PROJECT TITLE: Precious Corals in the Hawaiian Islands: Management Units Determined by Molecular Genetics

P.I.: Craig Smith, George Roderick, Amy Baco.

OBJECTIVES: We proposed to examine the population genetic structure of three species of precious corals, the red coral Corallium regale, the pink coral Corallium secundum, and the gold coral Gerardia sp., to determine the appropriate management units (or "stocks") for each of these species. We proposed to study four precious coral beds in the main Hawaiian Islands to address the following specific hypotheses: (1) Beds of precious corals in the main Hawaiian Islands are genetically isolated units. (2) Rates of gene flow differ between species and are correlated with life histories. (3) Commercial harvest has resulted in a decrease in genetic diversity within and among populations of precious corals relative to non-harvested species with similar distributions. (4) Precious corals in the WesPac "Refugium" do not supply sufficient propagules to replenish commercial beds of corals throughout the Hawaiian Islands.

METHODS: Precious corals were collected at four precious coral beds in 1998 (Fig. 1); the Makapu’u Bed, the precious coral Refugium between Nihoa and Necker Islands, East French Frigate Shoals, and 2 sites around Southeast Brooks Banks. Collections were made during six dives of the submersible PISCES V. Ten to thirty individuals of each species were collected at each site where they were present. Samples were placed into separate jars and returned to the surface where they were immediately frozen in liquid nitrogen for genetic analyses. Video observations were also made using the RCV-150. Stock identifications will be estimated using recently developed microsatellite and nuclear intron techniques. Both sets of genetic markers are highly variable, but more importantly, co-dominant, meaning that both alleles at a locus can be scored, facilitating the estimation of population genetic parameters.

RATIONALE: The precious coral retail industry in Hawaii is currently valued at over $25 million (Grigg, 1994), yet little is known about the life history and dispersal of the exploited species. Recently, a "Refugium" was established in Hawaii at the WesPac Bed in the Northwest Hawaiian Islands. This location represents the only such reserve for corals in the Hawaiian Island or Emperor Seamount Chains. However, there is currently no evidence, genetic or otherwise, that the refugium populations produce propagules that reach other island locations.

Fisheries for precious corals worldwide have followed boom-bust cycles, emphasizing the need for management of the fishery (Grigg, 1994). As for any heavily harvested or potentially over-fished species, population viability will depend on the "stock structure", defined by such parameters as dispersal (or connectedness) between populations, rates and patterns of re-establishment, and basic life-history patterns. Understanding these factors is critical to both management and conservation (Lande, 1988, Avise, 1996). Results from our study can be used to define minimal stocks or management units that can be incorporated into management models to ensure a viable fishery as well as to preserve limited resources.

BENEFITS: This project will provide key information for managing the precious coral fishery by helping to (1) determine the stock structure of the harvested species, (2) provide information on dispersal and recruitment in these species as a function of life history, and (3) elucidate the effectiveness of the designated "Refugium" bed in the Northwest Hawaiian Islands for re-seeding exploited populations of precious corals. In particular, we expect to find that the WesPac Refugium is not reseeding precious coral beds on the main Hawaiian Islands, suggesting refugia should be established along the entire length of the archipelago. This information will substantially improve our ability to manage the Hawaiian coral fishery as a sustainable resource.

PROGRESS: We report progress in 2 areas, (1) collections and (2) DNA marker development.

Collections. Collections were made in 4 areas (Table 1, Fig. 1). The collections to date will provide sufficient material for development of several different types of genetic markers. It is likely that many markers will work in all species. In addition, from these samples we will obtain a preliminary determination of population structure, and in particular, the extent to which populations are likely exchanging propagules. While in 3 of the 4 sites we were able to obtain sufficient numbers of each of 3 species, the WesPac Refuge bed appeared to have a much lower density and abundance of corals than other beds sampled. It is possible this observation may be an artifact of where on the bed we happened to dive. It should be pointed out that the beds were too large to cover in one dive.

Note: Numbers (n) are samples taken, which will provide n*2 alleles per locus.

Development of DNA Markers. To date, we have examined three types of nuclear genetic markers, introns, allozymes, and microsatellites. Such nuclear markers are preferred for population genetic studies over markers from mitochondrial DNA, because mitochondrial DNA is inherited as a single locus. In addition, the effective population size of mitochondrial DNA is typically 1/4 that of nuclear loci, meaning that mitochondrial DNA is much more subject to random variation and loss of genetic material. Also, the multiple loci available with nuclear markers provides replication of findings across loci, a feature not available with mitochondrial DNA.

