Chapter 8: Mating Systems Different Mating Systems The Ecology and Evolution of Polygynous Mating Systems Multiple Mating Systems in a Single Population?

Different Mating Systems FIGURE 8.1. Four mating systems. These are (A) monogamy (1 male, 1 female), (B) polygyny (1 male, more than 1 female), (C) polyandry (1 female, more than 1 male), and (D) polygynandry (more than 1 male, more than 1 female). Each mating system can be further subdivided in a number of ways.

Different Mating Systems TABLE 8.1. Mating combinations

Different Mating Systems Monogamy FIGURE 8.2. Long-term monogamy in the oldfield mouse. From data on 500 oldfield mouse burrows, Foltz found that 90 percent of the offspring in a family group were fathered by the male in their burrow. Behavioral observations also suggest that many females remained with the same mates across litters, suggesting long-term monogamy. (Photo credit: © James F. Parnell)

Different Mating Systems Monogamy FIGURE 8.3. Who fathers whom? In the oldfield mouse (Peromyscus polionotus), the male found in the burrow, on average, fathers 90 percent of the pups in that burrow.

Different Mating Systems Monogamy FIGURE 8.4. Fitness consequences of choice in monogamous systems. Researchers compared the number of pups sired by a male in two different treatments in each of two experiments (as shown in A and B). (Based on K. K. Ryan and Altmann, 2001, pp. 438, 439)

Different Mating Systems Polygamy Polygamy: Either males or females have more than one mate per breeding cycle/ season Simultaneous or Sequential Polygyny: males breed with more than female Polyandry: females breed with more than male Chapter 8 Opener

Different Mating Systems Female Defense Polygyny Female Defense Polygyny Females short-lived, low fecundity, only inseminated once Females breed shortly after they become adults Females grouped together in space and time FIGURE 8.7. Epsilon wasps and female defense polygyny. Male wasps wait at the nest for females to emerge from their brood cells. Pictured here is one male (left) on the nest and a female (at arrow) that is starting to emerge from a hole in the mud nest. (Photo credit: © Bonnie Heim, 2008. All rights reserved)

Different Mating Systems Leks FIGURE 8.8a. Peacocks on leks. The benefits to mating on leks have been measured in the peacock. (A) Four males gather on a lek before any females arrive (one of the males is under the brush in the top left corner). (B) When a female appears on the lek, the male displays his tail in an attempt to get her to choose him as her mate. (Photo credits: Marion Petrie; Frans Lanting/Minden Pictures)

Different Mating Systems Evolution of polygyny in warblers Polygynous: Great Reed Warbler (Acrocephalus arundinaceous) FIGURE 8.9a. Warbler mating systems. The phylogeny of mating systems has been studied in warblers, including (A) the polygynous great reed warbler (Acrocephalus arundinaceous) and (B) the monogamous Seychelle warbler (Acrocephalus sechellensis). (Photo credits: John Hawkins/FLPA; M. D. England/www.ardea.com) Monogamous: Seychelle Warbler (Acrocephalus seychellensis)

Different Mating Systems Evolution of polygyny in warblers FIGURE 8.10. Phylogeny of warbler mating systems. (A) Paternal effort is represented as the proportion of a pie chart that is green (when the pie chart was more than 60 percent filled, researchers classified the system as full paternal care). This paternal effort was mapped onto the warbler phylogeny. (B) The relationship between paternal care and food supply in several species of warblers is shown by the data points. Where there was less food, there was greater paternal care; where there was more food, there was less paternal care. Values on the x-axis and the y-axis can be negative because of statistical transformations associated with this analysis. (From Leisler et al., 2002, p. 384)

Different Mating Systems Polyandry in social insects FIGURE 8.11. Polyandry and disease resistance in honeybees. One benefit of polyandry is resistance to disease. Honeybee colonies were inoculated with spores of Paenibacillus larvae, a bacterium that causes a highly virulent disease called American foulbrood. The mean number of brood infected did not differ among treatments, but the variance was significantly greater in colonies in which queens were inseminated by only one male. (Adapted from Seeley and Tarpy, 2007)

