Lloyd L. Loope

Effects of the Argentine ant on arthropod fauna of Hawaiian high-elevation shrubland.

Human-caused biological invasions by an alien species are a worldwide phenomenon. They are particularly significant on isolated oceanic islands and represent a serious threat to endemic biota. The Argentine ant (Iridomyrmex humilis) has become established in portions of the high-elevation shrubland of Haleakala National Park, Maui, Hawaii, over the past 25 yr. This ecosystem lacks native ants but possesses many locally endemic and rare arthropod species. Pitfall trapping and under-rock surveys were conducted to determine the effects of I. humilis on the local arthropod fauna. More than 180 taxa were sampled, mostly Arthropoda. Presence of the Argentine ant is associated with reduced populations of many native and non-native arthropod species, including important predator species and major pollinators of native plants. Effects of ant invasion were particularly severe at higher elevations of Haleakala volcano where endemic species normally exist at low densities. Some taxa, primarily alien species, were more abundant in the presence of ants. Invasion of the Argentine ant has locally reduced the abundance of many endemic species in the shrubland ecosystem. Although the spread of this ant species is slow, I. humilis appears to have the potential to invade a much larger area of Haleakala National Park than it now occupies. Active management of Argentine ant populations will be nec- essary if the endemic fauna is to be preserved.

Deliberate Introductions of Species: Research Needs Benefits can be reaped, but risks are high

The silent invasion of Hawaii by insects, disease organisms, snakes, weeds and other pests is the single greatest threat to Hawaii’s economy and natural environment.... Even one new pest-like the brown tree snake--could forever change the character of our islands. (Coordinating Group on Alien Pest Species 1996, P. 1). Reforestation in the tropics is so vastly behind deforestation that we cannot wait to fully appraise all the potential negative elements of domestication. Weediness is of consequence perhaps in Honolulu, but not in Addis or Delhi. (James Brewbaker, quoted by Hughes 1994, p. 244 ).

Vulnerability of Island Tropical Montane Cloud Forests to Climate Change, with Special Reference to East Maui, Hawaii

Island tropical montane cloud forests may be among the most sensitive of the worlds ecosystems to global climate change. Measurements in and above a montane cloud forest on East Maui, Hawaii, document steep microclimatic gradients. Relatively small climate-driven shifts in patterns of atmospheric circulation are likely to trigger major local changes in rainfall, cloud cover, and humidity. Increased interannual variability in precipitation and hurricane incidence would provide additional stresses on island biota that are highly vulnerable to disturbance-related invasion of non-native species. Because of the exceptional sensitivity of these microclimates and forests to change, they may provide valuable ‘listening posts’ for detecting the onset of human-induced global climate change.

Comparative Conservation Biology of Oceanic Archipelagoes Hawaii and the Galdpagos

Oceanic islands have had an important role in the history of evolutionary biology and are continuing to serve as crucial sites for evolutionary studies. The Hawai- ian Islands and the Galipagos Islands are two archipelagoes where much biological investigation has been, and continues to be, performed. Both ar- eas have also received attention be- cause of the vulnerability of their endemic animals and plants to dam- age by humans and organisms intro- duced by humans. The Hawaiian bio- ta has, in general, undergone much more destruction than that of the Galipagos. For example, whereas the Hawaiian archipelago has lost over 75% of its original endemic land bird fauna through prehistoric and histor- ic extinctions (Olson and James 1984, Scott et al., page 238-253 this issue), the Galipagos archipelago as a whole is not known to have lost a single land bird species. Oceanic islands are extremely vul- nerable to certain types of human- related biological invasions because of their long isolation from some of the selective forces that have shaped the evolution of continental orga- nisms. These forces include browsing and trampling by herbivorous mam- mals, predation by ants, virulent dis-

Introduced species in Hawaii. biological effects and opportunities for ecological research

The articles in this volume illustrate that the Hawaiian islands are perhaps the most extraordinary living museum of evolution on the planet. However, Hawaiis value as a museum has diminished as the products of millions of years of evolutionary radiation have been lost to habitat destruction and biological invasions by exotic species. Human-caused habitat destruction can largely be controlled in parks and preserves, but exotic species do not respect park boundaries and can degrade native communities within protected areas. On the other hand, invasions by exotic species provide a dynamic laboratory of ecological processes at the same time as they erode the value of the evolutionary museum.

Reducing Negative Effects of Introduced Animals on Native Biotas in Hawaii: What is Being Done, What Needs Doing, and the Role of National Parks

The endemic Hawaiian biota, having evolved in nearly complete isolation from continental organisms, and lacking as it does many major continental groups, is highly vulnerable to introduced ungulate herbivores, vertebrate predators, predacious and parasitoid insects, predacious snails, and yet other animal and plant groups. Although most of the Hawaiian lowland biota has been obliterated by Man and his introductions, relatively intact ecosystems survive at higher elevations in Hawaiis national parks and elsewhere. Long-term survival of these native ecosystems will depend largely upon the quality, intensity, and endurance, of continuing active management.

