Competitive Exclusion of Aphytis lingnanensis by A. melinus: Potential Role of Host Size

Luck, Robert F.; Podoler, H.

doi:10.2307/1940553

Cited by 113 publications

(101 citation statements)

References 20 publications

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“…The displacement of the native asexual gecko Lepidodactylus lugubris by the introduced sexual species Hemidactylus frenatus in the tropical Pacific (Case et al 1994;Petren and Case 1996) and that of Aphytis lingnanensis, a parasitoid of the red scale (Aonidiella aurantii), by its congener Aphytis melinus in southern California (Luck and Podoler 1985;Murdoch et al 1996) provide some of the more well studied examples. These observations suggest that, in some cases at least, spatial processes cannot counteract competitive exclusion because of insufficient spatial variance in competitive ability.…”

Section: Discussionmentioning

confidence: 99%

“…Typically, one would expect such large-scale exclusion to occur when competitive ability is determined by traits that are fixed within and across populations. For example, A. melinus gains a competitive advantage over A. lingnanensis because of a life-history difference; A. melinus is able to obtain female offspring from a smaller-sized scale than A. lingnanensis (Luck and Podoler 1985). Using a stage-structured host-parasitoid model, Murdoch et al (1996) showed that this subtle difference is sufficient to explain the rapid displacement of A. lingnanensis from inland areas of southern California.…”

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confidence: 99%

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Spatial Heterogeneity, Source‐Sink Dynamics, and the Local Coexistence of Competing Species

Amarasekare¹,

Nisbet²

2001

The American Naturalist

316

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Patch occupancy theory predicts that a trade-off between competition and dispersal should lead to regional coexistence of competing species. Empirical investigations, however, find local coexistence of superior and inferior competitors, an outcome that cannot be explained within the patch occupancy framework because of the decoupling of local and spatial dynamics. We develop two-patch metapopulation models that explicitly consider the interaction between competition and dispersal. We show that a dispersal-competition trade-off can lead to local coexistence provided the inferior competitor is superior at colonizing empty patches as well as immigrating among occupied patches. Immigration from patches that the superior competitor cannot colonize rescues the inferior competitor from extinction in patches that both species colonize. Too much immigration, however, can be detrimental to coexistence. When competitive asymmetry between species is high, local coexistence is possible only if the dispersal rate of the inferior competitor occurs below a critical threshold. If competing species have comparable colonization abilities and the environment is otherwise spatially homogeneous, a superior ability to immigrate among occupied patches cannot prevent exclusion of the inferior competitor. If, however, biotic or abiotic factors create spatial heterogeneity in competitive rankings across the landscape, local coexistence can occur even in the absence of a dispersal-competition trade-off. In fact, coexistence requires that the dispersal rate of the overall inferior competitor not exceed a critical threshold. Explicit consideration of how dispersal modifies local competitive interactions shifts the focus from the patch occupancy approach with its emphasis on extinctioncolonization dynamics to the realm of source-sink dynamics. The key to coexistence in this framework is spatial variance in fitness. Unlike in the patch occupancy framework, high rates of dispersal * Present address: Department of Ecology and Evolution, University of Chicago, Chicago, Illinois 60637-1573; e-mail: amarasek@uchicago.edu. † E-mail: nisbet@lifesci.ucsb.edu.Am. Nat. 2001. Vol. 158, pp. 572- can undermine coexistence, and hence diversity, by reducing spatial variance in fitness.Keywords: competition, coexistence, spatial heterogeneity, source-sink dynamics, immigration, dispersal-competition trade-off.The issue of how species coexist in patchy environments is central to both basic and applied ecology. When competition for resources is asymmetric, a life-history tradeoff between competitive and dispersal abilities can lead to coexistence in a patchy environment (Skellem 1951). This idea has been formalized in the patch occupancy metapopulation framework (Levins 1969(Levins , 1970. The patch occupancy approach assumes that local competitive interactions occur on a much faster time scale relative to extinction-colonization dynamics (Cohen 1970;Levins and Culver 1971;Slatkin 1974;Hastings 1980;Nee and May 1992;Tilman et al. 1994). For instance,...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Spatial Heterogeneity, Source‐Sink Dynamics, and the Local Coexistence of Competing Species

Amarasekare¹,

Nisbet²

2001

The American Naturalist

316

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“…Butternut) (Raciti et al, 2003). In order to keep background parasitism by naturally occurring A. melinus low, the trial was carried out in a period (June-July) when the parasitoid is scarce in the field (Lizzio et al, 1998;Siscaro et al, 1999) and California red scale is mainly present as virgin females, which is the preferred instar of the parasitoid (Luck & Podoler, 1985;Heimpel et al, 1997;Pekas et al, 2010a).…”

