Mating Systems in Birds II: Factors Affecting Choice JodyLee Estrada Duek, Ph.D. With assistance from Dr. Gary Ritchison How he moves King bird of paradise How he looks Wilson’s bird of paradise How he sounds Wilson’s warbler How he builds Weaver bird

Decision making and mates How does a female choose? (or a male in polyandrous situations?) (Bower bird video Attenborough about 20% down page) or use: Nature's Master Builder - video powered by Metacafe Satin bower bird with robotic female fembot Attraction: Structural

Vogelkop Bowerbird, Amblyornis inornatus

Major Histocompatibility Complex: MHC The major histocompatibility complex (MHC) is a large genomic region found in most vertebrates. most gene-dense region of the mammalian genome, important role in the immune system, autoimmunity, and reproductive success. The proteins encoded by the MHC expressed on the surface of cells in all jawed vertebrates, and display both self antigens (peptide fragments from the cell itself) and nonself antigens (e.g. fragments of invading microorganisms) to a type of white blood cell called a T cell that has the capacity to kill or co-ordinate the killing of pathogens, infected or malfunctioning cells. Helps the body recognize itself, and target nonself invaders Genetically advantageous to outcross for variability in MHC genome T-shirt study by Wedekind, et al, 1995

MHC-dependent mate preferences in humans One substantial benefit of sexual reproduction could be that it allows animals to react to a continuously changing environmental selection pressure such as coevolving parasites. This would be most efficient if females able to provide their progeny with allele combinations for loci crucial in the parasite-host arms race, e.g MHC MHC influences both body odours and body odour preferences in humans, and that the women's preferences depend on their hormonal status. Female and male students were typed for their HLA-A, -B and -DR. – Each male student wore a T-shirt for two consecutive nights. – The next day, each female student was asked to rate the odours of six T-shirts. – They scored male body odours as more pleasant when they differed from the men in their MHC than when they were more similar. – This difference in odour assessment was reversed when the women rating the odours were taking oral contraceptives. – Furthermore, the odours of MHC-dissimilar men remind the test women more often of their own actual or former mates than do the odours of MHC-similar men. – This suggests that the MHC or linked genes influence human mate choice today. Proc Biol Sci Jun 22;260(1359): Wedekind C, Seebeck T, Bettens F, Paepke AJ. PMID: [PubMed - indexed for MEDLINE]Wedekind CSeebeck TBettens FPaepke AJ

The ideal weaver bird nest: large opening, flattened at the bottom, well attached to a branch Attraction: Structural The weaver bird saga… you attract her with a fine nest… Weaver birds, Dikololo Preserve, S. Africa

Weber’s law the ability of an individual to discriminate a difference between stimuli decreases with the size or intensity of those stimuli. if females choose mates based, in part, on tail length, it's more difficult for females to distinguish between males that differ slightly in tail length as the length of tails (over evolutionary time) increases. Blue bird of paradise

Blue Bird of Paradise, Paradisaea rudolphi The Strangest Bird Sounds - video powered by Metacafe Blue Bird of Paradise, Paradisaea rudolphi The Strangest Bird Sounds - video powered by Metacafe Attraction Sounds

Peak shift if a female acquires a 'preference' (e.g.,by imprinting on some characteristic or characteristics of her father), then, later in life, she may exhibit a preference for males that exhibit an 'enhanced' version of that (or those) characteristic(s). Lesser bird of paradise

Attraction sounds & displays Courtship display of Clark's Grebes about 25% down

Best-of-n females 'samples' a certain number of males (e.g., perhaps a migrant female arrives in a breeding area and visits five males and territories), then chooses as her mate the 'best' of those sampled males.

Attraction sounds & displays Andean cock-of-the-rock (Rupicola peruviana) about 20% down

Threshold a female may have a 'standard' in terms of mate quality and chooses as her mate the first male that meets or exceeds that standard.

Attraction Sounds & Displays Superb Bird of Paradise

Female Choice The flow of information is from the male to the behavioral output of the female. The assumption is that male quality translates into his traits – visual, auditory, behavioral (and other?) – cues for the female. Her choice is based on her ability to perceive trait(s) of the male and then use that information to decide. The information from one male will be compared to other males; affected by the female’s: cognitive abilities memory ability to process information from multiple sources simultaneously (Bateson and Healy 2005).

Attraction Sounds & Displays Satin Bowerbird

Mechanisms of mate choice evolution 1.Direct phenotypic effects Female preference for a male ornament can evolve as a result of direct phenotypic benefits if the ornament reflects: – the ability of the male to provide material advantages. – a high-quality territory, nutrition, parental care or protection. – There is considerable empirical support for this mechanism.

Mechanisms of mate choice evolution 2.Sensory bias. Female preference favouring a male ornament can initially evolve under natural selection for other reasons E.g. context of foraging or predator avoidance. Males evolving traits that exploit this bias then become favoured by mate choice. There is increasing phenotypic evidence that some male ornaments initially evolved through female sensory biases, but the evolution of female sensory bias itself requires more testing.

Attraction dance Note the changing postures of the female Cape Gannet Chilean Flamingos (Phoenicopterus chilensis) Chilean Flamingos (Phoenicopterus chilensis)

Mechanisms of mate choice evolution 3. Fisherian sexy sons. If there are genetic components to variance in female preference and male trait, a female choosing a male with a large trait bears daughters and sons that – both carry alleles for a large trait – and alleles for the preference for it. This genetic coupling might lead to self-reinforcing coevolution between trait and preference. Direct critical testing of this mechanism is difficult, but molecular genetics offers new possibilities.

Mechanisms of mate choice evolution 4. Indicator mechanisms (‘good genes’ or ‘handicap mechanisms’) attractive male traits reflect broad genetic quality. Inherent in such mechanisms is the maintenance of genetic variation, the ‘paradox of the lek’, and parasite- and pathogen-mediated mechanisms have been suggested as potential solutions. In addition, other advantageous genes and relative freedom from deleterious mutations might lead to high male condition and expression of sex traits. Female preference for such traits can provide genetic benefits to those of her offspring that inherit favourable alleles from their father. The resolution of the lek paradox remains a crucial area for sexual selection research. (to be continued…)

Attraction dance Wilsons Bird Of Paradise - video powered by Metacafe Wilsons Bird Of Paradise - video powered by Metacafe Wilson’s bird of paradise

Mechanisms of mate choice evolution 5. Genetic compatibility mechanisms. As well as additive genetic benefits reflected by indicator traits, there might be non- additive benefits from choosing a mate with alleles that complement the genome of the chooser. Examples have been found for instance in major histocompatibility complex (MHC) genes, and compatibility advantages might be one adaptive reason for multiple mating by females.

Mechanisms of mate choice evolution The evolution of mate choice is based either on direct selection of a preference that gives a fitness advantage (mechanisms 1, 2) or on indirect selection of a preference as it becomes genetically correlated with directly selected traits (mechanisms 3, 4). In addition, rather than favouring any particular display trait, mate choice might evolve because it conveys non-additive genetic benefits (mechanism 5). These mechanisms are mutually compatible and can occur together, rendering the evolution of mating preferences a multiple- causation problem (From: Andersson and Simmons 2006).