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Jarvis GC, Marshall DJ. Fertilization Mode Covaries with Body Size. Am Nat 2023; 202:448-457. [PMID: 37792921 DOI: 10.1086/725864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
AbstractThe evolution of internal fertilization has occurred repeatedly and independently across the tree of life. As it has evolved, internal fertilization has reshaped sexual selection and the covariances among sexual traits, such as testes size, and gamete traits. But it is unclear whether fertilization mode also shows evolutionary associations with traits other than primary sex traits. Theory predicts that fertilization mode and body size should covary, but formal tests with phylogenetic control are lacking. We used a phylogenetically controlled approach to test the covariance between fertilization mode and adult body size (while accounting for latitude, offspring size, and offspring developmental mode) among 1,232 species of marine invertebrates from three phyla. Within all phyla, external fertilizers are consistently larger than internal fertilizers: the consequences of fertilization mode extend to traits that are only indirectly related to reproduction. We suspect that other traits may also coevolve with fertilization mode in ways that remain unexplored.
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2
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Henshaw JM, Bittlingmaier M, Schärer L. Hermaphroditic origins of anisogamy. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220283. [PMID: 36934747 PMCID: PMC10024982 DOI: 10.1098/rstb.2022.0283] [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: 09/01/2022] [Accepted: 11/23/2022] [Indexed: 03/21/2023] Open
Abstract
Anisogamy-the size dimorphism of gametes-is the defining difference between the male and female sexual strategies. Game-theoretic thinking led to the first convincing explanation for the evolutionary origins of anisogamy in the 1970s. Since then, formal game-theoretic models have continued to refine our understanding of when and why anisogamy should evolve. Such models typically presume that the earliest anisogamous organisms had separate sexes. However, in most taxa, there is no empirical evidence to support this assumption. Here, we present a model of the coevolution of gamete size and sex allocation, which allows for anisogamy to emerge alongside either hermaphroditism or separate sexes. We show that hermaphroditic anisogamy can evolve directly from isogamous ancestors when the average size of spawning groups is small and fertilization is relatively efficient. Sex allocation under hermaphroditism becomes increasingly female-biased as group size decreases and the degree of anisogamy increases. When spawning groups are very small, our model also predicts the existence of complex isogamous organisms in which individuals allocate resources equally to two large gamete types. We discuss common, but potentially unwarranted, assumptions in the literature that could be relaxed in future models. This article is part of the theme issue 'Half a century of evolutionary games: a synthesis of theory, application and future directions'.
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Affiliation(s)
- Jonathan M. Henshaw
- Institute of Biology I, University of Freiburg, Hauptstraße 1, D-79104 Freiburg, Germany
| | - Markus Bittlingmaier
- Institute of Biology I, University of Freiburg, Hauptstraße 1, D-79104 Freiburg, Germany
- Theoretical and Experimental Ecology Station, CNRS, 2 route du CNRS, 09200 Moulis, France
| | - Lukas Schärer
- Zoological Institute, Department of Environmental Sciences, University of Basel, Basel CH-4051, Switzerland
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3
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Jarvis GC, White CR, Marshall DJ. Macroevolutionary patterns in marine hermaphroditism. Evolution 2022; 76:3014-3025. [PMID: 36199199 PMCID: PMC10091813 DOI: 10.1111/evo.14639] [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: 09/30/2021] [Revised: 08/08/2022] [Accepted: 08/23/2022] [Indexed: 01/22/2023]
Abstract
Most plants and many animals are hermaphroditic; whether the same forces are responsible for hermaphroditism in both groups is unclear. The well-established drivers of hermaphroditism in plants (e.g., seed dispersal potential, pollination mode) have analogues in animals (e.g., larval dispersal potential, fertilization mode), allowing us to test the generality of the proposed drivers of hermaphroditism across both groups. Here, we test these theories for 1153 species of marine invertebrates, from three phyla. Species with either internal fertilization, restricted offspring dispersal, or small body sizes are more likely to be hermaphroditic than species that are external fertilizers, planktonic developers, or larger. Plants and animals show different biogeographical patterns, however: animals are less likely to be hermaphroditic at higher latitudes-the opposite to the trend in plants. Overall, our results suggest that similar forces, namely, competition among offspring or gametes, shape the evolution of hermaphroditism across plants and three invertebrate phyla.
