Molecular data reveal high taxonomic diversity of allogromiid Foraminifera in Explorers Cove (McMurdo Sound, Antarctica)

Abstract

Allogromiids are organic-walled or agglutinated, single-chambered Foraminifera, common in deep-sea and polar benthic communities. The simple forms and paucity of distinctive features make allogromiid identi®cation dicult by traditional means. Molecular phylogenetic methods oer alternative tools for species identi®cation and are used here to investigate allogromiid diversity. We obtained 135 partial smallsubunit ribosomal DNA sequences of allogromiids collected in Explorers Cove, McMurdo Sound, Antarctica. In contrast to the 27 morphotypes identi®ed, phylogenetic analysis revealed 49 molecular types (considered separate species) that dier by more than 5% of sequence divergence. The 49 genetic types form 28 molecular supra-groups that dier by more than 20% and probably represent distinct genera or families. Large genetic distances separating the molecular types indicate unexpectedly high taxonomic diversity. Comparison of our data with sequences of non-Antarctic allogromiids suggests that Explorers Cove species might be endemic and only distantly related to comparable northern hemisphere fauna.

The evolution of early Foraminifera

“…Species with carnivorous habits similar to those of modern larger agglutinated Foraminifera (45) might even have helped shape early animal evolution by forcing prey organisms to adopt various avoidance or resistance modalities. It may not be coincidental that one of the most diverse assemblages of modern unilocular Foraminifera is found in the macrofauna-poor benthic community of Explorers Cove, Antarctica (15,46). This cold and relatively undisturbed coastal setting, characterized by low animal diversity and seasonally pulsed planktonic productivity (47), may serve as a useful model of the Neoproterozoic marine benthic ecosystem.…”

“…A fragment of the small subunit (SSU) rRNA gene was amplified by using foraminiferalspecific primers s14F3 (5Ј-ACG CA(AC) GTG TGA AAC TTG) and sB (5Ј-TGA TCC TTC TGC AGG TTC ACC TAC). PCR amplifications, cloning, and sequencing were done as described (15). Several clones were sequenced for each isolate, and, whenever it was possible, several isolates were sequenced for each morphospecies.…”

Widespread intra-specific genetic homogeneity of coastal Antarctic benthic foraminifera

“…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).…”

A New Allogromiid Foraminifer from Coastal Georgia, USA: The Case for an Unusual Form of Chloroplast Sequestration

“…Representatives are known from marginal marine settings to the deep sea, and in selected freshwater settings and terrestrial soils [3]. Molecular studies [4][5] have shown that the biodiversity of allogromiids is considerably higher than that recognized using traditional collecting methods, and as a result we know little about the adaptations and modes of life of this group.The many mudflats associated with the expansive salt marshes of coastal Georgia host an interesting array of mostly undescribed allogromiids in addition to other foraminiferal taxa. Among the new allogromiids is a small (<200 µm) translucent monothlamous species (Fig.…”

“…Representatives are known from marginal marine settings to the deep sea, and in selected freshwater settings and terrestrial soils [3]. Molecular studies [4][5] have shown that the biodiversity of allogromiids is considerably higher than that recognized using traditional collecting methods, and as a result we know little about the adaptations and modes of life of this group.…”