1
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Smithson CH, Duncan EJ, Sait SM, Bretman A. Sensory perception of rivals has trait-dependent effects on plasticity in Drosophila melanogaster. Behav Ecol 2024; 35:arae031. [PMID: 38680228 PMCID: PMC11053361 DOI: 10.1093/beheco/arae031] [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: 09/13/2023] [Revised: 03/05/2024] [Accepted: 04/23/2024] [Indexed: 05/01/2024] Open
Abstract
The social environment has myriad effects on individuals, altering reproduction, immune function, cognition, and aging. Phenotypic plasticity enables animals to respond to heterogeneous environments such as the social environment but requires that they assess those environments accurately. It has been suggested that combinations of sensory cues allow animals to respond rapidly and accurately to changeable environments, but it is unclear whether the same sensory inputs are required in all traits that respond to a particular environmental cue. Drosophila melanogaster males, in the presence of rival males, exhibit a consistent behavioral response by extending mating duration. However, exposure to a rival also results in a reduction in their lifespan, a phenomenon interpreted as a trade-off associated with sperm competition strategies. D. melanogaster perceive their rivals by using multiple sensory cues; interfering with at least two olfactory, auditory, or tactile cues eliminates the extension of mating duration. Here, we assessed whether these same cues were implicated in the lifespan reduction. Removal of combinations of auditory and olfactory cues removed the extended mating duration response to a rival, as previously found. However, we found that these manipulations did not alter the reduction in lifespan of males exposed to rivals or induce any changes in activity patterns, grooming, or male-male aggression. Therefore, our analysis suggests that lifespan reduction is not a cost associated with the behavioral responses to sperm competition. Moreover, this highlights the trait-specific nature of the mechanisms underlying plasticity in response to the same environmental conditions.
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Affiliation(s)
- Claire H Smithson
- School of Biology, Faculty of Biological Sciences, University of Leeds, Clarendon Road, Leeds, West Yorkshire, LS2 9JT, United Kingdom
| | - Elizabeth J Duncan
- School of Biology, Faculty of Biological Sciences, University of Leeds, Clarendon Road, Leeds, West Yorkshire, LS2 9JT, United Kingdom
| | - Steven M Sait
- School of Biology, Faculty of Biological Sciences, University of Leeds, Clarendon Road, Leeds, West Yorkshire, LS2 9JT, United Kingdom
| | - Amanda Bretman
- School of Biology, Faculty of Biological Sciences, University of Leeds, Clarendon Road, Leeds, West Yorkshire, LS2 9JT, United Kingdom
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2
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Playing to the crowd: Using Drosophila to dissect mechanisms underlying plastic male strategies in sperm competition games. ADVANCES IN THE STUDY OF BEHAVIOR 2023. [DOI: 10.1016/bs.asb.2022.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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3
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Corbel Q, Londoño-Nieto C, Carazo P. Does perception of female cues modulate male short-term fitness components in Drosophila melanogaster? Ecol Evol 2022; 12:e9287. [PMID: 36177144 PMCID: PMC9471061 DOI: 10.1002/ece3.9287] [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: 04/27/2022] [Revised: 08/08/2022] [Accepted: 08/18/2022] [Indexed: 11/28/2022] Open
Abstract
Phenotypic plasticity in reproductive behavior can be a strong driver of individual fitness. In species with high intra‐sexual competition, changes in socio‐sexual context can trigger quick adaptive plastic responses in males. In particular, a recent study in the vinegar fly (Drosophila melanogaster) shows that males derive net fitness benefits from being shortly exposed to female cues ahead of access to mating (termed sexual perception), but the underlying mechanisms of this phenomenon remain unknown. Here, we investigated the short‐term effects of female perception on male pre‐ and post‐copulatory components of reproductive performance: (a) mating success, (b) mating latency and duration, (c) sperm competitiveness, and (d) ejaculate effects on female receptivity and reproductive rate. We found that brief sexual perception increased mating duration, but had no effect on the other main pre‐ and post‐copulatory fitness proxies recorded. This suggests that perception of female cues may not yield net fitness benefits for males in the short‐term, but we discuss alternative explanations and future avenues of research.
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Affiliation(s)
- Quentin Corbel
- Ethology Lab, Ethology, Ecology and Evolution Group, Cavanilles Institute of Biodiversity and Evolutionary Biology University of Valencia Valencia Spain
| | - Claudia Londoño-Nieto
- Ethology Lab, Ethology, Ecology and Evolution Group, Cavanilles Institute of Biodiversity and Evolutionary Biology University of Valencia Valencia Spain
| | - Pau Carazo
- Ethology Lab, Ethology, Ecology and Evolution Group, Cavanilles Institute of Biodiversity and Evolutionary Biology University of Valencia Valencia Spain
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4
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Louâpre P, Muller K, Bettencourt-Amarante S, Thiery D, Moreau J. Sexual audience affects male's reproduction investment without consequences on reproductive outputs. INSECT SCIENCE 2022; 29:1170-1180. [PMID: 34897988 DOI: 10.1111/1744-7917.12990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 10/15/2021] [Accepted: 11/17/2021] [Indexed: 06/14/2023]
Abstract
Males evolved plastic strategies to respond to male-male competition and exhibit adaptive traits and behaviors maximizing their access to the females and limiting sperm competition. Mating behaviors allow males to express quick responses to current sexual audience, that is, the number of nearby conspecifics prone to mate. In contrast, physiological responses are frequently delayed because they are constrained by the time and resources having to be mobilized to produce and export sperm and associated products. This is especially critical in species for which males produce spermatophores. Here we investigated in what extend moth males (the tortricid moth Lobesia botrana) producing spermatophores exhibit plastic behavioral and physiological responses to different sexual audiences before and during mating and the consequences for their reproductive output. We found that males adjusted their mating behaviors and spermatophore size to a potentially elevated risk of sperm competition perceived before mating. In addition, males responded to the closed presence of females during mating by reducing their mating duration. Surprisingly, the various behavioral and physiological responses we highlighted here were not fully reflected in their reproductive performance as we did not reveal any effect on fecundity and fertility of their mate. The selective pressure exerted on males experiencing male-male competition could thus be sufficient to trigger adjustment in male mating behaviors but constrains physiological responses according to the perception of competition.
