Ciliates and the Rare Biosphere—Community Ecology and Population Dynamics

Weisse, Thomas

doi:10.1111/jeu.12123

Cited by 42 publications

(32 citation statements)

References 162 publications

(276 reference statements)

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“…In the protistan 'rare biosphere', rare species may be of importance because they can become abundant if conditions change favoring different species with certain characteristics (Caron and Countway, 2009). Admittedly, rare species can also be of minor ecological importance, as in members of the 'accidental rare biosphere' (Weisse, 2014). Regardless of the nature of the rare tintinnid species we found, their numbers decreased markedly with latitude ( Figure 5).…”

Section: Resultsmentioning

confidence: 76%

“…For example, a smaller range of consumer species could have a lower capacity to exploit changes in the size or qualities of available prey items. Alternatively, lower species richness may represent only fewer forms present in very low concentrations, outside their usual habitat, members of the 'accidental biosphere' (Weisse, 2014). These species likely have low actual or potential ecological impact.…”

Section: Introductionmentioning

confidence: 99%

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Declines in both redundant and trace species characterize the latitudinal diversity gradient in tintinnid ciliates

et al. 2016

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The latitudinal diversity gradient is a well-known biogeographic pattern. However, rarely considered is how a cline in species richness may be reflected in the characteristics of species assemblages. Fewer species may equal fewer distinct ecological types, or declines in redundancy (species functionally similar to one another) or fewer trace species, those occurring in very low concentrations. We focused on tintinnid ciliates of the microzooplankton in which the ciliate cell is housed inside a species-specific lorica or shell. The size of lorica oral aperture, the lorica oral diameter (LOD), is correlated with a preferred prey size and maximum growth rate. Consequently, species of a distinct LOD are distinct in key ecologic characteristics, whereas those of a similar LOD are functionally similar or redundant species. We sampled from East Sea/Sea of Japan to the High Arctic Sea. We determined abundance distributions of biological species and also ecological types by grouping species in LOD size-classes, sets of ecologically similar species. In lower latitudes there are more trace species, more size-classes and the dominant species are accompanied by many apparently ecologically similar species, presumably able to replace the dominant species, at least with regard to the size of prey exploited. Such redundancy appears to decline markedly with latitude in assemblages of tintinnid ciliates. Furthermore, the relatively small species pools of the northern high latitude assemblages suggest a low capacity to adapt to changing conditions.

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Section: Resultsmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Declines in both redundant and trace species characterize the latitudinal diversity gradient in tintinnid ciliates

et al. 2016

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“…Recently, the existence of networks has been demonstrated for the ubiquitous marine SAR11 bacteria cluster; Steele et al (2011) detected multiple instances where bacteria and eukaryotes (including ciliates) were connected. Weisse (2014) postulated that rare ciliates may directly or indirectly require other organisms to survive. For instance, rare species may take refuge from parasites in the presence of an abundant, closely related species.…”

Section: Ciliates In Planktonic Food Websmentioning

confidence: 99%

“…There is no strict separation between the classical grazer food chain and the microbial food web, and ciliates and some other protists are at the interface of the two aspects of the pelagic food web; 'HNF' = heterotrophic nanoflagellates (modified from Weisse 2003Weisse , 2006 conspecific corresponds to, on average, 200x its body length (in linear dimensions). Most ciliate species in the oligotrophic open ocean or in remote alpine lakes are even smaller and their abundances are <1 mL −1 (Sonntag et al 2011a;Weisse 2014), further increasing the theoretical distance to the next neighbour. For example, in one millilitre (mL) in a productive system, we find 550 ciliates, 7 rotifers, and 90 × 10 6 bacteria (Ong'ondo et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Ciliates in Planktonic Food Webs: Communication and Adaptive Response

