1
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Hegyi G, Laczi M, Szabó G, Sarkadi F, Török J. Plumage color degradation indicates reproductive effort: an experiment. Sci Rep 2023; 13:18770. [PMID: 37907494 PMCID: PMC10618437 DOI: 10.1038/s41598-023-45348-0] [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: 07/03/2023] [Accepted: 10/18/2023] [Indexed: 11/02/2023] Open
Abstract
Plumage color has traditionally been regarded as a static ornamental trait, but evidence is accumulating for significant color changes without molt that typically reduce the conspicuousness of ornamentation. In some species, the social partner seems to increase its reproductive investment if the color trait is experimentally enhanced, suggesting that color change could act as a signal. However, the information content of this signal is so far unclear. For example, birds in poor condition or making greater effort may deteriorate more severely. We used brood size manipulations to alter the reproductive effort of male and female collared flycatchers Ficedula albicollis. Both sexes showed less severe decline in some reflectance attribute of their white breast when their brood was experimentally reduced. In each sex, greater deterioration of the reflectance trait affected by the manipulation was accompanied by increased feeding rate by the partner. These feeding patterns do not prove, but are consistent with, a compensatory response by the partner to induced degradation. The manipulation effects on color change we detected confirm for the first time that plumage color deterioration can indicate current reproductive effort, thereby providing a potential fitness advantage to social partners that react to such deterioration.
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Affiliation(s)
- Gergely Hegyi
- Behavioral Ecology Group, Department of Systematic Zoology and Ecology, ELTE Eötvös Loránd University, 1117 Pázmány Péter sétány 1/C, Budapest, Hungary.
- HUN-REN-ELTE-MTM Integrative Ecology Research Group, 1117 Pázmány Péter sétány 1/C, Budapest, Hungary.
| | - Miklós Laczi
- Behavioral Ecology Group, Department of Systematic Zoology and Ecology, ELTE Eötvös Loránd University, 1117 Pázmány Péter sétány 1/C, Budapest, Hungary
- HUN-REN-ELTE-MTM Integrative Ecology Research Group, 1117 Pázmány Péter sétány 1/C, Budapest, Hungary
- Barn Owl Foundation, Temesvári út 8, 8744, Orosztony, Hungary
| | - Gyula Szabó
- Behavioral Ecology Group, Department of Systematic Zoology and Ecology, ELTE Eötvös Loránd University, 1117 Pázmány Péter sétány 1/C, Budapest, Hungary
| | - Fanni Sarkadi
- Behavioral Ecology Group, Department of Systematic Zoology and Ecology, ELTE Eötvös Loránd University, 1117 Pázmány Péter sétány 1/C, Budapest, Hungary
| | - János Török
- Behavioral Ecology Group, Department of Systematic Zoology and Ecology, ELTE Eötvös Loránd University, 1117 Pázmány Péter sétány 1/C, Budapest, Hungary
- HUN-REN-ELTE-MTM Integrative Ecology Research Group, 1117 Pázmány Péter sétány 1/C, Budapest, Hungary
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2
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Sawada A, Iwasaki T, Akatani K, Takagi M. Mate choice for body size leads to size assortative mating in the Ryukyu Scops Owl Otus elegans. Ecol Evol 2022; 12:e9578. [PMCID: PMC9745103 DOI: 10.1002/ece3.9578] [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: 07/19/2022] [Revised: 11/16/2022] [Accepted: 11/18/2022] [Indexed: 12/15/2022] Open
Abstract
Understanding evolutionary phenomena that involve size assortative mating requires elucidating the generating mechanisms on which assortment is based. Although various mechanisms have been suggested, their relative importance may differ across taxonomic groups. Males selecting for large, fecund females combined with the dominance of large males in the competition for females has been suggested as a major mechanism in specific groups. However, raptors do not appear to conform to this, because the selection for smallness among males (assumed in a theory of reversed sexual size dimorphism) and the selection for largeness among males (assumed in the theory of size assortative mating) are in opposite directions. We studied the assortative mating during a long‐term study of the Ryukyu Scops Owls Otus elegans interpositus. Significant assortative mating was found for culmen length (from the base to the tip of the bill) and wing length (from the bend of the wing to the tip of the longest primary). Statistical control of the spatial and temporal accessibility of potential mates did not affect the assortment. Males with short wings had slightly higher fitness components than those with long wings, and females settling early tended to have small wings. Considering that early‐settling females can preferentially choose their mates, these results suggest that smaller females have an advantage when choosing smaller males with good reproductive performance. Improved flying and hunting ability of smaller individuals may be the background of choosing smaller individuals. We propose that, not passive process like similarity between individuals and their potential mates, but active mate choice for small individuals is an explanation for the assortative mating in this owl.