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Affiliation(s)
- George C Jarvis
- School of Biological Sciences/Centre for Geometric Biology, Monash University, Melbourne, VIC 3800, Australia
| | - Craig R White
- School of Biological Sciences/Centre for Geometric Biology, Monash University, Melbourne, VIC 3800, Australia
| | - Dustin J Marshall
- School of Biological Sciences/Centre for Geometric Biology, Monash University, Melbourne, VIC 3800, Australia
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4
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Anisogamy explains why males benefit more from additional matings. Nat Commun 2022; 13:3893. [PMID: 35794148 PMCID: PMC9259586 DOI: 10.1038/s41467-022-31620-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Accepted: 06/23/2022] [Indexed: 12/05/2022] Open
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5
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Brand JN, Harmon LJ, Schärer L. Mating behavior and reproductive morphology predict macroevolution of sex allocation in hermaphroditic flatworms. BMC Biol 2022; 20:35. [PMID: 35130880 PMCID: PMC8822660 DOI: 10.1186/s12915-022-01234-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 01/18/2022] [Indexed: 11/10/2022] Open
Abstract
Background Sex allocation is the distribution of resources to male or female reproduction. In hermaphrodites, this concerns an individual’s resource allocation to, for example, the production of male or female gametes. Macroevolutionary studies across hermaphroditic plants have revealed that the self-pollination rate and the pollination mode are strong predictors of sex allocation. Consequently, we expect similar factors such as the selfing rate and aspects of the reproductive biology, like the mating behaviour and the intensity of postcopulatory sexual selection, to predict sex allocation in hermaphroditic animals. However, comparative work on hermaphroditic animals is limited. Here, we study sex allocation in 120 species of the hermaphroditic free-living flatworm genus Macrostomum. We ask how hypodermic insemination, a convergently evolved mating behaviour where sperm are traumatically injected through the partner’s epidermis, affects the evolution of sex allocation. We also test the commonly-made assumption that investment into male and female reproduction should trade-off. Finally, we ask if morphological indicators of the intensity of postcopulatory sexual selection (female genital complexity, male copulatory organ length, and sperm length) can predict sex allocation. Results We find that the repeated evolution of hypodermic insemination predicts a more female-biased sex allocation (i.e., a relative shift towards female allocation). Moreover, transcriptome-based estimates of heterozygosity reveal reduced heterozygosity in hypodermically mating species, indicating that this mating behavior is linked to increased selfing or biparental inbreeding. Therefore, hypodermic insemination could represent a selfing syndrome. Furthermore, across the genus, allocation to male and female gametes is negatively related, and larger species have a more female-biased sex allocation. Finally, increased female genital complexity, longer sperm, and a longer male copulatory organ predict a more male-biased sex allocation. Conclusions Selfing syndromes have repeatedly originated in plants. Remarkably, this macroevolutionary pattern is replicated in Macrostomum flatworms and linked to repeated shifts in reproductive behavior. We also find a trade-off between male and female reproduction, a fundamental assumption of most theories of sex allocation. Beyond that, no theory predicts a more female-biased allocation in larger species, suggesting avenues for future work. Finally, morphological indicators of more intense postcopulatory sexual selection appear to predict more intense sperm competition. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01234-1.
