El perfil del comprador extranjero en la Comunidad Valenciana

Nematode ecosystem functioning is often inferred from their assumed feeding groups based on their morphological characteristics, especially their mouth structure (Wieser, 1953; Yeates et al., 1993), and sometimes from a combination of morphology and life-history based traits (Schratzberger et al., 2007). For every trait considered, however, a limited number of trait groups are defined and hence, many

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nematode species are lumped together in each trait group. Increasingly, studies are showing that these trait groups do not adequately represent the functional diversity of nematodes (e.g. Vafeiadou et al., 2014; Monteiro et al., 2018; chapter 3 of the present study).

Because of the biomass requirements for most biomarker studies, and because of the above- mentioned taxonomic challenges, it is tempting to lump species together in ‘community samples’ or at best according to feeding types when performing stable isotope or fatty acid studies. The results of chapter 3 underline that this is essentially useless, because diversity in trophic strategies within and between feeding groups is similarly large. Hence, we make a strong plea for studies which focus at the level of individual species. Although lumping species within a genus or family may sometimes be necessary, one should not forget that functional roles of nematodes may differ even among congeneric species (De Mesel et al., 2004; Vafeiadou et al., 2014; De Meester et al., 2016).

In addition, an often neglected feature in ecology is inter-individual variation and its importance for the dynamics of populations and communities (a.o. Bolnick et al., 2007; Ashton et al., 2010; Violle et al., 2012). Indeed, when we assign species to a particular trait group, we implicitly assign the same mean trait value to all individuals belonging to that species. This may lead to a severe underestimation of a species’ ability to tolerate, and/or adapt to, stressful environmental conditions. It may also lead to an underestimation of the niche breadth of a species, and therefore of the degree of niche overlap and hence competition between species (Ashton et al., 2010; Violle et al., 2012). Hence, if we want to fully understand how species interactions may contribute to coexistence in multispecies communities, we may have to consider interindividual variation within species as well. Complex though this may seem, technology is rapidly developing the means to achieve this. Whereas until recently, it was impossible to obtain reliable diet information on individual nematodes, microbiome and eukaryotic biome analyses can now be performed on single specimens (see above), and techniques like NanoSIMS (Nanoscale secondary ion (emission) mass spectrometry) (Herrmann et al., 2007), although complex and tedious, equally allow detailed SI analyses on single individuals and even substructures/tissues/cells of organisms. Although the degree of expertise required for, and the costs associated with these analyses still hamper a more routine use, they will undoubtedly become cheaper in the future, and be complemented by yet newer technological advancements. The challenge will be to ‘advertise’ meiofauna/nematodes as sufficiently interesting model organisms to attract sufficient funding so that we can readily incorporate these novel technological evolutions into our research.

Acknowledgements

Acknowledgements go to Sandra Vanhove (Vanhove unpubl.), Tania Nara Bezerra (Bezerra, unpubl.) and Nele De Meeste (De Meeste et al., unpubl.) for using their unpublished data.

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