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Affiliation(s)
- Philippe Louâpre
- UMR CNRS 6282 Biogeosciences, Université Bourgogne Franche-Comté, Dijon, France
| | - Karen Muller
- UMR CNRS 6282 Biogeosciences, Université Bourgogne Franche-Comté, Dijon, France
| | | | - Denis Thiery
- INRA UMR 1065 Santé et Agroecologie du Vignoble, Institut des Science de la Vigne et du Vin, Villenave d'Ornon, Cedex, France
- INRA UMR 1065, Save, Université de Bordeaux, Bordeaux Sciences Agro, Villenave d'Ornon, Cedex, France
| | - Jérôme Moreau
- UMR CNRS 6282 Biogeosciences, Université Bourgogne Franche-Comté, Dijon, France
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5
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Corbel Q, Serra M, García-Roa R, Carazo P. Male adaptive plasticity can explain the evolution of sexual perception costs. Am Nat 2022; 200:E110-E123. [DOI: 10.1086/720404] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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6
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Lymbery SJ, Tomkins JL, Buzatto BA, Hosken DJ. Kin-mediated plasticity in alternative reproductive tactics. Proc Biol Sci 2021; 288:20211069. [PMID: 34344179 PMCID: PMC8334832 DOI: 10.1098/rspb.2021.1069] [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] [Received: 05/07/2021] [Accepted: 07/12/2021] [Indexed: 11/12/2022] Open
Abstract
Conditional strategies occur when the relative fitness pay-off from expressing a given phenotype is contingent upon environmental circumstances. This conditional strategy model underlies cases of alternative reproductive tactics, in which individuals of one sex employ different means to obtain reproduction. How kin structure affects the expression of alternative reproductive tactics remains unexplored. We address this using the mite Rhizoglyphus echinopus, in which large males develop into aggressive 'fighters' and small males develop into non-aggressive 'scramblers.' Because only fighters kill their rivals, they should incur a greater indirect fitness cost when competing with their relatives, and thus fighter expression could be reduced in the presence of relatives. We raised mites in full-sibling or mixed-sibship groups and found that fighters were more common at higher body weights in full-sibling groups, not less common as we predicted (small individuals were almost exclusively scramblers in both treatments). This result could be explained if relatedness and cue variability are interpreted signals of population density, since fighters are more common at low densities in this species. Alternatively, our results may indicate that males compete more intensely with relatives in this species. We provide the first evidence of kin-mediated plasticity in the expression of alternative reproductive tactics.
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Affiliation(s)
- Samuel J. Lymbery
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn TR10 9EZ, Cornwall, UK
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley 6009, Western Australia, Australia
| | - Joseph L. Tomkins
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley 6009, Western Australia, Australia
| | - Bruno A. Buzatto
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley 6009, Western Australia, Australia
- Department of Biological Sciences (E8C 209), Macquarie University, Sydney 2109, New South Wales, Australia
| | - David J. Hosken
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn TR10 9EZ, Cornwall, UK
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7
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Bhaisare LY, Paraste S, Kaushik S, Chaudhary DD, Al-Misned F, Mahboob S, Al-Ghanim K, Ansari MJ. Reproductive success in Zygogramma bicolorata: A role of post-insemination association of male and female. Saudi J Biol Sci 2021; 28:1539-1543. [PMID: 33732037 PMCID: PMC7938115 DOI: 10.1016/j.sjbs.2020.12.030] [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: 11/16/2020] [Revised: 12/15/2020] [Accepted: 12/16/2020] [Indexed: 11/28/2022] Open
Abstract
Reproductive success is attained by various mechanisms in insects. Prolonged post insemination association is one such mechanism to increase the reproductive success. The present study was conducted to assess the role of post insemination association of mating partners on reproductive performance in Chrysomelidae beetle, Zygogramma bicolorata Pallister. The matings were disrupted at different time intervals and fecundity and percent egg viability of the females were recorded. In addition, the mounting attempts, mating attempts, time to commencement of mating and latent period were also recorded. It was hypothesized that: (1) the mounting and mating attempts would not exist, (2) copulation duration, would not affect the reproductive performance, and (3) the beetle would not exhibit the mate guarding behaviour. Interestingly, results revealed that 6.00 ± 1.3 and 6.59 ± 0.93 mounting and mating attempts are needed to establish successful mating. The results revealed that males improved their percent egg viability with a mating duration ranging from nearly 30-50 min. While fecundity increased with a mating duration of above 30 min and up to a duration of 60 min. This result concluded that males of this beetle display post copulatory mate guarding behaviour after 60 min in which male rides on female's back with his aedeagus inserted in the female genital tract.
