Genetic and morphological characterization of a coral Species of Concern, Montipora dilatata, in Kaneohe Bay, Oahu, Hawaii

Executive Summary Montipora dilatata (a stony coral endemic to Hawaii) is one of the rarest corals known; only a few colonies have ever been found despite extensive surveys. The taxonomic status of M. dilatata is unclear, in part because coral species boundaries in general are poorly understood. In order to examine evolutionary relationships in Montipora, a suite of molecular markers (mitochondrial: COI, CR, Cyt-B,16S, ATP6; nuclear: ATPsβ, ITS-2) were tested for polymorphism on samples collected from Hawaii and the Phoenix Islands. ATPsβ and the putative mitochondrial Control Region (CR) were selected for a broad survey of 13 morphospecies, followed by a more focused analysis of 6 representative Hawaiian taxa with all markers. The mitochondrial markers consistently showed clear and statistically supported divisions that are likely to be ancient given the slow rate of evolution of Anthozoan mitochondrial DNA. Hawaiian samples generally sorted into three distinct clades: I) M. patula/M. verrilli; II) M. dilatata/M. turgescens/M. flabellata; and III) M. capitata. ATPsβ trees of all sequences resolved no groups, but when heterozygous and non-Hawaiian taxa were excluded from the analysis, four strongly supported groups emerged. Unexpectedly, all markers indicated that M. dilatata, M. turgescens, and M. flabellata share identical or very similar sequences, indicating that they are either close relatives, morphological variants of the same species, or members of the same " hybrid species complex ". In order to distinguish among these competing hypotheses, it is necessary to focus on morphological variation and/or reproductive relationships. This preliminary study echoes findings of other molecular studies on reef building coral, indicating that morphology obscures genetic relationships and limits our understanding of coral evolution and biodiversity. Now that the closest relatives of M. dilatata have been identified, gene flow, morphological, and reproductive characteristics can be more closely examined to further elucidate the nature of coral species so they can be better understood and more effectively managed. Introduction Montipora dilatata is thought to be one of the rarest corals known. It has only been found in two locations: Kaneohe Bay, Oahu, and Maro reef (M. c.f.dilatata) in the Northwestern Hawaiian Islands (Fenner 2005; NOAA 2007). In 2000, extensive surveys identified only three colonies of M. dilatata in Kaneohe Bay, where previously it was thought to be more abundant (NOAA 2007). The apparent decline of this species in Kaneohe Bay may be attributed to coral bleaching, freshwater kills, sedimentation/habitat degradation, overgrowth by alien algae (e.g., Figure 1), …