Cryptic diversity and ecosystem functioning: a complex tale of differential effects on decomposition
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Marine ecosystems are experiencing accelerating population and species loss. Some ecosystem functions are decreasing and there is growing interest in the link between biodiversity and ecosystem functioning. The role of cryptic (morphologically identical but genetically distinct) species in this biodiversity–ecosystem functioning link is unclear and has not yet been formally tested. We tested if there is a differential effect of four cryptic species of the bacterivorous nematode Litoditis marina on the decomposition process of macroalgae. Bacterivorous nematodes can stimulate or slow down bacterial activity and modify the bacterial assemblage composition. Moreover, we tested if interspecific interactions among the four cryptic species influence the decomposition process. A laboratory experiment with both mono- and multispecific nematode cultures was conducted, and loss of organic matter and the activity of two key extracellular enzymes for the degradation of phytodetritus were assessed. L. marina mainly influenced qualitative aspects of the decomposition process rather than its overall rate: an effect of the nematodes on the enzymatic activities became manifest, although no clear nematode effect on bulk organic matter weight loss was found. We also demonstrated that species-specific effects on the decomposition process existed. Combining the four cryptic species resulted in high competition, with one dominant species, but without complete exclusion of other species. These interspecific interactions translated into different effects on the decomposition process. The species-specific differences indicated that each cryptic species may play an important and distinct role in ecosystem functioning. Functional differences may result in coexistence among very similar species.
KeywordsBiodiversity–ecosystem functioning link Competition Functional differences Litoditis marina Marine nematodes
Funding for this research was obtained from the Flemish Fund for Scientific Research (FWO) through project G038715 N, and from Ghent University through projects 011060002 and 01GA1911 W. Annick Van Kenhove is acknowledged for help with the set-up and sampling of the experiments. The authors would also like to thank Charlotte Heynssens, Bhabananda Biswas and Tara Grosemans for help with the qPCR analysis.
All data of the experiment will be available after publication in the Integrated Marine Information System (IMIS) database (VLIZ): http://www.vliz.be/en/imis?module=dataset&dasid=5109.
Author contribution statement
NDM, RG, TM and SDR conceived and designed the experiments. NDM, AR, RG, TM and SDR performed the experiments, NDM analyzed the data. NDM wrote the manuscript; other authors provided editorial advice.
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