Phytoliths as a tool for archaeobotanical, palaeobotanical and palaeoecological studies in Amazonian palms

Abstract

Phytoliths are silica bodies found in vascular plants, often diagnostic at the family level in angiosperms. They are especially abundant in palms (Arecaceae), occurring in all organs, with the highest concentrations in leaves. Phytoliths can remain in the soil for thousands or even millions of years, providing physical evidence of taxa in time and space. As such, they can be used to reconstruct ancient floras and landscapes, interpret events in plant evolution and document plant use by ancient peoples. In palms, studies of phytoliths remain scarce and guides for identifying those of regional floras are needed, especially in the Amazon, where palms are a dominant floristic and cultural element. We surveyed contemporary phytoliths in 92 species of Amazonian palms, representing 29 genera across four subfamilies. Previous studies have recognized only two palm phytolith morphotypes (globular echinate and conical), but here we recognize eight types that provide diagnostic information at the levels of subfamily, tribe, genus and, in some cases, species. With this degree of taxonomic resolution, phytoliths are proving to be a powerful line of evidence linking palms to past human activity in Amazonia and we expect their use to be expanded to interpret palaeoecological changes in this region across geological time.

Palm Phytoliths of Mid-Elevation Andean Forests

“…All species and plant parts sampled produced abundant phytoliths, and contained one to four morphotypes ( Table 2). We identified several new subtypes of globular echinate and conical morphotypes, which were previously characterized by other researchers (e.g., Piperno, 2006;Morcote-Ríos et al, 2016; Figure 1). The newly identified subtypes were defined by the following characteristics:…”

“…All samples were analyzed under a Leica Axiophot microscope with differential interference contrast (DIC) at 630x magnification using immersion oil. Categorization was based on Morcote-Ríos et al (2016), but new (sub)categories were created for newly identified morphotypes. A total of 300 phytoliths was counted per sample to quantify the relative abundances of morphotypes.…”

“…Phytoliths are commonly used in paleoecological and archaeological reconstructions, and provide evidence of localscale vegetation dynamics because they are typically deposited directly beneath the parent plant when it dies and decays (Piperno, 2006). Palms are known to be particularly prolific phytolith producers, and can often be identified to the subfamily or genus level (Piperno, 2006;Morcote-Ríos et al, 2016).…”

“…There have been recent advances in the ability to identify palm phytoliths in tropical settings, particularly in the Amazonian lowland forests, and in an archaeological context (Morcote-Ríos et al, 2016). The phytoliths of Andean palm species, however, remain relatively unstudied.…”

Holocene increases in palm abundances in north‐western Amazonia

“…We used Piperno (2006) for identification of grass and arboreal phytoliths. For each palm species occurring in Amacayacu, we identified the phytolith morphotypes they produce using recently published reference guides (Huisman, Raczka, & McMichael, 2018;Morcote-Ríos, Bernal, & Raz, 2016) and the phytolith reference collection at the University of Amsterdam.…”