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Affiliation(s)
- Lankesh Yashwant Bhaisare
- Behavioural & Molecular Ecology & Biocontrol Research Laboratory, Department of Zoology, Indira Gandhi National Tribal University, Amarkantak, Madhya Pradesh 484887, India
| | - Sweta Paraste
- Behavioural & Molecular Ecology & Biocontrol Research Laboratory, Department of Zoology, Indira Gandhi National Tribal University, Amarkantak, Madhya Pradesh 484887, India
| | - Sandeep Kaushik
- Department of Environmental Science, Indira Gandhi National Tribal University, Amarkantak, Madhya Pradesh 484887, India
| | - Desh Deepak Chaudhary
- Behavioural & Molecular Ecology & Biocontrol Research Laboratory, Department of Zoology, Indira Gandhi National Tribal University, Amarkantak, Madhya Pradesh 484887, India
| | - Fahad Al-Misned
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Shahid Mahboob
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Khalid Al-Ghanim
- Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Mohammad Javed Ansari
- Department of Botany, Hindu College Moradabad (Mahatma Jyotiba Phule Rohilkhand University Bareilly), India
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8
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Liu J, Zhang Y, Zheng X, He XZ, Wang Q. Combined cues of male competition influence spermatozoal investment in a moth. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13554] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Junyan Liu
- School of Agriculture and Environment Massey University Palmerston North New Zealand
| | - Yujing Zhang
- Guangxi Key Laboratory of Agric‐Environment and Agric‐Products Safety National Demonstration Center for Experimental Plant Science Education College of Agriculture Guangxi University Nanning China
| | - Xia‐Lin Zheng
- Guangxi Key Laboratory of Agric‐Environment and Agric‐Products Safety National Demonstration Center for Experimental Plant Science Education College of Agriculture Guangxi University Nanning China
| | - Xiong Z. He
- School of Agriculture and Environment Massey University Palmerston North New Zealand
| | - Qiao Wang
- School of Agriculture and Environment Massey University Palmerston North New Zealand
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9
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Jehan C, Chogne M, Rigaud T, Moret Y. Sex-specific patterns of senescence in artificial insect populations varying in sex-ratio to manipulate reproductive effort. BMC Evol Biol 2020; 20:18. [PMID: 32013878 PMCID: PMC6998128 DOI: 10.1186/s12862-020-1586-x] [Citation(s) in RCA: 10] [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: 11/13/2019] [Accepted: 01/24/2020] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND The disposable soma theory of ageing assumes that organisms optimally trade-off limited resources between reproduction and longevity to maximize fitness. Early reproduction should especially trade-off against late reproduction and longevity because of reduced investment into somatic protection, including immunity. Moreover, as optimal reproductive strategies of males and females differ, sexually dimorphic patterns of senescence may evolve. In particular, as males gain fitness through mating success, sexual competition should be a major factor accelerating male senescence. In a single experiment, we examined these possibilities by establishing artificial populations of the mealworm beetle, Tenebrio molitor, in which we manipulated the sex-ratio to generate variable levels of investment into reproductive effort and sexual competition in males and females. RESULTS As predicted, variation in sex-ratio affected male and female reproductive efforts, with contrasted sex-specific trade-offs between lifetime reproduction, survival and immunity. High effort of reproduction accelerated mortality in females, without affecting immunity, but high early reproductive success was observed only in balanced sex-ratio condition. Male reproduction was costly on longevity and immunity, mainly because of their investment into copulations rather than in sexual competition. CONCLUSIONS Our results suggest that T. molitor males, like females, maximize fitness through enhanced longevity, partly explaining their comparable longevity.
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Affiliation(s)
- Charly Jehan
- UMR CNRS 6282 BioGéoSciences, Équipe Écologie Évolutive, Université Bourgogne-Franche Comté, Dijon, France.
| | - Manon Chogne
- UMR CNRS 6282 BioGéoSciences, Équipe Écologie Évolutive, Université Bourgogne-Franche Comté, Dijon, France
| | - Thierry Rigaud
- UMR CNRS 6282 BioGéoSciences, Équipe Écologie Évolutive, Université Bourgogne-Franche Comté, Dijon, France
| | - Yannick Moret
- UMR CNRS 6282 BioGéoSciences, Équipe Écologie Évolutive, Université Bourgogne-Franche Comté, Dijon, France.
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10
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Lymbery SJ, Simmons LW. Gustatory cues to kinship among males moderate the productivity of females. Behav Ecol 2019. [DOI: 10.1093/beheco/arz158] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AbstractMales of many species harm females as a byproduct of intrasexual competition, but this harm can be reduced if males are less competitive in the presence of familiar relatives. We determined the cue males use to identify competitors in this context. We assessed genetic variance in a putative kin recognition trait (cuticular hydrocarbons) in male seed beetles Callosobruchus maculatus and found that five hydrocarbons had significant components of additive genetic variance and could serve as relatedness cues. Next, we tested whether hydrocarbons were the mechanism males use to distinguish the social identities of competitors when strategically adjusting their competitiveness/harmfulness. Pairs of female and male C. maculatus were mated in the presence of hydrocarbons extracted from males that differed in their relatedness and familiarity to the focal male. Females were more productive after mating in the presence of extracts from the focal male’s nonrelatives, if those extracts were also unfamiliar to the focal male. Relatedness had no effect on productivity when extracts were familiar to the focal male. These results may be reconciled with those of previous studies that manipulated the relatedness and familiarity of competing males if the difference between the effect of harmfulness on productivity following a single mating and the effect on lifetime reproductive fitness after multiple matings is accounted for. This study provides a novel demonstration of the mechanism of social recognition in the moderation of sexual conflict.
