Evidence from deoxyribonucleic acid DNA studies of birds, mammals, and other species has shown that extra-pair copulations can result in fertilized eggs so that a presumably "monogamous" male or female may in fact have more than one mate. Which mating system evolves is influenced by the relative parental investment of each sex and the ability of one sex to monopolize members of the opposite sex, which in turn may be driven by the abundance and distribution of resources such as food or nesting sites.
Because resources vary among and within habitats, this leads to variation in mating systems, even within species.
An excellent example of this is the mating system of the dunnock, a European songbird. The amount of food available affects the size of the area over which a female must forage, and this in turn affects how many females can be monopolized by one male and how many males can be attracted by a female.
Within a single population of dunnocks, there may be monogamous pairs as well as birds in polygynous and polyandrous relationships.
Temporary color changes have been recognized in some frogs, and biologists have been investigating the phenomenon in detail in a handful of species. Archived from the original PDF on Some scientists have suggested that peripheral changes are essential to allow animals to develop species-specific behaviors, including mating, but it has not been possible to determine whether this was the main or only site of change in the nervous system. One pathway forms a so-called excitatory interneuron that encourages mating, and the other an inhibitory interneuron to damp the urge. Transformation, unlike transduction or conjugation, depends on numerous bacterial gene products that specifically interact to perform this complex process, [16] and thus transformation is clearly a bacterial adaptation for DNA transfer. For the mating of mechanical components, see Engineering fit.
Because of differences in the amount of energy invested in producing gametes eggs are costly, sperm are not , finding a mate, and rearing offspring, the costs and benefits of a particular mating system may be different for males and females. In addition, not all individuals of the same sex in a population experience the same costs and benefits of a particular mating system for example, some males in a polygynous mating system may have several mates whereas other males may have none.
Dunnock Behaviour and Social Evolution. Oxford University Press, Sherman, and Martin L.
A male frigate bird with its throat pouch inflated to attract females. Bibliography Davies, Nicholas B. Other articles you might like: Comment about this article, ask questions, or add new information about this topic: Show my email publicly. Type the code shown: Temporary color changes have been recognized in some frogs, and biologists have been investigating the phenomenon in detail in a handful of species.
But since the bright hues do not last long, they can be easy to miss, and no one knew just how many species have males who change color for the breeding season. Now, after searching for evidence of such a color change in thousands of frog species, Rayna Bell , a research zoologist and curator of amphibians and reptiles at the museum, said the phenomenon is surprisingly widespread: Bell said she first learned that some male frogs switch colors for the breeding season while exploring male and female color differences across the frog tree of life.
The temporary color changes had also caught the attention of Associate Professor Martin Whiting and undergraduate honors student Grant Webster at Macquarie University, who had uncovered many examples of the phenomenon in Australian frogs.
After Bell published a review article on the topic, the two Australian scientists contacted her and proposed they work together to broaden the search. The three scientists teamed up to find as many examples of temporary color changes in male frogs as they could.
Some had already been documented, and Webster had noted many in his own field work. But generally, scientists have not paid much attention to the role of color in communication between frogs, focusing instead on their vocal communications, Bell said. She and her collaborators examined a wide array of frog photos looking for evidence of color change.
To evaluate each species, the team compared photos of males engaging in breeding behavior--either actively calling for a mate or in a mating posture with a female--to photos of males outside the breeding season and to females. The team evaluated 2, different frog species and identified whose males temporarily change color when it is time to breed, with most turning a bright yellow. Like the three best-studied species of color-changing frogs, most are species that breed in large, chaotic groups, where the males' distinct coloration may improve the chances of successful pairings.