Ecological differentiation and reproductive isolation of two closely related sympatric species of Oenanthe (Apiaceae)

• Published in: Biological journal of the Linnean Society Vol. 101; no. 3; pp. 526 - 535
• Main Authors: WESTBERG, ERIK, POPPENDIECK, HANS-HELMUT, KADEREIT, JOACHIM W
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.11.2010; Blackwell Publishing Ltd; Wiley-Blackwell
• Subjects: AFLP; Apiaceae; Biological and medical sciences; Biological evolution; divergence; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; local adaptation; Oenanthe; Oenanthe aquatica; transplantation experiment; water dropworth; Germany, Elbe R; Eurasia; Germany; Germany, Hamburg; water dropworth; Reproductive isolation; Biological evolution; transplantation experiment; Sympatry; Ecology; Transplantation; divergence; local adaptation; Dicotyledones; Angiospermae; AFLP; Spermatophyta; Umbelliferae; Differentiation; Amplified fragment length polymorphism marker; Adaptation
• ISSN: 0024-4066; 1095-8312
• DOI: 10.1111/j.1095-8312.2010.01487.x

Oenanthe conioides is a lower Elbe endemic plant species growing in the freshwater tidal zone around Hamburg (Germany). Its closest relative Oenanthe aquatica is widely distributed in Eurasia and grows in calm and shallow freshwater. The two species differ in habitat requirements but are otherwise sympatrically distributed, suggesting that ecological divergence has to be maintained in the face of gene flow. In the present study, we investigated ecological differentiation and reproductive isolation in these two species. An amplified fragment length polymorphism analysis found clear genetic differentiation between the two species implying reproductive isolation. A reciprocal transplantation experiment including artificial F₁ hybrids showed strong selection against immigrants. In the two parental habitats, the non-native species are less fit than the native species. Hybrids are less fit in the habitat of Oe. aquatica but perform as well as the native species in the habitat of Oe. conioides. We hypothesize that selection against immigrants is the most important component of reproductive isolation between the two species, and that selection against immigrants is the result of exposure to cold and wind in the tidal habitat of Oe. conioides and to herbivory in the habitat of Oe. aquatica. These results are congruent with a role for differential ecological selection in the formation and maintenance of these two species.