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Reformulation of Trivers-Willard hypothesis for parental investment. Commun Biol 2022; 5:371. [PMID: 35440689 PMCID: PMC9018816 DOI: 10.1038/s42003-022-03286-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 03/17/2022] [Indexed: 11/08/2022] Open
Abstract
The Trivers-Willard hypothesis (TWH) plays a central role in understanding the optimal investment strategies to male and female offspring. Empirical studies of TWH, however, yielded conflicting results. Here, we present models to predict optimal comprehensive multi-element parental strategies composed of primary sex ratio, brood size, resource allocation among offspring, and the resultant secondary sex ratio. Our results reveal that the optimal strategy depends on sex differences in the shape of offspring fitness function rather than in fitness variance. Also, the slope of the tangent line (through the origin) to the offspring fitness function can be used to predict the preferred offspring sex. We also briefly discuss links between the model and the empirical research. This comprehensive reformulation of TWH will offer a thorough understanding of multi-element parental investment strategies beyond the classical TWH.
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2
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Díaz-Lora S, Pérez-Contreras T, Azcárate-García M, Peralta-Sánchez JM, Martínez-Bueno M, José Soler J, Martín-Vivaldi M. Cosmetic coloration of cross-fostered eggs affects paternal investment in the hoopoe ( Upupa epops). Proc Biol Sci 2021; 288:20203174. [PMID: 33947236 PMCID: PMC8097196 DOI: 10.1098/rspb.2020.3174] [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: 12/22/2020] [Accepted: 04/06/2021] [Indexed: 11/12/2022] Open
Abstract
The signalling hypothesis suggests that avian eggshell coloration is a sexually selected female signal advertising her quality to its male partner, thereby stimulating his provisioning rate. This hypothesis has been tested for structural eggshell pigments, but not for cosmetic colorations, such as that produced by the uropygial secretion on eggshells. During the breeding season, female hoopoes (Upupa epops) host in their uropygial glands symbiotic bacteria. Females actively smear the eggshells with their secretion, protecting embryos from pathogenic trans-shell infections and changing eggshell coloration. Because the colour of the secretions is related to their antimicrobial potential, cosmetic eggshell coloration may act as a cue or even as a post-mating sexually selected signal if it affects male provisioning rates. To experimentally test this hypothesis, we cross-fostered already-smeared clutches between hoopoe nests, and quantified male feeding behaviour to females before and after the experiment. This approach allows disentanglement of the effects of female quality and of egg coloration on male investment. In accordance with the hypothesis, males adjusted their provisioning rate to the eggshell cosmetic coloration. This is, to our knowledge, the first experimental demonstration that egg colour stained with uropygial secretion could act as a post-mating sexual signal of female quality to males.
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Affiliation(s)
- Silvia Díaz-Lora
- Departamento de Zoología, Facultad de Ciencias, Universidad de Granada (UGR), Granada, Spain
| | - Tomás Pérez-Contreras
- Departamento de Zoología, Facultad de Ciencias, Universidad de Granada (UGR), Granada, Spain
- Unidad asociada: Coevolución: cucos, hospedadores y bacterias simbiontes, Universidad de Granada (UGR), Granada, Spain
| | - Manuel Azcárate-García
- Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas (EEZA-CSIC), Almería, Spain
| | | | - Manuel Martínez-Bueno
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada (UGR), Granada, Spain
- Unidad asociada: Coevolución: cucos, hospedadores y bacterias simbiontes, Universidad de Granada (UGR), Granada, Spain
| | - Juan José Soler
- Unidad asociada: Coevolución: cucos, hospedadores y bacterias simbiontes, Universidad de Granada (UGR), Granada, Spain
- Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas (EEZA-CSIC), Almería, Spain
| | - Manuel Martín-Vivaldi
- Departamento de Zoología, Facultad de Ciencias, Universidad de Granada (UGR), Granada, Spain
- Unidad asociada: Coevolución: cucos, hospedadores y bacterias simbiontes, Universidad de Granada (UGR), Granada, Spain
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3
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Eyolfson E, Bhatt D, Wang M, Lohman AW, Mychasiuk R. Paternal exposure to exercise and/or caffeine and alcohol modify offspring behavioral and pathophysiological recovery from repetitive mild traumatic brain injury in adolescence. GENES, BRAIN, AND BEHAVIOR 2021; 20:egbb12736. [PMID: 33876557 DOI: 10.1111/gbb.12736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 04/16/2021] [Accepted: 04/17/2021] [Indexed: 11/30/2022]
Abstract
