Interactions among bacterial-feeding nematode species at different levels of food availability
Accurate prediction of the biodiversity–ecosystem functioning relationship requires adequate understanding of the interactions among species in a community. Effects of species diversity on ecosystem functioning are usually considered more pronounced with increasing functional dissimilarity, although species within functional groups may also perform non-identical functions and interact with each other. Here we present results of a laboratory experimental study aimed at elucidating whether interspecific interactions among species within a single nematode trophic group, bacterivores, (1) affect population development and community structure, and (2) depend on food availability. We studied the population growth of Rhabditis (Pellioditis) marina, a rhabditid nematode known to favour very high food densities when in monoculture, and of Diplolaimelloides meyli and D. oschei, congeneric Monhysteridae known to perform better in monocultures at intermediate food availability. Both Diplolaimelloides species showed significantly different patterns of food-density dependence in combination culture compared to monoculture. At very high food availability, the rhabditid nematode facilitated growth of both monhysterid species, probably as a result of down-regulation of bacterial density. At the lowest food availabilities, the presence of even low numbers of monhysterid nematodes lead to exclusion of the rhabditid, which at such low food availability has a very inefficient food uptake. At intermediate food availabilities, abundances of both Diplolaimelloides species were strongly depressed in the combination culture, as a result of food depletion by the rhabditid, indirect inhibitory interactions between the two congeneric species, or both. The complexity of the species interactions render predictions on the outcome and functional consequences of changes in within-trophic-group diversity highly problematic.
KeywordsFood Availability Nematode Species Interspecific Interaction Population Development Food Density
This work was financially supported by a CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) grant to the first author, and by Ghent University through BOF projects 0110600002 and 01GZ0705. S.D. and T.M. are postdoctoral fellows with the Flemish Science Foundation.
- Aller RC, Aller JY (1992) Meiofauna and solute transport in marine muds. Limnol Oceanogr 37:1018–1033Google Scholar
- Derycke S, Van Vynckt R, Vanoverbeke J, Vincx M, Moens T (2007) Colonization patterns of Nematoda on decomposing algae in the estuarine environment: community assembly and genetic structure of the dominant species Pellioditis marina. Limnol Oceanogr 52:992–1001Google Scholar
- dos Santos GAP, Derycke S, Fonsêca-Genevois VG, Coelho LCBB, Correia MTS, Moens T (2008) Differential effects of food availability on population growth and fitness of three species of estuarine, bacterial-feeding nematodes. J Exp Mar Biol Ecol 355:27–40. doi: 10.1016/j.jembe.2007.11.015 CrossRefGoogle Scholar
- Heip C, Vincx M, Vranken G (1985) The ecology of marine nematodes. Oceanogr Mar Biol Annu Rev 23:399–489Google Scholar
- Ilieva-Makulec K (2001) A comparative study of the life strategies of two bacterial-feeding nematodes under laboratory conditions. III. Influence of the initial nematode density on the interactions of Acrobeloides nanus (De Man 1880) Anderson and Dolichorhabditis dolichura (Schneider 1866) Andrassy 1983 in mixed cultures. Pol J Ecol 49:137–144Google Scholar
- Moens T, Yeates GW, De Ley P (2004) Use of carbon and energy sources by nematodes. Nematol Monogr Perspect 2:529–545Google Scholar
- Postma-Blaauw MB, de Vries FT, de Goede RGM, Bloem J, Faber JH, Brussaard L (2005) Within-trophic group interactions of bacterivorous nematode species and their effects on the bacterial community and nitrogen mineralization. Oecologia 142:428–439. doi: 10.1007/s00442-004-1741-x PubMedCrossRefGoogle Scholar
- Sokal RR, Rohlf FJ (2001) Biometry, 3rd edn. WH Freeman, New YorkGoogle Scholar
- Vranken G, Heip C (1983) Calculation of the intrinsic rate of natural increase, rm, with Rhabditis marina Bastian 1865 (Nematoda). Nematologica 29:468–477Google Scholar
- Warwick RM (1987) Meiofauna: their role in marine detrital systems. In: Moriarty DJW, Pullin RSV (eds) Detritus and microbial ecology in aquaculture. ICLARM conference proceedings 14. International Center for Living Aquatic Resources Management, Manila, pp 282–295Google Scholar
- Wieser W (1953) Die Beziehung zwishen Mundhöhlengestalt, Ernährungsweise und Vorkommen bei freilebenden marinen Nematoden. Ark Zool 4:439–484Google Scholar