Lori Lach

Environmental and Economic Costs of Nonindigenous Species in the United States

[Extract] Aproximately 50,000 nonindigenous (non-native) species are estimated to have been introduced to the United States. Some of these are beneficial; for example, species introduced as food crops (e.g., corn, wheat, and rice) and as livestock (e.g., cattle and poultry) now provide more than 98% of the US food system, at a value of approximately

Managing the whole landscape: historical, hybrid, and novel ecosystems

800 billion per year (USBC 1998). Other exotic species have been introduced for landscape restoration, biological pest control, sport, pets, and food processing, also with significant benefits. Some nonindigenous species, however, have caused major economic losses in agriculture, forestry, and several other segments of the US economy, in addition to harming the environment. One study reported that 79 exotic species had caused approximately

Invasive ants: unwanted partners in ant-plant interactions?

97 billion in damages during the period 1906–1991 (OTA 1993).

Increased risk of lymphoid and nonlymphoid malignancies in patients with lymphomatoid papulosis

The reality confronting ecosystem managers today is one of heterogeneous, rapidly transforming landscapes, particularly in the areas more affected by urban and agricultural development. A landscape management framework that incorporates all systems, across the spectrum of degrees of alteration, provides a fuller set of options for how and when to intervene, uses limited resources more effectively, and increases the chances of achieving management goals. That many ecosystems have departed so substantially from their historical trajectory that they defy conventional restoration is not in dispute. Acknowledging novel ecosystems need not constitute a threat to existing policy and management approaches. Rather, the development of an integrated approach to management interventions can provide options that are in tune with the current reality of rapid ecosystem change.

Interference and exploitation competition of three nectar-thieving invasive ant species

As invasive ants spread, their interactions with plants are inevitable and have potentially great implications for agriculture and conservation. When considered in the context of pre-existing models of ant-plant interactions, the higher abundance, aggressive nature, and attraction to high-carbohydrate resources typically associated with invasive ants lead to hypotheses about how invasive ants may differ from native ants in protecting plants from herbivores, tending of Homoptera, and interactions affecting plant reproduction. Examples demonstrate that all three of these traits common to invasive ants can influence the outcome of interactions between invasive ants and plants, but ant biology and attributes of other organisms also determine the consequences for the plant. Drawing from these examples and considering traits of the invasive ants, plants, and other organisms that interact with the plant, I offer predictions for the contexts in which plants will be at high and low risk of adverse outcomes or may benefit from interacting with an invasive ant. The potential for effects of invasive ants on plants to counteract, and the complexity and context-dependency that are hallmarks of ant-plant interactions generally, preclude drawing simple conclusions about the net impacts of invasive ants on plants. Further research on interactions between invasive ants and plants will contribute directly to conservation and agriculture, and provide insights to invasion ecology and our understanding of ant-plant interactions.

A MUTUALISM WITH A NATIVE MEMBRACID FACILITATES POLLINATOR DISPLACEMENT BY ARGENTINE ANTS

Lymphomatoid papulosis (LyP) is a rare skin disease with malignant potential. The long term outcomes of patients with this disease have not been adequately assessed.

Epidemiology of lymphomatoid papulosis

Summary.Plant and insect exudates are known to play a key role in structuring tropical ant communities, but less is known about the utilization of these resources in communities dominated by invasive ants. Invasive ants are thought to require large amounts of carbohydrates such as honeydew or nectar to maintain their high abundances. Invasive ants that consume floral nectar may compete with legitimate floral visitors through interference or exploitation competition. I compared the nectar-thieving behavior of three widespread invasive ant species: long-legged ants (Anoplolepis gracilipes), Argentine ants (Linepithema humile), and big-headed ants (Pheidole megacephala) in inflorescences of the native Hawaiian ‘ōhi’a tree, an important food source for native fauna. A. gracilipes was least likely to leave inflorescences unvisited and visited inflorescences in higher numbers than both L. humile and P. megacephala. A. gracilipes and L. humile visited more flowers in an inflorescence and were less likely to retreat from a flower with a competitor than P. megacephala. A. gracilipes was able to take 5.5 and 11.3 times the amount of nectar than L. humile and P. megacephala, respectively. Thus, A. gracilipes may be effective at both interference and exploitation competition against other nectarivores, L. humile may be effective at interference competition, and P. megacephala may be relatively weak at both types of competition against other nectarivores. Ascertaining the competitive abilities of invasive ants against legitimate floral visitors will be especially important in agricultural and other systems that are nectar or pollinator limited.

Floral visitation patterns of two invasive ant species and their effects on other hymenopteran visitors

The loss of biodiversity and associated ecosystem services are major threats posed by the spread of alien invasive species. Invasive ants are frequently associated with declines in the diversity of ground-dwelling arthropods but also may affect plants through their attraction to floral nectar and tending of hemipterans. Protea nitida is a tree native to the South African fynbos that hosts a native membracid, Beaufortiana sp., which is tended by ants. Here I compare Argentine ants (Linepithema humile) to native ants in their attraction to P. nitida inflorescences in the presence and absence of the membracid, and their effects on other floral arthropod visitors, seed set, and ovule predation. Argentine ant discovery of inflorescences increased at least 13-fold when membracids were present on the branch, whereas native ant discovery of inflorescences was only doubled by membracid presence at one site in one study year and was unaffected in the other three site-years. Excluding Argentine ants from inflorescences resulted in an increase in several arthropod taxa and potential pollinators; native ant exclusion had no positive effects. Thus the mutualism between Argentine ants and the membracid is facilitating pollinator deterrence by the ants. Though Argentine ants were not associated with a decline in P. nitida seed set or ovule predation, declines in generalist insect pollinators may have ramifications for the 83% of fynbos plants that are insect pollinated. Pitfall traps showed that Argentine ants were not more abundant than native ants in non-invaded sites. Focusing only on abundance on the ground and displacement of ground-dwelling arthropod fauna may lead to an underestimate of the effects of invasive ants on their adopted communities.

Contrasting effects of an invasive ant on a native and an invasive plant

Background. Lymphomatoid papulosis is a rare skin disease with malignant potential. Its epidemiology is largely unknown.

Climate mediates the effects of disturbance on ant assemblage structure

Abstract 1. Floral nectar of the native Hawaiian ‘ōhi’a tree, Metrosideros polymorpha, is an important food source for several native honeycreepers and yellow‐faced bees, Hylaeus spp., but is also attractive to invasive ants.