Evol Ecol Res 4: 603-621 (2002)     Full PDF if your library subscribes.

Intraspecific hybridization, developmental stability and fitness in Drosophila mercatorum

Ditte Holm Andersen,1,2,3* Cino Pertoldi,1,2 Valerio Scali3 and Volker Loeschcke1,4

1Department of Ecology and Genetics, Institute of Biological Sciences, University of Aarhus, Ny Munkegade, Building 540, DK-8000 Aarhus C, Denmark, 2Department of Landscape Ecology, National Environmental Research Institute, Kalø, Grenavej 14, DK-8410 Rønde, Denmark, 3Dipartimento di Biologia Evoluzionistica Sperimentale, Via Selmi 3, 40126 Bologna, Italy and 4Institute for Advanced Study, Kingsbury Centre, La Trobe University, Bundoora, Victoria 3086, Australia

Author to whom all correspondence should be addressed.
e-mail: ditte.andersen@biology.au.dk

ABSTRACT

One of the possible effects of intraspecific hybridization is outbreeding depression, due to a breakdown of coadapted gene complexes, which can lead to reduced fitness and decreased developmental stability in hybrids. Alternatively, increased fitness and increased developmental stability in hybrids (hybrid vigour) may be a result of hybridization, probably due to increased heterozygosity. Developmental stability is assumed to be correlated with fitness and is commonly measured as fluctuating asymmetry or phenotypic variance. Drosophila mercatorum is capable of reproducing sexually, but also parthenogenetically in the laboratory. When selecting for parthenogenesis, the flies become homozygous in one generation; strong selection, therefore, is acting on the genome of these flies for coadaptation among genes. Intraspecific hybridization is therefore expected to have an impact when coadaptation is disrupted. Intraspecific hybridization between a parthenogenetic and a sexually reproducing strain of Drosophila mercatorum resulted in significant changes in fecundity as well as fluctuating asymmetry and phenotypic variance for the number of sternopleural bristles and in the length of two wing traits over three generations after hybridization. We found a ‘hybrid vigour effect’ in F1 females with an increase in fecundity relative to their parental populations. The F2 and F3 females showed increased fluctuating asymmetry in several traits and reduced fecundity compared with the F1 females, probably due to a breakdown in coadapted gene complexes. The males followed the same pattern of fluctuating asymmetry for bristles but there was no increase in wing fluctuating asymmetry in the F2 and F3 generations. Trait differences in phenotypic variance were found between wings and bristles. We found an increase in phenotypic variance in the F1 generation for both sexes and all traits, which could be due to increased genetic variance after hybridization. The phenotypic variance increased further in generations F2 and F3 for bristle number. For the wings, phenotypic variance generally decreased in generations F2 and F3 when compared with F1, which we attribute to canalization and selection on the wings.

Keywords: developmental stability, Drosophila mercatorum, fitness, hybridization, outbreeding.

DOWNLOAD A FREE, FULL PDF COPY
IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.

 

        © 2002 Ditte Holm Andersen. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.