Can't Compete On Dung? Try Mating On Apple Pomace

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ScienceDaily (June 27, 2009) — In the mating world of yellow dung flies, large, brawny males almost always get the girl. However, a new study suggests that smaller males rule if presented with an opportunity to woo females when they are not hanging out on cow dung. It is the first time alternative male reproductive strategies have been observed in this species.

In a study published in the June 24 Proceedings of The Royal Society B, a group of Syracuse University (N.Y.) undergraduate students found that small male dung flies, which are traditionally unsuccessful at finding and keeping mates on dung pats, successfully mated with females feeding on composting apple pomace. In fact, large males were generally absent from the pomace mounds.
"This is a new chapter in the story of yellow dung flies," says Scott Pitnick, professor of biology in SU's College of Arts and Sciences. "No one has carefully studied this species off the dung. Small male dung flies can't compete with their larger counterparts on the dung, so in this case, they developed a different tactic to successfully pass their genes to the next generation."
Pitnick co-authored the study with the students. The students were enrolled in an advanced biology course designed to teach them to conduct original scientific research. Pitnick co-teaches the course with J. Albert C. Uy. As part of the course, the students were tasked with designing a study around the size and mating success of yellow dung flies.
"After we made our initial field observations for the class assignment, we could tell from our professors' reactions that our discovery was a piece of important information in the field," says Stephen Maheux '09, a biology major who graduated in May. "The course was designed to teach us how to be biologists; as such, we made a unique observation that ultimately resulted in a publication."
Until now, it was thought that yellow dung flies mated almost exclusively on manure. Females are drawn to the dung only when they are ready to mate. Little is known about the feeding habits of females when they are not at the dung pats, Pitnick says. On the other hand, males were thought to hang out almost exclusively around the manure, awaiting the arrival of the females. Competition on the dung among males is fierce and can result in injury or death to smaller males as well as females caught up in the struggle.
But, on Toad Hollow Farms in Nedrow, N.Y., the students noticed large numbers of females feeding on apple pomace in a field adjacent to the cow pasture where they were observing flies on dung pats. Much to the students' surprise, the females were frequently mating on the pomace, and with males that were significantly smaller in size than those found in the cow pasture. Furthermore, none of the sexually aggressive behaviors normally observed on the dung pats occurred on the pomace.
Owned by Bill Guptill, Toad Hollow Farms produces natural compost made from manure, leaf and yard waste, and fruit and vegetable waste from grocers in and around Central New York. Apple pomace is the pressed pulp that remains after juicing. The students' initial observations suggested that the availability of the pomace seemed to provide male dung flies with alternative mating opportunities.
Maheux and biology major Kali Henn, who will be a senior in the fall, continued working with Pitnick after the class concluded to collect and analyze additional data, re-confirm the initial class results, and help write the manuscript that was submitted for publication to The Royal Society.
"The class focuses on enabling students to experience the research process—from formulating questions and making the observations to designing the experiments, analyzing the data and writing the final manuscript," Pitnick says. "In this case, what started as a class exercise ended up as a significant finding in this field."
Adapted from materials provided by Syracuse University.

Boy Or Girl? In Lizards, Egg Size Matters

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ScienceDaily (June 22, 2009) — Whether baby lizards will turn out to be male or female is a more complicated question than scientists would have ever guessed, according to a new report published online on June 4th in Current Biology. The study shows that for at least one lizard species, egg size matters.

