Genetic Determinism vs. Phenotypic Plasticity in Protist Morphology

Abstract

Untangling the relationships between morphology and phylogeny is key to building a reliable taxonomy, but is especially challenging for protists, where the existence of cryptic or pseudocryptic species makes finding relevant discriminant traits difficult. Here we use Hyalosphenia papilio (a testate amoeba) as a model species to investigate the contribution of phylogeny and phenotypic plasticity in its morphology. We study the response of H. papilio morphology (shape and pores number) to environmental variables in (i) a manipulative experiment with controlled conditions (water level), (ii) an observational study of a within-site natural ecological gradient (water level), and (iii) an observational study across 37 European peatlands (climate). We showed that H. papilio morphology is correlated to environmental conditions (climate and water depth) as well as geography, while no relationship between morphology and phylogeny was brought to light. The relative contribution of genetic inheritance and phenotypic plasticity in shaping morphology varies depending on the taxonomic group and the trait under consideration. Thus, our data call for a reassessment of taxonomy based on morphology alone. This clearly calls for a substantial increase in taxonomic research on these globally still under-studied organisms leading to a reassessment of estimates of global microbial eukaryotic diversity.

Predator–prey mass ratio drives microbial activity under dry conditions in Sphagnum peatlands

“…This phenomenon, known as “community downsizing” (Lindo, ; Sheridan & Bickford, ), was reported as a universal response to global warming (Gardner, Peters, Kearney, Joseph, & Heinsohn, ). Indeed, warming‐induced declines in mean body size members within a given community have been reported in numerous ecosystems (Gardner et al., ; Yvon‐Durocher et al., ), including peatlands (Jassey et al., ; Lindo, ; Mulot et al., ). While community downsizing under warming is mostly determined by changes in individual growth rates, as well as competitive and predatory interactions within the food web (Ohlberger, ), it likely results from physical changes (e.g., habitat loss) under drought (Schimel et al., ).…”

Dispersal limitations and historical factors determine the biogeography of specialized terrestrial protists

“…Dating speciation events is difficult in testate amoebae as their lineages cannot be morphologically distinguished (Mulot et al, ); testate amoeba shell records in peat are rare before the Holocene. Nevertheless, it is still possible to infer a time window for the radiation of the lineages indirectly based on the very strict habitat specificity of this taxon.…”

Scaling laws explain foraminiferal pore patterns

“…However, within the limits observed for each of the three phylotypes, there is still substantial variability in porosity, which highlights a certain degree of ecophenotypic plasticity or intraspecific genetic variation. Intra-phylotype plasticity as an additional response to environmental conditions has earlier been shown in other protists 48 (i.e. the number of pores in different phylotypes of testate amoeba).…”