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Affiliation(s)
- Jeremias N Brand
- Department of Environmental Sciences, Zoological Institute, University of Basel, Vesalgasse 1, 4051, Basel, Switzerland. .,Department of Tissue Dynamics and Regeneration, Max Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, 37077, Göttingen, Germany.
| | - Luke J Harmon
- Department of Biological Sciences, University of Idaho, Life Sciences South 252, 875 Perimeter Dr MS 3051, Moscow, ID, USA
| | - Lukas Schärer
- Department of Environmental Sciences, Zoological Institute, University of Basel, Vesalgasse 1, 4051, Basel, Switzerland
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6
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Fertilization mode drives sperm length evolution across the animal tree of life. Nat Ecol Evol 2021; 5:1153-1164. [PMID: 34155385 DOI: 10.1038/s41559-021-01488-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 05/12/2021] [Indexed: 01/08/2023]
Abstract
Evolutionary biologists have endeavoured to explain the extraordinary diversity of sperm morphology across animals for more than a century. One hypothesis to explain sperm diversity is that sperm length is shaped by the environment where fertilization takes place (that is, fertilization mode). Evolutionary transitions in fertilization modes may transform how selection acts on sperm length, probably by affecting postcopulatory mechanisms of sperm competition and the scope for cryptic female choice. Here, we address this hypothesis by generating a macro-evolutionary view of how fertilization mode (including external fertilizers, internal fertilizers and spermcasters) influences sperm length diversification among 3,233 species from 21 animal phyla. We show that sperm are shorter in species whose sperm are diluted in aquatic environments (that is, external fertilizers and spermcasters) and longer in species where sperm are directly transferred to females (that is, internal fertilizers). We also show that sperm length evolves faster and with a greater number of adaptive shifts in species where sperm operate within females (for example, spermcasters and internal fertilizers). Our results demonstrate that fertilization mode is a key driver in the evolution of sperm length across animals, and we argue that a complex combination of postcopulatory forces has shaped sperm length diversification throughout animal evolution.
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7
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Cameron H, Johnson DW, Monro K, Marshall DJ. Multilevel Selection on Offspring Size and the Maintenance of Variation. Am Nat 2021; 197:448-460. [PMID: 33755536 DOI: 10.1086/712890] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractMultilevel selection on offspring size occurs when offspring fitness depends on both absolute size (hard selection) and size relative to neighbors (soft selection). We examined multilevel selection on egg size at two biological scales-within clutches and among clutches from different females-using an external fertilizing tube worm. We exposed clutches of eggs to two sperm environments (limiting and saturating) and measured their fertilization success. We then modeled environmental (sperm-dependent) differences in hard and soft selection on individual eggs as well as selection on clutch-level traits (means and variances). Hard and soft selection differed in strength and form depending on sperm availability-hard selection was consistently stabilizing; soft selection was directional and favored eggs relatively larger (sperm limitation) or smaller (sperm saturation) than the clutch mean. At the clutch level, selection on mean egg size was largely concave, while selection on within-clutch variance was weak but generally negative-although some correlational selection occurred between these two traits. Importantly, we found that the optimal clutch mean egg size differed for mothers and offspring, suggesting some antagonism between the levels of selection. We thus identify several pathways that may maintain offspring size variation: environmentally (sperm-) dependent soft selection, antagonistic multilevel selection, and correlational selection on clutch means and variances. Multilevel approaches are powerful but seldom-used tools for studies of offspring size, and we encourage their future use.
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Evans JP, Lymbery RA. Sexual selection after gamete release in broadcast spawning invertebrates. Philos Trans R Soc Lond B Biol Sci 2020; 375:20200069. [PMID: 33070722 DOI: 10.1098/rstb.2020.0069] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Broadcast spawning invertebrates offer highly tractable models for evaluating sperm competition, gamete-level mate choice and sexual conflict. By displaying the ancestral mating strategy of external fertilization, where sexual selection is constrained to act after gamete release, broadcast spawners also offer potential evolutionary insights into the cascade of events that led to sexual reproduction in more 'derived' groups (including humans). Moreover, the dynamic reproductive conditions faced by these animals mean that the strength and direction of sexual selection on both males and females can vary considerably. These attributes make broadcast spawning invertebrate systems uniquely suited to testing, extending, and sometimes challenging classic and contemporary ideas in sperm competition, many of which were first captured in Parker's seminal papers on the topic. Here, we provide a synthesis outlining progress in these fields, and highlight the burgeoning potential for broadcast spawners to provide both evolutionary and mechanistic understanding into gamete-level sexual selection more broadly across the animal kingdom. This article is part of the theme issue 'Fifty years of sperm competition'.