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Affiliation(s)
- Samuel J Lymbery
- Centre for Evolutionary Biology, School of Biological Sciences, The University of Western Australia, Crawley, WA, Australia
| | - Leigh W Simmons
- Centre for Evolutionary Biology, School of Biological Sciences, The University of Western Australia, Crawley, WA, Australia
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11
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Skwierzyńska AM, Plesnar-Bielak A, Kolasa M, Radwan J. Evolution of mate guarding under the risk of intrasexual aggression in a mite with alternative mating tactics. Anim Behav 2018. [DOI: 10.1016/j.anbehav.2018.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Bretman A, Rouse J, Westmancoat JD, Chapman T. The role of species-specific sensory cues in male responses to mating rivals in Drosophila melanogaster fruitflies. Ecol Evol 2017; 7:9247-9256. [PMID: 29187965 PMCID: PMC5696429 DOI: 10.1002/ece3.3455] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 08/14/2017] [Accepted: 08/15/2017] [Indexed: 12/02/2022] Open
Abstract
Complex sets of cues can be important in recognizing and responding to conspecific mating competitors and avoiding potentially costly heterospecific competitive interactions. Within Drosophila melanogaster, males can detect sensory inputs from conspecifics to assess the level of competition. They respond to rivals by significantly extending mating duration and gain significant fitness benefits from doing so. Here, we tested the idea that the multiple sensory cues used by D. melanogaster males to detect conspecifics also function to minimize “off‐target” responses to heterospecific males that they might encounter (Drosophila simulans, Drosophila yakuba, Drosophila pseudoobscura, or Drosophila virilis). Focal D. melanogaster males exposed to D. simulans or D. pseudoobscura subsequently increased mating duration, but to a lesser extent than following exposure to conspecific rivals. The magnitude of rivals’ responses expressed by D. melanogaster males did not align with genetic distance between species, and none of the sensory manipulations caused D. melanogaster to respond to males of all other species tested. However, when we removed or provided “false” sensory cues, D. melanogaster males became more likely to show increased mating duration responses to heterospecific males. We suggest that benefits of avoiding inaccurate assessment of the competitive environment may shape the evolution of recognition cues.
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Affiliation(s)
| | - James Rouse
- School of Biology University of Leeds Leeds UK
| | | | - Tracey Chapman
- School of Biological Sciences University of East Anglia Norwich UK
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13
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Affiliation(s)
- Desh D. Chaudhary
- Ladybird Research Laboratory; Department of Zoology; University of Lucknow; Lucknow Uttar Pradesh India
| | - Geetanjali Mishra
- Ladybird Research Laboratory; Department of Zoology; University of Lucknow; Lucknow Uttar Pradesh India
| | - Omkar
- Ladybird Research Laboratory; Department of Zoology; University of Lucknow; Lucknow Uttar Pradesh India
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14
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Rouse J, Bretman A. Exposure time to rivals and sensory cues affect how quickly males respond to changes in sperm competition threat. Anim Behav 2016. [DOI: 10.1016/j.anbehav.2016.09.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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15
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Márquez-García A, Canales-Lazcano J, Rantala MJ, Contreras-Garduño J. Is Juvenile Hormone a potential mechanism that underlay the "branched Y-model"? Gen Comp Endocrinol 2016; 230-231:170-6. [PMID: 27013379 DOI: 10.1016/j.ygcen.2016.03.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 03/17/2016] [Accepted: 03/19/2016] [Indexed: 10/22/2022]
Abstract
Trade-offs are a central tenet in the life-history evolution and the simplest model to understand it is the "Y" model: the investment of one arm will affect the investment of the other arm. However, this model is by far more complex, and a "branched Y-model" is proposed: trade-offs could exist within each arm of the Y, but the mechanistic link is unknown. Here we used Tenebrio molitor to test if Juvenile Hormone (JH) could be a mechanistic link behind the "branched Y-model". Larvae were assigned to one of the following experimental groups: (1) low, (2) medium and (3) high doses of methoprene (a Juvenile Hormone analogue, JHa), (4) acetone (methoprene diluents; control one) or (5) näive (handled in the same way as other groups; control two). The JHa lengthened the time of development from larvae to pupae and larvae to adults, resulting in adults with a larger size. Males with medium and long JHa treatment doses were favored with female choice, but had smaller testes and fewer viable sperm. There were no differences between groups in regard to the number of spermatozoa of males, or the number of ovarioles or eggs of females. This results suggest that JH: (i) is a mechanistic link of insects "branched Y model", (ii) is a double ended-sword because it may not only provide benefits on reproduction but could also impose costs, and (iii) has a differential effect on each sex, being males more affected than females.