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Affiliation(s)
- Akira Sawada
- Biodiversity DivisionNational Institute for Environmental StudiesTsukubaJapan
| | - Tetsuya Iwasaki
- Department of Biology and Geosciences, Graduate School of ScienceOsaka City UniversityOsakaJapan
| | - Kana Akatani
- Department of Biology and Geosciences, Graduate School of ScienceOsaka City UniversityOsakaJapan
| | - Masaoki Takagi
- Department of Natural History Science, Graduate School of ScienceHokkaido UniversitySapporoJapan
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3
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Gulotta NA, Mathot KJ. Does fluctuating selection maintain variation in nest defense behavior in Arctic peregrine falcons ( Falco peregrinus tundrius)? Ecol Evol 2022; 12:e9284. [PMID: 36177133 PMCID: PMC9471043 DOI: 10.1002/ece3.9284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 08/04/2022] [Accepted: 08/17/2022] [Indexed: 11/10/2022] Open
Abstract
Behavioral expression can vary both within- (i.e., plasticity) and among-individuals (i.e., animal personality), and understanding the causes and consequences of variation at each of these levels is a major area of investigation in contemporary behavioral ecology. Here, we studied sources of variation in both plasticity and personality in nest defense behavior in Arctic peregrine falcons (Falco peregrinus tundrius) in two consecutive years. We found that peregrines adjusted their nest defense in response to nesting stage and year, revealing plastic, state-dependent, adjustment of nest defense. At the same time, nest defense behavior was repeatable in peregrine falcons both within and between years. We tested if fluctuating selection on behavioral types (i.e., individuals average phenotypic expression) and/or assortative mating acted to maintain long-term among-individual differences in nest defense behavior. We found that selection on female nest defense differed across years; being positive in 1 year and negative in the other. We also found support for assortative mating in the first year, but disassortative mating in the second. We propose two potential explanations for the observed year-specific patterns of nonrandom mating: (1) year-specific plastic adjustment of nest defense and/or (2) changes in the age-structure of the breeding population. These posthoc explanations are speculative, and require further study. Unfortunately, we could not evaluate this directly with the available data, and future studies are needed with more than 2 years of data on nest-defense and fitness outcomes, and with a larger number of marked individuals, to properly evaluate these potential explanations.
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Affiliation(s)
- Nick A Gulotta
- Department of Biological Sciences University of Alberta Edmonton Alberta Canada.,Nunavut Wildlife Cooperative Research Unit University of Alberta Edmonton Alberta Canada.,Present address: Warnell School of Forestry and Natural Resources University of Georgia Athens Georgia USA
| | - Kimberley J Mathot
- Department of Biological Sciences University of Alberta Edmonton Alberta Canada.,Nunavut Wildlife Cooperative Research Unit University of Alberta Edmonton Alberta Canada
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4
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Class B, Dingemanse NJ. A variance partitioning perspective of assortative mating: Proximate mechanisms and evolutionary implications. J Evol Biol 2022; 35:483-490. [PMID: 35304800 DOI: 10.1111/jeb.13998] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 02/28/2022] [Accepted: 03/03/2022] [Indexed: 12/20/2022]
Abstract
Assortative mating occurs when paired individuals of the same population are more similar than expected by chance. This form of non-random assortment has long been predicted to play a role in many evolutionary processes because assortatively mated individuals are assumed to be genetically similar. However, this assumption may always hold for labile traits, or traits that are measured with error. For such traits, there is a variety of proximate mechanisms that can drive phenotypic resemblance between mated partners that, notably, have very different evolutionary repercussions. Bettering our understanding of the role of assortative mating in evolution will thus require insight into its proximate causes. To date, empirical research remains sparse, especially when for labile traits. This special issue aims to stimulate such research while promoting the usage and development of statistical approaches allowing the quantification of the relative roles of alternative proximate mechanisms causing assortative mating. To this end, we first describe how the phenotypic covariance between mated partners can be usefully partitioned into components that capture one or several of five distinct mechanisms. We then demonstrate why the importance of mechanisms causing genetic covariance between the traits of partners may often be overestimated. Finally, we detail how the evolutionary causes and consequences of the diverse mechanisms may be identified.
