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This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Intellectual merit – Ferns are a diverse and charismatic group of land plants that have historically been understudied compared to the flowering plants. Ferns are ubiquitous and evolutionarily important members of many of Earth’s ecosystems, yet relatively few studies have attempted to evaluate relationships among fern species, reconstruct their biogeographic patterns through time, or analyze relationships in polyploid complexes (polyploids are species that contain multiple genomes, often from separate parental species that have hybridized).

This project addressed these issues through an integrated study of evolution in the fern genus Dryopteris , a large and globally distributed group of ferns. We produced phylogenies (family trees showing species relationships) based on two genomes, the chloroplast and the nuclear genomes, and used these trees first to test the classification system of the genus and to reconstruct historical biogeographic patterns and perform molecular dating analyses. These studies revealed that the existing classification system for the genus (into subgenera and sections) does not reflect relationships between species, and needs revision. We also determined that the genus as a whole is approximately 42 million years old, and that the species found in the New World (North, Central, and South America) arrived over the course of millions of years from Asia, Africa, and Europe. Transoceanic long-distance dispersal events have been mostly responsible for the arrival of the species now found in Central and South America, while the history of the North American species has largely been shaped by vicariance, in which large ancestral ranges have broken up over time, leaving closely related species in now-distant locations. 

Next, we used phylogenies from the nuclear and plastid genomes to evaluate the frequency and causes of reticulate evolution in New World Dryopteris . Evolution is typically presented as bifurcating, or tree-like, but processes that cause branches of the tree to come back together (such as hybridization) can lead to net-like rather than tree-like patterns that are collectively referred to as reticulate evolution. We found evidence for extensive reticulate evolution among the Latin American species of Dryopteris , involving unknown ancestors from Asia. We hypothesize that at least one hybrid individual from Asia underwent transoceanic long-distance dispersal to reach the Americas, where it hybridized further with New World species to produce the complicated reticulate patterns among modern species that we see in our phylogenetic trees. 

Finally, we evaluated the reticulate history of the 13 Dryopteris species in North America. This group has long been suspected of having undergone extensive reticulate evolution, and includes five hybrid allopolyploids whose parental species are unknown, and whose identities have been a subject of speculation and debate. We used DNA sequence data from the nuclear and plastid genomes to test several hypotheses explaining these species’ origins, and our data unambiguously support an existing scenario known as the “semicristata” hypothesis, which involves an unknown, probably extinct species as a parent for two of the allopolyploids in North America. Our data also suggest that each of the allopolyploid species has formed just once, which is at odds with current research in other plant groups which suggests that polyploid species typically form multiple times, from repeated hybridization events between the same set of parental species. 

Broader Impacts – This project is one of the largest phylogenetic analyses of a widespread fern group to date, and is one of the first rigorous analyses of reticulate evolut...

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Archaeology Program - Doctoral Dissertation Research Improvement Grants (Arch-DDRIG)

View guidelines, important information about nsf’s implementation of the revised 2 cfr.

NSF Financial Assistance awards (grants and cooperative agreements) made on or after October 1, 2024, will be subject to the applicable set of award conditions, dated October 1, 2024, available on the NSF website . These terms and conditions are consistent with the revised guidance specified in the OMB Guidance for Federal Financial Assistance published in the Federal Register on April 22, 2024.

Important information for proposers

All proposals must be submitted in accordance with the requirements specified in this funding opportunity and in the NSF Proposal & Award Policies & Procedures Guide (PAPPG) that is in effect for the relevant due date to which the proposal is being submitted. It is the responsibility of the proposer to ensure that the proposal meets these requirements. Submitting a proposal prior to a specified deadline does not negate this requirement.

Supports doctoral laboratory and field research on archaeologically relevant topics, with the goal of increasing anthropologically focused understanding of the past.

The Archaeology Program supports anthropologically relevant archaeological research. This means that the value of the proposed research can be justified within an anthropological context. The program sets no priorities by either geographic region or time period. It also has no priorities in regard to theoretical orientation or question and it is the responsibility of the investigator to explain convincingly why the focus of their research  is significant and has the potential to contribute to anthropological knowledge. While the program, in order to encourage innovative research, neither limits nor defines specific categories of research, most applications either request funds for field research or the analysis of archaeological material through multiple approaches. The program also supports methodological projects which develop analytic techniques of potential archaeological value.

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Awards made through this program, related programs.

• Archaeology Program Senior Research Awards (Arch-SR)
• Archaeometry (AMTRY)
• High-Risk Research in Biological Anthropology and Archaeology (HRRBAA)

Organization(s)

• Directorate for Social, Behavioral and Economic Sciences (SBE)
• Division of Behavioral and Cognitive Sciences (SBE/BCS)