Systematics and phylogeography of Microdictyon (Cladophorales, Chlorphyta) in Hawai'i

Abstract

Algae play an important role in reef ecosystems by providing habitat and food for marine species. The green alga Microdictyon is common on reefs across the Hawaiian Islands and provides these ecological services to support Hawaiʻi’s marine life. To date, recorded data states M. umbilicatum and M. setchellianum as the two species found in Hawaiʻi. In addition, phylogeographic studies have not been completed for these species due to the limited availability of published reference data. DNA sequences from numerous locations globally are available for M. umbilicatum that can be used for comparison to samples from Hawaiʻi, but M. setchellianum does not have published sequences available, so reports of this taxon in Hawaiʻi are based on morphological identifications. This study compares sequences of Microdictyon samples from the Hawaiian Islands with those from Microdictyon and related species published elsewhere to determine taxonomy and distributional patterns. The partial nuclear Large Subunit (LSU) rDNA was amplified and sequenced for 18 specimens from the Hawaiian Islands. Phylogenetic analyses grouped Hawaiian specimens with three taxa M. umbilicatum, M. cf. boergesenii, and cf. Boodlea vanbosseae. Haplotype networks were constructed for each taxa and analyses revealed most haplotypes had low nucleotide diversity. Some geographic and depth patterns were observed among Hawaiian and globally distributed samples. Although this study was limited in terms of number of samples and reference data, baseline data was constructed. Further research is necessary for creating a full profile of Microdictyon around the Hawaiian Islands helping to understand geographic differences overall supporting efforts in conservation of these unique ecosystems.