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Affiliation(s)
- Armando Márquez-García
- Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta s/n, Noria Alta, 36050 Guanajuato, Mexico
| | | | - Markus J Rantala
- Turku Brain and Mind Center, Department of Biology, University of Turku, FIN-20014 Turku, Finland
| | - Jorge Contreras-Garduño
- ENES, UNAM, unidad Morelia, Antigua Carretera a Pátzcuaro No.8701, Col. Ex-Hacienda San José de la Huerta, Código Postal 58190 Morelia, Michoacán, Mexico.
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16
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Nandy B, Dasgupta P, Halder S, Verma T. Plasticity in aggression and the correlated changes in the cost of reproduction in male Drosophila melanogaster. Anim Behav 2016. [DOI: 10.1016/j.anbehav.2016.01.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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17
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Ng WC, Chin JSR, Tan KJ, Yew JY. The fatty acid elongase Bond is essential for Drosophila sex pheromone synthesis and male fertility. Nat Commun 2015; 6:8263. [PMID: 26369287 PMCID: PMC4579836 DOI: 10.1038/ncomms9263] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/04/2015] [Indexed: 11/21/2022] Open
Abstract
Insects use a spectacular variety of chemical signals to guide their social behaviours. How such chemical diversity arises is a long-standing problem in evolutionary biology. Here we describe the contribution of the fatty acid elongase Bond to both pheromone diversity and male fertility in Drosophila. Genetic manipulation and mass spectrometry analysis reveal that the loss of bond eliminates the male sex pheromone (3R,11Z,19Z)-3-acetoxy-11,19-octacosadien-1-ol (CH503). Unexpectedly, silencing bond expression severely suppresses male fertility and the fertility of conspecific rivals. These deficits are rescued on ectopic expression of bond in the male reproductive system. A comparative analysis across six Drosophila species shows that the gain of a novel transcription initiation site is correlated with bond expression in the ejaculatory bulb, a primary site of male pheromone production. Taken together, these results indicate that modification of cis-regulatory elements and subsequent changes in gene expression pattern is one mechanism by which pheromone diversity arises. Insect behaviours are often guided by chemical signals, but little is known about how pheromone diversity evolves. Here the authors show that loss of the gene bond in Drosophila eliminates the sex pheromone CH503, while silencing it reduces the fertility of males and their conspecific rivals.
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Affiliation(s)
- Wan Chin Ng
- Biological Mass Spectrometry, Temasek Life Sciences Laboratory, 1 Research Link NUS, 117604 Singapore, Singapore
| | - Jacqueline S R Chin
- Biological Mass Spectrometry, Temasek Life Sciences Laboratory, 1 Research Link NUS, 117604 Singapore, Singapore.,Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, 117543 Singapore, Singapore
| | - Kah Junn Tan
- Biological Mass Spectrometry, Temasek Life Sciences Laboratory, 1 Research Link NUS, 117604 Singapore, Singapore
| | - Joanne Y Yew
- Biological Mass Spectrometry, Temasek Life Sciences Laboratory, 1 Research Link NUS, 117604 Singapore, Singapore.,Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, 117543 Singapore, Singapore
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18
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Larsdotter‐Mellström H, Eriksson K, Janz N, Nylin S, Carlsson MA. Male butterflies use an anti‐aphrodisiac pheromone to tailor ejaculates. Funct Ecol 2015. [DOI: 10.1111/1365-2435.12521] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Helena Larsdotter‐Mellström
- Department of Zoology Stockholm University SE‐106 91 Stockholm Sweden
- Centre for Evolutionary Biology School of Animal Biology (M092) The University of Western Australia Crawley WA 6009 Australia
| | - Kerstin Eriksson
- Department of Zoology Stockholm University SE‐106 91 Stockholm Sweden
| | - Niklas Janz
- Department of Zoology Stockholm University SE‐106 91 Stockholm Sweden
| | - Sören Nylin
- Department of Zoology Stockholm University SE‐106 91 Stockholm Sweden
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19
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Lane SM, Solino JH, Mitchell C, Blount JD, Okada K, Hunt J, House CM. Rival male chemical cues evoke changes in male pre- and post-copulatory investment in a flour beetle. Behav Ecol 2015; 26:1021-1029. [PMID: 26167098 PMCID: PMC4495758 DOI: 10.1093/beheco/arv047] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 03/06/2015] [Accepted: 03/10/2015] [Indexed: 11/13/2022] Open
Abstract
Males can gather information on the risk and intensity of sperm competition from their social environment. Recent studies have implicated chemosensory cues, for instance cuticular hydrocarbons (CHCs) in insects, as a key source of this information. Here, using the broad-horned flour beetle (Gnatocerus cornutus), we investigated the importance of contact-derived rival male CHCs in informing male perception of sperm competition risk and intensity. We experimentally perfumed virgin females with male CHCs via direct intersexual contact and measured male pre- and post-copulatory investment in response to this manipulation. Using chemical analysis, we verified that this treatment engendered changes to perfumed female CHC profiles, but did not make perfumed females "smell" mated. Despite this, males responded to these chemical changes. Males increased courtship effort under low levels of perceived competition (from 1-3 rivals), but significantly decreased courtship effort as perceived competition rose (from 3-5 rivals). Furthermore, our measurement of ejaculate investment showed that males allocated significantly more sperm to perfumed females than to control females. Together, these results suggest that changes in female chemical profile elicited by contact with rival males do not provide males with information on female mating status, but rather inform males of the presence of rivals within the population and thus provide a means for males to indirectly assess the risk of sperm competition.
