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1. International Code for Phytolith Nomenclature (ICPN) 2.0

   https://doi.org/10.1093/aob/mcz064  

   International Committee for Phytolith Taxonomy ; Neumann, Katharina ; Strömberg, Caroline A. E. ; Ball, Terry ; Albert, Rosa Maria ; Vrydaghs, Luc ; Cummings, Linda Scott ( July 2019 , Annals of Botany)

   Opal phytoliths (microscopic silica bodies produced in and between the cells of many plants) are a very resilient, often preserved type of plant microfossil. With the exponentially growing number of phytolith studies, standardization of phytolith morphotype names and description is essential. As a first effort in standardization, the International Code for Phytolith Nomenclature 1.0 was published by the ICPN Working Group in Annals of Botany in 2005. A decade of use of the code has prompted the need to revise, update, expand and improve it.

   ICPN 2.0 formulates the principles recommended for naming and describing phytolith morphotypes. According to these principles, it presents the revised names, diagnosis, images and drawings of the morphotypes that were included in ICPN 1.0, plus three others. These 19 morphotypes are those most commonly encountered in phytolith assemblages from modern and fossil soils, sediments and archaeological deposits. An illustrated glossary of common terms for description is also provided.

    

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2. Phytolith assemblages reflect variability in human land use and the modern environment

   https://doi.org/10.1007/s00334-023-00932-2  

   Witteveen, Nina H. ; White, Cheryl ; Sanchez Martinez, Barbara A. ; Booij, Roemer ; Philip, Annemarie ; Gosling, William D. ; Bush, Mark B. ; McMichael, Crystal N. ( March 2024 , Vegetation History and Archaeobotany)

   Phytoliths preserved in soils and sediments can be used to provide unique insights into past vegetation dynamics in response to human and climate change. Phytoliths can reconstruct local vegetation in terrestrial soils where pollen grains typically decay, providing a range of markers (or lack thereof) that document past human activities. The ca. 6 million km²of Amazonian forests have relatively few baseline datasets documenting changes in phytolith representation across gradients of human disturbances. Here we show that phytolith assemblages vary on local scales across a gradient of (modern) human disturbance in tropical rainforests of Suriname. Detrended correspondence analysis showed that the phytolith assemblages found in managed landscapes (shifting cultivation and a garden), unmanaged forests, and abandoned reforesting sites were clearly distinguishable from intact forests and from each other. Our results highlight the sensitivity and potential of phytoliths to be used in reconstructing successional trajectories after site usage and abandonment. Percentages of specific phytolith morphotypes were also positively correlated with local palm abundances derived from UAV data, and with biomass estimated from MODIS satellite imagery. This baseline dataset provides an index of likely changes that can be observed at other sites that indicate past human activities and long-term forest recovery in Amazonia.

    

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3. A diatom-inferred water-depth transfer function from a single lake in the northern California Coast Range

   https://doi.org/10.1007/s10933-023-00281-0  

   Han, Jiwoo ; Kirby, Matthew ; Carlin, Joe ; Nauman, Benjamin ; MacDonald, Glen ( March 2023 , Journal of Paleolimnology)

   This study examines the relationship between water depth and diatom assemblages from lake-sediment-surface samples at Kelly Lake, California. A total of 40 surface-sediment samples (integrated upper 5 cm) were taken at various depths within the small (~ 3.74 ha) 5.7 m-deep lake. Secchi depths, water temperature, pH, salinity, conductivity, and total dissolved solids were also measured. Some diatom species showed distinct association with depth (e.g.,Fragilaria crotonensis, Nitzschia semirobusta). The relationship between the complete diatom assemblages and water depth was analyzed and assessed by depth-cluster analysis, a one-way analysis of similarity, principal components analysis and canonical correspondence analysis. Statistically significant differences were found between the assemblages associated with shallow depth (0–1.25 m), mid-depth (1.25–3.75 m), and deep-water (3.75–5.2 m) locations. The relationship between diatom assemblages and lake depth allowed two transfer models to be developed using the Modern Analogue Technique and Weighted Averaging Partial Least Squares. These models were compared and assessed by residual scatter plots. The results indicate that diatom-inferred transfer models based on surface-sediment samples from a single, relatively small and shallow lake can be a useful tool for studying past hydroclimatic variability (e.g., lake depth) from similar lakes in California and other regions where the large number of lakes required for traditional transfer-function development may not exist.