"We were astonished," said Richard Shine of the University of Sydney. "Our studies on small alpine lizards have revealed another influence on lizard sex: the size of the egg. Big eggs tend to give girls, and small eggs tend to give boys. And if you remove some of the yolk just after the egg is laid, it's likely to switch to being a boy, even if it has female sex chromosomes; and if you inject a bit of extra yolk, the egg will produce a girl, even if it has male sex chromosomes."
In many animals, the sex of offspring depends on specialized sex chromosomes. In mammals and many reptiles, for instance, males carry one X and one Y chromosome, while females have a pair of X chromosomes. In contrast, animals such as alligators depend on environmental cues like temperature to set the sex of future generations.
The new findings add to evidence that when it comes to genetic versus environmental factors influencing sex determination, it doesn't have to be an either/or proposition. In fact, Shine and his colleagues earlier found in hatchlings of the alpine-dwelling Bassiana duperreyi that extreme nest temperatures can override the genetically determined sex, in some cases producing XX boys and XY girls. His group had also noticed something else: large lizard eggs were more likely to produce daughters and small eggs to produce sons.
Despite the correlation, Shine said he had assumed that the association was indirect. In fact, his colleague Rajkumar Radder conducted studies in which he removed some yolk from larger eggs, more likely to produce daughters, to confirm that assumption.
"We were confident that there would be no effect on hatchling sex whatsoever," Shine said. "When those baby boy lizards started hatching out, we were gob-smacked."
Shine thinks there will be much more to discover when it comes to lizard sex determination.
"I suspect that the ecology of a species will determine how it makes boys versus girls, and that our yolk-allocation effect is just the tip of a very large iceberg," he said.
The authors include Rajkumar S. Radder, University of Sydney, Australia; David A. Pike, University of Sydney, Australia; Alexander E. Quinn, University of Canberra, Australia; and Richard Shine, University of Sydney, Australia.
Journal reference:
Rajkumar S. Radder, David A. Pike, Alexander E. Quinn, and Richard Shine. Offspring Sex in a Lizard Depends on Egg Size. Current Biology, 2009; DOI: 10.1016/j.cub.2009.05.027
Adapted from materials provided by Cell Press, via EurekAlert!, a service of AAAS.

Mate Selection: Honesty In Advertising Pays Off

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ScienceDaily (June 19, 2009) — Throughout the animal kingdom brilliant colors or elaborate behavioral displays serve as "advertisements" for attracting mates. But, what do the ads promise, and is there truth in advertizing? Researchers at Yale theorize that when males must provide care for the survival of their offspring, the males' signals will consistently be honest — and they may devote more of their energy to caring for their offspring than to being attractive.

The idea that males showcase their best qualities to attract females for mating isn't a new one, nor is the idea that they might be deceptive in what they are promoting. Instead, the new findings better predict the requirement for honesty in advertising as a function of the male's suitability for parenting, according to Natasha Kelly, a graduate student in ecology and evolutionary biology at Yale and lead author of the study.
The peacock's ornate fanned tail — or the primping and posturing of a guy in a bar — are "advertisements" or mating displays that take substantial energy to maintain. When a male's energy is heavily focused on keeping up his appearance, he may have little energy to devote to caring for offspring. But that may be okay, say the researchers — in species where he does not really need to tend to the kids.
Previous research suggested that, under certain circumstances, males could be dishonest about their parenting skills and still have high reproductive success. This new model, now appearing in the online version of the Proceedings of the Royal Society B, examines the reliability of males' mating signals when they must care for offspring — an aspect that was missing in earlier studies.
There are many species in which males could, but do not have to, provide parental care — because females will pick up the slack. The Yale researchers focused on those species, like stickleback fish, where females cannot pick up the slack and males who do not provide care risk the survival of their offspring.
"This new work shows that when males can not escape the cost of failing to provide care, their advertisements will tend to tend to reliably indicate how much care they will provide," said senior author Suzanne Alonzo, assistant professor of ecology and evolutionary biology at Yale.
"The qualifier in this case is where males are obligated to provide care," said Kelly. "In that case, the quiet guy in the corner might be giving the more reliable advertisement for fatherhood."
The National Science Foundation and Yale University funded this research.
Journal reference:
Kelly et al. Will male advertisement be a reliable indicator of paternal care, if offspring survival depends on male care? Proceedings of The Royal Society B Biological Sciences, 2009; DOI: 10.1098/rspb.2009.0599
Adapted from materials provided by Yale University, via EurekAlert!, a service of AAAS.

