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Zhou Y, Pan Y, Wang M, Wang X, Zheng X, Zhou Z. Fossil evidence sheds light on sexual selection during the early evolution of birds. Proc Natl Acad Sci U S A 2024; 121:e2309825120. [PMID: 38190528 PMCID: PMC10801838 DOI: 10.1073/pnas.2309825120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Accepted: 11/16/2023] [Indexed: 01/10/2024] Open
Abstract
The impact of sexual selection on the evolution of birds has been widely acknowledged. Although sexual selection has been hypothesized as a driving force in the occurrences of numerous morphological features across theropod evolution, this hypothesis has yet to be comprehensively tested due to challenges in identifying the sex of fossils and by the limited sample size. Confuciusornis sanctus is arguably the best-known early avialan and is represented by thousands of well-preserved specimens from the Early Cretaceous Jehol lagerstätte, which provides us with a chance to decipher the strength of sexual selection on extinct vertebrates. Herein, we present a morphometric study of C. sanctus based on the largest sample size of this taxon collected up to now. Our results indicate that the characteristic elongated paired rectrices is a sexually dimorphic trait and statistically robust inferences of the sexual dimorphism in size, shape, and allometry that have been established, providing the earliest known sexual dimorphism in avian evolution. Our findings suggest that sexual selection, in conjunction with natural selection, does act upon body size and limb length ratio in early birds, thereby promoting a deeper understanding of the role of sexual selection in large-scale phylogenetic evolution.
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Affiliation(s)
- Yibo Zhou
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Centre for Research and Education on Biological Evolution and Environment and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing210023, China
| | - Yanhong Pan
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Centre for Research and Education on Biological Evolution and Environment and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing210023, China
| | - Min Wang
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing100044, China
| | - Xiaoli Wang
- Institute of Geology and Paleontology, Linyi University, Linyi276000, Shandong, China
- Shandong Tianyu Museum of Nature, Pingyi273300, Shandong, China
| | - Xiaoting Zheng
- Institute of Geology and Paleontology, Linyi University, Linyi276000, Shandong, China
- Shandong Tianyu Museum of Nature, Pingyi273300, Shandong, China
| | - Zhonghe Zhou
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing100044, China
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Lerch BA, Servedio MR. Predation drives complex eco-evolutionary dynamics in sexually selected traits. PLoS Biol 2023; 21:e3002059. [PMID: 37011094 PMCID: PMC10101644 DOI: 10.1371/journal.pbio.3002059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 04/13/2023] [Accepted: 03/03/2023] [Indexed: 04/05/2023] Open
Abstract
Predation plays a role in preventing the evolution of ever more complicated sexual displays, because such displays often increase an individual's predation risk. Sexual selection theory, however, omits a key feature of predation in modeling costs to sexually selected traits: Predation is density dependent. As a result of this density dependence, predator-prey dynamics should feed back into the evolution of sexual displays, which, in turn, feeds back into predator-prey dynamics. Here, we develop both population and quantitative genetic models of sexual selection that explicitly link the evolution of sexual displays with predator-prey dynamics. Our primary result is that predation can drive eco-evolutionary cycles in sexually selected traits. We also show that mechanistically modeling the cost to sexual displays as predation leads to novel outcomes such as the maintenance of polymorphism in sexual displays and alters ecological dynamics by muting prey cycles. These results suggest predation as a potential mechanism to maintain variation in sexual displays and underscore that short-term studies of sexual display evolution may not accurately predict long-run dynamics. Further, they demonstrate that a common verbal model (that predation limits sexual displays) with widespread empirical support can result in unappreciated, complex dynamics due to the density-dependent nature of predation.
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Affiliation(s)
- Brian A Lerch
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Maria R Servedio
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
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Tuschhoff E, Wiens JJ. Evolution of sexually selected traits across animals. Front Ecol Evol 2023. [DOI: 10.3389/fevo.2023.1042747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Sexual selection is thought to be a major driver of phenotypic diversity and diversification in animals, but large-scale evolutionary patterns in sexually selected (SS) traits remain largely unknown. Here, we survey and analyze the evolution of these traits across animal phylogeny. We find that female mate choice appears to be the most widespread mechanism of sexual selection, but male-male competition appears to be almost as frequent in chordates and male mate choice is also common in arthropods. Among sensory types, tactile traits appear to be most widespread whereas auditory traits are relatively uncommon. Rather than being ubiquitous or randomly distributed across animals, most of these different types of SS traits are confined to clades in arthropods and chordates, which form “hotspots” for the evolution of these diverse trait types. Thus, different sensory types show accelerated rates of evolution in these clades. Moreover, different types of SS traits are strongly correlated with each other in their evolution across animals. Finally, despite the intensive interest in the role of sexual selection in speciation, we find only limited support for the idea that SS traits drive large-scale patterns of diversification and species richness across all animals.