Section: Insect Releasesmentioning

confidence: 99%

“…Heavily infested fruit may be downgraded in the packinghouse and, if population levels are high, trees can be seriously damaged. Aphytis melinus effectiveness could depend on the scale careful monitoring, on the use of selective insecticides to control other pests (Grafton-Cardwell et al, 2006;Suma et al, 2009;Planes et al, 2012;Vanaclocha et al, 2012), on the host instars available and their size (Luck & Podoler, 1985;Pekas et al, 2010a), on ant activity (James et al, 1997;Pekas et al, 2010b), on the fitness of the released insects (Vasquez & Morse, 2012) or on environmental conditions (DeBach & Sisojevic, 1960).…”

Section: Introductionmentioning

confidence: 99%

Dispersal of Aphytis melinus (Hymenoptera: Aphelinidae) after augmentative releases in citrus orchards

Zappalà¹,

Campolo²,

Grande³

et al. 2012

Eur. J. Entomol.

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Abstract. The efficacy of natural enemies in controlling pests under field conditions is largely correlated with their capacity to spread within infested crops. In this study the spatial dispersal of the California red scale parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) was evaluated in the field after augmentative releases. The experiment was conducted in 2007 in six 1-ha plots in a Sicilian citrus orchard under integrated pest management. A total of 180,000 A. melinus adults was released in each of three plots and the other plots were left as untreated control. The flight range of the parasitoid was evaluated, for 35 days after the release, on 16 trees per each plot, located at 20 and 40 m from the central release point using yellow sticky traps activated with Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae) sexual pheromone and by monitoring the percentage parasitism of the scale on fruits and twigs. The effects of the distance from the release point and density of susceptible stages of host on parasitoid dispersal were evaluated. The number of wasps captured during the whole trial was greater in the traps located 20 m from the release point than in those at 40 m and in the control plots. Aphytis melinus dispersed over distances less than 40 m based on both the lower percentage parasitism and numbers captured recorded at distances of 40 m. The results are discussed in the context of the biological control of California red scale in citrus orchards by means of wasp releases. In particular, the release points should be no more than 40 m apart for a quick and homogeneous colonization of the area treated.

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“…About 20% of the male scales are allocated a female Aphytis. About 70% of the third instar female scales are allocated a female Aphytis offspring, about 25% are allocated a male Aphytis offspring and about 5% are allocated two Aphytis offspring (usually a male and a female) (Luck et al, 1982;Luck and Podoler, 1985). The two eggs are laid during the same host visit and represent a case of gregariousness (Luck et al, 1982).…”

Section: Aphytis Life Historymentioning

confidence: 99%

Event-driven competing risks

Ewing

Yandell

Barbieri

et al. 2002

Ecological Modelling

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The California red scale Aonidiella aurantii (Maskell) (Homoptera: Diaspididae) is a major pest of California citrus, with infestations causing growers significant financial losses. It has recently developed resistance to traditional insecticide sprays. An alternative suppression tactic is the release of a biological control agent, Aphytis melinus DeBach (Aphelinidae: Hymenoptera) that feeds on red scale. Although many aspects of the red scale Á/Aphytis interaction are now understood, it is difficult to differentiate the effects of temperature and population fluctuations in the field. To investigate such complex interactions, we propose a new stochastic modeling technique, based on event-driven competing risks, that incorporates details of life histories as well as the host Á/parasitoid interaction. Our continuoustime, individual-oriented modeling approach quantifies relationships among individuals and describes the resulting coupling between the interacting populations. The event-structured simulation drives time in contrast to the usual timedriven stochastic dynamic programming. Our system, developed in the public domain using the R statistical package, allows for different biological clocks, since both red scale and Aphytis development respond to temperature (degreedays) while searching female Aphytis follow a diurnal time schedule, contingent upon temperature-dependent egg maturation. #

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Competitive Exclusion of Aphytis lingnanensis by A. melinus: Potential Role of Host Size

Cited by 113 publications

References 20 publications

Spatial Heterogeneity, Source‐Sink Dynamics, and the Local Coexistence of Competing Species

Spatial Heterogeneity, Source‐Sink Dynamics, and the Local Coexistence of Competing Species

Dispersal of Aphytis melinus (Hymenoptera: Aphelinidae) after augmentative releases in citrus orchards

Event-driven competing risks

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