Humans More Related To Orangutans Than Chimps, Study Suggests

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ScienceDaily (June 18, 2009) — New evidence underscores the theory of human origin that suggests humans most likely share a common ancestor with orangutans, according to research from the University of Pittsburgh and the Buffalo Museum of Science. Reporting in the June 18 edition of the Journal of Biogeography, the researchers reject as "problematic" the popular suggestion, based on DNA analysis, that humans are most closely related to chimpanzees, which they maintain is not supported by fossil evidence.

Jeffrey H. Schwartz, professor of anthropology in Pitt's School of Arts and Sciences and president of the World Academy of Art and Science, and John Grehan, director of science at the Buffalo Museum, conducted a detailed analysis of the physical features of living and fossil apes that suggested humans, orangutans, and early apes belong to a group separate from chimpanzees and gorillas. They then constructed a scenario for how the human-orangutan common ancestor migrated between Southeast Asia—where modern orangutans are from—and other parts of the world and evolved into now-extinct apes and early humans.
The study provides further evidence of the human-orangutan connection that Schwartz first proposed in his book "The Red Ape: Orangutans and Human Origins, Revised and Updated" (Westview Press, 2005).
Schwartz and Grehan scrutinized the hundreds of physical characteristics often cited as evidence of evolutionary relationships among humans and other great apes—chimps, gorillas, and orangutans—and selected 63 that could be verified as unique within this group (i.e., they do not appear in other primates). Of these features, the analysis found that humans shared 28 unique physical characteristics with orangutans, compared to only two features with chimpanzees, seven with gorillas, and seven with all three apes (chimpanzees, gorillas, and orangutans). Gorillas and chimpanzees shared 11 unique characteristics.
Schwartz and Grehan then examined 56 features uniquely shared among modern humans, fossil hominids—ancestral humans such as Australopithecus—and fossil apes. They found that orangutans shared eight features with early humans and Australopithecus and seven with Australopithecus alone. The occurrence of orangutan features in Australopithecus contradicts the expectation generated by DNA analysis that ancestral humans should have chimpanzee similarities, Schwartz and Grehan write. Chimpanzees and gorillas were found to share only those features found in all great apes.
Schwartz and Grehan pooled humans, orangutans, and the fossil apes into a new group called "dental hominoids," named for their similarly thick-enameled teeth. They labeled chimpanzees and gorillas as African apes and wrote in Biogeography that although they are a sister group of dental hominoids, "the African apes are not only less closely related to humans than are orangutans, but also less closely related to humans than are many" fossil apes.
The researchers acknowledge, however, that early human and ape fossils are largely found in Africa, whereas modern orangutans are found in Southeast Asia. To account for the separation, they propose that the last common human-orangutan ancestor migrated between Africa, Europe, and Asia at some point that ended at least 12 million to 13 million years ago. Plant fossils suggest that forests once extended from southern Europe, through Central Asia, and into China prior to the formation of the Himalayas, Schwartz and Grehan write, proposing that the ancestral dental hominoid lived and roamed throughout this vast area; as the Earth's surface and local ecosystems changed, descendant dental hominoids became geographically isolated from one another.
Schwartz and Grehan compare this theory of ancestral distribution with one designed to accommodate a presumed human-chimpanzee relationship. They write that in the absence of African ape fossils more than 500,000 years old, a series of "complicated and convoluted" scenarios were invented to suggest that African apes had descended from earlier apes that migrated from Africa to Europe. According to these scenarios, European apes then diverged into apes that moved on to Asia and into apes that returned to Africa to later become humans and modern apes. Schwartz and Grehan challenge these theories as incompatible with the morphological and biogeographic evidence.
Paleoanthropologist Peter Andrews, a past head of Human Origins at the London Natural History Museum and coauthor of "The Complete World of Human Evolution" (Thames & Hudson, 2005), said that Schwartz and Grehan provide good evidence to support their theory. Andrews had no part in the research, but is familiar with it.
"They have good morphological evidence in support of their interpretation, so that it must be taken seriously, and if it reopens the debate between molecular biologists and morphologists, so much the better," Andrews said. "They are going against accepted interpretations of human and ape relationships, and there's no doubt their conclusions will be challenged. But I hope it will be done in a constructive way, for science progresses by asking questions and testing results."
Schwartz and Grehan contend in the Journal of Biogeography that the clear physical similarities between humans and orangutans have long been overshadowed by molecular analyses that link humans to chimpanzees, but that those molecular comparisons are often flawed: There is no theory holding that molecular similarity necessarily implies an evolutionary relationship; molecular studies often exclude orangutans and focus on a limited selection of primates without an adequate "outgroup" for comparison; and molecular data that contradict the idea that genetic similarity denotes relation are often dismissed.
"They criticize molecular data where criticism is due," said Malte Ebach, a researcher at Arizona State University's International Institute for Species Exploration who also was not involved in the project but is familiar with it.
"Palaeoanthropology is based solely on morphology, and there is no scientific justification to favor DNA over morphological data. Yet the human-chimp relationship, generated by molecular data, has been accepted without any scrutiny. Grehan and Schwartz are not just suggesting an orangutan–human relationship—they're reaffirming an established scientific practice of questioning data."
Journal reference:
John R. Grehan1 and Jeffrey H. Schwartz. Evolution of the second orangutan: phylogeny and biogeography of hominid origins. Journal of Biogeography, 2009 DOI: 10.1111/j.1365-2699.2009.02141.x
Adapted from materials provided by University of Pittsburgh.

