Variation in senescence and associated traits between synpatric cactophilic sibling species of Drosophila

PABLO SAMBUCETTI; JESPER G. SORENSEN; V. LOESHCKE; FABIAN M. NORRY

Evolutionary Ecology Research

Evolutionary Ecology LTD.

Año: 2005 vol. 7 p. 915 - 930

1522-0613

ABSTRACT Main hypothesis: Longevity and early fecundity are negatively correlated both within and between sympatric but ecologically divergent sibling species that differ in life span, as predicted by evolutionary theories of ageing. Organism: Drosophila koepferae, which mainly breeds on the patchily distributed Trychocereus cacti, and D. buzzatii, which mainly occurs on the more abundant and uniformly distributed Opuntia cacti. Methods: Flies were reared under standardized conditions from three sympatric populations. Longevity and mortality rate were studied both at 25ºC and 29.5ºC. Age-specific fecundity was estimated at 25ºC. Other plausibly associated traits were also studied, including heat-shock resistance, Hsp70 expression and body size. Conclusions: Senescence rate was much faster in D. koepferae than in D. buzzatii in all populations at 25ºC but not at 29.5ºC. The interspecific difference in longevity at 25ºC shifted in sign in one of the populations at 29.5ºC. Neither the resistance to a heat shock nor the heat-induced Hsp70 expression showed significant interspecific variation. Body size was larger in D. koepferae than in D. buzzatii. Drosophila koepferae showed a massive reproductive output at early ages compared with D. buzzatii. Longevity and early fecundity at the non-stressful temperature (25ºC) were negatively correlated both within and between species. Genotype x temperature interactions can in turn affect interspecific variation in evolutionary trajectories of both mean longevity and demographic rate of senescence. Keywords: age-specific senescence rate, body size, Drosophila, early fecundity, genotype x temperature interaction, heat-stress resistance, Hsp70 expression.