Incomplete Reproductive Isolation in
the Blue Mussel (Mytilus edulis and M. trossulus)
Hybrid Zone in the Northwest Atlantic: Role of Gamete Interactions and Larval
Viability
Miranda, MBB,
Innes, DJ and Thompson, RJ (2010)
BIOLOGICAL BULLETIN 218(3):
266-281.
Key Words: Speciation, hybridization,
reproductive isolation, prezygotic, postzygotic, fertilization success
Abstract: Reproductive isolation in
free-spawning organisms may involve only small changes in the gamete surface
molecules that control fertilization, linking gamete incompatibility and
speciation. Most studies have focused on species in which natural hybrids are
absent and reproductive isolation is complete, but how gamete incompatibility
evolves remains unclear. Reproductive isolation is incomplete between two
sympatric mussel species (Mytilus edulis, M. trossulus) that hybridize in nature. In this study prezygotic and postzygotic
components of reproductive incompatibility were examined in laboratory crosses.
Conspecific crosses showed significantly greater
rates of fertilization than heterospecific crosses,
although some females of both species showed heterospecific
gamete compatibility. The proportion of fertilized eggs developing into normal
larvae was not significantly different between conspecific
and heterospecific crosses, but survival of normal
larvae was greater for conspecific crosses.
Mixed-species sperm experiments suggested that conspecific
sperm preference may further limit hybridization. The different components of
reproductive incompatibility and total incompatibility varied among females of
both species. Although our study has shown that partial reproductive isolation
between M. edulis
and M. trossulus
involves both prezygotic gamete interactions and postzygotic larval survival, further research is required
to determine the potential role of gamete incompatibility in the evolution of
complete reproductive isolation between these species.
http://www.biolbull.org/content/218/3/266.full
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