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Affiliation(s)
- Sarah M Lane
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK
| | - Joanna H Solino
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK , ; Liverpool School of Tropical Medicine, Vector Control Department , Pembroke Place, Liverpool L3 5QA , UK
| | - Christopher Mitchell
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK , ; Hawkesbury Institute for the Environment, University of Western Sydney, Hawkesbury Campus , Penrith, New South Wales 2751 , Australia , and
| | - Jonathan D Blount
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK
| | - Kensuke Okada
- Laboratory of Evolutionary Ecology, Graduate School of Environmental Science, Okayama University , Tsushima-naka 1-1-1, Okayama , Japan
| | - John Hunt
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK
| | - Clarissa M House
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus , Cornwall TR10 9EZ , UK
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Larsdotter-Mellström H, Wiklund C. Different mating expenditure in response to sperm competition risk between generations in the bivoltine butterfly Pieris napi. Behav Ecol Sociobiol 2015. [DOI: 10.1007/s00265-015-1919-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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21
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Pizzari T, Biernaskie JM, Carazo P. Inclusive fitness and sexual conflict: how population structure can modulate the battle of the sexes. Bioessays 2014; 37:155-66. [PMID: 25389109 DOI: 10.1002/bies.201400130] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Competition over reproductive opportunities among members of one sex often harms the opposite sex, creating a conflict of interest between individual males and females. Recently, this battle of the sexes has become a paradigm in the study of intersexual coevolution. Here, we review recent theoretical and empirical advances suggesting that - as in any scenario of intraspecific competition - selfishness (competitiveness) can be influenced by the genetic relatedness of competitors. When competitors are positively related (e.g. siblings), an individual may refrain from harming its competitor(s) and their mate(s) because this can improve the focal individual's inclusive fitness. These findings reveal that population genetic structure might be of paramount importance when studying the battle of the sexes. We conclude by identifying some new lines of research at the interface of sexual selection and social evolution.
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Affiliation(s)
- Tommaso Pizzari
- Edward Grey Institute, Department of Zoology, University of Oxford, Oxford, UK
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22
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Peso M, Elgar MA, Barron AB. Pheromonal control: reconciling physiological mechanism with signalling theory. Biol Rev Camb Philos Soc 2014; 90:542-59. [PMID: 24925630 DOI: 10.1111/brv.12123] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 05/07/2014] [Accepted: 05/13/2014] [Indexed: 11/28/2022]
Abstract
Pheromones are intraspecific chemical signals. They can have profound effects on the behaviour and/or physiology of the receiver, and it is still common to hear pheromones described as controlling of the behaviour of the receiver. The discussion of pheromonal control arose initially from a close association between hormones and pheromones in the comparative physiological literature, but the concept of a controlling pheromone is at odds with contemporary signal evolution theory, which predicts that a manipulative pheromonal signal negatively affecting the receiver's fitness should not be stable over evolutionary time. Here we discuss the meaning of pheromonal control, and the ecological circumstances by which it might be supported. We argue that in discussing pheromonal control it is important to differentiate between control applied to the effects of a pheromone on a receiver's physiology (proximate control), and control applied to the effects of a pheromone on a receiver's fitness (ultimate control). Critically, a pheromone signal affecting change in the receiver's behaviour or physiology need not necessarily manipulate the fitness of a receiver. In cases where pheromonal signalling does lead to a reduction in the fitness of the receiver, the signalling system would be stable if the pheromone were an honest signal of a social environment that disadvantages the receiver, and the physiological and behavioural changes observed in the receiver were an adaptive response to the new social circumstances communicated by the pheromone.
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Affiliation(s)
- Marianne Peso
- Department of Biological Sciences, Macquarie University, Building E8A, Eastern Road, North Ryde, New South Wales 2109, Australia
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23
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Carazo P, Fernández-Perea R, Font E. Quantity Estimation Based on Numerical Cues in the Mealworm Beetle (Tenebrio molitor). Front Psychol 2012; 3:502. [PMID: 23372554 PMCID: PMC3555739 DOI: 10.3389/fpsyg.2012.00502] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 10/26/2012] [Indexed: 11/25/2022] Open
Abstract
In this study, we used a biologically relevant experimental procedure to ask whether mealworm beetles (Tenebrio molitor) are spontaneously capable of assessing quantities based on numerical cues. Like other insect species, mealworm beetles adjust their reproductive behavior (i.e., investment in mate guarding) according to the perceived risk of sperm competition (i.e., probability that a female will mate with another male). To test whether males have the ability to estimate numerosity based on numerical cues, we staged matings between virgin females and virgin males in which we varied the number of rival males the experimental male had access to immediately preceding mating as a cue to sperm competition risk (from 1 to 4). Rival males were presented sequentially, and we controlled for continuous cues by ensuring that males in all treatments were exposed to the same amount of male–male contact. Males exhibited a marked increase in the time they devoted to mate guarding in response to an increase in the number of different rival males they were exposed to. Since males could not rely on continuous cues we conclude that they kept a running tally of the number of individuals they encountered serially, which meets the requirements of the basic ordinality and cardinality principles of proto-counting. Our results thus offer good evidence of “true” numerosity estimation or quantity estimation and, along with recent studies in honey-bees, suggest that vertebrates and invertebrates share similar core systems of non-verbal numerical representation.
