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This 4 page Class Notes was uploaded by Hiba Kouser on Monday February 22, 2016. The Class Notes belongs to BIOL 4700 at Clemson University taught by Michael J Childress in Fall 2016. Since its upload, it has received 39 views. For similar materials see Behavioral Ecology in Biology at Clemson University.
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Date Created: 02/22/16
L06 Notes: I. Mating systems A. Mating systems are not fixed and are often malleable depending on the environmental conditions 1. Mating system is measured over one reproductive season because they can change B. Monogamy (one male to one female) 1. If selection favors males to mate with many females, how can monogamy evolve? 2. Mate assistance a. Males will remain with one female because of male parental are and protection of offspring are essential for reproductive success b. Pups will likely die without male assistance c. Ex. Mongolian gerbil: males assist females in giving birth d. Malefemale partners become more efficient at raising offspring with experience i. The longer the pair stays together the higher the chance that the offspring will survive (thus leads to higher reproductive success) 3. Mate guarding a. Males will remain with one female because females are rare, receptive for only a short time, and/or widely dispersed b. Reproductive success is directly correlated with the ability to guard the mate c. Ex. Harlequin shrimp who live on host sea stars will sometimes abandon their own sea stars to find another one that has a female on it because finding females is often hard because they are rare and widely dispersed. d. Ex. Blue crabs: males guard females until they molt because mating can only occur when she molts and is in soft shell conditions (only then is she susceptible to fertilization) (note: blue crabs are not technically monogamous) 4. Mate enforced a. Mates remain with one partner because the partner prevents him/her from mating with others b. Monogamy is enforced by behavior of partner c. Ex. Wolves packs tend to have alpha males/females and alpha males will dominate the subordinate males to prevent mating and this can happen with alpha females too d. Ex. Certain songbird species i. Will only be aggressive to members of their own sex and their own species C. Polygyny 1. When should males switch from defending females to defending territories? a. When males tend to mate with more than one females and females tend to mate with just one male 2. Lek: location where males and females gather and males display for females in order to attain mates 3. Female Defense a. Males defend multiple females by preventing access by other males (males get exclusive access to females) i. Harem species female defense b. Effective only if females remain together and have reproductive synchrony 4. Resource defense a. Males defend a rich patch of resources visited by multiple females (usually will increase the male’s access to female because resources include food patches and water) b. Only effective if nesting locations are limited and easily defended by a single male 5. Lek a. Males compete directly for matings by displaying for multiple females i. Ex. Bower birds b. Movement of lek between breeding season suggests females come to the males rather than some resources they need D. Polyandry (when males mate with just one female and females get multiple males) 1. What are the costs of polyandry to females? a. Sex role reversal exists in coloration where females are more colorful than the males b. Costs can lead to changes in mating system c. Opportunity for femalefemale competition and male choice to evolve 2. How do females benefit from polyandry? a. No costs or less prevalent costs indicates that the mating system could favor polyandry b. Female egg production is faster than incubation time c. Females defend territories with multiple nests d. Males incubate the eggs while females mate with new males 3. Fertility insurance a. Increased genetic benefits due to maximizing the numbers of female eggs fertilized (assures that there is adequate sperm for all eggs to be fertilized if one male is not capable of fertilizing all eggs) 4. Good Genes a. Increased genetic benefits due to a greater chance of some offspring having a superior combination of genes b. Offspring have a greater chance of survival if the females mates with the right type for males c. Ex. In honeybees, when females mate with a single male, workers will share either 2575% of their alleles and are less susceptible to disease whereas if a female mates with a single mate, then all workers share 75% of their alleles i. Makes variable work force and makes them less susceptible to disease 5. More resources a. Increased material benefits due to nuptial gifts or extensive male parental care b. More resources gained by mating with multiple males and males can provide additional resources E. Polygynadry 1. When should species show flexibility in their mating system? 2. Scramble competition a. Males compete directly for fertilizations by spawning near females releasing eggs 3. Variable territory size a. Mate number depends on the number of overlapping territories b. All mating systems can occur even in same mating season 4. Increased protection a. Increased protection from harassment from other males b. Females that mate with multiple males benefit from their protection II. Mating system evolution A. Parental care model 1. Mating system is determined by distribution of parental care among sexes a. Male only: polyandry (doesn’t really exist in mammals) b. Biparental care: monogamy, polyandry c. Female only: polygyny, monogamy 2. Variations exist among polygynous and monogamous animals 3. When males are providing parental care, they mate with multiple females a. Fish have diverse mating system because you can start out male and can switch to female if it maximizes reproductive success B. Polygyny Threshold Model 1. Mating system is determined by the differences between the value of alternative male territories 2. Polygyny is favored when large differences between the resource value of male territories 3. PT= polygyny threshold a. How much better does a male’s territory have to be for a female to want to be in a polygynous household over a monogamous one b. Meaning that there exists conditions where it is better to be a polygynous female rather than a monogamous one C. Ecological Constraints Model 1. Mating system is determined by the combined influence of female reproductive synchrony and distribution of limiting resources 2. Polygyny favored when: a. Moderate reproductive synchrony b. High resource clumping 3. When resources are limited/widely dispersed then male parental care will increase and polygyny will decrease D. Genetic Constraints Model 1. Monogamous species often share traits a. High malefemale associations b. Biparental care offspring c. High aggression toward strangers d. High corticosterone and vasopressin e. Low testosterone 2. ex. Prairie voles and meadow voles look very similar, occupy burrow systems, and are in grassland habitats but one is polygynous and one is monogamous a. prairie voles usually found in malefemale pairs i. show elevated levels of parental care by both male and females ii. show elevated aggression toward others but elevated mating toward partners iii. females prefer to associate with odors of their partners over odors of a stranger male iv. females are sensitive to hormone oxytocin (released when performing parental care) also have a higher number of oxytocin receptors and are also sensitive to vasopressin (reduces aggression and is released along oxytocin) v. high concentrations of avrp1a receptors in their brain (due to mutation in the upstream regulator of this gene) vi. indicates that monogamy could have high genetic basis b. meadow voles usually found alone i. show moderate levels of parental care by females and almost none by males ii. do not prefer the odor of either partners or stranger male and prefer to be alone iii.when presence of avrp1a receptors is present, meadow vole males show parental care
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