Close Social Ties Make Baboons Better Mothers, Study Finds

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ScienceDaily (June 11, 2009) — Baboons whose mothers have strong relationships with other females are much more likely to survive to adulthood than baboons reared by less social mothers, according to a new study by researchers at UCLA, the University of Pennsylvania and other institutions.

"If you're a baboon, the strength of your mother's relationship with other females is the best predictor of whether you'll live to have children yourself," said Joan Silk, the study's lead author and a UCLA professor of anthropology. "The study adds to mounting evidence of the biological benefits of close relationships among females."
The findings are significant because "survivorship to reproduction is the gold standard in evolutionary biology," said co-author Dorothy Cheney, a professor of biology at the University of Pennsylvania. "Females who raise offspring to a reproductive age are more likely see their genes pass along, so these findings demonstrate an evolutionary advantage to strong relationships with other females. In evolutionary terms, social moms are the fittest moms — at least when it comes to baboons."
The study appears online in the Proceedings of the Royal Society B, a peer-reviewed journal published by the national academy of science of the United Kingdom and the Commonwealth.
Silk, Cheney and seven other researchers from the University of Pennsylvania, the University of Michigan and the University of St. Andrews in Kenya analyzed 17 years worth of records on more than 66 adult female baboons in the Moremi Game Reserve, a 2,000-square-mile national park in Botswana that teems with wildlife.
Collected on the ground by primatologists who tracked the baboons six days a week, 12 months a year, the records reflected the sex and survival rates of baboon offspring, as well as telling details of the mothers' social lives, including their ranking within the group, as measured by the direction of approach/retreat interactions, and the amount of social interactions they had with each of the group's other females.
In addition to showing how often one animal approached another, the records of social interactions included details of grooming, which is known to be the primary form of social interaction in Old World monkeys. The researchers noted how much time — frequency and duration — the females spent grooming each other and how often they solicited grooming from other females.
Of all the factors studied, the strength of a mother's social bonds with another female had the most significant effect on the survival rates of offspring. A mother's dominance rank proved to have no affect on the survival rate of her offspring.
"We really expected dominance status to be more influential than it proved to be," Silk said.
Offspring from the most social mothers turned out to be about one-and-a-half times more likely to survive to adulthood than offspring from the least social mothers.
The strongest social bonds were measured between mothers and adult daughters, followed by sisters and all other potential relationships, including aunts, nieces, cousins and baboons with no familial ties. Bonds between mothers and adult daughters proved to be three times stronger than those between sisters and 10 times stronger than relationships with other females.
"What really matter to these girls are mother-daughter bonds," Silk said. "They're really strong, and they last forever. If your mom is alive, she's one of your top partners, always. But more importantly, it's the strength of these bonds, because females whose bonds with their mothers and daughters were strong had higher offspring survival than females whose bonds with these relatives were weak."
Silk's past research with Jeanne Altmann, the Eugene Higgins Professor of Ecology and Evolutionary Biology at Princeton University, and Susan C. Alberts, a professor of biology at Duke University, on baboons in the Amboseli Basin of Kenya had found a higher survival rate for baboons with social mothers, but the research only tracked offspring through the first year of life.
For the new study, researchers followed offspring from 1 year of age through sexual maturity — roughly 5 years of age. The new study also differs from past baboon research by focusing on the strength and duration of relationships between pairs of females rather than on the amount of social interactions in general.
"The benefit comes not from being wildly social — it's about having close social bonds," said Cheney, who runs the Moremi baboon-tracking project with University of Pennsylvania psychology professor Robert M. Seyfarth.
"These females form strong relationships with particular partners," Silk said. "They don't treat everyone the same. They spend a lot more time with — and a lot more time grooming — some females than others, and these relationships tend to be very long-lasting."
Additional research is needed to determine how the female bonds improve infant survival, but it may have to do with such stress hormones as cortisol, Silk said. Research has shown that prolonged elevations of stress hormones in primates can lead to cardiovascular disease and other serious health problems. Research has also shown that grooming tends to lower these stress hormones in baboons.
"Our research suggests that somehow there is a link between the kind of social relationships you form and the natural, normal stresses that occur in everyday life, and that seems to have — at least in baboons — a long-term effect on reproductive success," Silk said.
Said to share 92 percent of their DNA with humans, baboons are close relatives of humans. Baboons and humans last shared a common ancestor about 18 million years ago. The new findings on social interactions among mothers parallel recent research that has shown health benefits for humans who enjoy particularly close social networks.
"Our findings suggest benefits from forming close relationships are built into us from a long way back," Silk said.
The research received funding from the National Geographic Foundation, the Research Foundation of the University of Pennsylvania, the Institute for Research in Cognitive Science at the University of Pennsylvania, the National Institute of Health and the National Science Foundation.
Adapted from materials provided by University of California - Los Angeles.