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Affiliation(s)
- Pau Carazo
- Edward Grey Institute, Department of Zoology, University of Oxford Oxford, UK ; Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Universidad de Valencia Valencia, Spain
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24
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Males use multiple, redundant cues to detect mating rivals. Curr Biol 2011; 21:617-22. [PMID: 21439827 DOI: 10.1016/j.cub.2011.03.008] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 01/30/2011] [Accepted: 03/02/2011] [Indexed: 11/20/2022]
Abstract
Across many species, males exhibit plastic responses when they encounter mating rivals. The ability to tailor responses to the presence of rivals allows males to increase investment in reproduction only when necessary. This is important given that reproduction imposes costs that limit male reproductive capacity, particularly when sperm competition occurs. Fruitfly (Drosophila melanogaster) males exposed to rivals subsequently mate for longer and thus accrue fitness benefits under increased competition, in line with theory. Here, we show that male D. melanogaster detect rivals by using a suite of cues and that the resulting responses lead directly to significant fitness benefits. We used multiple techniques to systematically remove auditory, olfactory, tactile, and visual cues, first singly and then in all possible combinations. No single cue alone was sufficient to allow males to detect rivals. However, the perception of any two cues from sound, smell, or touch permitted males to detect and respond adaptively to rivals through increased offspring production. Vision was only of marginal importance in this context. The findings indicate adaptive redundancy through the use of multiple, but interchangeable, cues. We reveal the robust mechanisms by which males assess their socio-sexual environment to precisely attune responses via the expression of plastic behavior.
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25
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Barbosa F. Copulation duration in the soldier fly: the roles of cryptic male choice and sperm competition risk. Behav Ecol 2011. [DOI: 10.1093/beheco/arr137] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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26
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Bretman A, Gage MJG, Chapman T. Quick-change artists: male plastic behavioural responses to rivals. Trends Ecol Evol 2011; 26:467-73. [PMID: 21680050 DOI: 10.1016/j.tree.2011.05.002] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 05/03/2011] [Accepted: 05/03/2011] [Indexed: 11/26/2022]
Abstract
Behavioural plasticity allows animals to attune their behaviour to rapid environmental changes. Here we focus on plasticity in male mating behaviour in response to socio-sexual conditions. We discuss existing theory, generate predictions to facilitate exploration of the benefits of plastic behaviour, and identify parameters with the highest leverage on fitness. Existing data are synthesised to assess whether plasticity occurs pre- and post-copulation, to determine the direction of changes in behaviour, and to examine if plastic behaviour is fully flexible. We find that plasticity in males is widespread and not dominated by responses that occur pre- or post-copulation. Our synthesis also highlights areas that are underexplored, such as the limited data on the ultimate fitness consequences of such plastic behaviour.
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Affiliation(s)
- Amanda Bretman
- School of Biological Sciences, University of East Anglia, Norwich NR47TJ, UK.
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27
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Kelly CD, Jennions MD. Sexual selection and sperm quantity: meta-analyses of strategic ejaculation. Biol Rev Camb Philos Soc 2011; 86:863-84. [PMID: 21414127 DOI: 10.1111/j.1469-185x.2011.00175.x] [Citation(s) in RCA: 214] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Clint D Kelly
- Department of Ecology, Evolution & Organismal Biology, Iowa State University, Ames, USA.
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28
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29
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Edward DA, Fricke C, Chapman T. Adaptations to sexual selection and sexual conflict: insights from experimental evolution and artificial selection. Philos Trans R Soc Lond B Biol Sci 2010; 365:2541-8. [PMID: 20643744 PMCID: PMC2935098 DOI: 10.1098/rstb.2010.0027] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Artificial selection and experimental evolution document natural selection under controlled conditions. Collectively, these techniques are continuing to provide fresh and important insights into the genetic basis of evolutionary change, and are now being employed to investigate mating behaviour. Here, we focus on how selection techniques can reveal the genetic basis of post-mating adaptations to sexual selection and sexual conflict. Alteration of the operational sex ratio of adult Drosophila over just a few tens of generations can lead to altered ejaculate allocation patterns and the evolution of resistance in females to the costly effects of elevated mating rates. We provide new data to show how male responses to the presence of rivals can evolve. For several traits, the way in which males responded to rivals was opposite in lines selected for male-biased, as opposed to female-biased, adult sex ratio. This shows that the manipulation of the relative intensity of intra- and inter-sexual selection can lead to replicable and repeatable effects on mating systems, and reveals the potential for significant contemporary evolutionary change. Such studies, with important safeguards, have potential utility for understanding sexual selection and sexual conflict across many taxa. We discuss how artificial selection studies combined with genomics will continue to deepen our knowledge of the evolutionary principles first laid down by Darwin 150 years ago.