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Affiliation(s)
- Barbara Class
- Global Change Ecology Research Group, University of the Sunshine Coast, Sippy Downs, Australia
| | - Niels J Dingemanse
- Behavioural Ecology, Department of Biology, Ludwig Maximilians University of Munich, Sippy Downs, Germany
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5
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Versluys TMM, Flintham EO, Mas-Sandoval A, Savolainen V. Why do we pick similar mates, or do we? Biol Lett 2021; 17:20210463. [PMID: 34813721 DOI: 10.1098/rsbl.2021.0463] [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] [Indexed: 12/12/2022] Open
Abstract
Humans often mate with those resembling themselves, a phenomenon described as positive assortative mating (PAM). The causes of this attract broad interest, but there is little agreement on the topic. This may be because empirical studies and reviews sometimes focus on just a few explanations, often based on disciplinary conventions. This review presents an interdisciplinary conceptual framework on the causes of PAM in humans, drawing on human and non-human biology, the social sciences, and the humanities. Viewing causality holistically, we first discuss the proximate causes (i.e. the 'how') of PAM, considering three mechanisms: stratification, convergence and mate choice. We also outline methods to control for confounders when studying mate choice. We then discuss ultimate explanations (i.e. 'the why') for PAM, including adaptive and non-adaptive processes. We conclude by suggesting a focus on interdisciplinarity in future research.
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Affiliation(s)
- Thomas M M Versluys
- Georgina Mace Centre for the Living Planet, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, United Kingdom
| | - Ewan O Flintham
- Georgina Mace Centre for the Living Planet, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, United Kingdom
| | - Alex Mas-Sandoval
- Georgina Mace Centre for the Living Planet, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, United Kingdom
| | - Vincent Savolainen
- Georgina Mace Centre for the Living Planet, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, United Kingdom
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6
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Tamin T, Doligez B. Assortative mating for between-patch dispersal status in a wild bird population: Exploring the role of direct and indirect underlying mechanisms. J Evol Biol 2021; 35:561-574. [PMID: 34480809 DOI: 10.1111/jeb.13925] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 07/15/2021] [Accepted: 07/30/2021] [Indexed: 11/26/2022]
Abstract
Previous studies have reported functional integration between dispersal and other phenotypic traits allowing individuals to alleviate dispersal costs, and such associations can affect dispersal evolution in return. In sexually reproducing species, assortative mating according to dispersal can shape the maintenance of such trait associations. Despite the potentially crucial consequences of dispersal in natural populations, assortative mating for dispersal and its underlying mechanisms remain largely unexplored. Here, we assessed assortative mating for between-patch dispersal status in a fragmented population of a small passerine bird, the collared flycatcher, and explored whether such assortative mating could result from (i) direct mate choice based on dispersal-related behavioural (aggressiveness and boldness) and morphological traits (tarsus and wing length), (ii) biased mating due to spatio-temporal heterogeneity in the distribution of dispersal phenotypes and/or (iii) post-mating adjustment of dispersal phenotype or dispersal-related traits. We found intrinsic assortative mating (i.e. positive among-pair correlation) for current dispersal status (in the year of mating) but not for natal dispersal status, even though we could not exclude it due to limited power. We also found assortative mating for boldness and age category (yearlings vs. older adults), and the probability for pair members to be assorted for current dispersal status was higher when both pair members were of similar boldness score and of the same age compared with mixed-age pairs. Mate choice based on boldness and age thus appears as a possible mechanism underlying assortative mating for dispersal status. Our analyses however remained correlative, and only an experimental manipulation of these traits could allow inferring causal links. Non-random mating for dispersal-related traits may affect the evolution of dispersal syndromes in this population. More work is nevertheless needed to fully assess the evolutionary implications of age- and behaviour-based assortative mating for dispersal.
