Evolution of the Two Sexes under Internal Fertilization and Alternative Evolutionary Pathways

Lehtonen, Jussi; Parker, Geoff A.

doi:10.1086/702588

Cited by 16 publications

(33 citation statements)

References 68 publications

(103 reference statements)

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“…Models of anisogamy evolution under gamete competition make testable predictions, some of which apply to the current model. A prediction that is transferrable to the current model is that gamete dimorphism is predicted to increase with increasing size and complexity of the adult organism [12,17,43], and this prediction has some empirical support from comparative studies [44][45][46]. In the superorganism model, the analogous prediction is that queen-male dimorphism is predicted to increase with increasing size (i.e.…”

Section: (C) Testable Predictions Arising From the Modelmentioning

confidence: 65%

Superorganismal anisogamy: queen–male dimorphism in eusocial insects

Lehtonen

Helanterä

2020

Proc. R. Soc. B.

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Colonies of insects such as ants and honeybees are commonly viewed as ‘superorganisms’, with division of labour between reproductive ‘germline-like’ queens and males and ‘somatic’ workers. On this view, properties of the superorganismal colony are comparable with those of solitary organisms to such an extent that the colony itself can be viewed as a unit analogous to an organism. Thus, the concept of a superorganism can be useful as a guide to thinking about life history and allocation traits of colonies as a whole. A pattern that seems to reoccur in insects with superorganismal societies is size dimorphism between queens and males, where queens tend to be larger than males. It has been proposed that this is analogous to the phenomenon of anisogamy at the level of gametes in organisms with separate sexes; more specifically, it is suggested that this caste dimorphism may have evolved via similar selection pressures as gamete dimorphism arises in the ‘gamete competition’ theory for the evolution of anisogamy. In this analogy, queens are analogous to female gametes, males are analogous to male gametes, and colony survival is analogous to zygote survival in gamete competition theory. Here, we explore if this question can be taken beyond an analogy, and whether a mathematical model at the superorganism level, analogous to gamete competition at the organism level, may explain the caste dimorphism seen in superorganismal insects. We find that the central theoretical idea holds, but that there are also significant differences between the way this generalized ‘propagule competition’ theory operates at the levels of solitary organisms and superorganisms. In particular, we find that the theory can explain superorganismal caste dimorphism, but compared with anisogamy evolution, a central coevolutionary link is broken, making the requirements for the theory to work less stringent than those found for the evolution of anisogamy.

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Section: (C) Testable Predictions Arising From the Modelmentioning

confidence: 65%

Superorganismal anisogamy: queen–male dimorphism in eusocial insects

Lehtonen

Helanterä

2020

Proc. R. Soc. B.

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“…Sexual conflict, where males benefit from mating while females might not, can complicate the maintenance of facultative sex (Gerber and Kokko 2016;Burke and Bonduriansky 2017), but this argument only applies to species with males (anisogamy). Science has made some progress toward understanding why anisogamy associates with being large and multicellular (Lehtonen and Parker 2019); why this should also often associate with obligate sex is an obvious followup question. Second, it may be useful to think of the demographic and genetic consequences of synchronous facultative sex.…”

Section: Discussionmentioning

confidence: 99%

When Synchrony Makes the Best of Both Worlds Even Better: How Well Do We Really Understand Facultative Sex?

Kokko

2020

The American Naturalist

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Biological diversity abounds in potential study topics. Studies of model systems have their advantages, but reliance on a few well-understood cases may create false impressions of what biological phenomena are the norm. Here I focus on facultative sex, which is often hailed as offering the best of both worlds, in that rare sex offers benefits almost equal to obligate sex and avoids paying most of the demographic costs. How well do we understand when and why this form of sexual reproduction is expected to prevail? I show several gaps in the theoretical literature and, by contrasting asynchronous with synchronous sex, highlight the need to link sex theories to the theoretical underpinnings of bet hedging, on the one hand, and to mate limitation considerations, on the other. Condition-dependent sex and links between sex with dispersal or dormancy appear understudied. While simplifications are justifiable as a simple assumption structure enhances analytical tractability, much remains to be done to incorporate key features of real sex to the main theoretical edifice.

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“…The subject of early divergence of two gametes of different sizes and morphologies is beyond the scope of this overview. The reader is referred to recent reviews that cover several aspects, including modeling, of the evolution of anisogamy (230,231,232,233) and how it integrates in the so-called sexual cascade (307).…”

Section: A Evolutionary Patterns In Spermatozoamentioning

confidence: 99%

Sperm bauplan and function and underlying processes of sperm formation and selection

Teves

Roldán

2022

Physiological Reviews

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The spermatozoon is a highly differentiated and polarized cell, with two main structures: the head, containing a haploid nucleus and the acrosomal exocytotic granule, and the flagellum, which generates energy and propels the cell; both structures are connected by the neck. The sperm's main aim is to participate in fertilization, thus activating development. Despite this common bauplan and function there is an enormous diversity in structure and performance of sperm cells. For example, mammalian spermatozoa may exhibit several head patterns and overall sperm lengths ranging from ~30 to 350 µm. Mechanisms of transport in the female tract, preparation for fertilization, and recognition and interaction with the oocyte also show considerable variation. There has been much interest in understanding the origin of this diversity, both in evolutionary terms and in relation to mechanisms underlying sperm differentiation in the testis. Here, relationships between sperm bauplan and function are examined at two levels. First, analyzing the selective forces that drive changes in sperm structure and physiology to understand the adaptive values of this variation and impact on male reproductive success. Second, examining cellular and molecular mechanisms of sperm formation in the testis that may explain how differentiation can give rise to such a wide array of sperm forms and functions.

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Evolution of the Two Sexes under Internal Fertilization and Alternative Evolutionary Pathways

Cited by 16 publications

References 68 publications

Superorganismal anisogamy: queen–male dimorphism in eusocial insects

Superorganismal anisogamy: queen–male dimorphism in eusocial insects

When Synchrony Makes the Best of Both Worlds Even Better: How Well Do We Really Understand Facultative Sex?

Sperm bauplan and function and underlying processes of sperm formation and selection

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