Social Amoebae: Environmental Factors Influencing Their Distribution and Diversity Across South-Western Europe

Abstract The social amoebae (dictyostelids) are the only truly multicellular lineage within the superkingdom Amoebozoa, the sister group to Ophistokonts (Metazoa+ Fungi). Despite the exceptional phylogenetic and evolutionary value of this taxon, the environmental factors that determine their distribution and diversity are largely unknown. We have applied statistical modeling to a set of data obtained from an extensive and detailed survey in the south-western of Europe (The Iberian Peninsula including Spain and Portugal) in order to estimate some of the main environmental factors influencing the distribution and diversity of dictyostelid in temperate climates. It is the first time that this methodology is applied to the study of this unique group of soil microorganisms. Our results show that a combination of climatic (temperature, water availability), physical (pH) and vegetation (species richness) factors favor dictyostelid species richness. In the Iberian Peninsula, dictyostelid diversity is highest in colder and wet environments, indicating that this group has likely diversified in relatively cold places with high levels of water availability

An expanded phylogeny of social amoebas (Dictyostelia) shows increasing diversity and new morphological patterns

<p>Abstract</p> <p>Background</p> <p>Social Amoebae or Dictyostelia are eukaryotic microbes with a unique life cycle consisting of both uni- and multicellular stages. They have long fascinated molecular, developmental and evolutionary biologists, and <it>Dictyostelium discoideum </it>is now one of the most widely studied eukaryotic microbial models. The first molecular phylogeny of Dictyostelia included most of the species known at the time and suggested an extremely deep taxon with a molecular depth roughly equivalent to Metazoa. The group was also shown to consist of four major clades, none of which correspond to traditional genera. Potential morphological justification was identified for three of the four major groups, on the basis of which tentative names were assigned.</p> <p>Results</p> <p>Over the past four years, the Mycetozoan Global Biodiversity Survey has identified many new isolates that appear to be new species of Dictyostelia, along with numerous isolates of previously described species. We have determined 18S ribosomal RNA gene sequences for all of these new isolates. Phylogenetic analyses of these data show at least 50 new species, and these arise from throughout the dictyostelid tree breaking up many previously isolated long branches. The resulting tree now shows eight well-supported major groups instead of the original four. The new species also expand the known morphological diversity of the previously established four major groups, violating nearly all previously suggested deep morphological patterns.</p> <p>Conclusions</p> <p>A greatly expanded phylogeny of Dictyostelia now shows even greater morphological plasticity at deep taxonomic levels. In fact, there now seem to be no obvious deep evolutionary trends across the group. However at a finer level, patterns in morphological character evolution are beginning to emerge. These results also suggest that there is a far greater diversity of Dictyostelia yet to be discovered, including novel morphologies.</p

Consistency of impact assessment protocols for non-native species

Standardized tools are needed to identify and prioritize the most harmful non-native species (NNS). A plethora of assessment protocols have been developed to evaluate the current and potential impacts of non-native species, but consistency among them has received limited attention. To estimate the consistency across impact assessment protocols, 89 specialists in biological invasions used 11 protocols to screen 57 NNS (2614 assessments). We tested if the consistency in the impact scoring across assessors, quantified as the coefficient of variation (CV), was dependent on the characteristics of the protocol, the taxonomic group and the expertise of the assessor. Mean CV across assessors was 40%, with a maximum of 223%. CV was lower for protocols with a low number of score levels, which demanded high levels of expertise, and when the assessors had greater expertise on the assessed species. The similarity among protocols with respect to the final scores was higher when the protocols considered the same impact types. We conclude that all protocols led to considerable inconsistency among assessors. In order to improve consistency, we highlight the importance of selecting assessors with high expertise, providing clear guidelines and adequate training but also deriving final decisions collaboratively by consensus

Synthesis and characterization of polyamide 1010 and evaluation of its cast-extruded films for meat preservation

