Genetic and phenotypic variation for flight ability in the cactophilic Drosophila species, D. aldrichi and D. buzzatii

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AbstractThe flight ability of Drosophila aldrichi (Patterson & Crow) and D. buzzatii (Patterson & Wheeler) using tethered flights, was measured with respect to age‐related changes, genetic variation and adult body size variation induced by rearing at different larval densities. Drosophila buzzatii flew for much longer than D. aldrichi, especially females, but age‐related changes in flight duration were significant only for D. aldrichi. Effects of body size on flight ability were significant in D. buzzatii, but not in D. aldrichi. In D. buzzatii, there was a significant genotype‐environment interaction (larval density × line) for flight duration, with short and average flight duration isofemale lines showing longer flights, but a long flight duration line shorter flights as body size decreased (i.e., as larval density increased). Heritability estimates for flight duration were similar in the two species, but flight duration showed no significant genetic correlations with developmental time, body size or wing dimensions (except for one wing dimension in D. buzzatii). Although not significantly different between the species, heritabilities for life‐history traits (adult size and developmental time) showed contrasting patterns ‐ with higher heritability for body size (body weight and thorax length) in D. buzzatii, and higher for developmental time in D. aldrichi. In agreement with limited previous field evidence, D. buzzatii is better adapted for colonization than is D. aldrichi.