We are using environmental DNA samples to assess habitat occupancy of the invasive southern house mosquito in Kīpahulu Valley, Maui. An understanding of mosquito distribution is critical to developing and implementing tools to prevent the transmission of avian malaria, a primary threat to Hawaiian forest birds.
Overview:
Kīpahulu Biological Reserve in Haleakalā National Park - HALE - is one of the most remote, intact, dramatic valleys in the Pacific containing remarkable biodiversity found nowhere else on the planet. HALE contains critical habitat for six native Hawaiian honeycreepers, including three restricted to Maui: the ‘Ākohekohe, Kiwikiu - both endangered - and Maui ʻAlauahio.
The primary threat to Hawaiian forest birds is the disease avian malaria, caused by a parasite - Plasmodium relicum – which is transmitted by the invasive Southern house mosquito, Culex quinquefasciatus. Low temperatures at high elevations limits mosquito distribution and disease transmission which provides disease-free sanctuary for forest birds. However, increases in temperatures and drought conditions due to climate change are allowing for the spread of mosquito populations to higher elevation areas. It’s anticipated that warming conditions will also lead to increases in disease transmission, causing the extinction of most remaining Hawaiian honeycreepers species. To protect the birds, development and launch of landscape-level mosquito control is a top management priority of HALE; as well as a top conservation concern for the U.S. Fish and Wildlife Service, Pacific Islands Fish and Wildlife Office and the State of Hawai’i Department of Land Natural Resources.
A promising strategy to suppress mosquito populations is the Incompatible Insect Technique – IIT. IIT uses a naturally occurring bacteria, Wolbachia to act as mosquito “birth control.” Wolbachia naturally infects many insects and plays an important role in insect reproduction. Male mosquitos infected with one strain of Wolbachia can only reproduce with females who carry a compatible strain. If they mate with a female that carries an incompatible strain of Wolbachia, or no Wolbachia at all, then the mosquito eggs won’t develop and hatch. For IIT, laboratory raised male mosquitos carrying an incompatible strain will be released on the landscape to mate with wild females, resulting in eggs that won’t hatch. Male mosquitoes do not feed on blood, only nectar, so they don’t spread disease. Consecutive releases of these male mosquitoes reduce the mosquito population over time. However, success of IIT depends on a sound understanding of the wild mosquito population dynamics.
Direct physical measurements of the wild mosquito population include trapping adult mosquitoes and larval surveys in waterbodies suitable for mosquitoes. Ongoing trapping for adult mosquitoes in Kīpahulu Valley can provide an estimate of mosquito abundance and the timing of population peaks. However, adult trapping doesn't tell us if the mosquitoes were produced nearby - a population source - or if they just fly up into the trapping area - a population sink. Searching for the immature mosquito larvae in their aquatic habitat can confirm if an area is a population source, but larvae can be hard to detect. In these cases, environmental DNA is an additional observation tool.
Environmental DNA (eDNA) is DNA left behind by organisms - skin, excrement etc. For this study, eDNA samples from water bodies in HALE provide a broader window of time to assess whether mosquito larvae have recently emerged - despite lack of visual confirmation.
Objectives:
The goal of this study is to use eDNA to provide key information on the distribution of mosquito populations in critical Hawaiian forest bird habitat. This can help guide where to apply IIT mosquitoes on the landscape and measure the success of mosquito suppression efforts.
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Develop and evaluate a genetic test that is specific to the southern house mosquito, Culex quinquefasciatus. This type of test (TaqMan assay) amplifies DNA of the target species using a process called quantitative Polymerase Chain Reaction (qPCR). A fluorescent probe is used to determine if DNA of the target species is present in the qPCR reaction.
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Develop water sampling protocols that can be used to recover DNA from environmental samples, in this case, water.
-
Collect water samples in potential mosquito breeding habitat in Kīpahulu Valley streams to screen for mosquito presence using the genetic assay.
Identifying Genetic Diversity of Wolbachia Bacteria for Mosquito Control
- Overview
We are using environmental DNA samples to assess habitat occupancy of the invasive southern house mosquito in Kīpahulu Valley, Maui. An understanding of mosquito distribution is critical to developing and implementing tools to prevent the transmission of avian malaria, a primary threat to Hawaiian forest birds.