[EN] This study holistically evaluates the potential of polyamide 1010 (PA1010) in the form of monolayer films for meat preservation applications. First, decamethylenediamine and sebacic acid, both derived from natural and renewable castor oil, were used to form a "nylon salt" that was subsequently polymerized at 230 degrees C by condensation reaction, yielding high-molecular-weight (MW) PA1010. The resulting fully bio-based polyamide was, thereafter, processed into 145-mu m films by cast extrusion and characterized to ascertain their effectiveness in food packaging. Results showed that the PA1010 films were highly transparent, thermally stable up to approximately 340 degrees C, and very balanced in terms of mechanical strength and ductility, breaking at elongations higher than 150%. The permeability tests revealed that the PA1010 films present a high barrier to water and aroma vapors and a medium barrier to oxygen. Interestingly, the oxygen barrier performance of PA1010 presented low moisture dependence, outperforming currently available biopolymers. Finally, the PA1010 films were applied to package fresh pork fillets in thermosealed bags, proving to be effective in preserving the physicochemical and microbiological quality of meat for up to seven days of storage at 5 degrees C.This work was carried out with the financial support of the Ramon y Cajal contract (RYC2019-027784-I) from the Spanish Ministry of Science and Innovation (MICI) and the program "Garantia Juvenil"(EDG-JID/2021/290) from Generalitat Valenciana (GVA).Hernandez-Garcia, E.; Pacheco-Romeralo, M.; Pascual-Ramírez, L.; Vargas, M.; Torres-Giner, S. (2023). Synthesis and characterization of polyamide 1010 and evaluation of its cast-extruded films for meat preservation. Food Packaging and Shelf Life. 36. https://doi.org/10.1016/j.fpsl.2023.1010583

Did terrestrial diversification of amoebas (Amoebozoa) occur in synchrony with land plants?

Evolution of lineage diversification through time is an active area of research where much progress has been made in the last decade. Contrary to the situation in animals and plants little is known about how diversification rates have evolved in most major groups of protist. This is mainly due to uncertainty about phylogenetic relationships, scarcity of the protist fossil record and the unknown diversity within these lineages. We have analyzed the evolutionary history of the supergroup Amoebozoa over the last 1000 million years using molecular dating and species number estimates. After an origin in the marine environment we have dated the colonization of terrestrial habitats by three distinct lineages of Amoebozoa: Dictyostelia, Myxogastria and Arcellinida. The common ancestor of the two sister taxa, Dictyostelia and Myxogastria, appears to have existed before the colonization of land by plants. In contrast Arcellinida seems to have diversify in synchrony with land plant radiation, and more specifically with that of mosses. Detection of acceleration of diversification rates in Myxogastria and Arcellinida points to a co-evolution within the terrestrial habitats, where land plants and the amoebozoans may have interacted during the evolution of these new ecosystems

Diversification rate shifts in Amoebozoa based on an 18S rDNA chronogram.

<p>The tree shown was derived and dated using BEAST [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074374#B35" target="_blank">35</a>] with the HKY substitution model. Colored branches indicate significant rate shifts detected by the birth-death model of MEDUSA [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074374#B37" target="_blank">37</a>]: red branches, green triangle (arcellinids) and blue triangle (Myxogastria) indicate faster rates and an orange branch indicates a single terminal clade with slower rates (<i>Acanthamoeba</i>). Alternative coding of the number of species for each terminal is indicated with a slash (see section 2.2). Violet vertical bar indicates the time span between the initial colonization of land by plants to the origin of the terrestrial ecosystems [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074374#B50" target="_blank">50</a>]. Bootstrap support (BS) values obtained from a maximum likelihood analysis using RAxML v 7.04 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074374#B27" target="_blank">27</a>] are indicated by black circles (BS>95%), black squares (BS>75) black triangles (BS>50).</p

Divergences times reconstructed from 6-protein and 18S rDNA data sets using different calibration schemes and models.

<p>Divergences times reconstructed from 6-protein and 18S rDNA data sets using different calibration schemes and models.</p

Reconstructed node ages and their 95% HPD distribution based on a 6-protein phylogeny.

<p>Reconstructed ages and 95% highest posterior density (HPD) from a 6-protein data set under different fossil constraints (four or two fossil -580-400 myr), models (WAG, with or without a gamma rate correction) and programs (BEAST or MCMCtree) for the following nodes: A) crown Amoebozoa B) crown Mycetozoa C) crown Dictyostelia and D) stem Arcellinida. Note the different scales among the plots. The exact values for nodes and HPDs are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074374#pone-0074374-t001" target="_blank">Table 1</a>.</p