Lack of genetic differentiation among members of the morphologically diverse plexus of the tropical planktonic foraminifer Globigerinoides sacculifer
1 : Laboratoire de Géologie de Lyon, Terre, Planètes, Environnement
(LGLTPE)
CNRS, Université Lyon 1
La Doua, Villeurbanne -
France
2 : Laboratoire de Géologie de Lyon, Terre, Planètes, Environnement
(LGLTPE)
CNRS, Université Lyon 1
La Doua, Villeurbanne -
France
3 : Department of Geosciences
Eberhard-Karls Universität Tübingen
Hölderlinstr. 12 72074 Tübingen -
Allemagne
4 : Station Biologique de Roscoff
(SBR)
Universitie Pierre et Marie Curie (Paris 06) et CNRS
Place G. Teissier, BP 74, 29682 Roscoff cedex, France -
France
5 : Department of Geosciences
Eberhard-Karls Universität Tübingen
Hölderlinstr. 12 72074 Tübingen -
Allemagne
6 : LEHNA
Université Lyon 1, Centre National de la Recherche Scientifique
Lyon -
France
7 : Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement
(CEREGE)
-
Website
Aix-Marseille Univ, CEREGE, UMR 6635, 13545 Aix en Provence cedex 4, France, CNRS, CEREGE, UMR 6635, 13545 Aix en Provence cedex 4, France, IRD, CEREGE, UMR 161, 13545 Aix en Provence cedex 4, France, Collège de France, CEREGE, 13545 Aix en Provence cedex 4, France
Europôle de l'Arbois, BP 80, 13545 Aix-en-Provence Cedex 04, France -
France
8 : Laboratoire de Géologie de Lyon, Terre, Planètes, Environnement
(LGLTPE)
CNRS, Université Lyon 1
La Doua, Villeurbanne -
France
9 : Station Biologique de Roscoff
(SBR)
Universitie Pierre et Marie Curie (Paris 06) et CNRS
Place G. Teissier, BP 74, 29682 Roscoff cedex, France -
France
10 : Department of Geosciences
Eberhard-Karls Universität Tübingen
Hölderlinstr. 12 72074 Tübingen -
Allemagne
Globigerinoides sacculifer is an abundant element of modern tropical planktonic foraminiferal assemblages. The species is characterized by large morphological variability, which has led to the proliferation of taxonomic names attributed to morphological end-members within the plexus. In order to clarify the taxonomic status of its morphotypes and to investigate the genetic connectivity among its disjunct tropical populations, we carried out a global survey of the ribosomal DNA genes (SSU and ITS-1) in various morphotypes of the plexus collected throughout the (sub)tropical surface waters. Unexpectedly, we find an extremely reduced genetic variation within the morphospecies and no correlation between genetic and morphological divergence. The lack of genetic diversity within the plexus suggests that the morphological diversity within the species has been taxonomically over-interpreted and that shell morphology in planktonic foraminifera may not be a consistent predictor of taxonomic status. The genetic homogeneity within the morphospecies is unexpected, considering its partly disjunct range in the tropical Atlantic and Indopacific and its old age (early Miocene). A minor sequence variant in the rapidly evolving ITS-1 region is found exclusively in the Atlantic Ocean, suggesting an episode of recent (last glacial) isolation, followed by subsequent reinstatement of unidirectional gene flow from the Indopacific into the Atlantic. These findings indicate that the gene flow among (sub)tropical waters of the world oceans can been strong enough on geological time scales to prevent persistent genetic isolation and that mechanisms other than geographical isolation alone may be required for speciation in planktonic foraminifera to occur.
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| Topics | : | Proxy calibration |
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