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Behavioural Ecology
Genetics, selfishness and altruism
| Question | Answer |
|---|---|
| How can behaviour evolve? | Behaviour is genetically controlled and heritable? Timespans of selection are sufficient for adaptation to happen? The unit of selection is the individual and its genes (not the group or the species) |
| Heritability | Proportion of phenotypic variance in a population that can be attributed to genotypic variance |
| Heritability | 0 heritability = variation completely environmentally determined 1 heritability = variation completely genetically determined 0 – 1 = mix of environmental and genetic determination |
| Measuring heritability | - breeding experiments - comparison of natural genotypes - measurement of mutants |
| Examples | Selection for mating speed in Drosophila Selection for maze learning in domestic rats |
| Is behaviour heritable? | Yes! Repeated selection experiments consistently show high heritability in animal behaviour |
| Heritability of behaviour in wild populations | Blackcap (Sylvia atricapilla) migration behaviour - motivation and direction affected by behaviour - breeding affects migration behaviour - crossbreeding creates hybrids that have altered patterns |
| Most heritable behaviour - polygenic (a result of many genes) | Most animal behaviour is also learnt, and is dependent on interactions with the environment Behavioural heritability is always <1.0 (rarely >0.5) Some are monogenic (single gene) but its rare |
| Single gene heritability of behvaiour | ie. drosphila mutant deficient in learning (dunces) - have the single gene with profound behavioural defects |
| Timespans of selection are sufficient for adaptation to happen? | = Behavioural evolution for ~500 to ~800+ million years |
| Altruism | Behaviour that increases another individual’s survival/reproduction at a cost to one’s own survival/reproduction |
| The problem with ‘for the good of the species’ (group selection) arguments | Selection occurs on individuals and genes Selection ‘for the good of the species’ would be inefficient Selection for selfishness in individuals generally overcomes group co-operation Few/no empirical examples of group selection |
| How can helping other individuals evolve and persist in nature????? | Is the existence of altruism evidence that behaviour evolves ‘for the good of the species’? |
| Why has altruistic helping evolved? | Helping improves current overall breeding success? Helping improves an individual’s future breeding success? Is helping behaviour higher when the helpers and recipients are related? |
| Helping among relatives increases their inclusive fitness | Inclusive fitness = fitness gained through personal reproduction PLUS fitness gained from aiding the survival and reproduction of non-descendant kin |
| However | Not all relatives are equally ‘valuable’ (for personal fitness) when it comes to inclusive fitness |
Created by:
reub8n
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