Characteristics of Poaceae pollen grains as a tool to assess palaeoecological grassland dynamics in South America

Abstract

During the Quaternary, in particular during glacial times, different grassland ecosystems played a much larger role and had a significantly larger distribution. Little is known yet about past development, biodiversity and dynamics of grassland ecosystems. In this innovative study, we attempt to distinguish between different South American grassland types in space and time based on morphological pollen grain characteristics of Poaceae. For this purpose >60–80 Poaceae pollen grains of 20 grassland samples were measured using their length, width and pore diameter as well as annulus width. Samples were taken from five sites in wet Páramo vegetation from the Late Pleistocene to the Late Holocene in South Ecuador and from two sites in the south-eastern Brazilian highlands (Campos do Altitude) of the same period. Additionally, we investigated two samples from a Pampa site as well as six samples from one Campos grassland site in southern Brazil from the Late Pleistocene to the Late Holocene. Subsets of samples of the Campos grasslands and of the Páramo were investigated in order to retrieve more detailed information on patterns within these vegetation types. Multivariate data analysis of the complete data set shows changes in taxonomic composition along an elevational gradient in the Páramo grasslands. Our results reveal a highly dynamic development of the individual grassland types; they also provide interesting information on Poaceae taxa composition patterns, development and possibly changes in biodiversity within these ecosystems. Moreover, our data provide an indication about the origin and dynamics of the Campos ecosystems in the southern Brazilian highlands during the Late Pleistocene and the Holocene before and after the onset of human activities.