COMPETITIVE DISPLACEMENT AND REDUCTIONINTRODUCTIONThe purpose of this chapter is to review the literature for evidence of competitive displacements of mosquitoes and to consider whether and how this phenomenon may be applied towards mosquito control. Competitive displacement is considered biological control in the context of a broad definition of the discipline, which includes conservation, augmentation, and introduction of natural enemies of pests or vectors (Lounibos and Frank 1. Because partial reductions of pest or vector populations are desirable and competitive displacements are unlikely to be complete, the term competitive reduction is coined to apply to any diminution of mosquito populations effected by interspecific competition less than local extinction. After reviewing origins of the concept, examples of inadvertent competitive reductions of mosquito populations, and a trial for biological control, I examine potential mechanisms, which are important to understand if competition is to be manipulated in the interests of mosquito control. The final sections of this chapter will consider opportunities and obstacles facing the development of this technique. THE CONCEPTCompetitive displacement is based upon the ecological principle that different species cannot simultaneously occupy the same niche (De. Bach 1. 96. 6). Seeds of the concept date at least to Darwin (1.
Grinnell (1. 92. 8) and Gause (1. Hardin (1. 96. 0) called the principle competitive exclusion based, in part, on various studies of competing laboratory populations in which one or another species eventually went extinct. The older literature cites relatively few examples of competitive displacement observed in action in nature. Connell (1. 96. 1) demonstrated by means of exclusion experiments on rocky seashores that the intertidal distribution of 2 barnacle species was determined by interspecific competition.
- A new species ofAphytis reared fromAonidiella orientalis collected from citrus in Saudi Arabia is described and compared morphologically with four other closely.
- Some Background. Aphids, members of the order Homoptera, are probably the most notorious pests in the world. With well over 4000 species of aphids in this huge order.
Ogasawara Okinawa Japan mainland Hawaii NAmerican OLE The University of California, Riverside (UCR or UC Riverside), is a public research university and one of the 10 general campuses of the University of California system. Mating Behavior and Species Status of Host-Associated Populations of the Polyphagous Thrips, Frankliniella schultzei. THE CONCEPT. Competitive displacement is based upon the ecological principle that different species cannot simultaneously occupy the same niche (DeBach 1966).
However, the contemporary distributions of these species are the result of competition having gone to completion in evolutionary time. Documentation of competitive exclusion in nature is possible when an accidentally or purposely introduced species displaces an ecological homolog over a relatively quick time span.
However, some instances of competitive displacement may occur in time frames that exceed ordinary observation periods, rendering documentation and experimental validation of causes less tractable. Well documented cases of competitive displacement occurred after the importation of Aphytis spp. Although competitive displacement was not the intention of the Aphytis spp.
De. Bach 1. 96. 4, Turnbull 1. Competitive displacement has appeared in recent limelight in the context of biological invasions and human- induced habitat modifications, both of which may threaten biodiversity if vulnerable or endangered species are displaced (e. Mack et al. Indeed, the concept of importing non- indigenous species for biological control has come under fire because of the potential undesirable effects of predation, parasitism, and competition on non- target native fauna and flora (Simberloff and Stiling 1. Ewel et al. A recent review of competitive displacement among insects and arachnids confirmed that in the majority of instances, exotic species displaced native species or previously established invaders (Reitz and Trumble 2.
INADVERTENT COMPETITIVE REDUCTIONS OF DISEASE VECTORS BY HUMAN INTERVENTIONSA diverse literature documents the occurrence of competitive reductions of mosquito populations following human- assisted habitat changes or establishments of invasive species. Several of these reductions involved malaria vectors of the Maculipennis Complex of Anopheles in southern Italy. The salt- tolerant vector An. Interestingly, this shift in balance between the 2 anopheline species in southern Italy was impermanent, as documented by increases during the ensuing 3.
Natural pollination using bumblebees (Bombus impatiens) is an effective way of increasing profits and reducing labor costs. Bumblebees can increase crop production. Title Length Color Rating : Life Cycle of the Malaria Parasite - What is the disease: Malaria is a mosquito-borne infectious disease to humans and other animals which.
An. The recrudescence of An. Marchi, pers. Therefore, recent changes in the relative abundances of these 2 species in southernmost Italy may not be associated with competitive interactions. In an experiment conducted in the 1. Kenya and northern Tanganyika (now Tanzania), residual house spraying with dieldrin led to the virtual disappearance of the vector An. Because larvae of the 2 species frequently co- occur, these authors conjectured that interspecific larval competition had suppressed An.
