Montag, 12. März 2007

The evolution of senescence - in 271 species of birds

At the moment we have no good and validated (generally accepted) theories of the evolution of senescence. A study in "Journal of Evolutionary Biology" (May 2006) discuss several of these theories and has found amoung 271 bird species no correlations between longevity and degree of breeding sociality (!) - but between longevity and age of first reproduction.

Relative longevity (...) increased with age at first reproduction, but not with degree of breeding sociality.

The results were partly contrary to the expected theory:

The objective of the present study was to test the prediction arising from evolutionary theories of senescence that the rate of ageing and hence the maximum record of longevity should increase in species with delayed onset of reproduction. (...) Hence, we should expect the rate of senescence to be slower in colonially than in solitarily breeding species of birds. In addition, colonially breeding species of birds should start to reproduce at an older age than solitary species.

(...) The main findings of this study were (...) (2) Colonially breeding species did not senesce at a slower rate than solitarily breeding species. (3) Species that started to reproduce relative late in their life senesced at a slower rate than species that started to reproduce early.

(...) I found no general relationship between evolution of senescence and evolution of coloniality in birds.

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