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Competition under (niche) construction

Periodic Reporting for period 2 - COMPCON (Competition under (niche) construction)

Reporting period: 2018-11-01 to 2020-04-30

Interspecific competition is arguably the best interaction to address the how individual trait variation and eco-evolutionary feedbacks shape species distributions and trait evolution, due to its indirect effects on the shared resource. However, a clear understanding of such feedbacks is only possible if each contributing factor can be manipulated independently. With COMPCON, we are addressing address the reciprocal interactions between individual variation, niche width, niche construction and the presence of competitors using a system amenable to anipulation of all these variables. The system is composed of two spider mite species, Tetranychus urticae and T. evansi, that up- and down-regulate plant defences (i.e. negative and positive niche construction, respectively). Mites are colonizing tomato plants with different cadmium concentrations, allowing quantitative variation of available niches. Tomato mutant plants with low defences are used as an environment in which niche construction is not expressed. Individual variation in niche width and niche construction are being measured in isogenic lines. Different combinations of lines will then be used to test how such variation in individual traits affects coexistence and evolution with competitors.
Data generated by COMPCON will strengthen the growing link between Ecology and Evolution, as it will test recent hypotheses concerning how individual variation, niche width, niche construction and competition interact to shape species distributions and trait evolution.
We are currently performing the experimental evolution protocol corresponding to tests involving niche width and competitive ability. We have measured several traits (adaptation, correlated responses, at generations 12-15 and we are analysing the data.
We have measured the individual variation for the fundamental and the realized niche in 20 isogenic lines. The data shows ample variation for these traits and also variation in the correlation across traits. We are finishing the data analysis.
We are measuring individual variation in niche construction (the ability to suppress plant defences).
The data collected in the experimental evolution may shed light on several key aspects of the evolutionary ecology of competition, namely: does evolving together facilitate coexistence? Does character displacement evolve in response to (co)evolution? Does hormesis evolve? How does adaptation to metal-based defences affect performance in other environments? We aim at performing another measure of these traits at a later generation such as to obtain robust answers to these questions.
We are performing comprehensive tests of individual niche variation in the fundamental and the realized niche and their potential correlation. This data set is unique in that (a) few studies have addressed the genetic basis of niche width and (b) none has addressed potential correlations among the fundamental and the realized niche width at the individual level. We will subsequently test how variation in individual niche width affects coexistence.
The data concerning individual variation in niche construction is as yet preliminary but it seems that we will find significant variation, which is very exciting. We will then use this data to test the effect of variation in niche construction in coexistence. We will also perform experimental evolution to test whether niche construction is maintained in an environment with cheaters or in which niche construction yields no benefit. This will be done after we finish the other experimental evolution protocol, due in September.