Molecular evidence for distinct Antarctic lineages in the cosmopolitan terrestrial diatoms Pinnularia borealis and Hantzschia amphioxys

Recent morphology-based studies indicate that freshwater diatom floras in the Antarctic comprise a significant share of endemics among a majority of apparently cosmopolitan species. Given the widespread (pseudo)cryptic species diversity in diatoms, we assessed the molecular divergence and temperature-dependent growth characteristics between Antarctic and non-Antarctic strains for two presumed species with a cosmopolitan distribution, namely Pinnularia borealis and Hantzschia amphioxys. Molecular phylogenies based on the plastid gene rbcL and the nuclear 28S rDNA (D1-D3 region) revealed that both taxa consist of multiple lineages, each including a distinct Antarctic lineage. A molecular clock estimates the origin of P. borealis at 35.8 (30-47) million years (Ma) ago, making this the oldest known diatom species complex. The Antarctic P. borealis lineage is estimated to have diverged 7.8 (2-15) Ma ago, after the geographical and thermal isolation of the Antarctic continent. Despite not being psychrophilic, the Antarctic lineages of P. borealis and H. amphioxys have a lower optimal growth temperature and upper lethal temperature than most lineages from more temperate regions, indicating niche differentiation. Together, this suggests that many presumed cosmopolitan Antarctic diatom species are in fact species complexes, possibly containing Antarctic endemics with low temperature preferences. © 2012 Elsevier GmbH.

Jaar van publicatie:2013

Trefwoorden:Cryptic diversity, Diatoms, LSU rDNA, Molecular time-calibration, RbcL, thermal niche, fresh water, RbcL protein, plastid, ribosome DNA, ribosome RNA, ribulosebisphosphate carboxylase, RNA, ribosomal, 26S, Antarctica, article, chemistry, classification, cluster analysis, cytology, diatom, DNA sequence, genetics, growth, development and aging, microbiology, microscopy, molecular evolution, molecular genetics, phylogeny, temperature, Antarctic Regions, Cluster Analysis, DNA, Ribosomal, Evolution, Molecular, Fresh Water, Microscopy, Molecular Sequence Data, Phylogeny, Ribulose-Bisphosphate Carboxylase, RNA, Ribosomal, Sequence Analysis, DNA, Temperature, Bacillariophyta, Hantzschia amphioxys, Pinnularia borealis