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Cramer ERA, Yilma ZB, Lifjeld JT. Selection on sperm size in response to promiscuity and variation in female sperm storage organs. J Evol Biol 2023; 36:131-143. [PMID: 36357998 PMCID: PMC10100110 DOI: 10.1111/jeb.14120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 09/30/2022] [Accepted: 10/05/2022] [Indexed: 11/12/2022]
Abstract
Sperm cells are exceptionally morphologically diverse across taxa. However, morphology can be quite uniform within species, particularly for species where females copulate with many males per reproductive bout. Strong sexual selection in these promiscuous species is widely hypothesized to reduce intraspecific sperm variation. Conversely, we hypothesize that intraspecific sperm size variation may be maintained by high among-female variation in the size of sperm storage organs, assuming that paternity success improves when sperm are compatible in size with the sperm storage organ. We use individual-based simulations and an analytical model to evaluate how selection on sperm size depends on promiscuity level and variation in sperm storage organ size (hereafter, female preference variation). Simulations of high promiscuity (10 mates per female) showed stabilizing selection on sperm when female preference variation was low, and disruptive selection when female preference variation was high, consistent with the analytical model results. With low promiscuity (2-3 mates per female), selection on sperm was stabilizing for all levels of female preference variation in the simulations, contrasting with the analytical model. Promiscuity level, or mate sampling, thus has a strong impact on the selection resulting from female preferences. Furthermore, when promiscuity is low, disruptive selection on male traits will occur under much more limited circumstances (i.e. only with higher among-female variation) than many previous models suggest. Variation in female sperm storage organs likely has strong implications for intraspecific sperm variation in highly promiscuous species, but likely does not explain differences in intraspecific sperm variation for less promiscuous taxa.
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Affiliation(s)
- Emily R A Cramer
- Sex and Evolution Research Group, Natural History Museum, University of Oslo, Oslo, Norway
| | | | - Jan T Lifjeld
- Sex and Evolution Research Group, Natural History Museum, University of Oslo, Oslo, Norway
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2
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Browne JH, Gwynne DT. Paternity sharing in insects with female competition for nuptial gifts. Ecol Evol 2022; 12:e9463. [PMID: 36329813 PMCID: PMC9618826 DOI: 10.1002/ece3.9463] [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: 05/26/2022] [Revised: 09/20/2022] [Accepted: 10/10/2022] [Indexed: 11/26/2022] Open
Abstract
Male parental investment is expected to be associated with high confidence of paternity. Studies of species with exclusive male parental care have provided support for this hypothesis because mating typically co‐occurs with each oviposition, allowing control over paternity and the allocation of care. However, in systems where males invest by feeding mates (typically arthropods), mating (and thus the investment) is separated from egg‐laying, resulting in less control over insemination, as male ejaculates compete with rival sperm stored by females, and a greater risk of investing in unrelated offspring (cuckoldry). As strong selection on males to increase paternity would compromise the fitness of all a female's other mates that make costly nutrient contributions, paternity sharing (males not excluded from siring offspring) is an expected outcome of sperm competition. Using wild‐caught females in an orthopteran and a dipteran species, in which sexually selected, ornamented females compete for male nuptial food gifts needed for successful reproduction, we examined paternity patterns and compared them with findings in other insects. We used microsatellite analysis of offspring (lifetime reproduction in the orthopteran) and stored sperm from wild‐caught females in both study species. As predicted, there was evidence of shared paternity as few males failed to sire offspring. Further support for paternity sharing is the lack of last‐male sperm precedence in our study species. Although paternity was not equal among sires, our estimates of paternity bias were similar to other insects with valuable nuptial gifts and contrasted with the finding that males are frequently excluded from siring offspring in species where males supply little more than sperm. This suggests paternity bias may be reduced in nuptial‐gift systems and may help facilitate the evolution of these paternal investments.
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Affiliation(s)
- Jessica H. Browne
- Department of Ecology and Evolutionary BiologyUniversity of Toronto MississaugaMississaugaOntarioCanada,Department of BiologyMount Allison UniversitySackvilleNew BrunswickCanada
| | - Darryl T. Gwynne
- Department of Ecology and Evolutionary BiologyUniversity of Toronto MississaugaMississaugaOntarioCanada
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3
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Matzke M, Toft S, Bechsgaard J, Pold Vilstrup A, Uhl G, Künzel S, Tuni C, Bilde T. Sperm competition intensity affects sperm precedence patterns in a polyandrous gift-giving spider. Mol Ecol 2022; 31:2435-2452. [PMID: 35178803 DOI: 10.1111/mec.16405] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 01/26/2022] [Accepted: 02/08/2022] [Indexed: 11/28/2022]
Abstract
Sperm competition drives traits that enhance fertilization success. The amount of sperm transferred relative to competitors is key for attaining paternity. Female reproductive morphology and male mating order may also influence fertilization, however the outcome for sperm precedence under intense sperm competition remains poorly understood. In the polyandrous spider Pisaura mirabilis, males offer nuptial gifts which prolong copulation and increase sperm transfer, factors proposed to alter sperm precedence patterns under strong sperm competition. First, we assessed the degree of female polyandry by genotyping wild broods. A conservative analysis identified up to 4 sires, with a mean of 2 sires per brood, consistent with an optimal mating female rate. Then we asked whether intense sperm competition shifts sperm precedence patterns from first male priority, as expected from female morphology, to last male advantage. We varied sexual selection intensity experimentally and determined competitive fertilization outcome by genotyping broods. In double matings, one male monopolised paternity regardless of mating order. A mating order effect with first male priority was revealed when females were mated to 4 males, however this effect disappeared when females were mated to 6 males, likely due to increased sperm mixing. The proportion of males that successfully sired offspring drastically decreased with the number of competitors. Longer copulations translated into higher paternity shares independently of mating order, reinforcing the advantage of traits that prolong copulation duration under intense competition, such as the nuptial gift. Sperm competition intensity enhances the impact of competitive sexual traits and imposes multiple effects on paternity.
