![]() truncatulinoides is a deep-dwelling planktonic foraminifer and their distributional pattern in the central and western Mediterranean Sea provides a tool to monitor the onset of the regional deep vertical mixing of the water column. truncatulinoides can be considered a potential marker for the Middle–Late Holocene chronological subdivision. The robust chronological frame allows us to date this bio-event to 4.8–4.4 ka Before Present (BP), very close to the base of the Meghalayan stage (4.2 ka BP). truncatulinoides during the Middle Holocene. High-resolution quantitative studies performed on sediment cores collected in the central and western Mediterranean Sea evidence a significant abundance of G. The planktonic foraminiferal species Globorotalia truncatulinoides is widely used as a biostratigraphic proxy for the Quaternary in the Mediterranean region. They highlight the importance of adaptation and heterochronic processes, leading to cryptic speciation, in planktic foraminifera. The evolutionary patterns recognized here by combining DNA and morphological analyses from plankton-tow specimens mirror and allow a new interpretation of the data available from Recent sediments. Species of the same regions are more similar in test shape but can be distinguished by coiling direction. This genetic dichotomy is associated with a morphological differentiation identified using outline analysis. By using an absolute molecular clock, we deduce the time of divergence between the subtropical and frontal/subantarctic species at ∼300 Ka, which is in agreement with stratigraphic data and suggests an adaptive radiation of the species allowing it to colonize the nutrient-rich and cold subantarctic waters. Species 1 and species 2 characterize subtropical waters, species 3 is abundant exclusively in the Subantarctic Convergence, while species 4 inhabits subantarctic waters. The different species are separated by significant genetic distances in several ribosomal genes (SSU, ITS-1, 5.8S, ITS-2). ![]() truncatulinoides corresponds to a complex of four genetic species adapted to particular hydrographic conditions. Here, we present the first molecular, morphological, and ecological evidence that G. truncatulinoides is associated with a latitudinal morphological variability considered as an ecophenotypic variation within a single species. ago in subtropical areas of the South Pacific, spread to all subtropical and temperate regions of the world ocean, and expanded its range to southern subantarctic waters between 500 and 200 Ka. ![]() Globorotalia truncatulinoides is an extant species of planktic foraminiferans commonly used for stratigraphic and paleoenvironmental analyses. ![]()
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