Only recently has the scope of parental research expanded to include the paternal sphere with epidemiological studies implicating stress, nutrition and alcohol consumption in the neurobiological and behavioral characteristics of offspring. This study was designed to determine if paternal exposure to caffeine, alcohol and exercise prior to conception would improve or exacerbate offspring recovery from adolescent repetitive mild traumatic brain injury (RmTBI). Sires received 7 weeks of standard drinking water, or caffeine and ethanol and were housed in regular cages or cages with running wheels, prior to being mated to control females. At postnatal day 40, offspring were administered RmTBI or sham injuries and were assessed for post concussive symptomology. Post-mortem quantitative real-time polymerase chain reaction (qRT-PCR) was used to assess gene expression in the prefrontal cortex (PFC), nucleus accumbens (NAc) and changes in telomere length. Additionally, enzyme-linked immunosorbent assay (ELISA's) were run on serum to detect levels of cytokines, chemokines and sex hormones. Paternal experience did not improve or exacerbate RmTBI behavioral outcomes. However, female and male offspring displayed unique responses to RmTBI and paternal experience, resulting in changes in physical, behavioral and molecular outcomes. Injury and paternal exercise modified changes in female offspring, whereas male offspring were affected by paternal exercise, caffeine and alcohol treatment. Additionally, paternal experience and RmTBI modified expression of many genes in the PFC, NAc, telomere length and levels of sex hormones. Although further exploration is required to understand the heterogeneity that exists in disease risk and resiliency, this study provides corroborating evidence that paternal experiences prior to conception influences offspring development.
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Affiliation(s)
- Eric Eyolfson
- Department of Psychology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
| | - Dhyey Bhatt
- Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
- Department of Cell Biology and Anatomy, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Melinda Wang
- Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
| | - Alexander W Lohman
- Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
- Department of Cell Biology and Anatomy, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Richelle Mychasiuk
- Department of Psychology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Calgary, Alberta, Canada
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, Victoria, Australia
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4
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Araya‐Ajoy YG, Westneat DF, Wright J. Pathways to social evolution and their evolutionary feedbacks. Evolution 2020; 74:1894-1907. [DOI: 10.1111/evo.14054] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Revised: 05/23/2020] [Accepted: 06/27/2020] [Indexed: 02/03/2023]
Affiliation(s)
- Yimen G. Araya‐Ajoy
- Centre for Biodiversity Dynamics (CBD), Department of Biology Norwegian University of Science and Technology (NTNU) Trondheim N‐7491 Norway
| | - David F. Westneat
- Department of Biology, 101 Morgan Building University of Kentucky Lexington KY 40506‐0225 USA
| | - Jonathan Wright
- Centre for Biodiversity Dynamics (CBD), Department of Biology Norwegian University of Science and Technology (NTNU) Trondheim N‐7491 Norway
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5
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Paquet M, Parenteau C, Ford LE, Ratz T, Richardson J, Angelier F, Smiseth PT. Females adjust maternal hormone concentration in eggs according to male condition in a burying beetle. Horm Behav 2020; 121:104708. [PMID: 32004551 DOI: 10.1016/j.yhbeh.2020.104708] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 12/10/2019] [Accepted: 01/25/2020] [Indexed: 11/21/2022]
Abstract
In birds and other vertebrates, there is good evidence that females adjust the allocation of hormones in their eggs in response to prenatal environmental conditions, such as food availability or male phenotype, with profound consequences for life history traits of offspring. In insects, there is also evidence that females deposit juvenile hormones (JH) and ecdysteroids (ESH) in their eggs, hormones that play a key role in regulating offspring growth and metamorphosis. However, it is unclear whether females adjust their hormonal deposition in eggs in response to prenatal environmental conditions. Here we address this gap by conducting an experiment on the burying beetle Nicrophorus vespilloides, in which we manipulated the presence of the male parent and the size of the carcass used for breeding at the time of laying. We also tested for effects of the condition (i.e., body mass) of the parents. We then recorded subsequent effects on JH and ESH concentrations in the eggs. We found no evidence for an effect of these prenatal environmental conditions (male presence and carcass size) on hormonal concentration in the eggs. However, we found that females reduced their deposition of JH when mated with heavier males. This finding is consistent with negative differential allocation of maternal hormones in response to variation in the body mass of the male parent. We encourage further work to investigate the role of maternally derived hormones in insect eggs.
