title: Phylogeography of the tropical planktonic foraminifera lineage globigerinella reveals isolation inconsistent with passive dispersal by ocean currents.
abstract: Morphologically defined species of marine plankton often harbor a considerable level of cryptic diversity. Since many morphospecies show cosmopolitan distribution, an understanding of biogeographic and evolutionary processes at the level of genetic diversity requires global sampling. We use a database of 387 single-specimen sequences of the SSU rDNA of the planktonic foraminifera Globigerinella as a model to assess the biogeographic and phylogenetic distributions of cryptic diversity in marine microplankton on a global scale. Our data confirm the existence of multiple, well isolated genetic lineages. An analysis of their abundance and distribution indicates that our sampling is likely to approximate the actual total diversity. Unexpectedly, we observe an uneven allocation of cryptic diversity among the phylogenetic lineages. We show that this pattern is neither an artifact of sampling intensity nor a function of lineage age. Instead, we argue that it reflects an ongoing speciation process in one of the three major lineages. Surprisingly, four of the six genetic types in the hyperdiverse lineage are biogeographically restricted to the Indopacific. Their mutual co-occurrence and their hierarchical phylogenetic structure provide no evidence for an origin through sudden habitat fragmentation and their limitation to the Indopacific challenges the view of a global gene flow within the warm-water provinces. This phenomenon shows that passive dispersal is not sufficient to describe the distribution of plankton diversity. Rather, these organisms show differentiated distribution patterns shaped by species interactions and reflecting phylogenetic contingency with unique histories of diversification rates.
authors.affiliation: MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
authors.forename: Agnes K M
authors.initials: AK
authors.lastname: Weiner
authors.affiliation: MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
authors.forename: Manuel F G
authors.initials: MF
authors.lastname: Weinkauf
authors.affiliation: Institute of Biogeosciences, Japanese Agency for Marine Earth Science and Technology, Yokosuka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kurasawa
authors.affiliation: School of Geosciences and Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Kate F
authors.initials: KF
authors.lastname: Darling
authors.affiliation: MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
authors.forename: Michal
authors.initials: M
authors.lastname: Kucera
authors.affiliation: Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden.
authors.forename: Guido W
authors.initials: GW
authors.lastname: Grimm
mesh_terms: D055669:Ecological and Environmental Phenomena; D019143:Evolution, Molecular; D056908:Foraminifera / Q000235:genetics* / Q000502:physiology*; D014644:Genetic Variation; D009792:Oceans and Seas; D058974:Phylogeography; D012335:RNA, Ribosomal / Q000235:genetics; D014329:Tropical Climate
chemical_list: D012335:RNA, Ribosomal