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

• Published in: Evolutionary ecology research Vol. 7; no. 6; pp. 915 - 930
• Main Authors: Sambucetti, P, Sorensen, J.G, Loeschcke, V, Norry, F.M
• Format: Journal Article
• Language: English
• Published: 01-10-2005
• Subjects: air temperature; Drosophila; Drosophila buzzatii; Drosophila koepferae; fecundity; genotype-environment interaction; heat stress; heat tolerance; longevity; Opuntia; senescence; sympatry
• ISSN: 1522-0613; 1937-3791

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 25 degree C and 29.5 degree C. Age-specific fecundity was estimated at 25 degree C. 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 25 degree C but not at 29.5 degree C. The interspecific difference in longevity at 25 degree C shifted in sign in one of the populations at 29.5 degree C. 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 (25 degree C) 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.