NSF Postdoctoral Fellowship in Biology: Was there a Tropical Forest in North America after the end-Cretaceous Extinction?

Harris, Gabriella Rossetto, Colorado Springs CO

Investigators

Abstract

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2023, Broadening Participation of Groups Underrepresented in Biology. The Fellowship supports a research and training plan for the Fellow that will increase the participation of groups underrepresented in biology. The project will examine a 63.8 million year old fossil plant deposit from Castle Rock, Colorado, USA, which was previously identified as the first tropical rainforest after the last mass extinction that killed the dinosaurs. The Fellow will determine whether the Castle Rock flora should be classified as an actual tropical rainforest or a temperate forest by analyzing the plant lineages present and their reproductive methods. The research will advance scientific knowledge of how flowering plants evolved and forests recovered after the last mass extinction, leading to the emergence of the prominent plant families living today. Understanding the origins of modern rainforests is significant because comparable modern habitats are threatened by extinction due to present-day climate change and human impacts. This project will also broaden participation with the training of the Fellow to implement bilingual science communication and public outreach and mentor high school and undergraduate students of diverse backgrounds. The research will involve an in-depth study of well-preserved fossil leaves and reproductive remains from Castle Rock to determine the composition of the flora, its biogeographic and structural analogs, and fruit and seed dispersal strategies. The Fellow will analyze fossil leaf architecture and cuticles from extensive existing collections (n=~5000) at the Denver Museum of Nature & Science alongside comprehensive tropical collections at the Field Museum Herbarium to make taxonomic identifications. The distribution of nearest living relatives and extant rainforest reference plot data will be used to better determine what biogeographic region is the modern analog for the Castle Rock forest, i.e., living low-latitude Old World or Neotropical rainforests or warm-temperate rainforests more similar to those in East Asia and eastern North America. The morphology and dispersal types of fossil reproductive structures will be evaluated using CT scans and comparisons to modern rainforests and other fossil forests to assess plant adaptations. Training objectives will involve learning additional skills in angiosperm systematics, cuticle preparation, and reproductive morphology. The Fellow will also train and mentor other students from underrepresented groups in STEM. The results of the work will be shared with museum visitors, remotely to underserved schools, and globally with a bilingual YouTube video. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.