Abstract
Invasive pest species may strongly affect biotic interactions in agro-ecosystems. The ability of generalist predators to prey on new invasive pests may result in drastic changes in the population dynamics of local pest species owing to predator-mediated indirect interactions among prey. On a short time scale, the nature and strength of such indirect interactions depend largely on preferences between prey and on predator behavior patterns. Under laboratory conditions we evaluated the prey preference of the generalist predator Macrolophus pygmaeus Rambur (Heteroptera: Miridae) when it encounters simultaneously the local tomato pest Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) and the invasive alien pest Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). We tested various ratios of local vs. alien prey numbers, measuring switching by the predator from one prey to the other, and assessing what conditions (e.g. prey species abundance and prey development stage) may favor such prey switching. The total predation activity of M. pygmaeus was affected by the presence of T. absoluta in the prey complex with an opposite effect when comparing adult and juvenile predators. The predator showed similar preference toward T. absoluta eggs and B. tabaci nymphs, but T. absoluta larvae were clearly less attacked. However, prey preference strongly depended on prey relative abundance with a disproportionately high predation on the most abundant prey and disproportionately low predation on the rarest prey. Together with the findings of a recent companion study (Bompard et al. 2013, Population Ecology), the insight obtained on M. pygmaeus prey switching may be useful for Integrated Pest Management in tomato crops, notably for optimal simultaneous management of B. tabaci and T. absoluta, which very frequently co-occur on tomato.
Highlights
In ecosystems, species interact directly or indirectly resulting in both short-term effects on species abundance and density, and long-term effects on population dynamics [1,2,3,4]
Our study confirmed the predation of M. pygmaeus on the local pest B. tabaci and the invasive pest T. absoluta as previously reported by Bompard et al [4]
We showed that the presence of T. absoluta on the plant affected the predation activity of M. pygmaeus in opposite ways for predator adults and juveniles: the presence of T. absoluta induced an increase of predation by predator adults whereas it led to decreased predation by juveniles
Summary
Species interact directly or indirectly resulting in both short-term effects on species abundance and density, and long-term effects on population dynamics [1,2,3,4]. Generalist predators are likely to trigger indirect interactions among prey species owing to their capacity to attack different prey [7,8,9]. The dispersion of predation pressure among multiple available prey species may result in increased prey population densities compared to densities in single prey systems. The nature of indirect interactions depends in part on predator preference [11,12]. Some of the prey characteristics that influence predator preference are nutritional quality of the prey and the ease of attack it presents [12]. Predation on prey of highest nutritive value increases the predator's fitness (higher survival, fecundity, etc...), this prey may not be systematically preferred [12]. Capture success generally depends on prey mobility and access to a refuge (enemy-free space) [12,13]
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