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Rowe L, Rundle HD. The Alignment of Natural and Sexual Selection. ANNUAL REVIEW OF ECOLOGY, EVOLUTION, AND SYSTEMATICS 2021. [DOI: 10.1146/annurev-ecolsys-012021-033324] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Sexual selection has the potential to decrease mean fitness in a population through an array of costs to nonsexual fitness. These costs may be offset when sexual selection favors individuals with high nonsexual fitness, causing the alignment of sexual and natural selection. We review the many laboratory experiments that have manipulated mating systems aimed at quantifying the net effects of sexual selection on mean fitness. These must be interpreted in light of population history and the diversity of ways manipulations have altered sexual interactions, sexual conflict, and sexual and natural selection. Theory and data suggest a net benefit is more likely when sexually concordant genetic variation is enhanced and that ecological context can mediate the relative importance of these different effects. Comparative studies have independently examined the consequences of sexual selection for population/species persistence. These provide little indication of a benefit, and interpreting these higher-level responses is challenging.
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Affiliation(s)
- Locke Rowe
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2
| | - Howard D. Rundle
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
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5
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Emberts Z, Wiens JJ. Do sexually selected weapons drive diversification? Evolution 2021; 75:2411-2424. [PMID: 33738793 DOI: 10.1111/evo.14212] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 02/16/2021] [Accepted: 03/02/2021] [Indexed: 12/15/2022]
Abstract
Sexual selection is often thought to promote speciation. This expectation is largely driven by the fact that sexually selected traits can influence mating patterns and contribute to reproductive isolation. Indeed, some comparative studies have shown that clades with sexually selected traits have increased rates of speciation and diversification. However, these studies have almost exclusively focused on one mechanism of sexual selection: female choice. Another widespread mechanism is male-male competition. Few empirical studies (if any) have investigated the role of this alternative mechanism in driving diversification. Nevertheless, recent reviews have suggested that male-male competition can increase speciation rates. Here, we investigated whether traits associated with precopulatory male-male competition (i.e., sexually selected weapons) have promoted speciation and diversification in insects. We focused on three clades with both weapons and suitable phylogenies: leaf-footed and broad-headed bugs (Coreidae+Alydidae; ∼2850 species), stick insects and relatives (Phasmatodea; ∼3284 species), and scarab beetles (Scarabaeoidea; ∼39,717 species). We found no evidence that weapon-bearing lineages in these clades have higher rates of speciation or diversification than their weaponless relatives. Thus, our results suggest that precopulatory male-male competition may not have strong, general effects on speciation and diversification in insects, a group encompassing ∼60% of all described species.
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Affiliation(s)
- Zachary Emberts
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721
| | - John J Wiens
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721
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Martins MJF, Hunt G, Thompson CM, Lockwood R, Swaddle JP, Puckett TM. Shifts in sexual dimorphism across a mass extinction in ostracods: implications for sexual selection as a factor in extinction risk. Proc Biol Sci 2020; 287:20200730. [PMID: 32811315 DOI: 10.1098/rspb.2020.0730] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Sexual selection often favours investment in expensive sexual traits that help individuals compete for mates. In a rapidly changing environment, however, allocation of resources to traits related to reproduction at the expense of those related to survival may elevate extinction risk. Empirical testing of this hypothesis in the fossil record, where extinction can be directly documented, is largely lacking. The rich fossil record of cytheroid ostracods offers a unique study system in this context: the male shell is systematically more elongate than that of females, and thus the sexes can be distinguished, even in fossils. Using mixture models to identify sex clusters from size and shape variables derived from the digitized valve outlines of adult ostracods, we estimated sexual dimorphism in ostracod species before and after the Cretaceous/Palaeogene mass extinction in the United States Coastal Plain. Across this boundary, we document a substantial shift in sexual dimorphism, driven largely by a pronounced decline in the taxa with dimorphism indicating both very high and very low male investment. The shift away from high male investment, which arises largely from evolutionary changes within genera that persist through the extinction, parallels extinction selectivity previously documented during the Late Cretaceous under a background extinction regime. Our results suggest that sexual selection and the allocation of resources towards survival versus reproduction may be an important factor for species extinction during both background and mass extinctions.
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Affiliation(s)
| | - Gene Hunt
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - Carmi Milagros Thompson
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - Rowan Lockwood
- Department of Geology, College of William and Mary, Williamsburg, VA, USA
| | - John P Swaddle
- Department of Biology, College of William and Mary, Williamsburg, VA, USA
| | - T Markham Puckett
- School of Biological, Environmental and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, USA
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