created synthesized calls
(lowest frequencies 700 Hz and 840 Hz or 840 Hz and 1120 Hz)
– Conducted choice tests for calls with females and satellite males
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Conditional satellite males in tree frogs
• Results:– Bourgeois males were
larger and produced lower-frequency calls than satellite males
– Females and satellite males preferred lowest-frequency calls
• Conclusion:– Males adopt a conditional
strategy
Featured Research
ESS and sunfish sneaker males
• Research question: What is the reproductive success of parental and sneaker male pumpkinseed sunfish? (Rio-Cardenas & Webster 2008)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
ESS and sunfish sneaker males
• Methods:– Pumpkinseed sunfish
(Lepomis gibbosus)– Mapped all nest
locations– Captured nesting males
(parentals), females, and sneakers at nest and all developing eggs
– Conducted genotype analysis
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
ESS and sunfish sneaker males
• Results:– Parentals larger and older than
sneakers– Parentals sired about 85% of
offspring in their nest– Sneakers are very rare in
population, and their reproductive success is proportional to their abundance
• Conclusion:– The two strategies have equal
fitness
Featured Research
Two examples of alternative mating tactics.
Bryan D. Neff, and Erik I. Svensson Phil. Trans. R. Soc. B 2013;368:20120045
©2013 by The Royal Society
Roughgarden 2004
Roughgarden 2004
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
11.6 Learning and mating
• Mate choice copying– When one individual observes and
copies the mating decisions of another individual
• Sexual imprinting –– mate choice influenced by traits seen
in ‘sensitive’ period (e.g., influenced by parents’ traits)
Mate copying in guppies
• Research question: Do females copy the mate choice of other females? (Dugatkin 1992)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate copying in guppies
• Methods:– Focal female mate choice test– Model female then placed next to
nonchosen male so that focal female could observe
– Focal female mate choice test
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Mate copying in guppies
• Results:– 17 out of 20 females spent more time
near the male that had been near the model female
• Conclusion:– Females switched their mate choice
preference to copy the mate choice of the model female
Featured Research
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
The benefit of mate copying
• Mate choice copying should only occur when discrimination among potential mates is difficult– Males are very similar– Females are inexperienced
Nonindependent mate choice by male mosquitofish
• Research question: Does the risk of sperm competition affect mate choice? (Wong & McCarthy 2009)
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Nonindependent mate choice by male mosquitofish• Methods:
– Focal male mate choice test– Rival male then placed next to
each female– Focal male mate choice test– Experiment 1 – focal male
cannot see rival– Experiment 2 – focal male
observes rival near chosen female
– Experiment 3 – focal male observes rival near nonchosen female
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Nonindependent mate choice by male mosquitofish
• Results:– Experiments 1 and 3 –
males preferred larger female
– Experiment 2 – focal male spent less time with chosen female during the last stage
• Conclusion:– Male mate choice is affected
by risk of sperm competition
Featured Research
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Megalagrion calliphya Beautiful Hawaiian Damselfly
Individual Type
Proportion Sexual InteractionsProportion Sexual Interaction Time
MaleGynomorphAndromorphMaleGynomorphAndromorph
1.0
0.8
0.6
0.4
0.2
0.0
Figure 6. The proportion of sexual interactions between Megalagrion calliphya focal andromorphs, gynomorphs, and males from Upper Mountain House Road (UMHR) (Wilcoxon Each Pair test, n=9 gynomorphs, n=8 males, n=8 andromorphs, p=0.0305 between males and andromorphs, p>0.05 for all other comparisons). In addition, the proportion of the total time spent sexually interacting between the three individual types at UMHR (Wilcoxon Each Pair test, n=10 gynomorphs, n=11 males, n=10 andromorphs, p=0.0365). The quartile method was used to calculate endpoints. Outliers are signified by the * symbol.
R. Rasmussen MAP Summer 2016
top related