Using the guild ratio to characterize pelagic rotifer communities

Abstract

Ecological research is moving from a species-based to a functional-based approach to better understand the underlying principles that govern community dynamics. Studies of functional-based ecology, however, have been limited for zooplankton and particularly for rotifers. While rotifers show a variety of trophi types and coronal shapes, suggesting the importance of niche differentiation in their feeding strategy, relatively little is known of how this relates to rotifer dynamics. We used the guild ratio (GR 0 , a ratio of raptorial to microphagous species), an index based on a functional trait (i.e. feeding strategy), as a novel approach to rotifer dynamics. We extracted the seasonal GR 0 by using seasonal trend decomposition and investigated similarities between study sites (Lake Washington, USA and Lake Caldonazzo, Italy) and its relation to cladocerans by cross-correlation analysis. Our study indicated that (i) raptorial and microphagous rotifers showed alternating dominance, and that raptorial rotifers and cladocerans had a synchronous pattern, (ii) the seasonal pattern of the GR 0 was consistent across different sampling frequencies, and (iii) the GR 0 was similar in both lakes. We interpreted these patterns as the general strength of the GR 0 : discernment of species-environment relationships and robustness across sampling regimes. The limitations of the GR 0 (i.e. species identity is neglected, simplification of food preferences) can also be seen as its strong point: synthesis of multi-species patterns. In addition, the independence of GR 0 from species-level identification and its potential to make use of datasets with infrequent sampling intervals and low taxon resolution could further support its innovative aspect.

Response of rotifer functional groups to changing trophic state and crustacean community

“…This interpretation is also corroborated by Obertegger et al (2010) that show that raptorials or microphagous species dominate when cladocerans increase or decrease, respectively. It seems that this is a general principle because it applies to three different lakes (this study and Lake Washington and Lake Caldonazzo in Obertegger et al 2011).…”

“…Recently, Obertegger et al (2011) proposed a modification of the original Guild Ratio (GR; Smith et al 2009), where planktonic rotifers are grouped into microphagous and raptorial species, based on food acquisition and processing, in order to assess the dominance of these two functional groups. The GR is calculated in the following way: GR = (biomass raptorialbiomass microphagous)/(total rotifer biomass), and values range from -1 to +1; values >0 indicate microphagous dominance while values <0 indicate raptorial dominance.…”

“…The GR is calculated in the following way: GR = (biomass raptorialbiomass microphagous)/(total rotifer biomass), and values range from -1 to +1; values >0 indicate microphagous dominance while values <0 indicate raptorial dominance. The GR permits integrating taxon-based classic approaches with an insight of their relation with the environment and ecosystem processes (Obertegger et al 2011).…”

Population growth potential of rotifers from a high altitude eutrophic waterbody, Madín reservoir (State of Mexico, Mexico): The importance of seasonal sampling

“…Gut contents revealed freshly collected fragments of Aphanothece but could not be confirmed. However, based on the functional role, all species of Gnesiotrocha including Horaella, Filinia and Conochilus, possess malleoramate trophi, well adapted to feed on bacteria or detritus or other smaller food particles (Obertegger et al, 2011). Since Aphanothece belongs to picocyanobacteria, their cell size is within the preferred range of Gnesiotrocha.…”

Physicochemistry and zooplankton of two karstic sinkholes in the Yucatan Peninsula, Mexico

“…by changes in feeding strategy as a function of temporality (Obertegger et al, 2011) was not so clear for the surveyed systems, because practically the whole zooplankton community was herbivorous. Except for the raptorial T. weberi (Smith, 2001), the omnivorous L. australis (Chaparro-Herrera et al, 2012), or the opportunistic species mentioned before, the zooplankton community in EP and MC consisted of microbivorous rotifers of the genus Anuraeopsis, Brachionus, Plationus, Dipleuchlanis, Lepadella, or Hexarthra (Smith, 2001) or herbivorous crustaceans including B. hagmanni and M. nesus (de Bernardi and Giussani, 1990;Cervantes-Martínez et al, 2005).…”