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Affiliation(s)
- Jonathan P Evans
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia
| | - Rowan A Lymbery
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia
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9
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Spermcast mating with release of zygotes in the small dioecious bivalve Digitaria digitaria. Sci Rep 2020; 10:12605. [PMID: 32724126 PMCID: PMC7387346 DOI: 10.1038/s41598-020-69457-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 07/06/2020] [Indexed: 11/29/2022] Open
Abstract
Digitaria digitaria, a small astartid usually less than 10 mm in length, has a non-brooding behaviour in spite of its limited space for gonad development. This species lives in highly unstable environments with strong currents, which represent a challenge for fertilization and larval settlement. The studied population of D. digitaria from the Strait of Gibraltar area was dioecious, with significant predominance of females and sexual dimorphism, where females are larger than males. The reproductive cycle is asynchronous throughout the year, without a resting period, but with successive partial spawning events. The presence of stored sperm in the suprabranchial chamber and inside the gonad of some females, together with the release of eggs along the dorsal axis of both gills, points to internal oocyte fertilization. Bacteriocytes were found in the female and male follicle walls, but no bacteria were observed inside any of the gametes. Digitaria digitaria could represent a “missing link” between spermcast mating bivalves with brooded offspring and bivalves with broadcast release of eggs and sperm. The small size, limiting the oocyte production, together with the unstable environment could represent evolutionary pressures towards sperm uptake in D. digitaria.
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10
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Henshaw JM, Fromhage L, Jones AG. Sex roles and the evolution of parental care specialization. Proc Biol Sci 2019; 286:20191312. [PMID: 31455191 DOI: 10.1098/rspb.2019.1312] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Males and females are defined by the relative size of their gametes (anisogamy), but secondary sexual dimorphism in fertilization, parental investment and mating competition is widespread and often remarkably stable over evolutionary timescales. Recent theory has clarified the causal connections between anisogamy and the most prevalent differences between the sexes, but deviations from these patterns remain poorly understood. Here, we study how sex differences in parental investment and mating competition coevolve with parental care specialization. Parental investment often consists of two or more distinct activities (e.g. provisioning and defence) and parents may care more efficiently by specializing in a subset of these activities. Our model predicts that efficient care specialization broadens the conditions under which biparental investment can evolve in lineages that historically had uniparental care. Major transitions in sex roles (e.g. from female-biased care with strong male mating competition to male-biased care with strong female competition) can arise following ecologically induced changes in the costs or benefits of different care types, or in the sex ratio at maturation. Our model provides a clear evolutionary mechanism for sex-role transitions, but also predicts that such transitions should be rare. It consequently contributes towards explaining widespread phylogenetic inertia in parenting and mating systems.
