Mating Tactics and Strategies

by

Stephen M. Shuster, Michael J. Wade

• LAST REVIEWED: 25 September 2023
• LAST MODIFIED: 25 September 2023
• DOI: 10.1093/obo/9780199941728-0150

Introduction

Alternative mating tactics and strategies are sex-limited reproductive polyphenisms and polymorphisms. They appear as discontinuous distributions of behavioral, developmental, or morphological traits, expressed among the members of one sex, and they occur within the context of reproductive competition. Polymorphic mating phenotypes are usually found in species in which sexual selection is strong, that is, in species in which the variance in fitness within one or both sexes is large. Polyphenisms and polymorphisms tend to be more obvious in the sex with greater variance in fitness. Thus, like many sexually selected traits, alternative mating tactics and strategies are expressed more often in males than in females, although polymorphic females also exist, especially when variance in female fitness is large. While classification schemes vary, alternative mating “tactics” usually describe flexible behavioral or developmental phenotypes that may change over brief periods of time, whereas alternative mating “strategies” generally describe less flexible morphological traits. The tactic-strategy dichotomy appears to have been identified to capture observed variation in behavior vis-à-vis morphology as studies documenting mating polymorphisms began to accumulate, and to stimulate future research. However, this typological framework has led to vigorous debate about whether genetic variation underlies observed polymorphic phenotypes and the nature of the evolutionary processes by which these polymorphisms may persist in the wild. Although the tactics-strategy dichotomy persists in even the most recent literature, accumulating results suggest that the range of mating polymorphisms, while variable in the circumstances in which they are favored, as well as in the timing and reversibility of their expression, are shaped by similar evolutionary processes, notably, negative frequency dependent selection; that is, when one tactic or strategy becomes common, the alternative has a fitness advantage. This article first considers fundamental literature describing mating polymorphisms beginning with observations by Darwin and his contemporaries. It then identifies books and collections of literature in which the subject of mating polymorphism and sex-specific polyphenisms are considered at length or with high frequency. Based on this framework, it next outlines contributions to these conceptual frameworks that have arisen to explain what mating polymorphisms are, why they exist, and how they persist. Lastly, it surveys contributions focused on the inheritance, expression, and evolution of mating polymorphisms, as well as specific considerations relating to active areas of current research.

Early Overviews

Observations on mating polymorphism, including behavioral as well as morphological variation, were first considered at length in Darwin 1874 (cited in Books), which summarizes examples from spiders (Theridion, by Canistrini, p. 269; Nephila by Rev. O. Cambridge, p. 270), crustaceans (Tanais, Orchestia, by F. Müller, p. 262, 275), birds (Uria by Graba, p. 418) and mammals (Cervus, Ovis, pp. 508–509), combining Darwin’s own observations with descriptions provided by his correspondents. Bateson and Brindley 1892 reports examples of dimorphisms among earwig and beetle males as did Oguma 1913 in damselflies, and Arrow 1928 in horned beetles, but these works provided mainly descriptions of the different morphological phenotypes they observed. Huxley 1932 asserts that such dimorphisms were anomalies explained by environmental influences on heterochrony. Morris 1952 describes female-mimicking behavior in male 10-spined sticklebacks but minimized the importance of this behavior in obtaining actual fertilizations. Barlow 1967 also documents “pseudo-female behavior” in male leaf fish with similar conclusions. Hogan-Warburg 1966 was among the first post-Darwinian descriptions to characterize mating polymorphism as adaptations, involving both plumage and behavioral variation in male ruffs. Parker 1970 describes variation in male tactics associated with mate acquisition by male dung flies, in which males varied their behavior to achieve equal fertilization rates. Wilson 1971 (pp. 169–170) notes the “peculiar phenomenon” of male morphological and behavioral dimorphism in halictine bees. Like Darwin 1874, Hogan-Warburg 1966, and Parker 1970, Gadgil 1972 considers equilibration of fitness between morphs necessary for the persistence of genetically determined, multiple male phenotypes and provides a theoretical argument in graphic form for the evolution and maintenance of alternative mating strategies.

• Arrow, G. J. 1928. Polymorphism in horned beetles. Transactions of the Royal Entomological Society of London 76:73–77.

  DOI: 10.1111/j.1365-2311.1928.tb01189.x

  Describes in detail both continuous and discontinuous variation in beetles exhibiting horns, documenting these traits in males and in females, but without interpretation. States, on p. 73, “These structures . . . are not independent features, capable, as Darwin supposed, of being improved, through Sexual Selection, without regard to any other feature.” And further, “The study of these facts should ultimately result in the discovery of principles which will throw light upon a variability which at present appears quite without order.”

