Environmental filtering drives assembly of diatom communities over evolutionary time‐scales

Abstract

Aim: Ecological communities are structured through the interplay of deterministic assembly processes such as competition and environmental filtering. Whereas the drivers of spatial community structure are frequently studied in extant communities, little is known about the relative importance of assembly processes in response to environmental factors over evolutionary time-scales. Here, we use an integrative framework to unravel community assembly processes since the inception of a longlived lake ecosystem.Location: Lake Ohrid. Time period:From lake formation 1.36 million years ago to the present.Major taxa studied: Planktonic diatoms. Methods:We constructed a dated phylogeny of extant and extinct diatoms and collected trait data for 380 fossil communities to quantify phylogenetic community structure and functional richness and to determine the relative importance of deterministic assembly processes over time. We then used regression analysis to correlate the phylogenetic community structure with palaeoenvironmental and intrinsic biological predictors and to identify primary drivers of assembly processes. Results:Our results suggest a dense packing of niche space with higher species richness and co-occurrence of closely related species. There are only two short episodes in the very recent past dominated by distantly related taxa. We found distinct changes in phylogenetic community structure upon speciation or extinction events and an increase in mean community relatedness over time.Main conclusions: Our finding of closely related co-occurring species implies environmental filtering as the primary assembly mechanism, with a minor but increasingly important role of competition towards the present, driven by evolutionary dynamics. Such an increase in the relative contribution of competition to the assembly of communities in relation to the aging of an insular ecosystem, together with a denser | 955 JOVANOVSKA et Al.

The geodynamic and limnological evolution of Balkan Lake Ohrid, possibly the oldest extant lake in Europe

“…2020; Jovanovska et al . 2022). For this paper, another 125 sediment samples were selected at intervals between 0.64 and 1.6 m in the sediment succession from below 447 m c.d.…”

“…2021; Jovanovska et al . 2022). Based on hydro‐acoustic data, the SCOPSCO project also provided new information on the geological history of the lake and particularly the tectonic activity (Fig.…”

“…2021; Jovanovska et al . 2022). Pollen provided regional information on vegetation and ecology changes in the catchment (e.g.…”

Distribution, diversity and diversification from DNA barcoding perspective: The case of Gammarus radiation in the ancient Lake Ohrid

“…MacDonald 3rd et al., 2005; Ronco et al., 2021), surprisingly little is known about the ancient lakes of Europe. Lake Ohrid is the only unquestionable European ancient lake, with a well‐documented geological history covering the last 1.3 My (Jovanovska et al., 2022; Wagner et al., 2017; Wilke et al., 2020). This oligotrophic and karstic lake is situated in a steep‐sided graben with a rift formation origin, in the South Adriatic–Ionian biogeographic region (Banarescu, 1991) on the Balkan Peninsula, at the border between North Macedonia and Albania.…”

Distribution, diversity and diversification from a DNA barcoding perspective: the case ofGammarusradiation in Europe’s oldest inland waterbody - the ancient Lake Ohrid

“…The history of Lake Ohrid is well-studied, thanks to the SCOPSCO drilling project (Wagner et al, 2014(Wagner et al, , 2017. In particular, the diatom fossil record of Lake Ohrid provided important information on speciation and extinction patterns throughout its geological history (Jovanovska et al, 2022;. However, the actual age of other species-flocks in Lake Ohrid, as well as their (in situ) diversification patterns, has not yet been properly studied.…”