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Affiliation(s)
- Jonathan M Henshaw
- Department of Biological Sciences, University of Idaho, 875 Perimeter MS 3051, Moscow, ID, USA.,Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, 40014 Finland
| | - Lutz Fromhage
- Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, 40014 Finland
| | - Adam G Jones
- Department of Biological Sciences, University of Idaho, 875 Perimeter MS 3051, Moscow, ID, USA
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11
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Lehtonen J, Dardare L. Mathematical Models of Fertilization—An Eco-Evolutionary Perspective. THE QUARTERLY REVIEW OF BIOLOGY 2019. [DOI: 10.1086/703633] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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12
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Lehtonen J, Parker GA. Evolution of the Two Sexes under Internal Fertilization and Alternative Evolutionary Pathways. Am Nat 2019; 193:702-716. [PMID: 31002575 DOI: 10.1086/702588] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Transition from isogamy to anisogamy, hence males and females, leads to sexual selection, sexual conflict, sexual dimorphism, and sex roles. Gamete dynamics theory links biophysics of gamete limitation, gamete competition, and resource requirements for zygote survival and assumes broadcast spawning. It makes testable predictions, but most comparative tests use volvocine algae, which feature internal fertilization. We broaden this theory by comparing broadcast-spawning predictions with two plausible internal-fertilization scenarios: gamete casting/brooding (one mating type retains gametes internally, the other broadcasts them) and packet casting/brooding (one type retains gametes internally, the other broadcasts packets containing gametes, which are released for fertilization). Models show that predictions are remarkably robust to these radical changes, yielding (1) isogamy under low gamete limitation, low gamete competition, and similar required resources for gametes and zygotes, (2) anisogamy when gamete competition and/or limitation are higher and when zygotes require more resources than gametes, as is likely as multicellularity develops, (3) a positive correlation between multicellular complexity and anisogamy ratio, and (4) under gamete competition, only brooders becoming female. Thus, gamete dynamics theory represents a potent rationale for isogamy/anisogamy and makes similar testable predictions for broadcast spawners and internal fertilizers, regardless of whether anisogamy or internal fertilization evolved first.
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13
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Kokko H. Give one species the task to come up with a theory that spans them all: what good can come out of that? Proc Biol Sci 2017; 284:20171652. [PMID: 29142112 PMCID: PMC5719169 DOI: 10.1098/rspb.2017.1652] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 10/16/2017] [Indexed: 01/01/2023] Open
Abstract
Does the progress in understanding evolutionary theory depend on the species that is doing the investigation? This question is difficult to answer scientifically, as we are dealing with an n = 1 scenario: every individual who has ever written about evolution is a human being. I will discuss, first, whether we get the correct answer to questions if we begin with ourselves and expand outwards, and second, whether we might fail to ask all the interesting questions unless we combat our tendencies to favour taxa that are close to us. As a whole, the human tendency to understand general biological phenomena via 'putting oneself in another organism's shoes' has upsides and downsides. As an upside, our intuitive ability to rethink strategies if the situation changes can lead to ready generation of adaptive hypotheses. Downsides occur if we trust this intuition too much, and particular danger zones exist for traits where humans are an unusual species. I argue that the levels of selection debate might have proceeded differently if human cooperation patterns were not so unique, as this brings about unique challenges in biology teaching; and that theoretical insights regarding inbreeding avoidance versus tolerance could have spread faster if we were not extrapolating our emotional reactions to incest disproportionately depending on whether we study animals or plants. I also discuss patterns such as taxonomic chauvinism, i.e. less attention being paid to species that differ more from human-like life histories. Textbooks on evolution reinforce such biases insofar as they present, as a default case, systems that resemble ours in terms of life cycles and other features (e.g. gonochorism). Additionally, societal norms may have led to incorrect null hypotheses such as females not mating multiply.