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Affiliation(s)
- Thibault Tamin
- Laboratoire de Biométrie et Biologie Evolutive, Université Lyon 1, UMR 5558, CNRS, Université de Lyon, Villeurbanne, France
| | - Blandine Doligez
- Laboratoire de Biométrie et Biologie Evolutive, Université Lyon 1, UMR 5558, CNRS, Université de Lyon, Villeurbanne, France.,Department of Ecology and Genetics, Animal Ecology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
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7
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Holtmann B, Dingemanse NJ. Strong phenotypic trait correlations between mating partners do not result from assortative mating in wild great tits (Parus major). J Evol Biol 2021; 35:552-560. [PMID: 34327779 DOI: 10.1111/jeb.13908] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 07/10/2021] [Accepted: 07/15/2021] [Indexed: 11/28/2022]
Abstract
There is considerable debate about the occurrence of assortative mating between phenotypic traits measured within natural populations. Meta-analyses have implied that assortative mating occurs generally in natural populations, but recent work indicates these conclusions largely result from biased data. Specifically, estimates of phenotypic correlations between mating partners do not solely result from nonrandom associations between individual-level traits of partners but also from other biological processes (joint phenotypic plasticity, indirect genetic effects), methodological practices (observer bias) and other unexplained residual correlations (e.g. correlated measurement error). This paper puts this critique to test. First, we estimated the overall phenotypic correlation between phenotypic traits of mating partners for a wild population of great tits. Second, we estimated various key variance components to reveal the extent to which phenotypic correlations between partners resulted from assortative mating, reversible plasticity, social partner effects and methodological practices. We performed our analyses for a range of phenotypic traits (body mass, breathing rate, exploration behaviour, wing and tarsus length) to derive general conclusions not hinging on the specifics of the traits involved. Our analyses support the conclusion that patterns of assortative mating exist at first glance but occur because of the biasing effects of correlated residuals likely caused by a combination of phenotypic responses to unknown environmental factors or measurement error-not because of intrinsic patterns of assortative mating.
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Affiliation(s)
- Benedikt Holtmann
- Behavioural Ecology, Department of Biology, Ludwig-Maximilians-University of Munich, Planegg-Martinsried, Germany
| | - Niels J Dingemanse
- Behavioural Ecology, Department of Biology, Ludwig-Maximilians-University of Munich, Planegg-Martinsried, Germany
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8
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Rios Moura R, Oliveira Gonzaga M, Silva Pinto N, Vasconcellos-Neto J, Requena GS. Assortative mating in space and time: patterns and biases. Ecol Lett 2021; 24:1089-1102. [PMID: 33617134 DOI: 10.1111/ele.13690] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 12/16/2020] [Accepted: 12/21/2020] [Indexed: 01/08/2023]
Abstract
Despite the important roles of assortative mating for understanding evolutionary processes, our knowledge on the variation in assortative mating across populations and breeding periods has been overshadowed by the greater attention given to general patterns. Obtaining data on mating pairs are difficult for most species; therefore, researchers often group data from different populations or breeding periods, which can increase positive biases in detecting and estimating assortative mating. We used a meta-analytic approach to investigate the biases caused by spatially or temporally pooling data and the assortative mating consistency across populations and breeding periods. We describe assortative mating patterns across and within animal taxa. We performed a systematic review to search studies reporting measures of size-assortative mating (SAM). Grouping data from multiple populations and seasons incurred positive biases. Overall, assortative mating moderately exhibited low repeatability in space and time, but it was inconsistent for most taxa. After excluding pooled measures, the average estimate for assortative mating was moderate and positive. Thus, our findings demonstrate that pooling data can produce misleading results. We also highlight the importance of further investigation of hypotheses that explain spatial and temporal variation in assortative mating, after its detection. Our study reinforces the significance of investigating mating patterns at various spatial and temporal scales before drawing broad conclusions.
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Affiliation(s)
- Rafael Rios Moura
- Núcleo de Extensão e Pesquisa em Ecologia e Evolução (NEPEE), Departamento de Ciências Biológicas, Universidade do Estado de Minas Gerais, Ituiutaba, Minas Gerais, Brazil.,Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, Minas Gerais, Brazil
| | | | - Nelson Silva Pinto
- Coordenação do Núcleo de Extensão, Pesquisa e Pós-graduação, Departamento de Biologia, Centro Universitário Araguaia, Goiânia, Goiás, Brazil
| | - João Vasconcellos-Neto
- Departamento de Biologia Animal, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
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9
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Rabdeau J, Badenhausser I, Gaffard A, Mangelinck C, Moreau J, Bretagnolle V, Monceau K. Assortative pairing for boldness and consequences for reproductive success in Montagu’s harrier. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blaa233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Behavioural combination within pairs depending on personality and plasticity might influence reproductive success. However, studies testing this hypothesis are rare, especially in the case of monogamous species with bi-parental care in which the sexes exhibit different behavioural roles. In this study, we investigated the pairing patterns for both boldness and boldness plasticity in Montagu’s harriers (Circus pygargus), a species with sex-specific care, and the consequences for their reproductive success. We measured individual boldness and plasticity for both sexes, and we assessed the pairing pattern in the Montagu’s harrier population for these two traits. We calculated four indices to characterize the behavioural association within pairs: pair boldness, boldness similarity within pairs, pair plasticity and plasticity similarity within pairs. The relationship between the behaviour of the parents and the reproductive success was then tested through these four indices. We found a pattern of assortative pairing based on both boldness and plasticity in the Montagu’s harrier population. Within-pair similarity of plasticity had a significant effect on the reproductive success, which was higher for less similar pairs than for more similar pairs. Our results question the origin of this pairing pattern and suggest that ecological constraint and not sexual selection could be the major driver.