Weisse

Sonntag

2016

Biocommunication of Ciliates

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Ciliates are key elements of aquatic food webs, acting as predators of bacteria, algae, other protists and even some metazoans. Planktonic ciliates are important food for zooplankton, and mixotrophic and functionally autotrophic species may significantly contribute to primary production in lakes and in the ocean. Ciliates are linked to other plankton organisms and to abiotic parameters by various direct (e.g., predation and parasitism) and indirect (e.g., nutrient release via excretion, competition for food) interactions. Communication is involved in many of those interactions, but direct evidence from the field is scarce. This is mainly because aquatic ciliates live in a dilute environment and most species occur in low cell numbers. Key processes of chemical and hydromechanical communication among ciliates, between ciliates and their predators and prey, and between ciliates and their endosymbionts have been studied in some detail in vitro. Results from microcosm experiments suggest that ciliates also cooperate with each other and use information mediated by different other organisms. Extrapolating those results obtained in small-scale laboratory experiments to the ocean level is a major challenge for future research. To this end, more communication and cooperation is needed between cell biologists, ecologists, and evolutionary biologists. In contrast to communication, adaptations of natural ciliate populations to their abiotic and biotic environment have been well documented in selected freshwater and marine species. The effect of individual environmental variables and, less often, the interactive effect of several variables on growth and survival rates of ciliates have been studied with a number of ciliate species in the laboratory and inferred from their seasonal occurrence in the field. However, more information is needed on the autecology of free-living ciliate species and their role in the planktonic community. In particular, the significance of indirect ('lateral') effects in the food web received little attention and awaits future research.

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“…Interestingly, facultative sex might actually be much more common than usually appreciated, especially if we do not only consider the textbook cases, such as cyclical parthenogenesis. For example, most protists divide by asexual means but are believed to engage in sex occasionally [22][23][24]. Likewise, most plants are capable of clonal (vegetative) reproduction in addition to sexually produced seeds [25].…”

Section: (B) Costs and Benefits Of Facultative Sexmentioning

confidence: 99%

Diapause and maintenance of facultative sexual reproductive strategies

Stelzer

Lehtonen

2016

Phil. Trans. R. Soc. B

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One contribution of 15 to a theme issue 'Weird sex: the underappreciated diversity of sexual reproduction'. Facultative sex combines sexual and asexual reproduction in the same individual (or clone) and allows for a large diversity of life-history patterns regarding the timing, frequency and intensity of sexual episodes. In addition, other life-history traits such as a diapause stage may become linked to sex. Here, we develop a matrix modelling framework for addressing the cost of sex in facultative sexuals, in constant, periodic and stochastically fluctuating environments. The model is parametrized using life-history data from Brachionus calyciflorus, a facultative sexual rotifer in which sex and diapause are linked. Sexual propensity was an important driver of costs in constant environments, in which high costs (always . onefold, and sometimes . twofold) indicated that asexuals should outcompete facultative sexuals. By contrast, stochastic environments with high temporal autocorrelation favoured facultative sex over obligate asex, in particular, if the penalty to fecundity in 'bad' environments was large. In such environments, obligate asexuals were constrained by their life cycle length (i.e. time from birth to last reproductive adult age class), which determined an upper limit to the number of consecutive bad periods they could tolerate. Nevertheless, when facultative asexuals with different sexual propensities competed simultaneously against each other and asex, the lowest sex propensity was the most successful in stochastic environments with positive autocorrelation. Our results suggest that a highly specific mechanism (i.e. diapause linked to sex) can alone stabilize facultative sex in these animals, and protect it from invasion of both asexual and pure sexual strategies.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'.

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Ciliates and the Rare Biosphere—Community Ecology and Population Dynamics

Cited by 42 publications

References 162 publications

Declines in both redundant and trace species characterize the latitudinal diversity gradient in tintinnid ciliates

Declines in both redundant and trace species characterize the latitudinal diversity gradient in tintinnid ciliates

Ciliates in Planktonic Food Webs: Communication and Adaptive Response

Diapause and maintenance of facultative sexual reproductive strategies

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