Uncovering diversity in the mesophotic zone of Hawai‘i: species new to science in the genera Halopeltis and Leptofauchea (Rhodymeniales, Rhodophyta)

Abstract

Macroalgal surveys in the mesophotic zone shed light on undocumented diversity in the Hawaiian Islands. This study highlights more newfound Rhodophyta diversity through the uncovering of multiple species in the genus Leptofauchea and a species new to science in the genus Halopeltis. Both genera belong to the diverse order, Rhodymeniales. Neither Halopeltis nor Leptofauchea have been previously documented from the Hawaiian Islands prior to this study and were only observed in the mesophotic zone. Samples were gathered at depths of 72 – 104 m, with most samples collected off the west coast of Molokaʻi. One Leptofauchea sample included in this analysis was collected from the Papahānaumokuākea Marine National Monument, demonstrating the large range this genus has within the Hawaiian mesophotic zone. Species identification was performed using the COI-5P (mitochondrial), rbcL (plastid), and LSU (nuclear) molecular markers, in combination with morphological and anatomical characterization. Sequencing of multiple markers aided in phylogenetic reconstruction of these Hawaiian samples in relation to currently described species. Morphological comparisons complemented the molecular analyses and were used to describe two species total. All Hawaiian species explored are more closely related to species in different localities than they are to each other, suggesting multiple colonizations. Links between Hawaiian, Asian, and Australian species were found. This study contributes to the baseline of knowledge of the red algal flora found in the mesophotic zone.