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Slater GJ. Topographically distinct adaptive landscapes for teeth, skeletons, and size explain the adaptive radiation of Carnivora (Mammalia). Evolution 2022; 76:2049-2066. [PMID: 35880607 PMCID: PMC9546082 DOI: 10.1111/evo.14577] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 06/08/2022] [Indexed: 01/22/2023]
Abstract
Models of adaptive radiation were originally developed to explain the early, rapid appearance of distinct modes of life within diversifying clades. Phylogenetic tests of this hypothesis have yielded limited support for temporally declining rates of phenotypic evolution across diverse clades, but the concept of an adaptive landscape that links form to fitness, while also crucial to these models, has received more limited attention. Using methods that assess the temporal accumulation of morphological variation and estimate the topography of the underlying adaptive landscape, I found evidence of an early partitioning of mandibulo-dental morphological variation in Carnivora (Mammalia) that occurs on an adaptive landscape with multiple peaks, consistent with classic ideas about adaptive radiation. Although strong support for this mode of adaptive radiation is present in traits related to diet, its signal is not present in body mass data or for traits related to locomotor behavior and substrate use. These findings suggest that adaptive radiations may occur along some axes of ecomorphological variation without leaving a signal in others and that their dynamics are more complex than simple univariate tests might suggest.
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Affiliation(s)
- Graham J. Slater
- Department of the Geophysical SciencesUniversity of ChicagoChicagoIllinois60637
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Abstract
AbstractEvolvability is best addressed from a multi-level, macroevolutionary perspective through a comparative approach that tests for among-clade differences in phenotypic diversification in response to an opportunity, such as encountered after a mass extinction, entering a new adaptive zone, or entering a new geographic area. Analyzing the dynamics of clades under similar environmental conditions can (partially) factor out shared external drivers to recognize intrinsic differences in evolvability, aiming for a macroevolutionary analog of a common-garden experiment. Analyses will be most powerful when integrating neontological and paleontological data: determining differences among extant populations that can be hypothesized to generate large-scale, long-term contrasts in evolvability among clades; or observing large-scale differences among clade histories that can by hypothesized to reflect contrasts in genetics and development observed directly in extant populations. However, many comparative analyses can be informative on their own, as explored in this overview. Differences in clade-level evolvability can be visualized in diversity-disparity plots, which can quantify positive and negative departures of phenotypic productivity from stochastic expectations scaled to taxonomic diversification. Factors that evidently can promote evolvability include modularity—when selection aligns with modular structure or with morphological integration patterns; pronounced ontogenetic changes in morphology, as in allometry or multiphase life cycles; genome size; and a variety of evolutionary novelties, which can also be evaluated using macroevolutionary lags between the acquisition of a trait and phenotypic diversification, and dead-clade-walking patterns that may signal a loss of evolvability when extrinsic factors can be excluded. High speciation rates may indirectly foster phenotypic evolvability, and vice versa. Mechanisms are controversial, but clade evolvability may be higher in the Cambrian, and possibly early in the history of clades at other times; in the tropics; and, for marine organisms, in shallow-water disturbed habitats.
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Mongiardino Koch N, Thompson JR, Hiley AS, McCowin MF, Armstrong AF, Coppard SE, Aguilera F, Bronstein O, Kroh A, Mooi R, Rouse GW. Phylogenomic analyses of echinoid diversification prompt a re-evaluation of their fossil record. eLife 2022; 11:72460. [PMID: 35315317 PMCID: PMC8940180 DOI: 10.7554/elife.72460] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 03/03/2022] [Indexed: 12/25/2022] Open
Abstract
Echinoids are key components of modern marine ecosystems. Despite a remarkable fossil record, the emergence of their crown group is documented by few specimens of unclear affinities, rendering their early history uncertain. The origin of sand dollars, one of its most distinctive clades, is also unclear due to an unstable phylogenetic context. We employ 18 novel genomes and transcriptomes to build a phylogenomic dataset with a near-complete sampling of major lineages. With it, we revise the phylogeny and divergence times of echinoids, and place their history within the broader context of echinoderm evolution. We also introduce the concept of a chronospace - a multidimensional representation of node ages - and use it to explore methodological decisions involved in time calibrating phylogenies. We find the choice of clock model to have the strongest impact on divergence times, while the use of site-heterogeneous models and alternative node prior distributions show minimal effects. The choice of loci has an intermediate impact, affecting mostly deep Paleozoic nodes, for which clock-like genes recover dates more congruent with fossil evidence. Our results reveal that crown group echinoids originated in the Permian and diversified rapidly in the Triassic, despite the relative lack of fossil evidence for this early diversification. We also clarify the relationships between sand dollars and their close relatives and confidently date their origins to the Cretaceous, implying ghost ranges spanning approximately 50 million years, a remarkable discrepancy with their rich fossil record.
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Affiliation(s)
- Nicolás Mongiardino Koch
- Department of Earth & Planetary Sciences, Yale University, New Haven, United States.,Scripps Institution of Oceanography, University of California San Diego, La Jolla, United States
| | - Jeffrey R Thompson
- Department of Earth Sciences, Natural History Museum, London, United Kingdom.,University College London Center for Life's Origins and Evolution, London, United Kingdom
| | - Avery S Hiley
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, United States
| | - Marina F McCowin
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, United States
| | - A Frances Armstrong
- Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, United States
| | - Simon E Coppard
- Bader International Study Centre, Queen's University, Herstmonceux Castle, East Sussex, United Kingdom
| | - Felipe Aguilera
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Omri Bronstein
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.,Steinhardt Museum of Natural History, Tel-Aviv, Israel
| | - Andreas Kroh
- Department of Geology and Palaeontology, Natural History Museum Vienna, Vienna, Austria
| | - Rich Mooi
- Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, United States
| | - Greg W Rouse
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, United States
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