Neogene paleoecology and biogeography of a Malvoid pollen in northwestern South America

Abstract

Western Amazonian landscapes evolved dynamically during the Neogene. Large wetlands developed responding to Andean uplift what promoted the rise and diversification of many plant groups. One such group is the well-documented Malvoid pollen Malvacipolloides maristellae from the Miocene of northwestern South America. In the present contribution, we compared the botanical affinity among fossil and extant Malvoid, reconstructed past distributions of the taxa and their relative abundance throughout the Neogene-Quaternary, and interpreted the biogeographical and paleoecology of the group. We found similar pollen morphologies among the fossil and 14 extant Malvoids, mainly Allosidastrum, Sphaeralcea, Monteiroa, Malvella, and Wissadula. These belong to the Malveae tribe (subtribes Abutilinae and Malvinae), which are extra-Amazonian, mostly found in drier-colder settings, in full light environments (savannahs, forest edges), and tolerating varied oligotrophic and hydric stress soils. We recorded widespread Miocene populations of the fossil, from western Amazonia to coastal Venezuela, with high abundances in the early Miocene, when the group first appeared, then dropped significantly from the late Miocene onwards. The gradual demise of M. maristellae is attributed to the negative effects of brackish water inundations and the gradual increase of humidity and forest cover following the decline of wetlands that narrowed the open, light-demanding ecological niche exploited by M. maristellae. In the Pliocene-Quaternary, no records were found in western Amazonia, attesting to its final displacement outside the forest structure. In its northern extension (Venezuela and Colombia), the fossil survived for longer due to available open-dry environments that developed in the latest Neogene. © 2019 Elsevier B.V.