Life History • life history is its lifetime pattern: • growth, • development • reproduction. • Physiological, morphological and behavioral adaptations are associated with an organism’s life history patterns • Reproductive adaptations are the most important to an organisms overall fitness (def.)
Asexual versus sexual reproduction • Asexual- • identical offspring well adapted to current environment • All individuals can reproduce • potentially higher population growth • No reproductive organs needed • (No gene recombination/no new genotypes) Hydra budding
Sexual Reproduction • 2 haploid gametes →diploid cell ( zygote ) • Higher genetic variability- each individual organism genetically unique which leads to broader range of responses to the environment • Energetically expensive- reproductive organs, courtship and mating behaviors • Only females reproduce • Half the genetic material from each parent
Can both be done? • Parthenogenesis • Virgin Birth • An egg cell can develop into an offspring without being activated by a sperm. • Offspring are genetically identical to mother and can be male or female, and haploid or diploid depending upon the species.
Parthenogenesis ex. • Whiptail lizards-live in southwestern US and northern Mexico • Parthenogenetic species arose from hybridization of sexual species
Sexual Reproduction • Dioecious-separate male and female individuals • Hermaphroditic-organisms possess both male and female organs • In plants • with bisexual flowers (perfect) • Monoecious-separate male and female flowers on the same plant
http://www.hiltonpond.org/images/HickoryShagbarkFlowerM01.jpghttp://www.hiltonpond.org/images/HickoryShagbarkFlowerM01.jpg ex. Juglandaceae http://www.duke.edu/~cwcook/trees/cala.html
Hermaphroditic animals • Possess ♂ & ♀ sex organs • Simultaneous- the ♂ organ of individual mates with ♀ organ of another & vice versa. • 2X offspring (ex. earthworm)
Hermaphroditic animals • Sequential hermaphrodites- Change from one sex to another • (at some point in the life cycle). • Change due to Δin sex ratio (in population). • Ex. “Nemo”
“NEMO” • In clownfish (those cute orange fish that live with anemones), only the largest female and male of a group reproduce. If this large female dies, her mate becomes a female. Then the largest juvenile in the family moves up, becoming the new male.
Other fish make more than one sex change • ex. Japanese reef gobies: • a ♀ will become ♂ if dominant ♂ leaves. • if larger ♂ joins group the new ♂ reverts back to ♀ form. • This sex change takes only four days.
Sequential Hermaphrodites • Jack-in-the-pulpit • Asexual, male or female depending on its energy reserves. • What is the energy benefit male vs female?
Mating systems • Mating systems-pattern of mating between ♂&♀ in a population • Monogamy- formation of a lasting pair bond between one male and one female • Common in birds • Rare in mammals • Except where cooperative rearing is required. • ex. Fox, beaver, weasel, wolf, prairie vole…..
Birds previously believed to be the paradigm, however… • In birds extra-pair offspring were found in approximately 90% of species. • In socially monogamous species, • over 11% (avg.) of offspring are result extra-pair paternity…. • “Cheating”
Mating systems • Promiscuity- • ♂ & ♀ mate with ≥ 1mate • form no pair bond. • Is rare because choosing mates usually is advantageous. Why? • Might arise when the environment is unpredictable or resources/territories can be monopolized
Mating Systems • Polygamy: 1 individual paired w/ 2+ unmated individuals • Polygyny- one ♂ with >1 ♀ (more common) • Female gains advantage in a variable environment. (red-winged blackbird) • Male benefit? • Polyandry- one ♀ with >1 ♂ (rare) • three groups of birds: • the jacanas • phalaropes • sandpipers
The Bateman principle– • ♂ reproductive success (RS) • increases with the number of mates • males benefit from mating with ++ females • ♀ RS • does not increase with ++mates • females to mate w/ high quality ♂’s • eg. ♂ protects rich resource vs. poor resource **Each strategy allows max. reproductive fitness but via different means. There is a not a conflict of interest per se
Sexual Selection • Intrasexual selection- involves male-to-male competition for the opportunity to mate. • Leads to: • large size • aggressiveness • Antlers/horns
Intersexual selection • Differential attractiveness of individuals of one sex to another. • Bright plumage, sexual displays, exaggerated horns and antlers. • Superior Courtship displays
http://news.nationalgeographic.com/news/2007/02/070221-riflebird-video.htmlhttp://news.nationalgeographic.com/news/2007/02/070221-riflebird-video.html Courtship display:
http://farm3.static.flickr.com/2366/2417051418_f4508fa954.jpghttp://farm3.static.flickr.com/2366/2417051418_f4508fa954.jpg • Leks (lěk)/ Arena- “single’s bars” of the animal world • Males defend small resource-less territories with conspicuous displays. Females visit to select mate (and move on). Sage Grouse
Resource based selection • Monogamous- can base choice on habitat or food that will improve fitness • Polygamous- share the male with superior habitat, or select inferior male without having to share.
