A Taxonomic Investigation into the Red Alga Plocamium within New Zealand

The red alga Plocamium is a cosmopolitan genus, known for its distinct branching pattern and rich chemical composition. Recent studies indicate morphological-based species delimitation approaches have failed to accurately discern diversity, distributions, and evolutionary relationship between species worldwide. Currently there are seven recognized species within New Zealand based on traditional morphological approaches and no molecular based work focused on discerning true diversity of New Zealand species in this genus. This thesis is the first to use molecular-assisted alpha taxonomy to investigate Plocamium within New Zealand. Phylogenetic analyses (Maximum Likelihood and Bayesian Inference) based on COI, rbcL, LSU and combined LSU/COI markers, three molecular species delimitation methods (Automatic Barcode Gap Discovery, General Mixed Yule Coalescent, and Bayesian implementation of the Poisson Tree Processes), and morphometric analyses of various characters (width of main axis (WMA), width of lowest basal ramuli (WLBR), length of lowest basal ramuli (LLBR), number of alternating series of ramuli (NASR), average number of ramuli per alternating series (ANRAS), curvature of basal ramuli (CBR) and serrations present or absent from basal ramuli (SERBR) were used to address this topic. The species delimitation methods revealed at least eleven (A-K) putative genetic species (with some incongruences) within the New Zealand specimens included in the study. Morphometric analyses indicated morphology reflects genetic diversity when multiple measures of multiple characters are used, however this is not the case when considering single characters. Phylogenetic analyses revealed possible monophyly of New Zealand candidate species C-K, and possible relationships to Australian, Chilean, and Taiwanese species. However these backbone relationships were poorly supported. The results of this study indicate that Plocamium diversity within New Zealand has been underestimated and provide the first steps in discovering the true species diversity of Plocamium within New Zealand.