Interference or exploitation competition? Experimental studies on the interspecific interactions of cryptic species and the importance of priority effects.

Master Thesis subject (30 ECTS)
Interference - one species interferes with the ability of another species to obtain resources - and exploitation competition – the superior species depletes the resource faster or better, not leaving enough resources available for inferior species - are the two main types of competitive interactions between closely related species. These types of competition mostly increase with relatedness between species, according to classical competition theory (Darwin, 1859). As a consequence, competition is predicted to be high in cryptic species –closely related species that are morphologically indistinguishable, but show consistent genetic differences. Cryptic diversity is prominently present in coastal nematodes and the best studied model ‘species’ in this context is Litoditis marina, which is mostly found associated with decomposing macroalgae. Both competition and facilitation between these cryptic species have been reported in closed, homogeneous microcosms. Changing the composition of the cryptic species changes the interactions between them and abiotic factors - temperature and salinity- also have an influence on the interactions between the species. The nature of this competition, however, is not clear yet. Moreover, species that start a new population early in a certain patch may have a greater chance of being dominant than later arriving species (priority effects) and this may help to explain why the species are able to co-occur in different species compositions in the field . In this master thesis, we will test whether interference competition and priority effects exist within the cryptic species complex of Litoditis marina. Marine nematodes produce mucus trails, which may interfere with the growth of other species. In lab experiments we can test if the presence of such mucus trails, without the presence of the nematodes, influences the population growth of other species. In other lab experiments, we can test if competitively inferior species may be able to remain dominant in a certain patch if they have a bigger starting population and/or an earlier arrival compared with a competitively superior species. This thesis will consist mainly of laboratory work (setting-up experiments, molecular techniques, …).
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contact person last name: 
De Meester
Other people involved: 
Tom Moens
Reference Number: RP-48381