Sources/Usage: Public Domain.Palikea stream in Kīpahulu Biological Reserve. Certain times of year, the streambed is almost completely dry. The still water left in rock pools provides habitat for invasive mosquitoes. Overview:
Kīpahulu Biological Reserve in Haleakalā National Park - HALE - is one of the most remote, intact, dramatic valleys in the Pacific containing remarkable biodiversity found nowhere else on the planet. HALE contains critical habitat for six native Hawaiian honeycreepers, including three restricted to Maui: the ‘Ākohekohe, Kiwikiu - both endangered - and Maui ʻAlauahio.
The primary threat to Hawaiian forest birds is the disease avian malaria, caused by a parasite - Plasmodium relicum – which is transmitted by the invasive Southern house mosquito, Culex quinquefasciatus. Low temperatures at high elevations limits mosquito distribution and disease transmission which provides disease-free sanctuary for forest birds. However, increases in temperatures and drought conditions due to climate change are allowing for the spread of mosquito populations to higher elevation areas. It’s anticipated that warming conditions will also lead to increases in disease transmission, causing the extinction of most remaining Hawaiian honeycreepers species. To protect the birds, development and launch of landscape-level mosquito control is a top management priority of HALE; as well as a top conservation concern for the U.S. Fish and Wildlife Service, Pacific Islands Fish and Wildlife Office and the State of Hawai’i Department of Land Natural Resources.
A promising strategy to suppress mosquito populations is the Incompatible Insect Technique – IIT. IIT uses a naturally occurring bacteria, Wolbachia to act as mosquito “birth control.” Wolbachia naturally infects many insects and plays an important role in insect reproduction. Male mosquitos infected with one strain of Wolbachia can only reproduce with females who carry a compatible strain. If they mate with a female that carries an incompatible strain of Wolbachia, or no Wolbachia at all, then the mosquito eggs won’t develop and hatch. For IIT, laboratory raised male mosquitos carrying an incompatible strain will be released on the landscape to mate with wild females, resulting in eggs that won’t hatch. Male mosquitoes do not feed on blood, only nectar, so they don’t spread disease. Consecutive releases of these male mosquitoes reduce the mosquito population over time. However, success of IIT depends on a sound understanding of the wild mosquito population dynamics.
Direct physical measurements of the wild mosquito population include trapping adult mosquitoes and larval surveys in waterbodies suitable for mosquitoes. Ongoing trapping for adult mosquitoes in Kīpahulu Valley can provide an estimate of mosquito abundance and the timing of population peaks. However, adult trapping doesn't tell us if the mosquitoes were produced nearby - a population source - or if they just fly up into the trapping area - a population sink. Searching for the immature mosquito larvae in their aquatic habitat can confirm if an area is a population source, but larvae can be hard to detect. In these cases, environmental DNA is an additional observation tool.
Sources/Usage: Public Domain.USGS volunteer Liliana uses a syringe to draw an eDNA water sample from a rock pool along the Puka Stream. The eDNA sampled by USGS field crews informs research on mosquito population dynamics. Environmental DNA (eDNA) is DNA left behind by organisms - skin, excrement etc. For this study, eDNA samples from water bodies in HALE provide a broader window of time to assess whether mosquito larvae have recently emerged - despite lack of visual confirmation.
Objectives:
The goal of this study is to use eDNA to provide key information on the distribution of mosquito populations in critical Hawaiian forest bird habitat. This can help guide where to apply IIT mosquitoes on the landscape and measure the success of mosquito suppression efforts.
-
Develop and evaluate a genetic test that is specific to the southern house mosquito, Culex quinquefasciatus. This type of test (TaqMan assay) amplifies DNA of the target species using a process called quantitative Polymerase Chain Reaction (qPCR). A fluorescent probe is used to determine if DNA of the target species is present in the qPCR reaction.
-
Develop water sampling protocols that can be used to recover DNA from environmental samples, in this case, water.
-
Collect water samples in potential mosquito breeding habitat in Kīpahulu Valley streams to screen for mosquito presence using the genetic assay.
-
- Science
Identifying Genetic Diversity of Wolbachia Bacteria for Mosquito Control
We are sequencing the DNA of Wolbachia bacteria found in mosquito populations in Hawai’i and those used for mosquito control. We are also developing sample processing techniques to increase the efficiency and accuracy of monitoring mosquito control efforts to help long-term survival and restoration of Hawaiian forest bird populations. - Multimedia
- Publications