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Affiliation(s)
- Matthieu Paquet
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK; Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-75007 Uppsala, Sweden.
| | - Charline Parenteau
- Centre d'Etudes Biologiques de Chizé, Centre National de la Recherche Scientifique- La Rochelle Université, UMR 7372, F-79360 Villiers en Bois, France
| | - Lucy E Ford
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK
| | - Tom Ratz
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK
| | - Jon Richardson
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK
| | - Frédéric Angelier
- Centre d'Etudes Biologiques de Chizé, Centre National de la Recherche Scientifique- La Rochelle Université, UMR 7372, F-79360 Villiers en Bois, France
| | - Per T Smiseth
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK
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Li MY, Geng ZS, Liao P, Wang XY, Yang TC, Wang JY, Wang DD, Gao LF, Du B. Trial marriage model-Female mate choice under male interference. J Anim Ecol 2020; 89:1851-1859. [PMID: 32329064 DOI: 10.1111/1365-2656.13240] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 04/14/2020] [Indexed: 11/28/2022]
Abstract
In sexually reproducing animals, the process of mate choice by females is often mixed with the process of male-male competition. Current models of female male choice focus mainly on how females identify the higher quality of males, but neglect the effect of male-male competition on the mate choice of females. Therefore, it remains controversial what is the relative importance of two processes in forming a social bond. We propose a new 'trial marriage' model for females' mate choice. The model assumes that females unconditionally accept any male they first encounter as their mating partner, and then conditionally switch mates to a new male of higher quality than their current partner when male-male competition occurs. This model was tested in the green weevil Hypomeces squamosus by exploring how females switched mates when males' mating interference was experimentally induced. The likelihood that females switched mates, as well as their conditional acceptance criteria of a new mate, was both raised with the intensity of males' mating interference that was manipulated in an enhanced encounter rate experiment, and in male introduction or stepwise removal experiments. These experimental findings confirm that a 'trial marriage' strategy occurs during females' mate choice. Compared with other strategies, it is more beneficial for females to choose a better mate without paying the costs of identifying males as suggested by the 'trial marriage' strategy. More importantly, using the current partner quality as the conditional acceptance threshold of new mates, females can choose better males in future encounters with potential mates. In the green weevils, males' preference for larger females and the higher possibility of the largest male winning an interference are mixed together when males' mating interference reaches a higher intensity. Therefore, the consequence of a male interference will determine which male could be chosen by a female. Under this condition, conditional acceptance of the winner becomes the most beneficial strategy of females in choosing their mates. We thus suggest that the 'trial marriage' strategy would be more efficient when males' mating interference becomes the determinant factor of females' mate choice.
