Investigating the Phylogenetic relationships of endemic New Zealand Anthozoans

Abstract

New Zealand sea anemones have received very little taxonomic investigation. Their species diversity has not been well characterised, the phylogenetic relationships among clades has not been examined, and the biogeographic origins of our endemic species are largely unknown. Sea anemones do not leave behind fossils of their structures, which have so often been used as the baselines for the relationships between extinct taxa of other groups. Current phylogeny of sea anemones is rooted in morphological classification, which phylogenetic studies show are rarely monophyletic. Gene sequences taken, from nine species sampled across 4 regions, targeted several mitochondrial and nuclear genes which were amplified and sequenced. A concatenated tree of each sequenced gene was constructed using BEAST. Geographic distributions were researched and unified with each species. BioGeoBears was used to unify the geographic, phylogenetic and molecular data. No morphologically cryptic species were identified, though the most promising grouping for morphologically cryptic species was the Oulactis muscosa, Aulactinia veratra, and Isactinia olivacea clade, which remains consistent with other phylogenetic studies. The only evidence for a distinctly New Zealand clade and species radiation came from Anthopleura rosea, Aulactinia veratra, and Isactinia olivacea, as the entire clade is endemic to New Zealand and is reciprocally monophyletic. Biogeographic analysis shows that the origins of New Zealand sea anemone has been shaped by the dominance of dispersal from the Pacific rather than by Gondwanan vicariant connections. New genetic sequences for endemic sea anemones were created, along with the first ever sequences for Anthothoe vagrans and Isoparactis ferax. These sequences produced the first phylogenetic analysis of endemic New Zealand sea anemones, showing that sea anemones colonised New Zealand multiple times in many unique events. Final analysis indicates that the driving factor of sea anemone biogeographic distributions may be extinction. Extant sea anemones show a far more restricted and regional distribution than the predicted distributions of ancestral species. Therefore, the current observed distributions are a result of localised extinction events. These localised extinction events cause reproductive isolation, which leads to speciation. The asexual reproduction and colonisation abilities of sea anemone may be a result of sea anemones being quite vulnerable to small scale extinction events and genetic isolation.