Angiosperm pollen grains in sedimentary profiles from two Brazilian Atlantic rainforests, northernmost coastal plain from Rio Grande do Sul, southern Brazil. Part II

The state of Rio Grande do Sul (RS) is located in the extreme south of Brazil, within a transition region between the tropical and subtropical zones of South America that has been frequently affected by fluctuations in climate and vegetation over the last millennia. Palynomorphs preserved in sediments have provided excellent study material for paleoenvironmental reconstitutions of this region, as they reveal the source organisms and their respective environments over geological time. The present study was conducted to provide additional palynological reference material preserved in Quaternary sediments from the RS coastal plain for paleoenvironmental reconstruction studies. Here, we present taxonomic descriptions of pollen from 29 angiosperm taxa extracted along two Quaternary sedimentary profiles: the Pirataba forest profile (29° 15’ S 49° 51’W) and the Faxinal forest profile (29° 21’ S 49° 45’ W), Torres municipality, in the extreme north of the coastal plain of RS. Ecological data and pollen photomicrographs accompany the taxonomic descriptions. This reference material, together with the other palynomorphs found in the two sedimentary profiles, was the basis for our study of paleoenvironments from the last millennia in southern Brazil, according to the dynamics of climate and vegetation.


Introduction
The state of Rio Grande do Sul (RS), in the extreme south of Brazil, is situated approximately halfway between the Equator and the Antarctic Polar Circle, within a transitional area between the tropical and subtropical zones of South America (Marchiori 2004).The state harbors an extensive coastal plain of more than 600 km in length that, on a global scale, is affected by changes in climate and sealevel fluctuations (Seeliger et al. 1998).In this coastal plain, lakes, lagoons, marshes, and forests allow for the preservation of palynomorphs in sediments, offering abundant material for paleoenvironmental reconstructions of the last millennia related to climate change and sealevel oscillations (Lorscheitter & Romero 1985;Cordeiro & Lorscheitter 1994;Neves & Lorscheitter 1995a;Lorscheitter & Dillenburg 1998;Neves 1998;Lorscheitter 2003;Macedo et al. 2007;Masetto & Lorscheitter 2019;Roth et al. 2021).Results of these reconstructions can provide information for environmental preservation and monitoring.
The present study completes the series of catalogs of palynomorphs preserved in Quaternary sediments from two sedimentary profiles of tropical Pirataba and Faxinal forests in the northernmost region of the RS coastal plain (Roth & Lorscheitter 2013;2016;2017).These catalogs have been used for the paleoenvironmental reconstitution of the last 24,000 years in the region (Roth et al. 2021).
The angiosperm pollen catalog presented here represents Part II of the angiosperm material previously described by Roth & Lorscheitter (2017) and includes morphological descriptions, measurements, and photomicrographs.Ecological data for the respective sporophytes accompany the descriptions.The objective is to provide more reference material for paleoenvironmental reconstitutions related to the late Quaternary of the coastal plain.

Study sites
The two sedimentary profiles were collected from the interior of two Atlantic rainforests sensu stricto (s.str.) located at approximately the same latitude in Torres municipality, on the extreme northernmost coastal plain of RS, southern Brazil: one profile (254 cm in length) was obtained from the Pirataba forest (29° 15' S 49° 51' W), 17 km from the coastline and the second profile (612 cm in length) was obtained from the Faxinal forest (29° 21' S 49° 45' W) 2 km from the coastline (Fig. 1).The profiles were obtained using a Hiller sampler (Faegri & Iversen 1989), and the subsamples were collected along the profiles at regular intervals about 5 cm.The radiocarbon age near the profile bases allowed us to determine the time interval (Roth et al. 2021).

Chemical treatment and analysis
The standard chemical treatment of the subsamples (one sample = 8 cm 3 ) involved treatment with hydrochloric acid, hydrofluoric acid, potassium hydroxide, and acetolysis, followed by filtration through 250-µm mesh (Faegri & Iversen 1989).The subsamples were mounted on slides in glycerol jelly (Salgado-Labouriau 1973;Faegri & Iversen 1989) and examined under light microscopy (DIAPLAN, Leitz, Wetzlar, Germany).Taxonomic identification was based on the pollen reference collection of the Palynology Laboratory, Department of Botany, Universidade Federal of Rio Grande do Sul, Brazil, and reference pollen catalogs (Erdtman 1952;Heusser 1971;Markgraf & D'Antoni 1978;Hooghiemstra 1984;Roubik & Moreno P. 1991;Lorente et al. 2017).Taxonomic ordination of orders was based on APG IV (Byng et al. 2016).Taxonomic names followed the Missouri Botanical Garden (MOBOT) nomenclature (2020).We identified the material to the lowest taxonomic level permitted by the pollen morphology and level of preservation.The word "type" was used when precise identification was not possible (Berglund 1986).Distinct materials within the same taxon were separated by numbers.A minimum of 300 angiosperm pollen grains was counted for each subsample (Birks & Gordon 1985), with this number determined using saturation curves (Roth et al. 2021).
For the taxonomic pollen descriptions, the morphological nomenclature was based on Punt et al. (2007).We tried to find 25 grains to each taxon to calculate the measurements.This number could not be reached at the rare taxa, indicated in the descriptions.In some cases, it was not possible to measure the polar axis because of their permanent position in polar view.At the end of each palynological description, we provide brief ecological information for the plant in southern Brazil, for use in future paleoenvironmental studies.Photomicrographs were captured using a digital camera (DFC295; Leica Microsystems, Wetzlar, Germany) connected to a light microscope.

Discussion
The 29 taxa included in our study represent the second and final part of the taxonomy of angiosperm pollen grains of Roth & Lorscheitter (2017).The angiosperm pollen analyzed here, taken from the same sedimentary profiles of the northernmost region of the RS coastal plain used by Roth & Lorscheitter (2013;2016;2017), contributed to paleoenvironmental reconstructions of the last 24,000 years for this region (Roth et al. 2021).Over this time interval, sets of distinct palynomorphs indicated phases of dry and humid grassland and herbaceous marsh, the Holocene marine transgression, and the development of the Atlantic rainforest s. str.(Roth et al. 2021).These novel results exemplify the need for a priori discrimination of palynomorphs obtained from sediment in paleoenvironmental analyses.
The results have deepened our understanding of climate and vegetation dynamics over the last millennia in southern Brazil and have thus provided crucial information for understanding natural trends in monitoring and conservation efforts.

Figure 1 .
Figure 1.Study sites.A. Map of South America with the location of Rio Grande do Sul (RS) in southern Brazil; B. Detailed relief map with the locations of the present-day Pirataba (1, left) and Faxinal (2, right) forests in Torres municipality, on the extreme northern RS coastal plain; C. Satellite image from Google Earth, 2021, indicating the locations of the two sedimentary profiles: Pirataba profile (1, left above: 29° 15' S 49° 51' W) and Faxinal profile (2, right below: 29° 21' S 49° 45' W).

Angiosperm pollen grains in sedimentary profiles from two Brazilian Atlantic rainforests, northernmost coastal plain from Rio Grande do Sul, southern Brazil. Part II Acta
(Sobral 1999)ta: herbs, shrubs, climbing plants, or trees, mostly in open environments(Mondim 1996).Elliptic in equatorial view, circular in polar view.Tricolporoidate, long ectoapertures.Microechinate.Exine with evident columellae.Polar axis: ca.29 µm; equatorial diameter: ca.36 µm.Ecological data: herbs or sub-shrubs, rarely climbing plants.They occur in grasslands, inland and along the margins of forests and wetlands, with a wide distribution(Sobral 1999).