Population Ecology

, Volume 55, Issue 1, pp 35–42 | Cite as

Mechanical reproductive isolation via divergent genital morphology between Carabus insulicola and C. esakii with implications in species coexistence

  • Kôhei Kubota
  • Kôji Miyazaki
  • Shiho Ebihara
  • Yasuoki Takami
Original article


The mechanical isolation hypothesis predicts that physical incompatibility between divergent reproductive morphologies hinders hybridization between populations. However, evidence for this hypothesis remains scarce. We examined this hypothesis using two parapatric carabid beetles, Carabus insulicola and C. esakii, which are of the subgenus Ohomopterus and exhibit a species-specific genital lock-and-key system. Our interspecific crossing experiment revealed that incompatibility of genital morphologies served as a strong postmating-prezygotic isolation barrier. This isolation was asymmetric: a decrease in female fitness was more costly in the cross with greater genitalic incompatibility between a C.esakii female and a C. insulicola male. These two species share a limited sympatric area, but the mechanism responsible for their coexistence is unclear given no evidence of premating isolation via male mate choice. A comparison of the present results with those of previous studies that quantified reproductive isolation between Ohomopterus species suggest that strong mechanical isolation via genitalic incompatibility plays a major role in species isolation, but that it may be less important in species coexistence.


Carabidae Genitalia Ground beetle Hybrid zone Lock-and-key Speciation 


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Copyright information

© The Society of Population Ecology and Springer 2012

Authors and Affiliations

  • Kôhei Kubota
    • 1
  • Kôji Miyazaki
    • 1
  • Shiho Ebihara
    • 1
  • Yasuoki Takami
    • 2
  1. 1.Laboratory of Forest Zoology, Graduate School of Agricultural and Life SciencesThe University of TokyoTokyoJapan
  2. 2.Graduate School of Human Development and EnvironmentKobe UniversityKobeJapan

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