Download Outline of: Bryja, J., Patzenhauerova, H., Albrecht, T., Mosansky, L

Outline of:
Bryja, J., Patzenhauerova, H., Albrecht, T., Mosansky, L., Stanko, M., Stopka, P. (2008).
Varying Levels of Female Promiscuity in Four Apodemus Mice Species. Behavioral Ecology
and Sociobiology, 63, 251-260. doi:10.1007/s00265-008-0656-7.
Outline by Alex Zolad, Moses Galvez, and Natasha Grabowski
For Dr. Mills’ Psych 310 Class, Spring 2011
A. INTRODUCTION
1. Evolution of Optimized strategies
a .Multiple-male mating (MMM)
b. Female Promiscuity
c. Benefits for females
i. Direct- Assurance of fertilization
ii. Indirect- Increased Genetic quality of offspring
2. Morphological traits correlating to promiscuous mating systems
a. Relative Testes Size- the larger, the more promiscuous.
b. Sperm Morphology
c. Size of Seminal vesicles and anterior prostate.
3. Ecological Factors
a. High population abundance
i. Dominant males can prevent copulations from subordinates
ii. Rate of female promiscuity lower during low abundance- lack of males
b. Highly synchronized reproductive period
c. Migratory behavior
d. Short life span
4. Study Goals
a. Identify species specificity and within species variation for MMM in 4 species of
Apodemus mice
b. Assess the role of ecological factors that might have shaped the evolution of
species-specific mating system
c. Use testes size to confirm level of multi-male mating
d. Test for Effects of season and abundance on mean number of father per litter
e. Test the predictions that multiple paternity is a result of forced copulations
f. Test prediction that fertilization by several males leads to increased litter size
B. MATERIALS AND METHODS OF RESEARCH
1. Pregnant Females
a. 127 from 4 species
b. 50 live or snap traps among four main habitat types: Poplar windbreaks, lowland
forests and shrubs, cultivated or abandoned fields, river valleys.
c.Uterus removed and embryos extracted
2. Testes Size
a. Males in full reproductive condition
i. Left testes length from fresh dissected testes
ii. Mass of both testes
3. Paternity Analysis
a. DNA extracted from embryos and tails of females
i.Genotypes determines using 8 micro-satellite loci.
ii.Compare genotypes of mother to offspring
iii.Greater than 2 paternal alleles at a locus in one litter = multiple paternity.
4. Statistical Analysis Techniques
a. Female- body length from muzzle to anus (mm)
b. Season- Number of days from beginning of the year to capture date
c. Number of Embryos (Litter size)
d. Abundance- Number of individuals per species captures per 100 trap nights
e. Paternity Status- Binary dependent variable
f. Species- Categorical predictor
g. Continuous explanatory variables
i. Population abundance
ii. Female body size
iii. Litter size
C. RESULTS
1. MMM detected in all analyzed species
a. Up to 2 fathers per litter in A. uralensis and A. flavicollis
b. Up to 3 fathers per litter in two A. sylvaticus females (9.1%) and seven A. agrarius
females (20.6%).
c. Least Promiscuous species- A. uralensis (only 43.5% of litters from multiple fathers)
d. Most Promiscuous species- A. sylvaticus (68.2%)
i. In early spring promiscuous mating can be skewed due to high winter mortality.
Results restricted to after mid-May yield A. agrarius as most promiscuous
(69.2%)
2. Relative Testes Size
a. Smallest testes size- A. uralensis
b. Largest testes size- A. agrarius
c. Strong relationship between mean relative testes size and proportion of multiple sires
litters after mid may.
3. Probability of MMM based on other variables
a. Together, probability of MMM independent of abundance, body size, litter size,
season,
species
b. Proportion of litters sired by more than 1 male decreased with season in A. uralensis
and increased with A. agrarius.
c. Higher abundance associated with increased multiple paternity in A. uralensis.
d. Body size unrelated to MMM in all species
D. CONCLUSIONS / DISCUSSION
1. Benefits and Evolution of MMM
a. Period of female receptivity is prolonged and more frequent in response to MMMAssures successful fertilization with fresh sperm.
b. Increased genetic diversity of litter
c. Obscures paternity, deterring infanticide.
2. A. uralensis differences
a. Low level of promiscuity
i. Rarely aggressive towards each other
ii. Rarely exchange allogrooming for sex
iii. Suggests that sex is not a commodity which may be bartered by females for
fitness benefits with several males
Test Questions for:
Bryja, J., Patzenhauerova, H., Albrecht, T., Mosansky, L., Stanko, M., Stopka, P. (2008).
