Faculty of Science at the University of Amsterdam
Institute for Biodiversity and Ecosystem Dynamics
Science Park 904
Amsterdam, 1098 XH
Abstracts (first author)
Discovering life-history trade-offs with suppression of tomato defence in the invasive spider mite Tetranychus evansiPDF
The herbivorous spider mite Tetranychus evansi is an invasive species specialized to feed on Solanaceous plants, including tomato. In its native range (South America) it is not considered as a pest, but in Africa and Southern Europe major crop losses have been recorded due to T. evansi outbreaks. Apart from predator release, two important factors appear to facilitate the spread of this species: (1) its ability to suppress tomato plant defense to below control levels, and (2) its very high population growth rate. Related species, such as the generalist two-spotted spider mite T. urticae, also have a high population growth rate, but cannot suppress tomato defence to the same extent as T. evansi.
Plants protect themselves in various ways against herbivores by producing toxins or attracting natural enemies. Therefore, suppressing these defences can benefit herbivores, and it has been shown that some herbivores indeed do so. However, T. evansi downregulates the defence of its host plant to levels that fall even below house-keeping levels of healthy unattacked plants. Downregulating host plant defence to below house-keeping levels is beneficial for herbivores, but – perhaps surprisingly - not observed before in nature. Given that herbivores do suppress plant defence but only to a limited extent, we hypothesize that suppression of host plant defense trades off with life history traits such as oviposition rate or making dense web to defend a suppressed-defence part of the host plant against competitors.
We are currently establishing T. evansi lines that differ in their ability to suppress tomato defense through crossing mites from different geographical locations and subsequent inbreeding, and through experimental evolution. Measurements of life-history characteristics can provide insight into genetic trade-offs for tomato defense suppression. In addition, competition experiments allow us to assess the relative fitness of different T. evansi strategies.