Molecular species discovery in the diatom Sellaphora and its congruence with mating trials.

Abstract

Many diatom and other microbial eukaryote morphospecies consist of a variable number of (pseudo)cryptic species, with obvious consequences for such fields as biogeography and community ecology. Here, we investigated the species limits of morphologically similar small-celled strains of the model diatom Sellaphora from the United Kingdom and Australia, using cox1 mitochondrial and rbcL chloroplast gene sequences. Based on cox1 sequence data, the sequenced strains belonged to six closely related lineages, presumably species, of which one corresponds to the previously described S. auldreekie D.g. mann & s.m. mCDonalD. Although rbcL displayed less sequence variation, the same six lineages were also recovered in an rbcL phylogeny of the genus. Molecular species discovery was compared to mating trials involving three of the lineages, showing that they were reproductively isolated. Incomplete evidence from a fourth lineage suggested that it too was reproductively isolated. A posteriori examination of light microscope morphology revealed no simple metrics or presence/absence characters that could consistently separate all species of the auldreekie complex, even though some do differ in pole width or stria density. While it is premature to make conclusions about their biogeography, it is obvious that a number of cryptic Sellaphora species thus far undetected in the UK are easily found at several localities in warm-temperate Australia.

Genetic and Physiological Diversity in the Diatom Nitzschia inconspicua

“…commun., and Vanormelingen et al. ), and considerably greater than between putative species of N. palea , some of which have been shown to be reproductively isolated (Trobajo et al. ).…”

“…Moreover, the results of recent molecular studies have revealed cryptic diversity, suggesting that diatom biodiversity has been greatly underestimated (Mann and Vanormelingen 2013). For example, genetically distinct entities have been found within morphologically circumscribed species in Asterionellopsis (Kaczmarska et al 2014), Berkeleya (Hamsher and Saunders 2014), Chaetoceros (Huseby et al 2012;Kooistra et al 2010), Cyclotella (Beszteri et al 2005(Beszteri et al , 2007, Cylindrotheca (Vanormelingen et al 2013b), Eunotia (Vanormelingen et al 2008), Frustulia (Vesel a et al 2012), Gomphonema (Kermarrec et al 2013), Hantzschia (Souffreau et al 2012), Navicula (Cr each et al 2006;Poul ı ckov a et al 2010;Vanelslander et al 2009), Nitzschia ), Pinnularia (Souffreau et al 2012), Pseudo-nitzschia (Amato et al 2007), Sellaphora Vanormelingen et al 2013a), Skeletonema (Kaeriyama et al 2011;Kooistra et al 2008;Saravanan and Godhe 2010), and Tabularia (Kaczmarska et al 2009). However, the functional significance of this cryptic diversity is still unclear because studies on the physiology, ecology or geographical distributions of cryptic and pseudocryptic species are still relatively scarce.…”

Phylogenetic diversity and environment form assembly rules for Arctic diatom genera—A study on recent and ancient sedimentary DNA

“…We tested the suitability of the 76bp metabarcode to assess proper phylogenetic distances within genera by comparing pairwise distances of reference sequences covering the short (76bp) and three longer rbcL fragments (1398bp, 939bp and 365bp). The 1398bp rbcL fragment have been successfully used to recover phylogenetic relationships in the genus Sellaphora (Evans et al, ; Vanormelingen, Evans, Chepurnov, Vyverman, & Mann, ) and a slightly shorter fragment was used to demonstrate phylogenetic relationships in Aulacoseira (Edgar & Theriot, ). Restricted by the available reference sequences, we could test intrageneric distances in 4 genera ( Sellaphora , Nitzschia , Navicula and Cyclotella ) by comparing the 1398bp and the 76bp rbcL barcode.…”

Connecting the morphological and molecular species concepts to facilitate species identification within the genus Fragilaria (Bacillariophyta)

“…, Vanormelingen et al. ). Appropriate short regions within selected genetic markers can be used as “DNA barcodes” for identification (e.g., Mann et al.…”