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Somjee U, Marting P, Anzaldo S, Simmons LW, Painting CJ. Extreme range in adult body size reveals hidden trade-offs among sexually selected traits. Evolution 2024; 78:1382-1395. [PMID: 38900629 DOI: 10.1093/evolut/qpae084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 05/13/2024] [Accepted: 05/24/2024] [Indexed: 06/22/2024]
Abstract
Sexually selected weapons used to monopolize mating opportunities are predicted to trade-off with traits used in competition for fertilization. Yet, the limited size range typically found among adults of a species often precludes clear comparisons between population-level and individual-level relative trait investment. The jousting weevil, Brentus anchorago (Coleoptera: Brentidae), varies more than 26-fold in body mass, which is among the most extreme adult body size ranges of any solitary terrestrial species. We reveal a trade-off at a population level: hypermetric scaling in male weapons (slope = 1.59) and a closely mirrored reversal in allocation to postcopulatory traits (slope = 0.54). Yet, at the individual level, we find the opposite pattern; males that invest relatively more in weapons for their size class also invest more in postcopulatory traits. Across 36 dung beetle and 41 brentine weevil species, we find the allometric slope explains more trait variation at larger body size ranges; in brentines, population-level scaling patterns become more detectable in species with a larger range in adult body size. Our findings reveal that population-level allometries and individual-level trade-offs can both be important in shaping relative trait allocation; we highlight that the adult body size range is rarely examined but may be integral to gaining a deeper understanding of trade-offs in reproductive allocation.
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Affiliation(s)
- Ummat Somjee
- Department of Integrative Biology, University of Texas, Austin, TX, United States
- Smithsonian Tropical Research Institute, Balboa, Panama
| | - Peter Marting
- Department of Biological Sciences, Auburn University, Auburn, AL, United States
| | - Salvatore Anzaldo
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Leigh W Simmons
- School of Biological Sciences, University of Western Australia, Perth, WA, Australia
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Yu G, Wong BH, Painting CJ, Li H, Yu L, Zhang Z, Zhang S, Li D. Males armed with big weapons win fights at limited cost in ant-mimicking jumping spiders. Curr Zool 2024; 70:98-108. [PMID: 38476142 PMCID: PMC10926263 DOI: 10.1093/cz/zoac101] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 12/18/2022] [Indexed: 03/14/2024] Open
Abstract
A core assumption of sexual selection theory is that sexually selected weapons, specialized morphological structures used directly in male contests, can improve an individual's reproductive success but only if the bearer can overcome associated costs, the negative effects on the bearer's fitness components. However, recent studies have shown that producing and wielding exaggerated weapons may not necessarily be costly. Rather, some traits can be selected for supporting, or compensating for, the expense of producing and wielding such exaggerated weapons. In the ant-mimicking jumping spider Myrmarachne gisti, exaggerated chelicerae are borne only by adult males and not females, showing sexual dimorphism and steep positive allometry with body size. Here, we determine the potential benefits of bearing exaggerated chelicerae during male contests and explore the potential for costs in terms of prey-capture efficiency and compensation between chelicera size and neighboring trait size. While males with longer chelicerae won most of their male-male contests, we found no significant differences in prey-capture efficiency between males and females regardless of whether prey was winged or flightless. Males' elongated chelicerae thus do not impede their efficiency at capturing prey. Furthermore, we found that the sizes of all neighboring traits are positively correlated with chelicera size, suggesting that these traits may be under correlational selection. Taken together, our findings suggest that M. gisti males armed with the exaggerated chelicerae that function as weapons win more fights at limited cost for performance in prey capture and compensate for neighboring structures.
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Affiliation(s)
- Guocheng Yu
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Boon Hui Wong
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Christina J Painting
- Te Aka Mātuatua School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
| | - Hongze Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Long Yu
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Zengtao Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Shichang Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Daiqin Li
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
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Farnworth B, Purdie S, Wehi PM, Painting CJ. Exaggerated mandibles are correlated with enhanced foraging efficacy in male Auckland tree wētā. Biol Lett 2023; 19:20230207. [PMID: 37964578 PMCID: PMC10646448 DOI: 10.1098/rsbl.2023.0207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 10/23/2023] [Indexed: 11/16/2023] Open
Abstract
Sexual selection has driven the evolution of weaponry for males to fight rivals to gain access to females. Although weapons are predicted to increase males' reproductive success, they are also expected to incur costs and may impair functional activities, including foraging. Using feeding assays, we tested whether the enlarged mandibles of Auckland tree wētā (Hemideina thoracica) impact feeding activity (the total volume of biomass consumed, bite rate, and number of foraging visits) and foraging behaviour (time spent moving, feeding, or stationary). We predicted that increased head capsule size in male wētā would hinder their foraging efficacy. However, we found that wētā with longer heads fed at a faster rate and spent less time foraging than wētā with smaller heads, regardless of sex. Contrary to expectations that weapons impede functional activities, our results demonstrate that exaggerated traits can improve feeding performance and may offer benefits other than increased mating success.
