Coiling dimorphism within a genetic type of the planktonic foraminifer Globorotalia truncatulinoides

• Published in: Marine Micropaleontology
• Main Authors: Ujiié, Yurika, de Garidel-Thoron, Thibault, Watanabe, S, Wiebe, P, de Vargas, Colomban
• Other Authors: Lab Ecol & Evolut, Dept Biol, Shinshu Univ, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia' Buenos Aires (MACN), Consejo Nacional de Investigaciones Científicas y Técnicas Buenos Aires (CONICET), Woods Hole Oceanographic Institution (WHOI), Evolution des Protistes et Ecosystèmes Pélagiques (EPEP), Adaptation et diversité en milieu marin (AD2M), Station biologique de Roscoff Roscoff (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff Roscoff (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), ANR-05-PADD-0012,PRODDIG,Promotion du Développement Durable par les Indications Géographiques(2005)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: Planktonic foraminifera; Genetic type; Coiling direction; Population; [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology
• Online Access: https://hal.archives-ouvertes.fr/hal-00869295; https://doi.org/10.1016/j.marmicro.2010.09.001

International audience The coiling direction sinistral (left-coiled) or dextral (right-coiled) of planktonic foraminiferal shells is a classical proxy used to assess past environmental changes and to understand their evolutionary patterns. Globorotalia truncatulinoides is composed of five different genetic types (I to V), each with a specific biogeographic distribution. So far, type II is the only type within which both coiling types have been frequently found. Here we examine the coiling direction as a dimorphic variation in a single genetic type, and show that the two forms with different coiling directions differ in ecology. The studied 140 left- and 137 right-coiled specimens from eight depth layers at four stations in the Sargasso Sea all belonged to Type II, based on the phylogenetic analyses of the ITS (internal transcribed spacer) region of ribosomal DNA. The distributions of left- and right-coiled Type II (Type II-L and II-R) differed strongly: Type II-L dominated between 400 and 200 m depth in the central water mass, whereas Type II-R was common in the top 200 m of the subtropical gyre. The left- and right-coiled forms are thus associated with different water masses. However, the vertical distribution along a temperature gradient indicates that their coiling direction is not determined by temperature, and might have some genetic basis. Our molecular phylogenetic analyses showed that the two forms probably share the same gene pool through their dispersals between different water masses. Moreover, the lineage of G. truncatulinoides is young (<3 Ma), which might not be long enough to evolve into two lineages with opposite coiling direction. We discuss the practical and theoretical usefulness of a simple genetic model for coil dimorphism, in order to build testable hypotheses regarding the evolutionary history of planktonic foraminifera at the population level.