About this Research Topic
The idea of 'living fossils' has been commonly invoked yet has troubled biologists for 150 years, starting with Darwin's explanation of such anomalous forms alongside expectations of natural selection and divergence. Meanings have multiplied and the label has been applied to entities as diverse as viruses, transposons, genomes, ribosomes, proteins, cell types, species and higher taxa. Today there is widespread dissatisfaction with this routinely invoked concept, including ill-defined or cross-cutting definitional criteria and conflicts among inferences from molecular genetic and phenotypic characters. Our recent publications respond to these complaints and argue that the discussion should move away from definitional debates to understanding the complex contours of the living fossil research program. The living fossil concept plays a primary role in delineating what phenomena need explanation morphological and molecular stability over long periods of evolutionary time suggesting that more intentional cross-disciplinary interaction will lead to both theoretical and empirical progress.
First, we aim to change the way researchers think about living fossils, moving researchers away from semantic debates by providing a more unified conceptual framework based on a different perception of what the concept can do in scientific investigation. Second, we aim to advance knowledge of molecular and morphological stasis across levels of biological organization. Our framework has the potential to facilitate interdisciplinary research on fundamental evolutionary questions surrounding morphological and molecular stability. The study of living fossils necessarily involves detailed comparisons of how evolutionary patterns are realized in deep time. This requires thinking in terms of parts and wholes. When should certain kinds of traits be considered proxies for the historical entities that bear them (e.g., species or genera)? When should they be considered entities in their own right? Each of these modes is important in understanding stasis but have been less explicit in research because different disciplines concentrate investigation on preferred subsets of entities. A Research Topic on these issues will encourage intentional explorations of living fossils across disciplinary boundaries from paleontologically defined geographic relics to endangered species in conservation biology; from conserved regulatory genes and ultraconserved elements to rapidly evolving transposons in canonical living fossil lineages; and more.
Because our framework for living fossils emphasizes a diversity of issues about morphological and molecular stability over long periods of evolutionary time, the scope of our Research Topic is a suite of research questions applied to different levels of biological organization: What mechanisms are responsible for the retention of groups of ancestral characters over long periods of time within a lineage? For slow rates of change, how are different characters related? Why do some but not all characters exhibit stasis over long periods of time? Why do characters that represent defining features of some species persist over long durations compared to other lineages? How are perceived declines in living fossil groups (from previous high levels of taxonomic diversity to low levels today) related to patterns in phylogenetic sister groups, and to origination and extinction dynamics? Why do some living fossils exhibit 'relict' geographic distribution? How is stasis affected by their manifestation at different junctures in a life history or levels in a biological hierarchy? What are our null expectations concerning living fossils?
First, we aim to change the way researchers think about living fossils, moving researchers away from semantic debates by providing a more unified conceptual framework based on a different perception of what the concept can do in scientific investigation. Second, we aim to advance knowledge of molecular and morphological stasis across levels of biological organization. Our framework has the potential to facilitate interdisciplinary research on fundamental evolutionary questions surrounding morphological and molecular stability. The study of living fossils necessarily involves detailed comparisons of how evolutionary patterns are realized in deep time. This requires thinking in terms of parts and wholes. When should certain kinds of traits be considered proxies for the historical entities that bear them (e.g., species or genera)? When should they be considered entities in their own right? Each of these modes is important in understanding stasis but have been less explicit in research because different disciplines concentrate investigation on preferred subsets of entities. A Research Topic on these issues will encourage intentional explorations of living fossils across disciplinary boundaries from paleontologically defined geographic relics to endangered species in conservation biology; from conserved regulatory genes and ultraconserved elements to rapidly evolving transposons in canonical living fossil lineages; and more.
Because our framework for living fossils emphasizes a diversity of issues about morphological and molecular stability over long periods of evolutionary time, the scope of our Research Topic is a suite of research questions applied to different levels of biological organization: What mechanisms are responsible for the retention of groups of ancestral characters over long periods of time within a lineage? For slow rates of change, how are different characters related? Why do some but not all characters exhibit stasis over long periods of time? Why do characters that represent defining features of some species persist over long durations compared to other lineages? How are perceived declines in living fossil groups (from previous high levels of taxonomic diversity to low levels today) related to patterns in phylogenetic sister groups, and to origination and extinction dynamics? Why do some living fossils exhibit 'relict' geographic distribution? How is stasis affected by their manifestation at different junctures in a life history or levels in a biological hierarchy? What are our null expectations concerning living fossils?
Keywords: character evolution, concepts, evolutionary rates, living fossil, stasis
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