Omiodes Moths

Will Haines, Cynthia King and Daniel Rubinoff


















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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