• Barlow, G. W. 1967. Social behavior of a South American leaf fish, Polycentrus schombuigkii, with an account of recurring pseudo-female behavior. American Midland Naturalist 78:215–234.

  DOI: 10.2307/2423382

  An elegant laboratory account of courtship, oviposition, and parental care in leaf fish including a description of “pseudo-female behavior” in males. Reviews additional articles concerning similar behavior in other fish, but like Morris 1952 does not consider it responsible for fertilizations.

• Bateson, W., and H. H. Brindley. 1892. On some cases of variation in secondary sexual characters, statistically examined. Proceedings of the Zoological Society of London: 585–594.

  DOI: 10.1111/j.1096-3642.1892.tb01785.x

  Analyzes bimodality in the distributions of dimorphic cephalic and caudal appendages in arthropods (Forficula, Xylotupa, Lucanus) but declines to speculate on its origin or persistence, stating (p. 589), “In cases of dimorphism some have thought fit to speculate on the possible utility of the phenomenon. We know no basis of fact from which these discussions may be properly attempted, and we leave these matters to those who are satisfied with such methods of biological inquiry and have leisure and ingenuity to pursue them.”

• Gadgil, M. 1972. Male dimorphism as a consequence of sexual selection. American Naturalist 106:574–580.

  DOI: 10.1086/282797

  Identifies male dimorphisms as traits shaped by sexual selection and suggests, after reviewing past literature, that dimorphism might persist because territorial males’ disproportionate investment in combat structures, allows males investing little in such structures to experience fitness equivalent to males investing heavily, and thereby persist within a population.

• Hogan-Warburg, A. J. 1966. Social behavior of the ruff, Philomachus pugnax (L.). Ardea 54:109–229.

  Drawn from a detailed dissertation, this is among the first clear post-Darwinian considerations of male polymorphism as alternative mating phenotypes evolving via negative frequency dependent selection. Describes male plumage polymorphism and its correlated behavioral variation and argues with data and scholarship that male variation in ruffs represents a stable behavioral polymorphism. Also distinguishes the male morphs as resident, marginal, and satellite males, terminology later used to describe other alternative mating tactics associated with territories.

• Huxley, J. S. 1932. Problems of relative growth. New York: Dial.

  Describes dimorphisms within neuter castes of insects and in cephalic and caudal arthropod appendages, but dismisses their importance, citing the range of variation in dimorphic structures as often overlapping, suggesting environmental variation as the cause, and stating, “The important point to notice is that the unusual and apparently abnormal fact of dimorphism in one sex has here been brought about by a combination of the two normal and common processes of moulting and heterogony” (p. 70).

• Morris, D. 1952. Homosexuality in the Ten-Spined Stickleback (Pygosteus pungitius L.). Behaviour 4: 233–261.

  DOI: 10.1163/156853951X00160

  Often cited as an example of alternative mating tactics, Morris in this and later studies describes male behavioral polymorphism in fish, particularly in the context of “homosexual” behavior, discounting the possibility that it leads to successful fertilizations. Also reviews examples in other species but again considers this behavior as resulting from motivation, i.e., “frustration,” or anomalous sensory interpretation.

• Oguma, K. 1913. Japanese dragonflies of the Family Calopterygidae with the descriptions of three new species and one new subspecies. The Journal of the College of Agriculture 5.6: 149–163.

  Mentions the existence of multiple male morphs in Mnais damselflies which has since been shown to represent a Mendelian genetic polymorphism, see Tsubaki 2003 (cited in Inheritance). Provides only species descriptions with no information on population frequencies of the dimorphism.

• Parker, G. A. 1970. The reproductive behavior and the nature of sexual selection in Scatophaga stercoraria. II. The fertilization rate and the spatial and temporal relationships of each around the site of mating and oviposition. Journal of Animal Ecology 39:205–228.

  DOI: 10.2307/2896

  Describes variation in male guarding and searching behavior in Scatophaga, in the second of a two-part series considering male behavior and female availability associated with oviposition sites in cattle dung. Postulates that males modify their mate searching behavior to produce an evolutionary equilibrium in which “all males achieve an approximately equal fertilization rate” (p. 277). Often cited as an example of alternative mating tactics associated with reproductive competition, the distribution of behavioral phenotypes is normal rather than bimodal.

• Wilson, E. O. 1971. The insect societies. Cambridge, MA: Harvard Univ. Press.

  Describes dimorphisms within the sterile cases of social insects which in hymenopterans are all female. Also (p. 169–170) notes that the “peculiar phenomenon” of male dimorphism in halictine bees “does not fit with in with the remainder of our knowledge of halictid sociobiology. . . . ”