Phenotypic and genetic responses of native Hawaiian plant and animal species to environmental changes along elevation gradients


Teams: 
Other Team Members (external): 
Peltin Pelep, TCBES Graduate Student, UH Hilo
Yohan Pillon, Post-Doctoral Associate, UH Hilo
Karl Magnacca, Post-Doctoral Associate, UH Hilo
Jennifer Johansen, Research Technician, UH Hilo
Tomoko Sakishima, Research Technician, UH Hilo
Karen Uy, TCBES Graduate Student, UH Hilo
Jill Ekar, TCBES Graduate Student, UH Hilo
Eva Brill, TCBES Graduate Student, UH Hilo
Thomas Fezza, TCBES Graduate Student, UH Hilo
Christine Short, TCBES Graduate Student, UH Hilo
Matthew Mueller, TCBES Graduate Student, UH Hilo
Keenan Morrison, TCBES Graduate Student, UH Hilo
Melissa Johnson, TCBES Graduate Student, UH Hilo
Colin Phifer, TCBES Graduate Student, UH Hilo
Andrea Moss, TCBES Graduate Student, UH Hilo
Corinna Pinzari, TCBES Graduate Student
Ala Malia Leka, Undergraduate Student, UH Hilo
Christopher Yakym, Undergraduate Student, UH Hilo

Location

Windward side of Hawaii Island – many locations
United States

Description

We are investigating the phenotypic and genetic changes in one insect and one plant group that occur along terrestrial elevational changes in Hawai'i. As global and local environmental changes occur over the next century it will be important to understand how animals and plants adapt to environmental changes. We are conducted a series of phenotypic and genetic analyses of a Hawaiian picture-winged Drosophila to determine the impact of environmental changes to an indicator species for impact of climate change on the terrestrial environment. We have developed the techniques for population genetic analysis of D. sproati in different locations on the Island of Hawai‘i. The primers for sequencing a portion of the cytochrome oxidase gene of the mitochondria and the yolk protein nuclear gene have been developed and are being used to sequence these genes in Hawaiian Drosophila populations. Microsatellite markers were developed from analysis of the D. grimshawi genome for use in D. sproati. For Metrosideros polymorpha, we have completed a large-scale genotyping project of this species on Hawai‘i Island and O'ahu. M. polymorpha on Hawai‘i Island comprises six varieties that partition along strong environmental gradients (i.e., elevational, successional, and proximity to rivers/streams) and on O'ahu comprises at least nine varieties along with three closely related species. This work on the neutral genetic structure of this system, using several nuclear microsatellite loci, sets the stage for future studies of short-term (ecological) and long-term (evolutionary) functional genetic and metabolomic responses within a widespread and hyper-diverse woody species. Companion studies are examining the strength and stages of reproductive isolation among these same varieties and species on Hawai‘i Island and O'ahu to examine associations between ecological divergence and reproductive barriers. Results will yield insight into the long-term (evolutionary) impacts of climate change on natural populations.

Recent Achievements

DNA sequencing and genotyping of the cytochrome oxidase gene of the mitochondria and the yolk protein nuclear gene for Drosophila sproati have been completed for 200 individuals from six different populations around Hawai‘i Island.  The analyses of the mitochondrial haplotype data show that there are very significant differences among populations.  Microsatellite genotype markers were developed from analysis of the D. grimshawi genome for use in D. sproati.  The results indicate that this species demonstrates sufficient population structure to permit studies of local adaptation to environmental changes.

Temperature tolerance studies were conducted on two populations of D. sproati located approximately 6 km apart along an elevational gradient. The higher elevation population was acclimated to lower temperatures than the lower elevation population. This finding suggests that climate change will have dramatic impacts on natural populations that are locally adapted to specific environments.  The work is continuing with another Hawaiian picture-winged Drosophila, D. silvestrisD. silvestris is considerably rarer, and Don Price and colleagues have determined that this species is more sensitive to temperature and desiccation changes associated with climate change. Genome-wide microarray analyses in collaboration with Indiana University have identified several highly significant candidate genes that are associated with the temperature tolerances of these two species.    

For Metrosideros polymorpha, genotyping (9 nuclear microsatellite loci) of 23 populations across Hawai‘i Island differentiated four of the five named varieties partitioned along strong environmental gradients (i.e. elevational, successional, and proximity to rivers/streams). The results revealed striking neutral genetic differentiation for two varieties that occupied extreme environments, one at the edge of the species’ elevation range and one restricted to riparian habitats.  A companion analysis of chloroplast markers supported the origin of the river specialist on Hawai‘i Island and, hence, the recent and rapid emergence of this variety (within ~500,000 years).  These findings have led the team to focus its metabolomic studies on the extreme habitat varieties of M. polymorpha on Hawai‘i Island.  Tests of reproductive barriers (the expected long-term consequences of local adaptation along strong environmental gradients) among these taxa show a complex evolution of partial pre- and post-zygotic isolation.  A project is just starting to examine differential adaptation of Hawai’i Island varieties to local soils and mycorrhizae.  Genotyping of 539 individuals of 14 taxa from the most Metrosideros-taxa-rich island, O’ahu, is almost complete; preliminary analysis reveals a broader range of genetic distance values among taxa, as expected with some unnamed varieties of M. polymorpha as genetically distinct as the three other Metrosideros species on the island.  Analysis of reproductive barriers among five O’ahu taxa are underway, as is a greenhouse study of ecological differentiation among eight O’ahu taxa.

Lastly, 454 genome sequencing of pooled transcriptomes from four Metrosideros taxa has been completed, and over 400 single-copy nuclear genes have been identified.  We are cuurrently designing primers for a large-scale, multi-gene phylogeography study of Hawaiian Metrosideros, including Pacific relatives.

Future Work

We are conducting genome sequencing of several species of Hawaiian Drosophila and several species of Metrosideros using next-generation genomic techniques. These genomic data will provide for better genetic tools for investigating population genetics and speciation processes and performing functional genomic analyses of local adaptation.

Researchers carry out experimental cross-pollinations between extreme-habitat varieties of ‘ohi’a to learn if adaptation to diff
Saddle Road Kipuka with Mauna Kea in the background.  Several species of Hawaiian Drosophila exist in these Kipuka.
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Collaborators & Partners

University of Florida
The University of Florida team is a leader in the bioinformatics analysis of next-generation DNA seq
  • W. Brad Barbazuk
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Virginia Bioinformatics Institute (VBI)
We are collaborating on the genomic sequencing and analyses of Hawaiian Drosophila. Submitted a pre-
  • Pawel Michalak
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