A palynological atlas of the Cerrado-Caatinga ecotone in northeastern Brazil

Abstract

Describing the diversity of Brazilian plant species, as well as the wide variety in the associated pollen grains, is crucial to understanding their evolution and ensuring effective conservation. The accurate identification of pollen is key to successful pollen studies and the consistent paleoecological interpretation of past vegetation changes. Pollen analysts usually identify plant taxa from reference collections built from herbaria material. In Brazil, pollen atlases primarily focus on three main vegetation domains, namely, the Amazon Forest, the Atlantic Forest, and the Cerrado, while information about Caatinga pollen taxa is dispersed across multiple studies; this significantly impedes efforts to further develop palynological research. To address this gap, we built a palynological atlas for the state of Piauí which is covered by the biomes Caatinga and Cerrado along with their transitional zones. These domains encompass various vegetation types, including dense shrubland, grassland, palm swamp formation, riverine forest, seasonal deciduous and semi-deciduous forests, as well as valley-side marshes. We collected flower buds from the Herbarium Prisco Bezerra (EAC) at the Federal University of Ceará and extracted the pollen grains for the pollen reference slides. The atlas comprises 398 species from 99 families, with the most represented families being Asteraceae, Bignoniaceae, Euphorbiaceae, Fabaceae, Lamiaceae, Malvaceae, Malpighiaceae, and Rubiaceae. Each taxa is presented with a description of the pollen grain, a photo showing polar and equatorial views, and ecological information as life form (liana/scandent/vine, herb, subshrub, shrub or tree), substrate, and vegetation type to support further studies.