    

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4. Palms of the past: can morphometric phytolith analysis inform deep time evolution and palaeoecology of Arecaceae?

   https://doi.org/10.1093/aob/mcae068  

   Brightly, W_H ; Crifò, C. ; Gallaher, T_J ; Hermans, R. ; Lavin, S. ; Lowe, A_J ; Smythies, C_A ; Stiles, E. ; Wilson_Deibel, P. ; Strömberg, C_A_E ( April 2024 , Annals of Botany)

   Palm fossils are often used as evidence for warm and wet palaeoenvironments, reflecting the affinities of most modern palms. However, several extant palm lineages tolerate cool and/or arid climates, making a clear understanding of the taxonomic composition of ancient palm communities important for reliable palaeoenvironmental inference. However, taxonomically identifiable palm fossils are rare and often confined to specific facies. Although the resolution of taxonomic information they provide remains unclear, phytoliths (microscopic silica bodies) provide a possible solution because of their high preservation potential under conditions where other plant fossils are scarce. We thus evaluate the taxonomic and palaeoenvironmental utility of palm phytoliths.

   We quantified phytolith morphology of 97 modern palm and other monocot species. Using this dataset, we tested the ability of five common discriminant methods to identify nine major palm clades. We then compiled a dataset of species’ climate preferences and tested if they were correlated with phytolith morphology using a phylogenetic comparative approach. Finally, we reconstructed palm communities and palaeoenvironmental conditions at six fossil sites.

   Best-performing models correctly identified phytoliths to their clade of origin only 59 % of the time. Although palms were generally distinguished from non-palms, few palm clades were highly distinct, and phytolith morphology was weakly correlated with species’ environmental preferences. Reconstructions at all fossil sites suggested that palm communities were dominated by Trachycarpeae and Areceae, with warm, equable climates and high, potentially seasonal rainfall. However, fossil site reconstructions had high uncertainty and often conflicted with other climate proxies.

   While phytolith morphology provides some distinction among palm clades, caution is warranted. Unlike prior spatially restricted studies, our geographically and phylogenetically broad study indicates phytolith morphology may not reliably differentiate most palm taxa in deep time. Nevertheless, it reveals distinct clades, including some likely to be palaeoenvironmentally informative.

    

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5. Evapotranspiration‐linked silica deposition in a basal tracheophyte plant (Lycopodiaceae: Lycopodiella alopecuroides ): implications for the evolutionary origins of phytoliths

   https://doi.org/10.1111/nph.18861  

   Whalen, Niall S. ; Hunt, Tyler C. ; Erickson, Gregory M. ( March 2023 , New Phytologist)

   Phytoliths, microscopic deposits of hydrated silica within plants, play a myriad of functional roles in extant tracheophytes – yet their evolutionary origins and the original selective pressures leading to their deposition remain poorly understood. To gain new insights into the ancestral condition of tracheophyte phytolith production and function, phytolith content was intensively assayed in a basal, morphologically conserved tracheophyte: the foxtail clubmossLycopodiella alopecuroides.

   Wet ashing was employed to perform phytolith extractions from every major anatomical region ofL. alopecuroides. Phytolith occurrence was recorded, alongside abundance, morphometric information, and morphological descriptions.

   Phytoliths were recovered exclusively from the microphylls, which were apicodistally silicified into multiphytolith aggregates. Phytolith aggregates were larger and more numerous in anatomical regions engaging in greater evapotranspirational activity.

   The tissue distribution ofL. alopecuroidesphytoliths is inconsistent with the expectations of proposed adaptive hypotheses of phytolith evolutionary origin. Instead, it is hypothesized that phytoliths may have arisen incidentally in theL. alopecuroides‐like ancestral plant, polymerizing from intraplant silicon accumulations arising via bulk flow and ‘leaky’ cellular micronutrient channels. This basal, nonadaptive phytolith formation model would provide the evolutionary ‘raw material’ for later modification into the useful, adaptative, phytolith deposits seen in later‐diverging plant clades.

    

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