Limiting Spread of a Unicolonial Invasive Insect and Characterization of Seasonal Patterns of Range Expansion

Limiting dispersal is a fundamental strategy in the control of invasive species, and in certain situations containment of incipient populations may be an important management technique. To test the feasibility of slowing the rapid spread of two Argentine ant (Linepithema humile) supercolonies in Haleakala National Park, Hawaii, we applied ant bait and toxicant within an experimental plot situated along a supercolony boundary. The 120×260 m plot simulated a small section of what could potentially be a 120 m wide treatment encompassing the entire expanding boundaries of both supercolonies. Foraging ant numbers at baited monitoring stations decreased sharply within two weeks after treatment, and ant spread was completely halted within the plot for at least one year. In contrast, an adjacent untreated colony boundary advanced an average of 65.2 m over the course of 1 year. Most of this spread took place in the summer and fall, at the time of highest ant abundance at bait monitoring stations, while no outward dispersal occurred during the spring and early summer. These patterns are consistent with the hypothesis that local budding dispersal in this unicolonial species stems from density dependent pressure rather than inherent founding behavior associated with mating. Based on results from this experiment, we are investigating the effectiveness of annual boundary treatments in slowing the Argentine ant invasion at Haleakala National Park. The goals of this program are to protect populations of native arthropods and to keep options open for eventual attempts at eradication.

Non-Indigenous Bamboo along Headwater Streams of the Luquillo Mountains, Puerto Rico: Leaf Fall, Aquatic Leaf Decay and Patterns of Invasion

The introduction of bamboo to montane rain forests of the Luquillo Mountains, Puerto Rico in the 1930s and 1940s has led to present-day bamboo monocultures in numerous riparian areas. When a non-native species invades a riparian ecosystem, in-stream detritivores can be affected. Bamboo dynamics expected to influence stream communities in the Luquillo Experimental Forest (LEF) were examined. Based on current distributions, bamboo has spread downstream at a rate of 8 m y −1 . Mean growth rate of bamboo culms was 15.3 cm d −1 . Leaf fall from bamboo stands exceeded that of native mixed-species forest by c. 30% over a 10-mo study. Bamboo leaves (k = −0.021), and leaves from another abundant riparian exotic, Syzygium jambos (Myrtaceae) (k = −0.018), decayed at relatively slow rates when submerged in streams in fine-mesh bags which excluded macro-invertebrate leaf processors. In a second study, with leaf processors present, bamboo decay rates remained unchanged (k = −0.021), while decay rates of S. jambos increased (k = −0.037). Elemental losses from bamboo leaves in streams were rapid, further suggesting a change in riparian zone / stream dynamics following bamboo invasion. As non-indigenous bamboos spread along Puerto Rico streams, they are likely to alter aquatic communities dependent on leaf input.

Plant invasions in protected areas of tropical pacific islands, with special reference to Hawaii

Isolated tropical islands are notoriously vulnerable to plant invasions. Serious management for protection of native biodiversity in Hawaii began in the 1970s, arguably at Hawaii Volcanoes National Park. Concerted alien plant management began there in the 1980s and has in a sense become a model for protected areas throughout Hawaii and Pacific Island countries and territories. We review the relative successes of their strategies and touch upon how their experience has been applied elsewhere. Protected areas in Hawaii are fortunate in having relatively good resources for addressing plant invasions, but many invasions remain intractable, and invasions from outside the boundaries continue from a highly globalised society with a penchant for horticultural novelty. There are likely few efforts in most Pacific Islands to combat alien plant invasions in protected areas, but such areas may often have fewer plant invasions as a result of their relative remoteness and/or socio-economic development status. The greatest current needs for protected areas in this region may be for establishment of yet more protected areas, for better resources to combat invasions in Pacific Island countries and territories, for more effective control methods including biological control programme to contain intractable species, and for meaningful efforts to address prevention and early detection of potential new invaders.

A Multiagency Containment Program for Miconia(Miconia calvescens)an Invasive Tree in Hawaiian Rain Forests

Invasiveness of a species in a particular part of the world can often be successfully predicted by the species’ invasive behavior in another part of the world with similar environmental conditions. When naturalized miconia(Miconia calvescens;Melastomataceae) was discovered on Maui, Hawaii, in 1990, biologists responsible for protecting native ecosystems paid attention because of the infamous reputation of this species in ecologically similar Tahiti (French Polynesia), where it has come to extensively dominate forests since its introduction there in 1937. This species was introduced to the Hawaiian Islands as an ornamental in the early 1960s without attracting any great attention and was sold at nurseries for 2 decades. As of 1996, miconia had aroused a battle cry throughout the state of Hawaii, and cooperative efforts for its control were underway on four islands.