Holocene Biogeography of Mangroves along the Northern Gulf of Mexico Coast, U.S.A.

Keywords: Mangroves, disjunct distribution, Holocene biogeography, pollen records, Gulf of Mexico
Session Type: Virtual Paper Abstract
Day: Tuesday
Session Start / End Time: 3/1/2022 02:00 PM (Eastern Time (US & Canada)) - 3/1/2022 03:20 PM (Eastern Time (US & Canada))
Room: Virtual 16

Abstract

Populations of the three species of mangroves show a classic disjunct distribution along the northern Gulf of Mexico coast. Was the disjunction a result of range contraction due to past climate changes, or long-distance dispersal due to recent global warming? Little is known about the Holocene biogeographic history of mangroves around the Gulf of Mexico to answer this question. We reconstructed the Late Holocene history of mangroves along the northern Gulf Coast by means of palynological and stratigraphic analyses of sediment cores collected from coastal wetlands from Florida to Texas to document the timing of mangrove colonization and population dynamics at each site. Mangroves arrived in the Everglades, Florida, at least 3800 years ago as sea level rose. Avicennia (black mangrove) spread to Cedar Keys, Florida, at ~1300 yr BP, followed by Laguncularia (white mangrove) and Rhizophora (red mangrove). Avicennia and Rhizophora migrated to Dog Island, Apalachicola, Florida, less than 200 years ago, and to adjacent St. George Island only a decade ago. In Port Fourchon, Louisiana, where both Rhizophora and Laguncularia are absent, Avicennia pollen started to appear no more than 100 years ago and black mangrove has since proliferated in coastal wetlands. Mangroves never colonized the coastal areas of southwestern Louisiana during the Holocene. Our paleoecological data do not support the range contraction hypothesis. Instead, they are consistent with the scenario that mangroves migrated from the Everglades to Cedar Keys by diffusion along the coast but were dispersed to southern Louisiana and Apalachicola by jump dispersal.