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Affiliation(s)
- Hanna Kokko
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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14
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Parker GA, Ramm SA, Lehtonen J, Henshaw JM. The evolution of gonad expenditure and gonadosomatic index (GSI) in male and female broadcast-spawning invertebrates. Biol Rev Camb Philos Soc 2017; 93:693-753. [PMID: 28921784 DOI: 10.1111/brv.12363] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 07/22/2017] [Accepted: 08/09/2017] [Indexed: 01/05/2023]
Abstract
Sedentary broadcast-spawning marine invertebrates, which release both eggs and sperm into the water for fertilization, are of special interest for sexual selection studies. They provide unique insight into the early stages of the evolutionary succession leading to the often-intense operation of both pre- and post-mating sexual selection in mobile gonochorists. Since they are sessile or only weakly mobile, adults can interact only to a limited extent with other adults and with their own fertilized offspring. They are consequently subject mainly to selection on gamete production and gamete success, and so high gonad expenditure is expected in both sexes. We review literature on gonadosomatic index (GSI; the proportion of body tissue devoted to gamete production) of gonochoristic broadcast spawners, which we use as a proxy for gonad expenditure. We show that such taxa most often have a high GSI that is approximately equal in both sexes. When GSI is asymmetric, female GSI usually exceeds male GSI, at least in echinoderms (the majority of species recorded). Intriguingly, though, higher male GSI also occurs in some species and appears more common than female-biased GSI in certain orders of gastropod molluscs. Our limited data also suggest that higher male GSI may be the prevalent pattern in sperm casters (where only males release gametes). We explore how selection might have shaped these patterns using game theoretic models for gonad expenditure that consider possible trade-offs with (i) somatic maintenance or (ii) growth, while also considering sperm competition, sperm limitation, and polyspermy. Our models of the trade-off between somatic tissue (which increases survival) and gonad (which increases reproductive success) predict that GSI should be equal for the two sexes when sperm competition is intense, as is probably common in broadcast spawners due to synchronous spawning in aggregations. Higher female GSI occurs under low sperm competition. Sperm limitation appears unlikely to alter these conclusions qualitatively, but can also act as a force to keep male GSI high, and close to that of females. Polyspermy can act to reduce male GSI. Higher male than female GSI is predicted to be less common (as observed in the data), but can occur when ova/ovaries are sufficiently more resource-intensive to produce than sperm/testes, for which some evidence exists. We also show that sex-specific trade-offs between gonads and growth can generate different life-history strategies for males and females, with males beginning reproduction earlier. This could lead to apparently higher male GSI in empirical studies if immature females are included in calculations of mean GSI. The existence of higher male GSI nonetheless remains somewhat problematic and requires further investigation. When sperm limitation is low, we suggest that the natural logarithm of the male/female GSI ratio may be a suitable index for sperm competition level in broadcast spawners, and that this may also be considered as an index for internally fertilizing taxa.
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Affiliation(s)
- Geoff A Parker
- Department of Evolution, Ecology and Behaviour, Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, U.K
| | - Steven A Ramm
- Evolutionary Biology, Bielefeld University, 33615, Bielefeld, Germany
| | - Jussi Lehtonen
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, 2052, Australia
| | - Jonathan M Henshaw
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, 2601, Canberra, Australia.,Institute of Zoology, University of Graz, Graz, 8010, Austria
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15
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Rapuano H, Brickner I, Shlesinger T, Meroz-Fine E, Tamir R, Loya Y. Reproductive strategies of the coral Turbinaria reniformis in the northern Gulf of Aqaba (Red Sea). Sci Rep 2017; 7:42670. [PMID: 28195203 PMCID: PMC5307385 DOI: 10.1038/srep42670] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 01/13/2017] [Indexed: 02/07/2023] Open
Abstract
Here we describe for the first time the reproductive biology of the scleractinian coral Turbinaria reniformis studied during three years at the coral reefs of Eilat and Aqaba. We also investigated the possibility of sex change in individually tagged colonies followed over a period of 12 years. T. reniformis was found to be a stable gonochorist (no detected sex change) that reproduces by broadcast spawning 5-6 nights after the full moon of June and July. Spawning was highly synchronized between individuals in the field and in the lab. Reproduction of T. reniformis is temporally isolated from the times at which most other corals reproduce in Eilat. Its relatively long reproductive cycle compared to other hermaphroditic corals may be due to the high reproductive effort associated with the production of eggs by gonochoristic females. Sex ratio in both the Aqaba and Eilat coral populations deviated significantly from a 1:1 ratio. The larger number of males than of females may provide a compensation for sperm limitation due to its dilution in the water column. We posit that such sex allocation would facilitate adaptation within gonochoristic species by increasing fertilization success in low density populations, constituting a phenomenon possibly regulated by chemical communication.
