Genotype-dependent fecundity and temporal variation of spawning in hybrid mussel (Mytilus) populations

Marine Biology - Tập 105 - Trang 153-162 - 1990
J. P. A. Gardner1, D. O. F. Skibinski1
1School of Biological Sciences, University College of Swansea, Swansea, UK

Tóm tắt

Mussel samples were collected at 4 to 6 wk intervals throughout 1987 from two hybridMytilus edulis/M. galloprovincialis populations, at Croyde Bay and Whitsand Bay, in southwest England. These were analyzed at two polymorphic loci which are diagnostic for allozyme differences which typifyM. edulis andM. galloprovincialis. Dry mantle weight as a function of shell length was determined for all individuals of each sample. Size-frequency data for the two populations was obtained in September 1987 and March 1988. For all genotypes at both sites, fecundity was a function of shell length, and in both populations the frequency ofM. galloprovincialis alleles was positively correlated with shell length. At both sites, allozyme genotype explained a significant amount of variation in mantle weight either when assessed as a main effect or when assessed as an interaction with shell length or time of collection. At Croyde,M. galloprovincialis mussels had greater estimated fecundity per unit length than theM. edulis mussels. Differences in the timing of spawning activity between theM. edulis and theM. galloprovincialis mussels were inferred, and these differences might act to reduce the amount of interbreeding at Croyde. At Whitsand, a reduced level of variability in the timing of spawning activity and fecundity between the genotypes was observed and explained by a higher degree of genetic mixing. Because theM. galloprovincialis mussels had (1) a greater estimated fecundity at any length, and (2) a greater mean length than theM. edulis mussels, the mean genotypic annual fecundity perM. galloprovincialis mussel was 2.8 times greater than an individualM. edulis mussel at Croyde, and 2.2 times greater than an individualM. edulis mussel at Whitsand. This evidence thatM. galloprovincialis mussels have an advantage in fecundity, and thus perhaps in fertility, taken together with the evidence thatM. galloprovincialis also has a higher viability, indicates directional selection in favour of theM. galloprovincialis phenotype. Because of the observed temporal stability of the population it seems likely that this selection is counterbalanced by a massive imigration ofM. edulis spat from neighbouring populations.

Tài liệu tham khảo

Bayne, B. L. (1976). The biology of mussel larvae. In: Bayne, B. L. (ed.) Marine mussels. International Biological Programme, 10. Cambridge University Press, Cambridge, England, p. 81–120

Gardner, J. P. A. (1989). Ecological and population genetics of hybrid mussels from South-West England. Ph.D. thesis. University of Wales, UK

Gosling, E. M. (1984). The systematic status ofMytilus galloprovincialis in western Europe: a review. Malacologia 25: 551–568

Myint, U. M. (1971). The reproductive ecology ofMytilus edulis Linne. Ph.D. thesis. University of Wales, UK

Nie, N. H., Hull, C. H., Jenkins, J. G., Steinbrenner, K., Bent, D. H. (1975). Statistical package for the social sciences. 2nd ed. McGraw Hill, New York

Peterson, C. H., Fegley, S. R. (1986). Seasonal allocation of resources to growth of shell, soma, and gonads inMercenaria mercenaria. Biol. Bull. mar. biol. Lab., Woods Hole 171: 597–610

Seed, R. (1971). A physiological and biochemical approach to the taxonomy ofMytilus edulis L. andMytilus galloprovincialis Lmk from south-west England. Cah. Biol. mar. 12: 291–322

Seed, R. (1976). Ecology. In: Bayne, B. L. (ed.) Marine mussels. International Biological Programme, 10. Cambridge University Press, Cambridge, England, p. 13–66

Seed, R. (1978). The systematics and evolution ofMytilus galloprovincialis (Lmk). In: Battaglia, B., Beardmore, J. A. (eds.) Marine organisms: genetics, ecology and evolution. Plenum Press, New York, p. 447–468

Skibinski, D. O. F. (1983). Natural selection in hybrid mussel populations. In: Oxford, G. S., Rollinson, D. (eds.), Protein polymorphism: adaptive and taxonomic significance. Systematics Association, Academic Press, London and New York, p. 283–298. (Special Vol. No. 24)

Tracey, M. L., Bellet, N. F., Gravem, C. D. (1975). Excess homozygosity and breeding population structure in the musselMytilus californianus. Mar. Biol. 32: 303–311