The decreases in An. One concern following such shifts in species composition is whether the presumed non- vector species might assume vector status over time or upon closer inspection. Although An. 1. 99. Conspicuous shifts in the abundance of container- inhabiting Aedes mosquito species have been associated with human- assisted invasions of the broadly distributed Ae. Aedes aegypti, indigenous to Africa, is believed to have become established in tropical Asia towards the end of the 1. Smith 1. 95. 6). In cities such as Kuala Lumpur and Calcutta, the spread of the domestic form of Ae.
In Shanghai where Ae. Aedes albopictus spread from Asia into Pacific Islands during periods of social upheaval and human migration associated with World War II, leading to reductions by this invasive species of island- endemic mosquito species, such as Ae. Where insecticide treatments had previously suppressed Ae. Following its invasion of North America in the 1. Hawley et al. 1. 99.
O’Meara et al. The latter is the best documented example of a naturally occurring competitive reduction, including many experiments conducted to test hypothetical competitive mechanisms (Juliano and Lounibos 2. A FIELD TRIAL OF COMPETITIVE REDUCTION FOR MOSQUITO CONTROLLaboratory experiments at Johns Hopkins University showed that Ae. The displacement mechanism was presumed to be sterility induced by asymmetric reproductive competition (Gubler 1. Lowrie 1. 97. 3), or a combination of the two (Gubler 1. Based on the consistent outcome of interspecific competition in the laboratory, non- native strains of Ae.
The justification for this scheme was replacement of an important vector of human filariasis in Oceania by a non- vector of this parasite. Although the released Ae. Although the authors conjectured about possible causes, they were ultimately unable to explain the failure of Ae. Here, mechanisms are differentiated more broadly than a recent review, which embraced all in the context of exploitative (resource) or interference competition (Reitz and Trumble 2. These authors point out that multiple mechanisms may underlie many examples of competitive displacement. Reproductive Competition.
Asymmetric mating interference, whereby males of one species mate with a related species and produce inviable or less fit hybrid offspring, has been proposed as a method for the biological control of pests and vectors (Ribeiro 1. Ribeiro and Spielman 1. Reproductive competition through the production of inferior or inviable zygotes has also been central to some proposed and field- tested genetic techniques for mosquito control (e. Lorimer et al. Although there is some evidence to support the occurrence of this mechanism, also known as satyrization, in natural populations of ticks and tsetse flies (Ribeiro 1.
Among some non- vector arthropods, interspecific matings in hybrid zones where native and invasive species meet yield offspring with heterotic vigor (Perry et al. Spielman and Feinsod (1. Ae. Nasci et al. However, experimental evidence reported by these authors to support this claim has not been reproducible (Harper and Paulson 1. Estrada- Franco and Craig 1.
Apparent Competition. Apparent competition occurs through the differential effects of a parasite or predator on 2 co- occurring species (Holt and Lawton 1. Preliminary explanations for the recent range reductions of Ae. However, field surveys after the establishment of Ae. Juliano 1. 99. 8), and outdoor experiments in tires where the 2 species co- occur in Florida did not support a role for apparent competition mediated by A. Although this . This example shows that physical displacement may occur even before the competing life stages, such as larvae, encounter one another. Models indicate that shifts in habitat selection based on interspecific effects on oviposition strategies may prominently influence population sizes of the competing species (Spencer et al.
Larval Resource or Interference Competition. In traditional views, competition has been viewed as either exploitation, wherein individuals compete for limiting food resources, or interference, whereby individuals inhibit the growth and development of competitors by physical or chemical means (Morin 1. Both types are known to operate among larval mosquitoes (e.
Dye 1. 98. 2, 1. 98. Broadie and Bradshaw 1. Juliano 1. 99. 8) and may act concurrently in the same system. Interspecific larval competition was proposed as a likely mechanism to explain the invasion success of Ae. Although Ae. 1. 98. Ae. 1. 99. 1, O’Meara et al. However, in competition experiments using leaf litter as the basal resource, Ae.
The same competitive outcome was observed in experiments conducted in nature that manipulated resident populations of these 2 species in Brazil (Braks et al. Birungi and Munstermann 2. The current distributions of Ae. Experiments at exclusion and coexistence sites indicate that higher egg mortality of Ae. Thus, although sites of co- existence and exclusion may be similar in aquatic environments (Juliano et al.
Therefore, abiotic and biotic factors may influence the outcome of competitive reductions through effects on different life history stages. Superiority of Culex quinquefasciatus in larval competition with Cx. However, the shift in numbers in traps may also reflect the consequences of human- induced habitat changes that favor increases in the eutrophic larval environments preferred by Cx. In addition to the failed predictions of release experiments (Rosen et al. Moore and Fisher 1.
Black et al. 1. 98.