The Phylogeography and Conservation Genetics of the Endemic Seagrass Halophila Hawaiiana on Oahu, Hawaii
Loading...
Authors
Kyla Richards
Issue Date
Type
Language
Keywords
Marine Science
Alternative Title
Abstract
Seagrasses are globally important in coastal marine ecosystems primarily for a number of ecological services they provide: extensive habitat and food for fish, invertebrates, epiphytic algae and microbes; carbon sequestration; forage for rare and endangered species including manatees and sea turtles; improvement of water quality by absorbing nutrients; and the stabilization of sediments in meadows that protect coastal zones and reefs from wave damage and erosion. Seagrass populations are declining globally, but in order to work towards restoration there is a need for ongoing and enhanced assessments of the ecology and conservation status of seagrass populations, including those in Hawaii. The endemic species Halophila hawaiiana is patchily distributed on multiple islands in the Hawaiian high islands, but this species is understudied especially in regard to its genetic diversity. This study uses a noncoding nuclear region, the internal transcribed spacer regions (ITS1 and ITS2) to create a phylogeny of H. hawaiiana relative to other Halophila species. Haplotype networks also clearly show the close genetic affinity between H. hawaiiana and the Indonesia/Australia lineage of H. ovalis. The haplotype network is also an unambiguous way to visualize this close relationship as well as the difference in patterns of haplotype diversity between a sexually reproducing seagrass in H. ovalis, and an asexually reproducing species, H. hawaiiana. In addition, seven microsatellite loci were amplified and scored to compare the genetic diversity among and between Windward and Leeward seagrass populations on Oahu. Our results indicate H. hawaiiana is most closely related to H. ovalis from Australia and Indonesia based on the ITS gene fragment. We see two subunits in the clade of H. ovalis where the phylogeographic pattern shown seems to correspond to and follow the biogeographic division depicted by Wallace's Line. This is the first time that this theoretical phylogeographic break has been observed in a marine angiosperm. When assessing genetic diversity between the Windward and Leeward H. hawaiiana populations, we saw uniformity in the results at all seven microsatellite loci. The lack of genetic diversity in both the microsatellite alleles and ITS haplotypes may have arisen due to predominately asexual reproduction. These low genetic variability patterns raise questions of how the species would be impacted by future changes in environmental pressure.
Description
Thesis
Citation
Publisher
Hawaii Pacific University