Longitudinal differentiation among pelagic populations in a planktic foraminifer

Abstract

Evolutionary processes in marine plankton have been assumed to be dependent on the oceanic circulation system, which transports plankton between populations in marine surface waters. Gene flow facilitated by oceanic currents along longitudinal gradients may efficiently impede genetic differentiation of pelagic populations in the absence of confounding marine environmental effects. However, how responsible oceanic currents are for the geographic distribution and dispersal of plankton is poorly understood. We examined the phylogeography of the planktic foraminifer Pulleniatina obliquiloculata in the Indo-Pacific Warm Pool (IPWP) by using partial small subunit ribosomal DNA (SSU rDNA) sequences. We found longitudinal clines in the frequencies of three distinct genetic types in the IPWP area. These frequencies were correlated with environmental factors that are characteristic of three water masses in the IPWP. Noteworthy, populations inhabiting longitudinally distant water masses at the Pacific and Indian sides of the IPWP were genetically different, despite transportation of individuals via oceanic currents. These results demonstrate that populations of pelagic plankton have diverged genetically among different water masses within a single climate zone. Changes of the oceanic circulation system could have impacted the geographic patterns of dispersal and divergence of pelagic plankton.

Assessing SSU rDNA Barcodes in Foraminifera: A Case Study using Bolivina quadrata

“…; Ujiié et al. ; Weber and Pawlowski ), a feature also reported for other single‐cell organisms (Gong et al. ; Miranda et al.…”

“…; Ujiié et al. ). Recently grouped in the taxonomic super‐group SAR (Stramenopiles, Alveolates, and other Rhizaria; Adl et al.…”

“…; Ujiié and Lipps ; Ujiié et al. ), or, on the other hand, it may lead to taxonomic overinterpretation (André et al. ).…”

“…; Ujiié et al. ; Weber and Pawlowski ) and that for some species there is not a clear gap to distinguish between and within species when each SSU rDNA hypervariable region is examined individually (i.e. Conqueria laevis, Notodendrodes hyalinosphaira, Cassidulina laevigata, Stainforthia fusiformis ), the application of foraminiferal SSU rDNA‐based barcodes to the investigation of environmental samples requires caution (Weber and Pawlowski ).…”

Planktic Foraminifera

“…On the other hand, there are reports of vertical niche partitioning of genotypes (depth-parapatric speciation) in the world ocean; this partitioning is likely related to water column structure. Ujiié et al (2012) investigated the biogeographic and phylogenetic distributions of three genotypes of Pulleniatina obliquiloculata in the IndoPacific Warm Pool (IPWP). They found longitudinal and vertical gradients in the frequencies of each P. obliquiloculata genotype inhabiting the IPWP, and they suggested that passive transportation by ocean currents was not sufficient to account for the genotype distributions.…”