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Affiliation(s)
- Juliette Rabdeau
- UMR 7372, Centre d’Etudes Biologiques de Chizé, La Rochelle Université & CNRS, Villiers en Bois, France
| | - Isabelle Badenhausser
- INRAE, Unité de Recherche Pluridisciplinaire Prairies Plantes Fourragères, Lusignan, France
| | - Agathe Gaffard
- UMR 7372, Centre d’Etudes Biologiques de Chizé, La Rochelle Université & CNRS, Villiers en Bois, France
| | - Camille Mangelinck
- UMR 7372, Centre d’Etudes Biologiques de Chizé, La Rochelle Université & CNRS, Villiers en Bois, France
| | - Jérôme Moreau
- UMR 7372, Centre d’Etudes Biologiques de Chizé, La Rochelle Université & CNRS, Villiers en Bois, France
- UMR CNRS 6282 Biogéosciences, Équipe Écologie Évolutive, Université de Bourgogne-Franche-Comté, Dijon, France
| | - Vincent Bretagnolle
- UMR 7372, Centre d’Etudes Biologiques de Chizé, La Rochelle Université & CNRS, Villiers en Bois, France
- LTSER ‘Zone Atelier Plaine & Val de Sèvre’, CNRS, Villiers-en-Bois, France
| | - Karine Monceau
- UMR 7372, Centre d’Etudes Biologiques de Chizé, La Rochelle Université & CNRS, Villiers en Bois, France
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10
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Dingemanse NJ, Class B, Holtmann B. Nonrandom Mating for Behavior in the Wild? Trends Ecol Evol 2020; 36:177-179. [PMID: 33279252 DOI: 10.1016/j.tree.2020.11.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Revised: 11/10/2020] [Accepted: 11/13/2020] [Indexed: 12/17/2022]
Affiliation(s)
- Niels J Dingemanse
- Behavioural Ecology, Department of Biology, Ludwig Maximilians University of Munich, 82152 Planegg-Martinsried, Germany.
| | - Barbara Class
- Global Change Ecology Research Group, University of the Sunshine Coast, Sippy Downs, QLD, Australia
| | - Benedikt Holtmann
- Behavioural Ecology, Department of Biology, Ludwig Maximilians University of Munich, 82152 Planegg-Martinsried, Germany
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11
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Class B, Brommer JE. Shared environmental effects bias phenotypic estimates of assortative mating in a wild bird. Biol Lett 2019; 14:rsbl.2018.0106. [PMID: 29997185 DOI: 10.1098/rsbl.2018.0106] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 06/20/2018] [Indexed: 11/12/2022] Open
Abstract
Assortative mating is pervasive in wild populations and commonly described as a positive correlation between the phenotypes of males and females across mated pairs. This correlation is often assumed to reflect non-random mate choice based on phenotypic similarity. However, phenotypic resemblance between mates can also arise when their traits respond plastically to a shared environmental effect creating a (within-pair) residual correlation in traits. Using long-term data collected in pairs of wild blue tits and a covariance partitioning approach, we empirically demonstrate that such residual covariance indeed exists and can generate phenotypic correlations (or mask assortative mating) in behavioural and morphometric traits. These findings (i) imply that residual covariance is likely to be common and bias phenotypic estimates of assortative mating, which can have consequences for evolutionary predictions, (ii) call for the use of rigorous statistical approaches in the study of assortative mating, and (iii) show the applicability of one of these approaches in a common study system.
