Unraveling the life history of successful invaders

Sol D., Maspons J., Vall-llosera M., Bartomeus I., García-Peña G.E., Piñol J., Freckleton R.P. (2012) Unraveling the life history of successful invaders. Science. 337: 580-583.
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Doi: 10.1126/science.1221523

Resum:

Despite considerable current interest in biological invasions, the common life-history characteristics of successful invaders remain elusive. The widely held hypothesis that successful invaders have high reproductive rates has received little empirical support; however, alternative possibilities are seldom considered. Combining a global comparative analysis of avian introductions (>2700 events) with demographic models and phylogenetic comparative methods, we show that although rapid population growth may be advantageous during invasions under certain circumstances, more generally successful invaders are characterized by life-history strategies in which they give priority to future rather than current reproduction. High future breeding expectations reduce the costs of reproductive failure under uncertain conditions and increase opportunities to explore the environment and respond to novel ecological pressures.

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Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

Piñol J., Espadaler X., Cañellas N., MartíNez-Vilalta J., Barrientos J.A., Sol D. (2010) Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove. Ecological Entomology. 35: 367-376.
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Doi: 10.1111/j.1365-2311.2010.01190.x

Resum:

Predation-exclusion experiments have highlighted that top-down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. We conducted 1-year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant-excluded than in control trees, whereas only dermapterans were more abundant in bird-excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator-prey system. © 2010 The Authors. Journal compilation © 2010 The Royal Entomological Society.

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