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Affiliation(s)
- Hanna Rapuano
- Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Itzchak Brickner
- Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Tom Shlesinger
- Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Efrat Meroz-Fine
- The Interuniversity Institute for Marine Sciences, P.O. Box 469, Eilat 8810369, Israel
| | - Raz Tamir
- Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
- The Interuniversity Institute for Marine Sciences, P.O. Box 469, Eilat 8810369, Israel
| | - Yossi Loya
- Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
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16
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Lehtonen J, Parker GA, Schärer L. Why anisogamy drives ancestral sex roles. Evolution 2016; 70:1129-35. [PMID: 27110661 DOI: 10.1111/evo.12926] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/23/2016] [Accepted: 04/01/2016] [Indexed: 01/15/2023]
Abstract
There is a clear tendency in nature for males to compete more strongly for fertilizations than females, yet the ultimate reasons for this are still unclear. Many researchers-dating back to Darwin and Bateman-have argued that the difference is ultimately driven by the fact that males (by definition) produce smaller and more numerous gametes than females. However, this view has recently been challenged, and a formal validation of the link between anisogamy and sex roles has been lacking. Here, we develop mathematical models that validate the intuition of Darwin and Bateman, showing that there is a very simple and general reason why unequal gamete numbers result in unequal investment in sexually competitive traits. This asymmetry does not require multiple mating by either sex, and covers traits such as mate searching, where the male bias has been difficult to explain. Furthermore, our models show males and females are predicted to diverge more strongly when the fertilization probability of each female gamete is high. Sex roles thus ultimately trace back to anisogamy and the resulting consequences for the fertilization process.
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Affiliation(s)
- Jussi Lehtonen
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, 2052, Australia. .,Evolutionary Biology, Zoological Institute, University of Basel, Vesalgasse 1, CH-4051, Basel, Switzerland.
| | - Geoff A Parker
- Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, United Kingdom
| | - Lukas Schärer
- Evolutionary Biology, Zoological Institute, University of Basel, Vesalgasse 1, CH-4051, Basel, Switzerland
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Okamoto DK. Competition among Eggs Shifts to Cooperation along a Sperm Supply Gradient in an External Fertilizer. Am Nat 2016; 187:E129-42. [DOI: 10.1086/685813] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Affiliation(s)
- G. A. Parker
- Institute of Integrative Biology; University of Liverpool; Liverpool UK
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Henshaw JM, Kokko H, Jennions MD. Direct reciprocity stabilizes simultaneous hermaphroditism at high mating rates: A model of sex allocation with egg trading. Evolution 2015; 69:2129-39. [PMID: 26150086 DOI: 10.1111/evo.12717] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 06/17/2015] [Accepted: 06/19/2015] [Indexed: 01/14/2023]
Abstract
Simultaneous hermaphroditism is predicted to be unstable at high mating rates given an associated increase in sperm competition. The existence of reciprocal egg trading, which requires both hermaphroditism and high mating rates to evolve, is consequently hard to explain. We show using mathematical models that the presence of a trading economy creates an additional fitness benefit to egg production, which selects for traders to bias their sex allocation toward the female function. This female-biased sex allocation prevents pure females from invading a trading population, thereby allowing simultaneous hermaphroditism to persist stably at much higher levels of sperm competition than would otherwise be expected. More generally, our model highlights that simultaneous hermaphroditism can persist stably when mating opportunities are abundant, as long as sperm competition remains low. It also predicts that reciprocity will select for heavier investment in the traded resource.
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Affiliation(s)
- Jonathan M Henshaw
- Research School of Biology, The Australian National University, Australia.
| | - Hanna Kokko
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Switzerland
| | - Michael D Jennions
- Research School of Biology, The Australian National University, Australia
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