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Affiliation(s)
- Barbara Class
- Department of Biology, University of Turku, University Hill, 20014 Turku, Finland
| | - Jon E Brommer
- Department of Biology, University of Turku, University Hill, 20014 Turku, Finland.,NOVIA University of Applied Sciences, Campus Raseborg, 10600 Ekenäs, Finland
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12
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Wang D, Forstmeier W, Valcu M, Dingemanse NJ, Bulla M, Both C, Duckworth RA, Kiere LM, Karell P, Albrecht T, Kempenaers B. Scrutinizing assortative mating in birds. PLoS Biol 2019; 17:e3000156. [PMID: 30789896 PMCID: PMC6400405 DOI: 10.1371/journal.pbio.3000156] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 03/05/2019] [Accepted: 02/05/2019] [Indexed: 11/18/2022] Open
Abstract
It is often claimed that pair bonds preferentially form between individuals that resemble one another. Such assortative mating appears to be widespread throughout the animal kingdom. Yet it is unclear whether the apparent ubiquity of assortative mating arises primarily from mate choice (“like attracts like”), which can be constrained by same-sex competition for mates; from spatial or temporal separation; or from observer, reporting, publication, or search bias. Here, based on a conventional literature search, we find compelling meta-analytical evidence for size-assortative mating in birds (r = 0.178, 95% CI 0.142–0.215, 83 species, 35,591 pairs). However, our analyses reveal that this effect vanishes gradually with increased control of confounding factors. Specifically, the effect size decreased by 42% when we used previously unpublished data from nine long-term field studies, i.e., data free of reporting and publication bias (r = 0.103, 95% CI 0.074–0.132, eight species, 16,611 pairs). Moreover, in those data, assortative mating effectively disappeared when both partners were measured by independent observers or separately in space and time (mean r = 0.018, 95% CI −0.016–0.057). Likewise, we also found no evidence for assortative mating in a direct experimental test for mutual mate choice in captive populations of Zebra finches (r = −0.020, 95% CI −0.148–0.107, 1,414 pairs). These results highlight the importance of unpublished data in generating unbiased meta-analytical conclusions and suggest that the apparent ubiquity of assortative mating reported in the literature is overestimated and may not be driven by mate choice or mating competition for preferred mates. Human mate choice is characterized by assortative mating (‘like attracts like’) and similarity of partners is also often reported for birds. A meta-analysis of published and previously unpublished datasets shows that the reported assortative mating in birds may mostly reflect biases in estimation rather than mate choice. Research on mate choice in birds has attracted much attention, partly because many birds form monogamous pair bonds like humans do. Human mate choice is characterized by the phenomenon of “like attracts like,” meaning that partners resemble each other in multiple ways (“assortative mating”). Assortative mating is also frequently reported for birds, but it is unclear whether this in turn implies that birds also have preferences for a similar partner. Here, we show that a range of methodological issues may provide a simpler and more accurate explanation for the frequent observation of assortative mating in birds. First, studies that report assortative mating may achieve greater visibility than studies that yield no such finding. Hence, the scientific literature may be biased toward positive results. Second, in field studies, it is logistically impossible to measure all birds accurately and under standardized conditions. Hence, fluctuations in, for instance, environmental conditions may induce a spurious similarity between partners when these are measured together in space or time. After accounting for such methodological issues, we conclude that mate preferences for a similar partner may be less common than previously thought.
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Affiliation(s)
- Daiping Wang
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Wolfgang Forstmeier
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany
- * E-mail:
| | - Mihai Valcu
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Niels J. Dingemanse
- Behavioural Ecology, Department of Biology, Ludwig Maximilians University of Munich, Planegg-Martinsried, Germany
| | - Martin Bulla
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany
- NIOZ Royal Netherlands Institute for Sea Research, Department of Coastal Systems and Utrecht University, Den Burg, the Netherlands
- Department of Ecology, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká, Prague, Czech Republic
| | - Christiaan Both
- Conservation Ecology Group, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, the Netherlands
| | - Renée A. Duckworth
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Lynna Marie Kiere
- Center for the Study of Biodiversity and Conservation (CIByC), Autonomous University of the State of Morelos, Cuernavaca Morelos, Mexico
- Institute of Ecology, Department of Evolutionary Ecology, Universidad Nacional Autónoma de México, Mexico City, Distrito Federal, Mexico
| | - Patrik Karell
- Bioeconomy Research Team, Novia University of Applied Sciences, Raseborgsvägen, Ekenäs, Finland
| | - Tomáš Albrecht
- Institute of Vertebrate Biology of the Czech Academy of Sciences, Brno, and Faculty of Science, Charles University, Prague, Czech Republic
| | - Bart Kempenaers
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany
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