Energy Budget • Energy is limited. • Budget must include: growth, maintenance, acquiring food, defending territory, escaping predators &... • Reproductive effort: Time &energy for reproduction. • frequency of reproduction varies between organisms. Ultimate goal of fitness - leave the most surviving offspring (genes). • Energy spent= production of offspring + cost of care and nourishment.
Trade off • Energy for reproduction • Can’t be used for other purposes • Trade-offs/compromizes constant • Breed this year or next? • Decreased growth affects • Ability to compete • survival • future reproduction….. • Repro. Investment • determines fitness (# offspring who reproduce)
Maximizing Fitness • Maximizing surviving/breeding offspring • Involves: • timing of reprod. • investment in reproduction • number of offspring • size of offspring • care & defense of offspring ***End of material for test 2-Mar. 30, 2009***
Timing • Semelparity – • invest all energy into growth, development and energy storage. • One suicidal act of reproduction. • (ex: most insects, some invertebrates and many salmon) • (ex: plants- “annuals,” bamboo, century plant…) http://en.wikipedia.org/wiki/File:CenturyPlants.jpg
Timing • Iteroparous – • Repeated reproduction (timing varies between organisms). • relatively fewer offspring/ reprod. cycle • Iteroparity is of great value to organisms when the survivorship of the offspring is uncertain. • Reproductive trade-off (dilemma). • Earlier reproduction- less growth, earlier maturity, reduced survivorship and reduced future reproduction • Delayed reproduction- increased growth, later maturity, increased survivorship, but less time for reproduction.
Timing • Delayed reproduction • greater number of offspring produced. • Delay allows organisms to reach an adequate size. (More obvious in indeterminate growth species).
This does not mean that larger species have higher fecundity than smaller species. • Only describes within species.
Care/Parental investment • Large #’s Offspring • Little investment in each • Small number’s of offspring • More investment in each • Amount investment varies due to: • #, size, maturity at birth (of offspring)
Care/Parental investment • Precocial animals • long incubation • advanced development (at birth/hatching) • mobile & self foraging (shortly after) • (Ex. Chickens, turkeys, ducks, geese, ungulates) • Altricial animals • short incubation • underdeveloped young (at birth/hatching) • much care required • (ex. Songbirds, mice, dogs….) • Degree of care varies (highly) • cod vs. bass • most reptiles vs. crocodilians • social insects vs. most insects
Factors affecting reproduction • Food supply- • can affect size of organisms thereby lowering fecundity • Food shortage may necessitate reduction in young (after production). • Asynchronous hatching • different aged brood mates • favors older siblings • Younger siblings survive in “good” years • Siblicide • insurance against infertile eggs • survivor monopolizes resources (helps assures own fitness)
Factors affecting reproduction • Higher Latitude- • Birds: higher clutch sizes • Mammals: larger litter • Lower latitude- • smaller clutches • earlier reproduction • higher adult mortality
Why Latitude effect? • Lack’s hypothesis- clutch size is an adaptation to food availability. • Cody’s hypothesis- periodic local climate catastrophes in temperate regions holds population below carrying capacity. • populations respond large clutch size. • Ashmole’s hypothesis- high winter mortality means more food for breeding population. • clutch size inverse to winter food supply
Factors affecting reproduction • Habitat selection- process of choosing a specific habitat to inhabit. • Key aspects of habitat: • Food availability • Shelter/cover • Predators & human presence • Disturbance • Physical structure examples: • Types of terrain (ex. wetland, steams, mountains..) • Gross vegetation (ex. grassland, forest…) • Structure of plants (vertical layers present?) • Species of plants present • Structural features of plants (food, nesting locations, perches, shelter…) **All directly affect fecundity. Best habitats fill up fast, Poor last http://www.helsinki.fi/science/metapop/Research/Project_bear.htm Examples of limiting factors in habitat: - Crotalus Hibernacula & humans - Wood duck nest sites - Monarch & milkweed - Blackfooted ferret & prairie dogs - Ivory-bill woodpecker & old growth - song-bird nests & cowbirds - etc. etc. etc. …..
Fig. 8-16 Habitat Selection