Abstract
AbstractDNA sequence data have become a crucial tool in assessing the relationship between morphological variation and genetic and taxonomic groups, including in the Antarctic biota. Morphologically distinct populations of submersed aquatic vascular plants were observed on sub-Antarctic Marion Island, potentially representing the two species of such plants listed in the island's flora, Limosella australis R.Br. (Scrophulariaceae) and Ranunculus moseleyi Hook.f. (Ranunculaceae). To confirm their taxonomic identity, we sequenced a nuclear locus (internal transcribed spacer; ITS) and two plastid loci (trnL-trnF, rps16) from three specimens collected on Marion Island and compared the sequences with those in public sequence databases. For all three loci, sequences from the Marion Island specimens were nearly identical despite morphological dissimilarity, and phylogenetic analyses resolved them to a position in Limosella. In phylogenetic trees and comparisons of species-specific sequence polymorphisms, the Marion Island specimens were closest to a clade comprising Limosella aquatica L., L. curdieana F.Muell. and L. major Diels for ITS and closest to L. australis for the plastid loci. Cytonuclear discordance suggests a history of hybridization or introgression, which may have consequences for morphological variability and ecological adaptation.
Highlights
The comparison of DNA sequence data, enabled especially by the availability of sequences in large public sequence databases, can help us to resolve phylogenetic relationships and reveal cryptic taxa, contributing to a broader understanding of evolutionary and ecological patterns and processes (e.g. Ito et al 2016, Webster et al 2020)
Several species of mosses and vascular plants grow on saturated substrates or are emergent or floating-leaved in standing water, only two species listed in the vascular plant flora grow submersed on the bottom of waterbodies, namely Limosella australis R.Br. (Scrophulariaceae) and Ranunculus moseleyi Hook.f. (Ranunculaceae) (Gremmen & Smith 2008)
Leaf tissues were preserved on silica gel and voucher specimens were deposited at the University of Pretoria herbarium (PRU)
Summary
The comparison of DNA sequence data, enabled especially by the availability of sequences in large public sequence databases, can help us to resolve phylogenetic relationships and reveal cryptic taxa, contributing to a broader understanding of evolutionary and ecological patterns and processes (e.g. Ito et al 2016, Webster et al 2020). Low herbaceous vegetation covers much of the island below the high unvegetated peaks, growing in the cool, wet conditions that characterize the sub-Antarctic terrestrial region (Smith & Mucina 2006). Limosella australis was first recorded on Marion Island by botanist Brian Huntley during the first extensive floristic survey of the island on the 1965–1966 South African Biological and Geological Expedition to Marion and Prince Edward Islands (Huntley 1971) and has been collected sporadically since . Ranunculus moseleyi was first recorded on Marion Island during the 1965–1966 Expedition (Huntley 1971), but only one herbarium specimen of this species from Marion Island is Downloaded from https://www.cambridge.org/core. IP address: 54.146.7.40, on 02 Nov 2021 at 10:25:58, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms.
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