Fifteen important questions in the spatial ecology of diatoms

Abstract

Recently, studies about the spatial distribution of microbial species and communities have increased substantially. Freshwater diatoms are used as one of the most popular model taxa in such macroecological studies, but the most exciting patterns in the spatial ecology of diatoms have not been reviewed. Here, we identify 15 important questions about freshwater diatom ecology, review the major findings, and suggest novel research avenues. We found that diatoms do not support classical latitudinal diversity gradient, species–area relationship or Rapoport's rule. We found some, albeit inconsistent support for an elevational diversity gradient, Bergmann's rule and niche conservation. Diatoms do support a positive interspecific abundance–occupancy relationship like nearly all other taxa. With regards to metacommunity dynamics, diatom communities are typically structured by species sorting, but neutral dynamics or mass effects are also evident at large or small spatial scale, respectively. Taken together, this review suggests that diatoms follow some classical biogeographical patterns similarly to larger taxa, but patterns are typically weaker than for macro‐organisms. This may result because diatoms are typically relatively strongly controlled by local factors and often exhibit efficient stochastic dispersal processes both at small and large scales. More research is needed to build a more comprehensive view of diatom species–area relationships and latitudinal gradients in diversity, for example. In the future, well‐replicated macroecological field experiments, diatom studies with intercontinental or global coverage, trait‐based approaches, and DNA‐based species identification would be fruitful avenues to shed more light into the spatial ecology of diatoms.

Diatoms define a novel freshwater biogeography of the Antarctic

“…For most other groups of aquatic organisms, however, the prevailing view was that they mostly have cosmopolitan distributions resulting from their generally large population sizes and high dispersal capacities (Fontaneto 2019). Consequently, local occurrence of most aquatic taxa is thought to be largely determined by environmental selection (Soininen and Teittinen 2019), and the application of broad morphological species concepts reinforced this idea (Vyverman et al 2010). Recent taxonomic studies, however, based on multiple lines of evidence (including genetic data), have revealed the existence of widespread (semi‐)cryptic diversity, restricted geographical distributions and regional endemism in many groups (April et al 2011, Kotov and Taylor 2019).…”

Identifying environmental drivers of benthic diatom diversity: the case of Mediterranean mountain ponds

“…Within this framework, Soininen & Teittinen (2019) have recently summarized the main open questions concerning the spatial ecology of diatoms. This paper answers specifically their question 1 dealing with the key factors explaining diversity patterns in diatoms.…”

The impacts of nutrient supply and imbalance on subcontinental co‐occurrence networks and metacommunity composition of stream algae

“…Conversely, at the subcontinental scale of our metacommunities, geographic barriers among the discrete hydrologic systems that comprised their habitats, may have contributed to dispersal limitation subsuming some of the climatic effect. Although environmental factors predict better the variance in diatom metacommunities compared to space (Soininen and Teittinen 2019), these factors are generally associated with nutrient level (Soininen 2007), which in our case was accounted for by nutrient context. Thus, nutrient contexts apparently determined the contribution of dispersal processes to community variation or influenced spatially‐structured climatic drivers.…”