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Multiplicative selection for the use of host plants and host induced phenotypic plasticity shaping phytophagous specialists in the face of gene flow
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  • Kei Matsubayashi,
  • Tetsuo Kohyama,
  • Sih Kahono,
  • Haruo Katakura
Kei Matsubayashi
Kyushu University

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Tetsuo Kohyama
Hokkaido University
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Sih Kahono
Indonesian Institute of Science – LIPI
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Haruo Katakura
Hokkaido University
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Ecological specialisation has been an attractive topic in its relationship with biological diversification. However, there is little knowledge about how much niche specialisation itself promotes speciation, and how they maintain boundary of specialists. To elucidate the issue, we conducted a simple rearing experiment using F1 and backcross generations of two specialist host races of the phytophagous ladybird beetle Henosepilachna diekei, with special attention to host search efficiency and host fidelity. The results showed that divergence in numerous ecological traits that were mostly resulted in divergent natural selection multiplicatively reduced hybrid fitness and maintained current specialisation in both pre-/post-mating stages. Also, larval feeding experience influences host choice in F1 hybrid adults, and it appears in the face of gene flow and reduces further gene exchange. This speciation event show that multiple ecological traits adaptive to different host plants synthetically shape divergent specialists without other isolating barriers.