Chapter 10 Part 3 Flashcards
Inbreeding avoidance hypothesis
in the context of mating, females mate polyandrously to avoid inbreeding with their social partner
Avian examples providing evidence for inbreeding avoidance hypothesis
red-backed fairy-wren: females paired with genetically similar males most likely to produce offspring with extra pair males that were more heterozygous than offspring produced with pair mate
purple-crowned fairy wren: highly incestuous species; limited dispersal opportunities forces pair-bonding with ones own offspring if pair-mate dies; these relationships lead the female to have extra-pair copulations and resulting extra pair offspring (43% of incestous pairs resulted in extra pair offspring vs. only 3% of nonincestous pairs)
Direct benefits of polyandry can be explained by what three hypothesis?
additional resources hypothesis, additional care hypothesis, and infanticide reduction hypothesis
Additional resources hypothesis
females mate polyandrously to gain access to additional resources from their partner
Examples providing support for the additional resources hypothesis
female red-winged blackbirds - can forage for food on territories of male they’v have extra pair relations with
bees - can collect nectar and pollen if they’ve mated with extra pair males; also seminal fluid from males may combat dehydration in females
insect species - nutritious spermatophores - more mates, more of these
polyandrous butterfly species - more protein in spermatophores, may be up to 15% of males body weight (good gift!); the more males they mate with the greater output of eggs
Additional care hypothesis
females mate polyandrously to gain more caregivers to help rear young
Examples providing support for the additional care hypothesis
Dunnock (european songbird) - encourage subordinate males to stick around by copulating with them when their pair-mate dominate males are away; can mate 12x/hour and may mate hundreds of times before laying a clutch of eggs; then utilizes parental care from both alpha and beta males
superb starling - unpaired males that mate with a paired female will help raise brood
infanticide reduction hypothesis
females mate polyandrously to create greater uncertainty about the paternity of offspring in order to reduce the risk of infanticide
Examples providing support for the infanticide reduction hypothesis
hanuman langur - males ignore the baby if they’ve previously mated with the mother
Polygyny = multiple mating by ______
males
What four hypotheses help explain polygyny in males?
female defense polygyny hypothesis, resource defense polygyny hypothesis, lek polygyny hypothesis, and scramble competition polygyny hypothesis
What is the most common mating system in nature?
polygyny
Female defense hypothesis
hypothesis explaining polygyny; when resources are evenly distributed in space but females form groups to better access those resources or to help dilute the risk of predation, males will follow and guard a group of females
Resource defense hypothesis
hypothesis explaining polygyny; when resources are clumped, attract multiple females, and are easily defensible, males will guard the resources - and by extension the females - by setting up a territory
lek hypothesis
hypothesis explaining polygyny; when resources are distributed heterogeneously and females are widespread and do not form groups, males will wait for females to come to them
scramble competition hypothesis
hypothesis explaining polygyny; when resources are distributed heterogeneously and females are widespread and do not form groups, males will seek out females
Evidence for female defense polygyny
siphonoecetine amphipods - females with elaborate cases may be glued to male (up to 3)
male lions - pride of females that have gathered together to defend permanent hunting territories and protection against infanticidal males
Montezuma oropendola (tropical blackbird) - nesting females group nests; dominant male can secure up to 80% of matings if he drives other potential mates away
plains zebra - females practice harem defense polygyny; females form groups to defend against risk of predation and advances of bachelor males; makes it easy for males to monopolize the entire group; females associated with dominate males are able to feed 10% longer/day
social monogamy (frequently, always, never) occurs in mammal species in which females form groups
never
in most polygynous species, the behavior of the ________ dictates the behavior of the _______ and ultimately the type of mating system
1) female
2) male
Grevy’s zebra and resource defense polygyny
females do not group together nor are overseen by males; females tend to be found in locations where food resources are scarce and unevenly spread; males dominate the resource rich areas (water) where receptive females tend to be
African cichlid fish and resource defense polygyny
males acquire a midden (batch) of empty snail shells that females use to lay their eggs in: the more shells he has the more females he will have
black-winged damselflies and resource defense polygyny
defend floating vegetation that serves as safe location for eggs (and a defensible resource)
antlered flies and resource defense polygyny
fight for rot spots on fallen trees that serve as nesting locations for females
neotropical harvestman spider and resource defense polygyny
males parental care, shown if he already has eggs in his burrow, and the resource of the burrow itself leads to additional female
When resources were experimentally redistributed among a dunnock songbird populations territory..
females given extra resources began to have reduced ranges and fewer social mates and female polyandry was replaced by female monogamy (males were also better able to monitor females kept in smaller territories)
Lek polygyny
lek = display area used to attract females; not necessarily full of any useful resources
Ex. white-bearded manakin; preferred males occupy central locations within the lek and engage in more aggressive displays
high reproductive skew is standard among lekking species (high inequalities in male mating success)
Ex. Topi lek; older males are preferred mates centered in the middle of the lek
Ex. west African hammer-headed bat; 6% of the males accounted for 80% of matings
Lekking evolves when..
other mating tactics do not pay off for males, typically due to a wide and even distribution of females
Hypothesis explaining lekking behaviors
hotspot hypothesis, hotshot hypothesis, and female preference hypothesis
hotspot hypothesis
males cluster in places (called “hotspots”) where the routes frequently traveled by receptive females intersect
hotshot hypothesis
subordinate males cluster around highly attractive males to have a chance to interact with females drawn to these “hotshots”
female preference hypothesis
males cluster because females prefer sites with large groups of males, where they can more quickly, or more safely, compare the quality of many potential mates
Evidence in support of the hotshot hypothesis
removal of a preferred male in the great snipe sandpiper led to dispersion of subordinate males away from that area
evidence in support of the hotspot hypothesis
indian peacocks gather in locations where females would have increased presence; tropical manakins are located in areas rich in resources that are attractive to females
evidence in support of the female preference hypothesis
minimal support
Scramble Competition Polygyny
when the costs of establishing territories exceed the benefits, males may simply seek scarce receptive females
Examples of scramble competition polygyny
photinus firefly; thirteen-lined group squirrels
explosive breeding assemblage
the temporary formation of a large group of mating individuals
Ex. horseshoe crab, wood frog
Polygynandry
tends to occur in species that form social groups; driven by density of the species and of resources
Examples of polygynandry
dunnocks (who display all types of mating systems) - most groups are made up of 2 males and 2 females
alpine accentor - typically made up of 1 dominant male, 1-3 subordinate males, and 2-4 females
Promiscuity
most common in species lacking parental care
examples of promiscuity
great tinamou - young are precocial requiring minimal parental care and enhanced parental freedom (females are the promiscuous sex)
marine snail - both sexes mate freely and frequently and only the females provide parental care only until eggs hatch
seaweed fly - no parental care is provided by either sex (convenience polyandry)
convenience polyandry
a form of polyandry in which a female will struggle with a male but acquiesces t his mating attempts in order to save time and energy