Different Mating Systems Promiscuous mating systems 1. Promiscuity 2. Polygynandry FIGURE 8.12. Dunnock mating system. The dunnock mating system is extremely versatile and includes monogamy, polyandry, polygyny, and polygynandry. Here we see a female with a newly hatched offspring (just visible in egg). (Photo credit: Nick Davies)

Different Mating Systems Promiscuous mating systems FIGURE 8.13. Incredible variation in dunnock breeding systems. Female territories are shown in green, while alpha male territories are depicted by solid red lines and beta male territories are shown by dashed red lines. In a single dunnock population, we can find mating systems ranging from monogamy to polygamy, polyandry, and polygynandry. (From Davies, 1992, p. 27)

Ecology and Evolution of Polygynous Mating Systems FIGURE 8.15. Migration, climate change, and mating systems. The relation among migration patterns, climate change, and mating systems has been studied across many migratory species of birds. Pictured here are black-bellied plovers (Pluvialis squatarola) during their spring migration. (Photo credit: Jason Stone/ NHPA)

Ecology and Evolution of Polygynous Mating Systems Polygyny Threshold Model FIGURE 8.16. Female choice of territories. Imagine a female deciding among territories. She should choose the territory with the highest quality, that is, with the most food available or the most shade and so on, regardless of whether she would be the lone female (monogamous territory) or one of several females (polygynous territory), because such a choice would provide her with the greatest fitness. A female should choose the territory with the highest quality, that is, with the most food available or the most shade and so on, regardless of whether she would be the lone female (monogamous territory) or one of several females (polygynous territory), because such a choice would provide her with the greatest fitness.

Ecology and Evolution of Polygynous Mating Systems Polygyny Threshold Model FIGURE 8.17. The polygyny threshold model. In the lark bunting, shade is a limiting resource, as it affects nestling survival. Females may choose the territory of a male with good shade cover (territory 1) over a territory with less shade cover (territory 2), even if this decision means entering a polygynous relationship rather than a monogamous one.

Ecology and Evolution of Polygynous Mating Systems Extra Pair Copulations FIGURE 8.18a. Indigo buntings. (A) A female indigo bunting. Although socially monogamous, female indigo buntings are often involved in extrapair copulations. (B) A male indigo bunting. Males defend their territories against intruders. (Photo credits: David Westneat)

Ecology and Evolution of Polygynous Mating Systems Sperm competition FIGURE 8.20. Sperm competition. The reproductive system of domestic fowl. Sperm storage occurs in sperm storage tubules (SST) at the uterovaginal junction. Females in many species can store sperm from multiple males, setting the stage for sperm competition. Only a small proportion of sperm makes it into the SST. (Based on Birkhead and Møller, 1992)

Ecology and Evolution of Polygynous Mating Systems Sperm competition FIGURE 8.21. Dungfly mating. In dungflies, sperm competition can be intense, with the last male copulating with a female fathering up to 80 percent of her offspring. (Photo credits: Geoff Parker)

Ecology and Evolution of Polygynous Mating Systems Sperm competition FIGURE 8.23. Sperm velocity and fertilization. In sea urchins, slower sperm fare poorly. The slower the sperm, the more sperm needed to fertilize a female’s eggs. (Based on Levitan, 2000)

Ecology and Evolution of Polygynous Mating Systems Sperm competition FIGURE 8.25. Variability in sperm morphology. Sperm competition is one of the many forces that have led to incredible variability in insect sperm morphology. Pictured here are (A) sperm from Eosentonon transitorium, (B) fishlike sperm from Telmatoscopus albipuntus, (C) sperm bundle from the fishfly Parachauliodes japonicus, (D) 1 mm sperm from the dung beetle Onthophagus taurus, (E) short and long sperm from Plodia interpunctella, (F) paired sperm from the water beetle Dytiscus marginalis, (G) giant 58 mm sperm from Drosophila bifurca, and (H) hook-headed sperm from Tessellana tesselata. (Based on Simmons, 2001) Sperm competition Kamikaze sperm hypothesis (Baker and Bellis (1988) Cryptic mate choice (Eberhard, 1996)