Varying Levels of Female Promiscuity in Four Apodemus Mice Species. Behavioral Ecology
and Sociobiology, 63, 251-260. doi:10.1007/s00265-008-0656-7
Test Questions by Alex Zolad, Moses Galvez, and Natasha Grabowski
For Dr. Mills’ Psych 310 Class, Spring 2011
1) True or false, larger testes size is often correlated with an increased level of promiscuity in
animals?
2) True or false, larger female animals are more likely to be forced into copulation?
3) True or False, both males and females benefit from Promiscuous mating systems?
4) What is MMM?
a) Multiple-Male Monogamy
b) Masculine Male Mating
c) Multiple-Male Mating
d) Male Mating Morphology
5) Which of the following is a mating system?
a) Polygyny
b) Polyandry
c) Promiscuity
d) Monogamy
e) All of the above
6) Benefits of promiscuous mating systems?
a) Decreased fertility
b) Assurance of Successful Fertilization
c) Increased Genetic Diversity
d) Both b and c
ANSWER KEY
1) True
2) False
3) True
4) C) Multiple-Male Mating
5) E) All of the Above
6) D) Both b and c
Critical Review for:
Bryja, J., Patzenhauerova, H., Albrecht, T., Mosansky, L., Stanko, M., Stopka, P. (2008).
Varying Levels of Female Promiscuity in Four Apodemus Mice Species. Behavioral Ecology
and Sociobiology, 63, 251-260. doi:10.1007/s00265-008-0656-7
Critical Review by Alex Zolad, Moses Galvez, and Natasha Grabowski
For Dr. Mills’ Psych 310 Class, Spring 2011
Interesting and Informative
1. One of the major foundations of this article was that multiple sires were found for many of the
litters. This is interesting because it seems unusual to think that in one litter born at the same
time there can be multiple fathers, since in humans there is only one father per pregnancy.
This definitely shows why males need to be able to produce as much sperm as possible to
compete with the sperm of other males.
2. It was interesting that sub-species that were more promiscuous tended to have correlating
larger sized testes. This is because in the more promiscuous sub-species, the more sperm
competition. Thus the males with the largest testes and the most amount of sperm would have
a higher chance of fathering a larger percent of the litter and passing on their genes to future
generations.
3. Another informative aspect of the article dealt with the least promiscuous sub species (A.
uralensis). Not only did the least promiscuous sub-species have comparatively smaller
testicles, but they also exhibit different behaviors than the others. They are less aggressive
towards one another, and don’t exchange allogrooming for sex nearly as often as the most
promiscuous sub-species (A. agrarius). We are interested in the cause and effect relationship
of their aggressiveness vs. testes size. Are they less aggressive because they have smaller
testes and thus less testosterone, or are their testes smaller because there is less competition
between males for mating partners than in more promiscuous species?
Concerns with the Study
1. One of our major concerns with the results of this study were the small sample sizes used to
collect the data. The largest sample size was 46 litters for one of the sub-species. Yet one of
the sub-species only had 22 litters total for testing. We do not believe that either of these are
large enough to give a true enough characterization of the species at a whole.
2. In their introduction the researchers claim that their goals are to prove how environmental
factors effect promiscuity, yet environmental factors aren’t really part of their testing protocol
other than the fact that each sub-species came from a different area. The sub species are
compared with each other to see which had higher rates of promiscuity and testes size, yet the
results are never discussed in relation to the environment each sub species came from. For
example, A. uralensis was found to be the least promiscuous. But what is it about their
environment that makes them less promiscuous than A. agrarius (the most promiscuous)? The
only factor the researchers take into account that could be thought of as en environmental
factor is the abundance (the amount caught per 100 trap nights). Yet for that to truly take into
account environmental factors, it would also have to include what about each specific
environment affected the abundance itself.
3. Finally, the lack of actual observation of the species is a definite problem in the study if a true
full understanding of their mating practices is to be obtained. The data obtained for this study
was all taken from deceased mice (whether they were killed in the trap or after being caught).
While a good understanding can be taken from these results, they would be much more powerful
if observable actions fit the same pattern. For example, the researchers hypothesized that there
would be more forced copulations when the females were of smaller size, and thus less likely to
be able to defend themselves. Yet, the measurements of female size didn’t yield any significant
results from the study. If the species had actually been observed, a more definite answer could
have been obtained. It should be noted, however, that the researchers themselves do recognize
this fault in their study.