动物学 7.pptVIP

Extraordinary lifespans inants：a test of evolutionarytheories of ageing 1、Research purpose To prove that evolution of eusociality is associated with a 100-fold increase in insect lifespan. Use phylogeny tree for the comparative analysis of independent contrasts to prove that 2、TWO hypotheses Evolutionary hypotheses propose that ageing evolves as the necessary cost of processes increasing early reproductive success， or because of weaker selection against late-acting mutations Non-adaptive,purely mechanistic hypotheses invoke damage to DNA, cells,tissues and organs as being the unique cause of senescence and ineluctable death of organisms What Evolutionary hypotheses predict They predict that ageing rate should generally increase and average lifespan should decrease as the rate of age- and condition-independent (extrinsic) mortality increases and that it should be higher in those organisms whose fecundity does not increase markedly after maturity compared to those showing such an increase What Purely physiological theories of senescence predict They predict no relationship between extrinsic mortality, age-dependent fecundity, and rate of senescence. They frequently predict an association between duration of life and metabolic rate, whereby organisms with lower metabolic rates should have greater lifespans 3、Proofs of the hypotheses From the data of Lifespans of 87 solitary insect species from eight orders and 61 species of eusoicial insects： the mean average longevities of ant, termite and honeybee queens is 10.0±6.6, 11.5±5.4 and 5.6 years，respectively (overall mean for eusocial insects 10.1±6.4 years; whereas that of 87 solitary insect species from eight orders is only 0.1±0.2 years (Fig. 1) Details on the order Hymenoptera is given for several families because eusociality evolved independently in the genus Apis and in Formicidae (ants). The complete phylogeny used for the comparative analysis of independent contrasts is available from L.K. This revea