Male Deer Are Born To Live Fast, Die Young

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http://www.sciencedaily.com/releases/2007/08/070831123426.htm

Science Daily — In the September issue of The American Naturalist, Juan Carranza (Biology and Ethology Unit, University of Extremadura, Spain) and Javier Pérez-Barbería (Macaulay Institute, United Kingdom) offer a new explanation for why males of ungulate species subjected to intense competition are born with lower survival expectancies than females.

The research reveals that male ungulates have smaller molars relative to their body size -- and hence less durable teeth that will wear out sooner, which might contribute to their shorter lives compared with females.
Natural selection favors reproduction rather than survival; the cost of reproduction compromises survival. Males of species subjected to intense male-male competition for access to females are known to have shorter life expectancies than females. Earlier aging in males might be related to higher reproductive costs, especially when lifetime reproductive success in males takes place within the few years when they can win contests and maintain their dominance.
By comparing body and dental size of males and females of 123 species of ungulates, the authors offer another compelling explanation for why male ungulates lead shorter lives. They estimated the pattern of change of these traits along the evolutionary development of the group and found that for species where a single male has many females and where the males and females are different sizes, the rate of increase of dental size was lower than that of body size.
As a result, smaller teeth (in comparison to body size) are produced in males. It is possible that natural selection did not produce larger, more durable teeth because there was no reproductive return from it, since males in these species do not generally increase their success by living longer after prime age.
"These findings," the authors state, "provide us with interesting insights into how natural and sexual selection design our bodies and their longevity."
Reference: Juan Carranza and F. Javier Pérez-Barbería, "Sexual selection and senescence: male size-dimorphic ungulates evolved relatively smaller molars than females", The American Naturalist (2007) volume 170:370--380. DOI: 10.1086/519852
Note: This story has been adapted from a news release issued by University of Chicago Press Journals.

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