Cretaceous (Turonian) Angiosperm Flowers from New Jersey (USA): Structural Diversity, Systematics, and Phylogenetic/Evolutionary Implications

Cornell Univ - State: Awds Made Prior May 2010, Ithaca NY

Investigators

Abstract

Drs. Crepet and Nixon have been awarded a grant to study significant deposits of fossil flowering plants. These deposits represent some of the finest fossil sites ever discovered including a virtual treasure trove of exquisitely preserved fossil flowers-a kind of fossil with enormous potential scientific value and one once thought to be prohibitively rare and beyond the reach of science(at least 200 species-more than all other reports of similar aged fossils combined). Flowering plants are the most dominant, diverse, economically [including medicinally], and ecologically important groups of existing plants. Uncertainties exist as to origins, relationships and reasons for their success. Together, these unknowns circumscribe "Darwin's Abominable Mystery" and it constitutes one of the most visible voids in our understanding of the history of life. In spite of recent progress based on breakthroughs using molecular data to determine taxonomic relationships, extinct missing links would be helpful in understanding the history, relationships and success of the flowering plants by filling some of the gaps now separating living species and by introducing "historical testability" to hypotheses of relationships that are based exclusively on comparisons among living species. In other words, if hypothesized relationships are inconsistent with newly discovered fossil taxa (that is, if the attributes of the fossils cause them not to fit into and thus challenge modern hypotheses), then the hypothesis or the interpretation of the fossil is incorrect and a careful study should ensue. Also, the pattern of appearance of different species generated by such studies should be roughly compatible with the evolutionary sequence implied by hypotheses based only on living species-if there is a conflict further examination of all data and interpretations is in order. Yet another particularly significant benefit of this investigation is its contribution to establishing a sequence of appearance of different floral types through time. In addition to including many of the taxonomically important structural characteristics of angiosperms, flowers provide a key to the reproductive biology of their species, particularly pollination biology. Knowing the pattern of appearance of various modes of pollination from fossil evidence will be most helpful in evaluating various hypotheses seeking to explain angiosperm success-especially those relating angiosperm diversity to mode of pollination. Thus studies of fossils at this locality stand to provide important insights into what has widely been recognized as a major gap in our knowledge. The proposed research will include a diverse set of approaches to and interests in angiosperm fossil history, floral evolution, history of pollination and insect-plant interactions, phylogenetic relationships of angiosperm groups, origin of angiosperms, history of monocots, Cretaceous gymnosperm and fern diversification, and theoretical and practical aspects of cladistic analysis and phylogenetic reconstruction involving new algorithms and approaches to placing the fossils in phylogenetic context. Drs. Crepet and Nixon will continue fieldwork aimed at discovering additional species. They continue to find additional taxa of great interest and potential importance. Existing and newly collected fossils will be intensively studied in order to elucidate the structural details and taxonomic affinities of as many as possible. Particular attention will be paid to certain groups of critical interest that are well or uniquely represented in the collections. The careful explication of fossil structure depends upon light and electron microscopy (particularly SEM). Fossils, once described, will further require a significant curation and databasing effort. The next step is the evaluation of the relationships of the fossils through the process of contrasting their characteristics with those of all other known flowering plants. This process, phylogenetic analysis, involves computer algorithms and results are testable and reproducible and provide accurate assessments of the taxonomic affinities of the fossils. Thus, a carefully produced reliable pattern of angiosperm floral history is established. These fossils already encompass the earliest evidence of numerous angiosperm lineages and they include the oldest documented examples of numerous features and species with important implications for the pattern and timing of evolution of pollination mechanisms. In toto these fossils provide a breathtaking array of floral innovations from a relatively early and critical period in angiosperm diversification. The fossils include enough representatives of major taxonomic groups, including the earliest reliable evidence of the monocots (wheat, grasses, orchids etc.) to strongly alter our perception of the timing of flowering plant evolution. The project has the potential to provide quantities of unique data that will be relevant to many other workers in these areas including especially angiosperm systematists and pollination biologists. These data will in the form of primary (descriptions, phylogenetic matrices), and secondary results (e.g. phylogenetic trees including fossils, insights into the history of angiosperm-insect relationships, and minimum ages of extinct lineages). In addition to publishing the results and cooperatively sharing them with colleagues including graduate students being trained in this area, a website will be maintained that will make specific data and photographs available to the scientific community. The PI's will continue to publish results of their work in the form of popular articles in order to reach a broad segment of the public.