DNA has been isolated from 20 individuals (where available) of each of the red and pink species from each site where they were collected. To date, isolation of DNA from the gold corals has not been as straightforward. However, such difficulties are not uncommon for many marine invertebrate taxa, and we should be able to resolve the difficulty for this species shortly.

A series of intron markers for red and pink corals were examined: two loci of beta-tubulins, cytochrome c, and elongation factors. Each of these markers produced multiple bands after DNA amplification by the polymerase chain reaction (PCR). By way of cloning, we were able to sequence some or all of the bands in an effort to obtain the target loci. This work is on-going. We also examined approximately 20-25 allozymes in 2 different buffers for the gold corals. This method shows some promise, but needs further refining to obtain adequate resolution. To date, we have examined variation in one microsatellite, Sput1f. The microsatellite and beta-tubulin introns were documented from scleractinian corals, and it is likely that markers from these other corals may also be useful.

Future Efforts: Presently, we are searching for additional variable microsatellite DNA markers to increase the number of useful nuclear loci. We are isolating these markers using a procedure in which amplified genomic DNA fragments are hybridized to biotintylated di-, tri-, and tetra- repeat oligonucleotides. The microsatellite enriched DNA is then removed with streptavidin coated magnetic beads, and ligated into a plasmid vector. We are now sequencing the resulting products. It is anticipated that in the next few months, we should have a series of markers for the corals species examined to date. A preliminary analysis of variation and population structure will be completed at that time. We are currently scheduled for additional dives in Sept. of 2000 to complete sampling at 3-4 additional coral beds. Preliminary results from this work will be presented at the First Deep-Sea Coral Symposium in July 2000 and at the Coral Reef Meeting in October 2000.

Publications from this work:

Davies, N., F.X. Villablanca, and G.K. Roderick. 1999. Determining the sources of individuals in recently founded populations: multilocus genotyping in non-equilibrium genetics. Trends in Ecology and Evolution 14:17-21.

Davies, N., and G.K. Roderick. in press. Determining the pathways of marine bioinvasion: genetical and statistical approaches. In J. Pederson (ed.), Marine Bioinvasions. Plenum Press.

Gillespie, R.G., and G.K. Roderick. in press. Biodiversity in the Hawaiian Islands. Endangered Species Bulletin.

Roderick, G.K. in press. Are new associations different from old? Ecological opportunity, adaptation, and co-evolution in island ecosystems. ALISO.

Publications related to this work:

Baco, A.R., C.R. Smith, A.S. Peek, G.K. Roderick, and R.C. Vrijenhoek. 1999. The phylogenetic relationships of whale-fall vesicomyid clams based on mitochondrial COI DNA sequences. Marine Ecology Progress Series 182:137-147.

Gillespie, R.G., F.G. Howarth, and G.K. Roderick. in press. Adaptive Radiation. In S.A. Levin (ed.), Encyclopedia of Biodiversity. pp. . New York, Academic Press.

Kimbell, J.R., M.J. McFall-Ngai, and G.K. Roderick. in review. Evidence for two genetically distinct populations of the Hawaiian bobtail squid, Euprymna scolopes, on the island of Oahu. Marine Biotechnology.

Roderick, G.K., and F.G. Howarth. in press. Invasion genetics. In M. Shiyomi, D. Andow, K. Matsuo, and E. Yano (eds.), Biological Invasions of Pests and Beneficial Organisms. Kluwer.

Additional manuscripts are being prepared by Baco and Davies describing the genetic markers we have developed.

Websites highlighting this work:

http://www.nurp.noaa.gov/news.html

http://www.oar.noaa.gov/nurp/spotlite/spot_corals.shtml

PARTICIPATING PERSONNEL

Craig Smith, Professor, Oceanography

George Roderick, Associate Researcher, Center for Conservation Research and Training

Amy Baco, Graduate Student, Oceanography

Paul Armstrong, Graduate Student, Center for Conservation Research and Training

LITERATURE CITED

Avise, J.C. 1996. The scope of conservation genetics. In J.C. Avise and J.L. Hamrick (eds.), Conservation Genetics. pp. 1-9. New York, Chapman & Hall.

Grigg, R.W. 1994. History of the precious coral fishery in Hawaii. Precious Corals and Octocoral Research 3:1-18.

Lande, R. 1988. Genetics and demography in biological conservation. Science 24:1455-1460.