Factors influencing differential mortality within a marine mussel (Mytilus spp.) hybrid population in southwestern England: reproductive effort and parasitism

Two species of marine mussel, Mytilus edulis and M. galloprovincialis hybridize on the coasts of western Europe. Studies of hybrid mussel populations have shown that natural selection favors M. galloprovincialis-like genotypes within this hybrid zone. Many hypotheses have been proposed to explain di...

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Bibliographic Details
Published in:Marine biology 2001-04, Vol.138 (4), p.731-739
Main Authors: SECOR, C. L, DAY, A. J, HILBISH, T. J
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal populations
Animal reproduction
Animal, plant and microbial ecology
Animals
Autoecology
Biological and medical sciences
British Isles, England
Fundamental and applied biological sciences. Psychology
Genotypes
Marine
Marine biology
Mollusks
Mortality
Mytilus edulis
Mytilus galloprovincialis
Parasites
Parasitism
Protozoa. Invertebrata
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Summary:Two species of marine mussel, Mytilus edulis and M. galloprovincialis hybridize on the coasts of western Europe. Studies of hybrid mussel populations have shown that natural selection favors M. galloprovincialis-like genotypes within this hybrid zone. Many hypotheses have been proposed to explain differential mortality in these populations. This study tests two hypotheses addressing factors of mortality in a population, and describes yearly energy storage and reproductive cycles of these two species and their hybrids. No evidence was found that the two taxa have different overall levels of reproductive effort or parasite infestation. They do, however, have asynchronous spawning periods and divergent energy storage strategies. In the year of this study, 1993, the M. edulis genotypic class spawned as a group in June and July. After spawning, they built up a high level of mantle energy-storage tissues that are probably used for gametogenesis in the following winter and spring. The M. galloprovincialis genotypic group, however, spawned asynchronously, beginning in June and finishing by August, and did not build up high levels of energy-storage tissues in summer. These results add a temporal component to the interpretation of selective forces acting to shape this hybrid zone. Vulnerability of each species to mortality factors may differ because of their divergent reproductive and energy-storage cycles.
ISSN:0025-3162
1432-1793
DOI:10.1007/s002270000418