Genetic differentiation between Arctic and Antarctic monothalamous foraminiferans

Abstract

Monothalamous (single-chambered) foraminifers are a major component of the benthic meiofauna in high latitude regions. Several morphologically similar species are common in the Arctic and Antarctic. However, it is uncertain whether these morphospecies are genetically identical, or whether their accurate identiWcation is compromised by a lack of distinctive morphological features. To determine the relationship between Arctic and Antarctic species, we have compared SSU rDNA sequences of specimens belonging to four morphotaxa: Micrometula, Psammophaga, Gloiogullmia, and one morphospecies Hippocrepinella hirudinea from western Svalbard (Arctic) and McMurdo Sound (Antarctic). Wherever possible, we include in our analyses representatives of these taxa from the deep Arctic and Southern Oceans, as well as from Northern European fjords. We found that in all cases, the bipolar populations were clearly distinct genetically. As expected, Arctic specimens were usually more closely related to those from Northern Europe than to their Antarctic representatives. The deep-sea specimens from Weddell Sea branched as a sister to the McMurdo Sound population, while those from the Arctic Ocean clustered with ones from Norwegian fjords. Our study has revealed a high number of cryptic species within each of the examined genera, and demonstrates the unexplored potential of monothalamous foraminifers for use as a tool to evaluate the origin and biogeography of polar meiofauna.

Characteristics of meiofauna in extreme marine ecosystems: a review

“…This sympagic meiofauna consists of both metazoans and protozoans (Gradinger 1999). Monothalamous foraminiferans are a major component of the benthic meiofauna in high-latitude regions (Pawlowski et al 2008). In the Antarctic Peninsula, foraminiferans accounted for up to 83% of all meiofaunal organisms and comprised species also found in other oceanic regions (Cornelius and Gooday 2004).…”

Widespread intra-specific genetic homogeneity of coastal Antarctic benthic foraminifera

“…Molecular studies of four morphotypes of shallow-water allogromiid foraminifera showed the presence of separate genotypes or cryptic species in the Arctic and Antarctic, questioning the presence of true bipolarity among these organisms (Pawlowski et al 2008). These results contrasted sharply with observations from the deep sea, where gene flow between Antarctica and the Arctic was documented in three common abyssal polythalamous calcareous species (Pawlowski et al 2007b).…”

“…Numerous genetic studies revealed cryptic species within planktonic (e.g., de Vargas et al 1999;Darling and Wade 2008), rotaliid (e.g., Holzmann 2000), and monothalamous foraminifera (e.g., Habura et al 2004;Pawlowski et al 2008). Similarly, high hidden diversity within Antarctic planktonic Neogloboquadrina pachyderma sinistral (Darling et al 2004) as well as among monothalamids was revealed using a single-cell sequencing approach (Pawlowski et al 2002b) and by probing environmental DNA (eDNA) extracted from coastal or deep Southern Ocean sediments (Habura et al 2004;Lejzerowicz et al 2014).…”

“…A broad distribution of some Antarctic morphospecies was suggested by some early foraminiferal workers (e.g., Earland 1934) and more recently confirmed by Mikhalevich (2004), who concluded that the majority of foraminiferal morphospecies on the Antarctic shelf have circumpolar distributions. The idea is based, however, exclusively on morphological studies, which have been shown to underestimate the true foraminiferal diversity revealed in many cases by genetic data (e.g., de Vargas et al 1999;Holzmann 2000;Pawlowski et al 2002bPawlowski et al , 2008Habura et al 2004).…”

First bipolar benthic brooder

“…For example, Darling et al (2000) and Pawlowski et al (2007) have found complete sequence identity between Arctic and Antarctic morphospecies of pelagic and benthic foraminifera, respectively. On the other hand, Pawlowski et al (2008) were able to show genetic differentiation between morphologically identical Arctic and Antarctic monothalamous foraminifera. The widely distributed (but not bipolar) Celleporella hyalina complex is an example of a cheilostome bryozoan where morphologically similar species were separated into sibling species both using molecular and mating experiments (Gomez et al 2007a,b).…”