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Affiliation(s)
| | | | - Tracey Chapman
- School of Biological Sciences, University of East Anglia, Norwich, Norfolk NR4 7TJ, UK
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30
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Ramm SA, Stockley P. Male house mice do not adjust sperm allocation in response to odours from related or unrelated rivals. Anim Behav 2009. [DOI: 10.1016/j.anbehav.2009.06.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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31
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Larsdotter Mellström H, Wiklund C. Males use sex pheromone assessment to tailor ejaculates to risk of sperm competition in a butterfly. Behav Ecol 2009. [DOI: 10.1093/beheco/arp109] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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32
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Bretman A, Fricke C, Chapman T. Plastic responses of male Drosophila melanogaster to the level of sperm competition increase male reproductive fitness. Proc Biol Sci 2009; 276:1705-11. [PMID: 19324834 DOI: 10.1098/rspb.2008.1878] [Citation(s) in RCA: 175] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Evolutionary and plastic responses by males to the level of sperm competition (SC) are reported across widespread taxa, but direct tests of the consequences for male reproductive success in a competitive context are lacking. We varied male perception of SC to examine the effect on male competitive reproductive success and to test whether the outcomes were as predicted by theory. Exposure to rival males prior to mating increased a male's ejaculate investment (measured as mating duration); by contrast, exposure to rival males in the mating arena decreased mating duration. The results therefore suggested that SC intensity is important in shaping male responses to SC in this system, although the patterns were not strictly in accord with existing theory. We then tested whether males that responded to the level of SC had higher reproductive fitness in a competitive context. We found that males kept with rivals prior to mating again mated for longer; furthermore, they achieved significantly higher paternity share regardless of whether they were the first or second males to mate with a female. The plastic strategies employed by males therefore resulted in significantly increased reproductive success in a competitive context, even following subsequent rematings in which the majority of sperm were displaced.
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Affiliation(s)
- Amanda Bretman
- School of Biological Sciences, University of East Anglia, Norwich, Norfolk NR4 7TJ, UK
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33
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Thomas ML, Simmons LW. Male-derived cuticular hydrocarbons signal sperm competition intensity and affect ejaculate expenditure in crickets. Proc Biol Sci 2009; 276:383-8. [PMID: 18854298 DOI: 10.1098/rspb.2008.1206] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Female sexual promiscuity can have significant effects on male mating decisions because it increases the intensity of competition between ejaculates for fertilization. Because sperm production is costly, males that can detect multiple matings by females and allocate sperm strategically will have an obvious fitness advantage. The presence of rival males is widely recognized as a cue used by males to assess sperm competition. However, for species in which males neither congregate around nor guard females, other more cryptic cues might be involved. Here, we demonstrate unprecedented levels of sperm competition assessment by males, which is mediated via the use of chemical cues. Using the cricket Teleogryllus oceanicus, we manipulated male perception of sperm competition by experimentally coating live unmated females with cuticular compounds extracted from males. We found that males adjusted their ejaculate allocation in response to these compounds: the viability of sperm contained within a male's ejaculate decreased as the number of male extracts applied to his virgin female partner was increased. We further show that males do not respond to the relative concentration of male compounds present on females, but rather to the number of distinct signature odours of individual males. Our results conform to sperm competition theory, and show for the first time, to our knowledge, that males can detect different intensities of sperm competition by using distinct chemical cues of individual males present on females.
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Affiliation(s)
- Melissa L Thomas
- Centre for Evolutionary Biology, School of Animal Biology, The University of Western Australia, Crawley, Western Australia 6009, Australia.
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Quantity discrimination in Tenebrio molitor: evidence of numerosity discrimination in an invertebrate? Anim Cogn 2009; 12:463-70. [PMID: 19118405 DOI: 10.1007/s10071-008-0207-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Revised: 12/12/2008] [Accepted: 12/15/2008] [Indexed: 10/21/2022]
Abstract
Numerosity discrimination, the ability to distinguish between sets with more and less items, is recognised as the foundation for higher numerical abilities. Understanding numerosity discrimination from a comparative perspective is hence pivotal in tracing the evolution of numerical representation systems. However, numerosity discrimination has been well studied only in vertebrates, where two innate systems of number representation have been described: an 'analog magnitude system' used to discriminate among numerosities by representing them as cardinal magnitudes and a 'parallel individualisation system' that allows precise discrimination among small arrays of items (< or =4) by representing objects individually. We investigated the existence of quantity discrimination in an insect species (Tenebrio molitor) by using a spontaneous two-choice procedure in which males were exposed to substrates bearing odours from different numbers of females (< or =4) in increasing numerosity ratios (1:4, 1:3 and 1:2). We show that males can discriminate sources of odours reflecting 1 versus 4 and 1 versus 3 females, but not 2 versus 4 or 1 versus 2, indicating that T. molitor males exhibit a marked preference for sources reflecting more female donors only when numerosity ratios are below 1:2. We discuss the functional significance of this finding and whether our pattern of results could be best explained by summation of a non-numerical continuous variable or by the existence of a numerosity discrimination mechanism with an operational signature ratio of 1:2.
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Abstract
Theory predicts that when sperm compete numerically, selection will favor males who vary the number of sperm they transfer with the immediate level of sperm competition. In this study, I measured male mating investment in response to both female mating status (virgin vs. mated) and the number of foreign sperm stored by females in a previous mating in the scorpionfly Panorpa cognata. Female sperm storage was manipulated by interrupting copulations at different time points. Female mating status did not significantly influence male mating investment, but resource-limited males invested strategically in relation to the amount of sperm stored by females in a previous mating. I found continuously decreasing male investment in response to increasing amounts of competing sperm. These results demonstrate an unprecedented male ability to assess the number of sperm stored by females. As a result, males are capable of an extraordinarily fine-tuned reaction to the intensity of sperm competition.
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Affiliation(s)
- Leif Engqvist
- Department of Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, Bonn, Germany.
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