108-9 Drynaria willdenowii (Polypodiaceae), A Fern from Volcanoes National Park, Rwanda as a Modern Analogue for the K-Pg "Fern Spike"

Session: The Cretaceous-Paleogene (K-Pg) Boundary Interval: From Large-Scale Geological Events to Mass Extinction Mechanisms (Posters)

Presenting Author:

Authors:

Abstract:

Modern analogues in paleontology are used as tools for reconstructing the functional biology and ecological relationships of fossil organisms and the past environments they inhabited. This method requires being able to draw parallels between the ancient system we study and identifying the closest, equivalent modern counterparts.

The volcanic terrains and affiliated surface processes in the regions surrounding Volcanoes National Park, Rwanda, serve as a good analogue for K-Pg boundary “disaster floras” occurring in the early Paleocene right after the boundary. These floras document extensive fern communities, representing the families Schizaeaceae, Gleicheniaceae, and Dicksoniaceae. Based on the occurrence of massive numbers of fern spores in relation to a much smaller angiosperm pollen component, researchers have referred to this as the "fern spike". Two models have been proposed in the literature for the occurrence of the fern spike: 1) these fern families were opportunists and rapidly occupied open and disturbed habitats and 2) ferns arose from large spore banks. The early Paleocene (Danian) fern spikes are attributed to Anemia-like schizaeaceous ferns, which have dimorphic fronds.

A modern analogue for these pioneering fern species is found in populations on the Ellen Campus of the Dian Fossey Gorilla Fund Campus, Rwanda. The fern Drynaria willdenowii (Polypodiaceae) has a widespread distribution, an ability to thrive in both lithic and epiphytic regions, and dimorphic fronds. This adaptability in pioneering habitats is potentially linked, to some degree, with their specialized rhizome and roots. Drynaria also has mutualistic interactions with fungi that enhance nutrient absorption. The modern analogue provides us with some additional insights regarding the role of mutualistic relationships and specialized underground organs in facilitating the rapid colonization of ferns in disturbed habitats across the K-Pg boundary.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10593

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.