Bird species that have relatively long incubation periods and short nestling periods for their body size have higher concentration of androstenedione than those species whose developmental time is shifted towards relatively longer stays in the nest than in the egg. This is an advantage depending on the predators. There is a relationship between egg levels of androstenedione and colony size, suggesting that mothers prepare their offspring for the social conditions.
Current research emphasizes the role of maternal effects in fostering the adaptation of organisms to a changing environment. In birds, mothers pass androgens to their eggs, and these hormones have been shown to influence the development and behavior of nestlings. Since these effects may persist in adulthood, it has been suggested that avian mothers may engineer, so to speak, the adult phenotype of their offspring.
Although abundant research in a variety of species has examined these questions, little is known on whether differences between species in levels of egg androgens are related to differences in the ecology of species.
Diego Gil, from the Spanish Museum of Natural History, and coauthors (Clotilde Biard, André Lacroix, Claire Spottiswoode, Nicola Saino, Marisa Puerta, and Anders P. Møller) from several universities in Europe, show in a paper in the June issue of The American Naturalist that several differences in avian life history have coevolved with differences in yolk androgens. Thus, the relative amount of time that a developing bird spends in the egg and in the nest is positively related to androstenedione, one of the main egg androgens. That is to say, bird species that have relatively long incubation periods and short nestling periods for their body size have higher concentration of androstenedione than those species whose developmental time is shifted towards relatively longer stays in the nest than in the egg.
Another pattern that emerges is a positive relationship between egg levels of androstenedione and colony size, suggesting that mothers prepare their offspring for the social conditions that they will experience as adults. These data provide evidence that facultative maternal effects at the individual level are linked to evolutionary transitions between species, suggesting a role of phenotypic plasticity in supporting adaptative patterns.
Source: University of Chicago
Related stories:
Female fish see right through false suitors' pickup acts
In a dark, damp corner of a University of Wisconsin-Madison laboratory, Jenny Boughman dropped a 3-inch, three-spined female fish into a fish tank, and waited. She sat perfectly still as she watched a male fish swim out slowly from its nest, beneath a cracked flower pot.
Border Patrol also guards against foreign bugs
(AP) -- Alishia Beckham is on the front lines defending the United States from foreign invaders - armed with weapons that include a hand mirror and a flashlight.
Geometric model could mean breakthrough in saving endangered kakapo
(PhysOrg.com) -- A mathematical model used to assess the nutrient balance of the kakapo diet has the potential to help solve one of the main challenges to saving the endangered native parrot.
Using live fish, new tool a sentinel for environmental contamination
Researchers have harnessed the sensitivity of days-old fish embryos to create a tool capable of detecting a range of harmful chemicals.
New evidence implicates humans in prehistoric animal extinctions
Research led by UK and Australian scientists sheds new light on the role that our ancestors played in the extinction of Australia's prehistoric animals. The study, published this week in the journal
Proceedings of the National Academy of Sciences of the USA, provides the first evidence that Tasmania's giant kangaroos and marsupial 'rhinos' and 'leopards' were still roaming the island when humans first arrived. The findings suggest that the mass extinction of Tasmania's large prehistoric animals was the result of human hunting, and not climate change as previously believed.
Maelstrom quashes jumping genes
Scientists have known for decades that certain genes (called transposons) can jump around the genome in an individual cell. This activity can be dangerous, however, especially when it arises in cells that produce eggs and sperm. Such changes can threaten the offspring and the success of a species. To ensure the integrity of these cells, nature developed a mechanism to quash this genetic scrambling, but how it works has remained a mystery.
Duck-billed dinosaurs outgrew predators to survive
With long limbs and a soft body, the duck-billed hadrosaur had few defenses against predators such as tyrannosaurs. But new research on the bones of this plant-eating dinosaur suggests that it had at least one advantage: It grew to adulthood much faster than its predators, giving it superiority in size.
World's smallest snake found in Barbados
(PhysOrg.com) -- The world's smallest species of snake, with adults averaging just under four inches in length, has been identified on the Caribbean island of Barbados. The species -- which is as thin as a spaghetti noodle and small enough to rest comfortably on a U.S. quarter --was discovered by Blair Hedges, an evolutionary biologist at Penn State. Hedges and his colleagues also are the discoverers of the world's smallest frog and lizard species, which too were found on Caribbean islands. The most recent discovery will be published on 4 August 2008 in the journal
Zootaxa.