Cyphoderia ampulla(Cyphoderiidae: Rhizaria), a tale of freshwater sailors: The causes and consequences of ecological transitions through the salinity barrier in a family of benthic protists

Abstract

The salinity barrier that separates marine and freshwater biomes is probably the most important division in biodiversity on Earth. Those organisms that successfully performed this transition had access to new ecosystems while undergoing changes in selective pressure, which often led to major shifts in diversification rates. While these transitions have been extensively investigated in animals, the tempo, mode, and outcome of crossing the salinity barrier have been scarcely studied in other eukaryotes. Here, we reconstructed the evolutionary history of the species complex Cyphoderia ampulla (Euglyphida: Cercozoa: Rhizaria) based on DNA sequences from the nuclear SSU rRNA gene and the mitochondrial cytochrome oxidase subunit I gene, obtained from publicly available environmental DNA data (GeneBank, EukBank) and isolated organisms. A tree calibrated with euglyphid fossils showed that four independent transitions towards freshwater systems occurred from the mid‐Miocene onwards, coincident with important fluctuations in sea level. Ancestral trait reconstructions indicated that the whole family Cyphoderiidae had a marine origin and suggest that ancestors of the freshwater forms were euryhaline and lived in environments with fluctuating salinity. Diversification rates did not show any obvious increase concomitant with ecological transitions, but morphometric analyses indicated that species increased in size and homogenized their morphology after colonizing the new environments. This suggests adaptation to changes in selective pressure exerted by life in freshwater sediments.

A needle in a haystack: a new metabarcoding approach to survey diversity at the species level of Arcellinida (Amoebozoa: Tubulinea)

“…The salinity barrier is one of the greatest ecological barriers, and those organisms that cross it must face important challenges through their evolutionary history. This characteristic has been shown in another group of testate amoebae, Cyphoderia (González-Miguéns, Soler-Zamora, Useros, et al, 2022). Therefore, it can be expected that further investigations in saline environments, both inland (saline endorheic) and marine systems will reveal new insights on Arcellinida diversity.…”

A needle in a haystack: A new metabarcoding approach to survey diversity at the species level of Arcellinida (Amoebozoa: Tubulinea)

“…Environmental sequences were distributed among Glutinoconcha infraorders in the following way: Hyalospheniformes 0 (0 cloned [C] and 0 Illumina [I]), Longithecina 1 (0 C and 1 I), Sphaerothecina 20 (15 C and 5 I), Cylindrothecina 10 (4 C and 6 I), Excentrostoma 86 (48 C and 38 I) and Incertae Sedis 4 (4 C and 0 I) (Figures 1, 3 and 4). Some of these ASVs, 12 in total, corresponded to organisms that had been previously isolated and barcoded (González‐Miguéns, Soler‐Zamora, Useros, et al, 2022; González‐Miguéns, Soler‐Zamora, Villar‐Depablo, et al, 2022). These taxa were Galeripora bufonipellita (3 ASVs assigned), Centropyxis aculeata (6 ASVs assigned) and Awerintzewia sp (3 ASVs assigned).…”

“…Two other ASVs were also recovered in estuarine sediment, corresponding respectively to a member of Sphaerothecina as well as an unidentified Longithecina. The salinity barrier is one of the greatest ecological barriers (González‐Miguéns, Soler‐Zamora, Useros, et al, 2022), and those organisms that cross it must face important challenges through their evolutionary history. This characteristic has been shown in another group of (filose) testate amoebae, Cyphoderia (González‐Miguéns, Soler‐Zamora, Useros, et al, 2022).…”

“…The salinity barrier is one of the greatest ecological barriers (González-Miguéns, Soler-Zamora, Useros, et al, 2022), and those organisms that cross it must face important challenges through their evolutionary history. This characteristic has been shown in another group of (filose) testate amoebae, Cyphoderia (González-Miguéns, Soler-Zamora, Useros, et al, 2022). Therefore, it can be expected that further investigations in saline environments, both inland (saline endorrheic) and marine systems will reveal new insights on Arcellinida diversity.…”

Their fates intertwined: diversification patterns of the Asian gliding vertebrates may have been forged by dipterocarp trees

“…Further, several studies that used CoMET, with varied clade sizes, crown ages, and sampling probabilities ( ρ ), do not show terminal declines in speciation rates (e.g. [77–81]). We therefore have confidence in the CoMET results, which are further substantiated by the other methods employed here.…”