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Affiliation(s)
| | | | | | - Christina J. Painting
- Te Aka Mātuatua School of Science, University of Waikato, Hamilton 3240, New Zealand
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Brzęk P. What do molecular laws of life mean for species: absolute restrictions or mere suggestions? J Exp Biol 2023; 226:jeb245849. [PMID: 37756603 DOI: 10.1242/jeb.245849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2023]
Abstract
Evolutionary biologists are interested in finding universal patterns of covariation between macroscopic and molecular traits. Knowledge of such laws of life can be essential for understanding the course of evolutionary processes. Molecular parameters are presumably close to fundamental limits set to all organisms by laws of physics and chemistry. Thus, laws of life that include such parameters are hypothesized to be similar at both wide interspecific levels of variation and narrower levels of intraspecific and intraindividual variation in different species. In this Commentary, I discuss examples where the significance or direction of such molecular laws of life can be compared at different levels of biological variation: (1) the membrane pacemaker theory of metabolism, (2) the correlation between variation in metabolic rate and mitochondrial efficiency and (3) the allometric scaling of metabolism. All three examples reveal that covariations within species or individuals that include molecular parameters do not always follow patterns observed between species. I conclude that limits set by molecular laws of life can be circumvented (at least to some degree) by changes in other traits, and thus, they usually do not impose strict limitations on minor within-species evolutionary changes (i.e. microevolution). I also briefly discuss some of the most promising perspectives for future studies on the universality of molecular laws of life.
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Affiliation(s)
- Paweł Brzęk
- Faculty of Biology, University of Białystok, Ciołkowskiego 1J, 15-245 Białystok, Poland
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Powell EC, Painting CJ, Machado G, Holwell GI. Juvenile leg autotomy predicts adult male morph in a New Zealand harvestman with weapon polymorphism. Behav Ecol 2023; 34:613-620. [PMID: 37434639 PMCID: PMC10332453 DOI: 10.1093/beheco/arad029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 03/08/2023] [Accepted: 03/29/2023] [Indexed: 07/13/2023] Open
Abstract
Intraspecific weapon polymorphisms that arise via conditional thresholds may be affected by juvenile experience such as predator encounters, yet this idea has rarely been tested. The New Zealand harvestman Forsteropsalis pureora has three male morphs: majors (alphas and betas) are large-bodied with large chelicerae used in male-male contests, while minors (gammas) are small-bodied with small chelicerae and scramble to find mates. Individuals use leg autotomy to escape predators and there is no regeneration of the missing leg. Here, we tested whether juvenile experience affects adult morph using leg autotomy scars as a proxy of predator encounters. Juvenile males that lost at least one leg (with either locomotory or sensory function) had a 45 times higher probability of becoming a minor morph at adulthood than intact juvenile males. Leg loss during development may affect foraging, locomotion, and/or physiology, potentially linking a juvenile's predator encounters to their final adult morph and future reproductive tactic.