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Affiliation(s)
- Magdalena Matzke
- Department of Biology, Ludwig Maximilian University of Munich, Großhaderner Str. 2, 82152, Planegg-Martinsried, Germany
| | - Søren Toft
- Department of Biology, Aarhus University, Ny Munkegade 116, DK-8000, Aarhus C, Denmark
| | - Jesper Bechsgaard
- Department of Biology, Aarhus University, Ny Munkegade 116, DK-8000, Aarhus C, Denmark
| | - Astrid Pold Vilstrup
- Department of Biology, Aarhus University, Ny Munkegade 116, DK-8000, Aarhus C, Denmark.,Department of Molecular Biology and Genetics, Aarhus University, DK-8000, Aarhus C, Denmark
| | - Gabriele Uhl
- General and Systematic Zoology, University of Greifswald, Zoological Institute and Museum, Loitzer Straße 26, D-17489, Greifswald, Germany
| | - Sven Künzel
- Department for Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, August-Thienemann Straße 2, D-24306, Plön, Germany
| | - Cristina Tuni
- Department of Biology, Ludwig Maximilian University of Munich, Großhaderner Str. 2, 82152, Planegg-Martinsried, Germany
| | - Trine Bilde
- Department of Biology, Aarhus University, Ny Munkegade 116, DK-8000, Aarhus C, Denmark
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5
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Turnell BR, Shaw KL, Reeve HK. Modeling strategic sperm allocation: Tailoring the predictions to the species. Evolution 2018; 72:414-425. [PMID: 29331038 DOI: 10.1111/evo.13423] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Revised: 12/06/2017] [Accepted: 12/14/2017] [Indexed: 12/01/2022]
Abstract
Two major challenges exist when empirically testing the predictions of sperm allocation theory. First, the study species must adhere to the assumptions of the model being tested. Unfortunately, the common assumption of sperm allocation models that females mate a maximum of once or twice does not hold for many, if not most, multiply and sequentially mating animals. Second, a model's parameters, which dictate its predictions, must be measured in the study species. Common examples of such parameters, female mating frequency and sperm precedence patterns, are unknown for many species used in empirical tests. Here, we present a broadly applicable model, appropriate for multiply, sequentially mating animals, and test it in three species for which data on all the relevant parameter values are available. The model predicts that relative allocation to virgin females, compared to nonvirgins, depends on the interaction between female mating rate and the sperm precedence pattern: relative allocation to virgins increases with female mating rate under first-male precedence, while the opposite is true under later-male precedence. Our model is moderately successful in predicting actual allocation patterns in the three species, including a cricket in which we measured the parameter values and performed an empirical test of allocation.
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Affiliation(s)
- Biz R Turnell
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853.,Current Address: Department of Biology, Technische Universität Dresden, 01062 Dresden, Germany
| | - Kerry L Shaw
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853
| | - H Kern Reeve
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853
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Parker DJ, Zaborowska J, Ritchie MG, Vahed K. Paternity analysis of wild-caught females shows that sperm package size and placement influence fertilization success in the bushcricketPholidoptera griseoaptera. Mol Ecol 2017; 26:3050-3061. [DOI: 10.1111/mec.14089] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/23/2017] [Accepted: 02/27/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Darren James Parker
- Centre for Biological Diversity; University of St Andrews; St Andrews KY16 9TH UK
- Department of Ecology and Evolution; University of Lausanne; Biophore Lausanne 1015 Switzerland
| | - Julia Zaborowska
- Centre for Biological Diversity; University of St Andrews; St Andrews KY16 9TH UK
- Institute of Environmental Sciences; Jagiellonian University; Gronostajowa 7 30-387 Kraków Poland
- Institute of Environmental Biology; Adam Mickiewicz University in Poznań; Umultowska 89 61-614 Poznań Poland
| | | | - Karim Vahed
- Environmental Sustainability Research Centre; University of Derby; Kedleston Road Derby DE22 1GB UK
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