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Affiliation(s)
- Meng-Yao Li
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
| | - Zhuo-Song Geng
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
| | - Peng Liao
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
| | - Xiao-Yang Wang
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
| | - Tian-Chang Yang
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
| | - Jing-Yuan Wang
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
| | - Dan-Dan Wang
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
| | - Li-Fang Gao
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
| | - Bo Du
- School of Life Sciences, Lanzhou University, Lanzhou City, Gansu Province, China
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7
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Stahlschmidt ZR, Chu I, Koh C. When do looks matter? Effects of mate quality and environmental variability on lifetime reproduction. Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-019-2790-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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8
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Pettitt BA, Bourne GR, Bee MA. Females prefer the calls of better fathers in a Neotropical frog with biparental care. Behav Ecol 2019. [DOI: 10.1093/beheco/arz172] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AbstractMale secondary sexual traits potentially function as indicators of direct or indirect fitness benefits to females. Direct benefits, such as paternal care, may be especially important to females in species with biparental care. In an experimental field study of the golden rocket frog (Anomaloglossus beebei), a Neotropical species with biparental care, we tested predictions from four hypotheses proposed to explain the evolutionary relationship between male secondary sexual traits and paternal care quality (the “good parent,” “differential allocation,” “trade-off,” and “essential male care” hypotheses). We examined: 1) the influence of paternal care on offspring survival, 2) the relationships between male calls and paternal care, maternal care, and opportunities for males to acquire multiple mates, and 3) female preferences for three acoustic properties of male advertisement calls. Our results reveal that paternal care positively impacts offspring survival, that males producing longer calls also provide higher-quality paternal care in the form of greater egg attendance and territory defense, and that females prefer longer calls. Females did not discriminate among potential mates based on differences in dominant frequency or call rate. These findings, which suggest male advertisement calls are indicators of potential direct benefits to females in the form of paternal care, are consistent with the good parent hypothesis and inconsistent with the trade-off, differential allocation, and essential male care hypotheses.
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Affiliation(s)
- Beth A Pettitt
- Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, MN 55108, USA
| | - Godfrey R Bourne
- Department of Biology, University of Missouri – St. Louis, St. Louis, MO 63121, USA
- CEIBA Biological Center, Linden Highway, Madewini, Guyana
| | - Mark A Bee
- Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, MN 55108, USA
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
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9
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Abstract
In many species that form pair bonds, males display to their mate after pair formation. These displays elevate the female's investment into the brood. This is a form of cooperation because without the display, female investment is reduced to levels that are suboptimal for both sexes. The presence of such displays is paradoxical as in their absence the male should be able to invest extra resources directly into offspring, to the benefit of both sexes. We consider that the origin of these displays lies in the exploitation of preexisting perceptual biases which increase female investment beyond that which is optimal for her, initially resulting in a sexual conflict. We use a combined population genetic and quantitative genetic model to show how this conflict becomes resolved into sexual cooperation. A cooperative outcome is most likely when perceptual biases are under selection pressures in other contexts (e.g., detection of predators, prey, or conspecifics), but this is not required. Cooperation between pair members can regularly evolve even when this provides no net advantage to the pair and when the display itself reduces a male's contributions to raising the brood. The findings account for many interactions between the sexes that have been difficult to explain in the context of sexual selection.
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10
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Champagne FA. Interplay between paternal germline and maternal effects in shaping development: The overlooked importance of behavioural ecology. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13411] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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11
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Wilson KM, Walker SE. Age at mating and male quality influence female patterns of reproductive investment and survival. Ecol Evol 2019; 9:5440-5449. [PMID: 31110692 PMCID: PMC6509372 DOI: 10.1002/ece3.5137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 02/06/2019] [Accepted: 03/15/2019] [Indexed: 01/28/2023] Open
Abstract
The trade-off between the allocation of resources toward somatic maintenance or reproduction is one of the fundamentals of life history theory and predicts that females invest in offspring at the expense of their longevity or vice versa. Mate quality may also affect life history trade-offs through mechanisms of sexual conflict; however, few studies have examined the interaction between mate quality and age at first mating in reproductive decisions. Using house crickets (Acheta domesticus), this study examines how survival and reproductive trade-offs change based on females' age at first reproduction and exposure to males of varying size. Females were exposed to either a large (presumably high-quality) or small male at an early (young), middle (intermediate), or advanced (old) age, and longevity and reproductive investment were subsequently tracked. Females mated at a young age had the largest number of eggs but the shortest total lifespans while females mated at older ages produced fewer eggs but had longer total lifespans. The trade-off between age at first mating and eggs laid appears to be mediated through higher egg-laying rates and shorter postmating lifespans in females mated later in life. Exposure to small males resulted in shorter lifespans and higher egg-laying rates for all females indicating that male manipulation of females, presumably through spermatophore contents, varies with male size in this species. Together, these data strongly support a trade-off between age at first reproduction and lifespan and support the role of sexual conflict in shaping patterns of reproduction.