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Affiliation(s)
- Erin C Powell
- Te Kura Mātauranga Koiora/School of Biological Sciences, University of Auckland, 3a Symonds St, Auckland 1010, New Zealand
| | - Christina J Painting
- Te Aka Mātuatua School of Science, University of Waikato, Gate 8, Hillcrest Road, Hamilton 3240, New Zealand
| | - Glauco Machado
- LAGE do Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, Travessa 14, no. 101, Cidade Universitária, São Paulo CEP 05.508-090, Brazil
| | - Gregory I Holwell
- Te Kura Mātauranga Koiora/School of Biological Sciences, University of Auckland, 3a Symonds St, Auckland 1010, New Zealand
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Sizing up swords: Correlated evolution of antlers and tusks in ruminants. J MAMM EVOL 2022. [DOI: 10.1007/s10914-022-09628-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Somjee U, Shankar A, Falk JJ. Can Sex-Specific Metabolic Rates Provide Insight Into Patterns of Metabolic Scaling? Integr Comp Biol 2022; 62:icac135. [PMID: 35963649 DOI: 10.1093/icb/icac135] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Females and males can exhibit striking differences in body size, relative trait size, physiology and behavior. As a consequence the sexes can have very different rates of whole-body energy use, or converge on similar rates through different physiological mechanisms. Yet many studies that measure the relationship between metabolic rate and body size only pay attention to a single sex (more often males), or do not distinguish between sexes. We present four reasons why explicit attention to energy-use between the sexes can yield insight into the physiological mechanisms that shape broader patterns of metabolic scaling in nature. First, the sexes often differ considerably in their relative investment in reproduction which shapes much of life-history and rates of energy use. Second, males and females share a majority of their genome but may experience different selective pressures. Sex-specific energy profiles can reveal how the energetic needs of individuals are met despite the challenge of within-species genetic constraints. Third, sexual selection often pushes growth and behavior to physiological extremes. Exaggerated sexually selected traits are often most prominent in one sex, can comprise up to 50% of body mass and thus provide opportunities to uncover energetic constraints of trait growth and maintenance. Finally, sex-differences in behavior such as mating-displays, long-distance dispersal and courtship can lead to drastically different energy allocation among the sexes; the physiology to support this behavior can shape patterns of metabolic scaling. The mechanisms underlying metabolic scaling in females, males and hermaphroditic animals can provide opportunities to develop testable predictions that enhance our understanding of energetic scaling patterns in nature.
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Affiliation(s)
- Ummat Somjee
- Smithsonian Tropical Research Institute, Panama
- University of Texas, Austin, TX
| | | | - Jay J Falk
- Smithsonian Tropical Research Institute, Panama
- University of Washington, Seattle, WA
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Female preference for super-sized male ornaments and its implications for the evolution of ornament allometry. Evol Ecol 2022. [DOI: 10.1007/s10682-022-10181-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractIt has been argued that disproportionately larger ornaments in bigger males—positive allometry—is the outcome of sexual selection operating on the size of condition dependent traits. We reviewed the literature and found a general lack of empirical testing of the assumed link between female preferences for large ornaments and a pattern of positive allometry in male ornamentation. We subsequently conducted a manipulative experiment by leveraging the unusual terrestrial fish, Alticus sp. cf. simplicirrus, on the island of Rarotonga. Males in this species present a prominent head crest to females during courtship, and the size of this head crest in the genus more broadly exhibits the classic pattern of positive allometry. We created realistic male models standardized in body size but differing in head crest size based on the most extreme allometric scaling recorded for the genus. This included a crest size well outside the observed range for the study population (super-sized). The stimuli were presented to free-living females in a manner that mimicked the spatial distribution of courting males. Females directed greater attention to the male stimulus that exhibited the super-sized crest, with little difference in attention direct to other size treatments. These data appear to be the only experimental evidence from the wild of a female preference function that has been implicitly assumed to drive selection that results in the evolution of positive allometry in male ornamentation.
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Dinh JP. Large and exaggerated sexually selected weapons comprise high proportions of metabolically inexpensive exoskeleton. Biol Lett 2022; 18:20210550. [PMID: 35135317 PMCID: PMC8826129 DOI: 10.1098/rsbl.2021.0550] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cost-minimization hypothesis proposes that positive allometry in sexually selected traits can be explained if the proportional energetic maintenance costs of weapons decrease as traits increase in size. Energetic maintenance costs are the costs of maintaining homeostasis. They are slow, persistent energy sinks that are distinct from ephemeral costs of growth. Because some tissues expend more energy on maintenance than others, energetic maintenance costs can be inferred from proportional tissue composition. For example, soft tissues require more energy for maintenance than exoskeleton, so an arthropod claw that is 50% soft tissue and 50% exoskeleton would have higher energetic maintenance costs than one that is 30% soft tissue and 70% exoskeleton. I tested the cost-minimization hypothesis using proportional tissue composition as a proxy for energetic maintenance costs in snapping shrimp (Alpheus heterochaelis and Alpheus estuariensis) and fiddler crabs (Uca pugilator). As predicted, larger weapons comprised proportionally less soft tissue mass and more exoskeleton mass than smaller weapons. Furthermore, I extended cost-minimization to explain trait exaggeration: individuals might exaggerate traits by investing more mass in exoskeleton. As predicted, exoskeleton mass proportional to weapon mass increased as exaggeration increased. These results support and extend the cost-minimization hypothesis to explain positive allometry and weapon exaggeration.
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Affiliation(s)
- Jason P. Dinh
- Department of Biology, Duke University, Durham, NC, USA
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