Anchialine habitats, land-locked pools of mixohaline water that fluctuate with the tides but have no surface connection to the sea, are common coastal features in the Hawaii Archipelago. Although the islands are home to the highest concentration of anchialine habitats in the world, the population genetics of the organisms that inhabit them have only begun to be examined. This is particularly troublesome given the significant negative impact that these habitats have experienced from anthropogenic causes. Using a variety of DNA markers, The Santos Lab has investigated the genetic structure and population history of the most common species found in these habitats, the endemic Hawaiian atyid shrimp Halocaridina rubra. Surveys of populations from 34 sites on the islands of Hawaii, Maui, and Oahu revealed 13 distinct genetic groups belonging to eight divergent lineages. In general, a Halocaridina genetic group or lineage was restricted to a particular region of a single Hawaiian Island, with no individuals being exchanged between them. This pattern stems from a combination of intrinsic organismal properties such as large egg size, abbreviated development, restricted larval habitat and larval feeding mode, and extrinsic obstacles to gene flow in the form of a marine barrier and geologic features that compartmentalize the islands' aquifers. The phylogeographic structuring on and between islands suggests evolutionary diversification in Halocaridina is driven by population fragmentation, isolation, and subsequent diversification in the aquifers of the Hawaiian Islands. Calibration of cytochrome oxidase subunit I sequence divergence between sister Halocaridina lineages to the geologic age of Kilauea volcano on Hawaii implies diversification in the genus is proceeding at a short-term rate of 20% per million years. These studies bring novel insight into the natural history of Halocaridina and have important implications for the future management of the species and their habitats. This project is part of a collaborative effort to better understand anchialine habitats and the organisms that inhabit them; complementary studies are being conducted at the University of Hawaii - Hilo (Atlantis Russ & Cam Muir) and the State of Hawaii Division of Aquatic Resources (Mike N. Yamamoto & Thomas Iwai).
Maps depicting the distribution of Halocaridina rubra lineages across the Hawaiian Islands (Current as of: April 2009). Maps of Hawaii, Maui and Oahu. Detailed map of Oahu.
Read a February 18, 2009 blog by Jan TenBruggencate of Raising Islands on Weese & Santos (2009) "Genetic identification of source populations for an aquarium-traded invertebrate" from the journal Animal Conservation, which documents the likely source populations of Halocaridina rubra from the aquarium trade.
Read a April 4, 2008 blog by Jan TenBruggencate of Raising Islands on a new anchialine shrimp fact sheet released by the U.S. Fish and Wildlife Service and the State of Hawaii Department of Land and Natural Resources Division of Aquatic Resources.
Read a December 17, 2007 blog by Jan TenBruggencate of Raising Islands highlighting this research project.
Read an article by Auburn graduate and nationally syndicated columnist Rheta Grimsley Johnson about her travel experience with Halocaridina rubra.
Read the June 12, 2006 article by Jan TenBruggencate of the Honolulu Advertiser about this research project.
Photo gallery of anchialine habitats, field collections and organisms from Hawaii, Maui and Oahu (2004 - 2009).
View/download the complete mitochondrial genome sequence of Halocaridina rubra (View the genome) (Download the genome as a GenBank format text file)
HALO-BLAST: Search the Halocaridina rubra DNA sequence database.
|