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Affiliation(s)
- Kerianne M. Wilson
- Department of Ecology and Evolutionary BiologyUniversity of CaliforniaIrvineCalifornia
| | - Sean E. Walker
- Department of Biological SciencesCalifornia State UniversityFullertonCalifornia
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12
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Males can evolve lower resistance to sexually transmitted infections to infect their mates and thereby increase their own fitness. Evol Ecol 2019. [DOI: 10.1007/s10682-019-09976-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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13
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Robart AR, Sinervo B. Females increase parental care, but not fecundity, when mated to high-quality males in a biparental fish. Anim Behav 2019. [DOI: 10.1016/j.anbehav.2018.11.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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14
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Ratikainen II, Haaland TR, Wright J. Differential allocation of parental investment and the trade-off between size and number of offspring. Proc Biol Sci 2018; 285:20181074. [PMID: 30068679 PMCID: PMC6111174 DOI: 10.1098/rspb.2018.1074] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 07/09/2018] [Indexed: 02/06/2023] Open
Abstract
When parents decide how much to invest in current versus future offspring and how many offspring to divide their current investments between, the optimal decision can be affected by the quality of their partner. This differential allocation (DA) is highly dependent on exactly how partner quality affects reproductive costs and offspring benefits. We present a stochastic dynamic model of DA in which females care for a series of clutches when mated with males of different quality. In each reproductive event, females choose the size and number of offspring. We find that if partner quality affects reproductive costs, then DA in total reproductive investment occurs only via changes in the number of offspring. DA in the optimal size of the offspring occurs only if partner quality affects the offspring benefit function. This is mostly in the form of greater female investment per offspring as male quality decreases. Simultaneously, we find that adaptive DA increases the number of offspring, and thus the amount of total investment, as male quality increases. Only certain model scenarios produce the positive DA in offspring size seen in empirical studies, providing a predictive framework for DA and how partner quality affects reproductive costs and offspring benefits.
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Affiliation(s)
- Irja Ida Ratikainen
- Department of Biology, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim, Norway
| | - Thomas Ray Haaland
- Department of Biology, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim, Norway
| | - Jonathan Wright
- Department of Biology, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim, Norway
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15
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Henshaw JM, Jennions MD, Kruuk LEB. How to quantify (the response to) sexual selection on traits. Evolution 2018; 72:1904-1917. [PMID: 30004126 DOI: 10.1111/evo.13554] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Revised: 06/16/2018] [Accepted: 07/07/2018] [Indexed: 01/01/2023]
Abstract
Natural selection operates via fitness components like mating success, fecundity, and longevity, which can be understood as intermediaries in the causal process linking traits to fitness. In particular, sexual selection occurs when traits influence mating or fertilization success, which, in turn, influences fitness. We show how to quantify both these steps in a single path analysis, leading to better estimates of the strength of sexual selection. Our model controls for confounding variables, such as body size or condition, when estimating the relationship between mating and reproductive success. Correspondingly, we define the Bateman gradient and the Jones index using partial rather than simple regressions, which better captures how they are commonly interpreted. The model can be applied both to purely phenotypic data and to quantitative genetic parameters estimated using information on relatedness. The phenotypic approach breaks down selection differentials into a sexually selected and a "remainder" component. The quantitative genetic approach decomposes the estimated evolutionary response to selection analogously. We apply our method to analyze sexual selection in male dusky pipefish, Syngnathus floridae, and in two simulated datasets. We highlight conceptual and statistical limitations of previous path-based approaches, which can lead to substantial misestimation of sexual selection.
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Affiliation(s)
- Jonathan M Henshaw
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Acton, ACT 2601, Canberra, Australia.,Institute of Zoology, University of Graz, Universitätsplatz 2, Graz, 8010, Austria
| | - Michael D Jennions
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Acton, ACT 2601, Canberra, Australia
| | - Loeske E B Kruuk
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Acton, ACT 2601, Canberra, Australia
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