Seasonal migration promoting assortative mating in Littorina brevicula on a boulder shore in Japan |
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Authors: | Yoshitake Takada |
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Institution: | (1) Amakusa Marine Biological Laboratory, Kyushu University, Reihoku, Amakusa, 863-25 Kumamoto, Japan |
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Abstract: | Littorina brevicula Philippi is one of the most common snails found in the upper intertidal zone of Japan. In Amakusa, some of the population
of L. brevicula migrate to the lower zone in the winter, while the rest stay in the upper zone. Thus, during the winter, which is its reproductive
season, the population of L. brevicula divides into two sub-populations. This leads to a hypothesis that the migration pattern in winter is genetically controlled
and this behavioural dimorphism is maintained by reproductive isolation between the two sub-populations. In order to test
this hypothesis, the following three points were investigated: (1) whether the same snails migrate in a similar way every
winter, (2) whether there is a significant tidal level preference in snails, and (3) whether reproductive isolation occurs
between the two sub-populations. The results showed (1) the migration behaviour of each snail was consistent over two successive
winters, i.e. the same group of snails migrated downward every winter and the same group of snails stayed in the upper zone
every winter, (2) transplanted snails moved toward the original zones where they were caught, suggesting that the snails actively
selected their tidal zone in winter, and (3) most of the snails copulated within each sub-population. Therefore, reproductive
isolation between the two sub-populations was considered to be established to some extent by the dimorphic migration behaviour.
In conclusion, the migratory behaviour of L. brevicula is determined separately for each individual and might be genetically controlled, and the behavioural dimorphism may be maintained
by partial reproductive isolation between the two sub-populations. |
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Keywords: | assortative mating migration behaviour habitat selection reproductive season boulder shore Littorina brevicula |
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