Omiodes Moths
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Two
graduate students worked with this Hawaiian radiation
of moths. Will Haines has been studying the systematics
of the genus Omiodes. Cynthia King has quantified
the non-target effects of introduced parasitoids on endemic
moths in this genus.
Phylogenetics of the Genus Omiodes (Lepidoptera: Crambidae)
William Haines
My main focus is the evolutionary history of a radiation of moths
in the genus Omiodes. The genus Omiodes contains
about 80 species worldwide, in both the neotropics and paleotropics.
Hawai‘i is home to 23 endemic species, all of which likely
descended from a single ancestor that colonized the islands some
millions of years ago.
The Hawaiian species show a range of host specificities, ranging
from generalists whose larvae feed on many types of native and non-native
grasses, to specialists which feed only on a single species of native
plant such as Dianella sandwicensis (ukiuki) . There is
also some variation in degree of geographic endemism; many species
are widespread and found on all the main Hawaiian Islands, while
others are restricted to a single island.
One of the oddest things about the evolutionary history of these
moths, and what inspired me to work on them, is that five species
of endemic Hawaiian Omiodes have apparently evolved to specialize
on the leaves of Polynesian cultivars of banana, a plant that was
introduced into Hawai‘i within the past 1,500 years. It has
been presumed that the divergence of these species from a palm-feeding
ancestor was triggered by the introduction of banana, implying a
very rapid rate of speciation, and presenting a rare opportunity
to examine speciation or host-race formation.
Unfortunately, partly due to the impacts of non-native predators
and parasitoids, many species of Omiodes, including four
of the banana-feeding species, have been listed as extinct, and Hawaiian
cultivars of banana are themselves threatened. However, we have
successfully rediscovered several
species of Omiodes formerly thought to be extinct, and I
am hopeful that extant populations of banana-feeding species exist.
Non-target impacts on Hawaiian Omiodes (Lepidoptera:
Crambidae)
Cynthia King
At present my research focuses on assessing the non-target impacts
of introduced parasitoids on endemic leaf-roller moths (Crambidae: Omiodes). The
genus Omiodes contains 23 endemic Hawaiian moth species,
and individuals in the group have adapted to a wide range of host
plants (including grasses, sedges, lilies, palms and legumes). Many
of the species have made recent host plant shifts, feeding on plants
such as banana and coconut which were introduced by Polynesians approximately
1500 years ago, as well as sugarcane, which arrived in the islands
closer to 150 years ago. Two species in this group O.
accepta (sugarcane leafroller) and O. blackburnii (coconut
leafroller) actually became pests of economic significance on sugarcane
and coconut, defying the stereotype that native insects do not become
pests. A variety of biocontrol agents were subsequently released
for their suppression. At present two-thirds of the other species
in the genus are listed as extinct, and the precipitous declines
have been attributed to the non-target effects of introduced parasitoids. In
the last two years however, five of the extinct species have been “rediscovered,” and
with additional surveys it is very possible that more may be detected.
My research attempts to quantify the non-target parasitism rates
in several Omiodes species. To accomplish this, Omiodes eggs
and larvae are exposed to parasitism under varying conditions, then
retrieved and reared until eclosion. Field trials were completed
on Maui during summer 2006 at upcountry field sites (Makawao FR,
Haleakala Ranch, UH Kula Agricultural Station) and lower elevation
sugarcane field sites. Additional trials are underway on Oahu
at HARC Maunawili, as well as at the UH Manoa Lyon Arboretum. In
this manner I hope to understand the impact which parasitism by non-native
parasitoids and the effects of predation has on these populations. Whether
indicative of low or high impacts by introduced parasitoids, results
will provide valuable information for future biological control efforts
in Hawai'i. This research is made possible by a Tropical and Subtropical
Agricultural Research Grant (TSTAR) from the Cooperative States Research
Education and Extension Service (CSREES), US Department of Agriculture.
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