Abstract We discuss a recent assessment by Dörken et al. (2021) regarding the affinities of the Eocene fossil species Huncocladus laubenfelsii from Laguna del Hunco (Patagonia, Argentina). We originally (Andruchow-Colombo et al., 2019) assigned this species to the conifer family Podocarpaceae as the first certain South American macrofossil record of the phyllocladoid lineage (Huncocladus+Phyllocladus), based on a combination of numerous macro- and micromorphological vegetative characters. However, Dörken et al. (2021) rejected the podocarpaceous affinity of H. laubenfelsii and considered it to be more closely related to the cycad genera Bowenia or Eobowenia. Their assessment was based almost entirely on two cuticular characters, with only superficial consideration of the abundant additional evidence available that included several diagnostic macromorphological features. We review the two characters mentioned by these authors, and other features, and find that their suggestion is contradicted by the available evidence, maintaining our original assignment. Critical characters include presence/absence of a midvein, secondary venation pattern, arrangement and general morphology of the photosynthetic structures, and morphology and disposition of epidermal cells.
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Phylogeography of the wild Lager-brewing ancestor ( Saccharomyces eubayanus ) in Patagonia: Saccharomyces eubayanus in Patagonia
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Premise Eocene floras of Patagonia document biotic response to the final separation of Gondwana. The conifer genus
Araucaria , distributed worldwide during the Mesozoic, has a disjunct extant distribution between South America and Australasia. Fossils assigned to AustralasianAraucaria Sect.Eutacta usually are represented by isolated organs, making diagnosis difficult.Araucaria pichileufensis E.W. Berry, from the middle Eocene Río Pichileufú (RP ) site in Argentine Patagonia, was originally placed in Sect.Eutacta and later reported from the early Eocene Laguna del Hunco (LH ) locality. However, the relationship ofA. pichileufensis to Sect.Eutacta and the conspecificity of theAraucaria material among these Patagonian floras have not been tested using modern methods.Methods We review the type material of
A. pichileufensis alongside large (n = 192) new fossil collections ofAraucaria fromLH andRP , including multi‐organ preservation of leafy branches, ovuliferous complexes, and pollen cones. We use a total evidence phylogenetic analysis to analyze relationships of the fossils to Sect.Eutacta .Results We describe
Araucaria huncoensis sp. nov. fromLH and improve the whole‐plant concept forAraucaria pichileufensis fromRP . The two species respectively resolve in the crown and stem of Sect.Eutacta .Conclusions Our results confirm the presence and indicate the survival of Sect.
Eutacta in South America during early Antarctic separation. The exceptionally complete fossils significantly predate several molecular age estimates for crownEutacta . The differentiation of twoAraucaria species demonstrates conifer turnover during climate change and initial South American isolation from the early to middle Eocene. -
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Abstract Heritable variation in gene expression is common within species. Much of this variation is due to genetic differences outside of the gene with altered expression and is trans-acting. This trans-regulatory variation is often polygenic, with individual variants typically having small effects, making the genetic architecture and evolution of trans-regulatory variation challenging to study. Consequently, key questions about trans-regulatory variation remain, including the variability of trans-regulatory variation within a species, how selection affects trans-regulatory variation, and how trans-regulatory variants are distributed throughout the genome and within a species. To address these questions, we isolated and measured trans-regulatory differences affecting TDH3 promoter activity among 56 strains of Saccharomyces cerevisiae, finding that trans-regulatory backgrounds varied approximately twofold in their effects on TDH3 promoter activity. Comparing this variation to neutral models of trans-regulatory evolution based on empirical measures of mutational effects revealed that despite this variability in the effects of trans-regulatory backgrounds, stabilizing selection has constrained trans-regulatory differences within this species. Using a powerful quantitative trait locus mapping method, we identified ∼100 trans-acting expression quantitative trait locus in each of three crosses to a common reference strain, indicating that regulatory variation is more polygenic than previous studies have suggested. Loci altering expression were located throughout the genome, and many loci were strain specific. This distribution and prevalence of alleles is consistent with recent theories about the genetic architecture of complex traits. In all mapping experiments, the nonreference strain alleles increased and decreased TDH3 promoter activity with similar frequencies, suggesting that stabilizing selection maintained many trans-acting variants with opposing effects. This variation may provide the raw material for compensatory evolution and larger scale regulatory rewiring observed in developmental systems drift among species.
