(Press-News.org) EUGENE, Ore. -- (May 28, 2015) -- Men and women often enter relationships with different long-term goals. In the animal world, differences in approaches to reproductive success can lead to sexual conflict.
Male fruit flies, for example, transfer proteins during mating that can alter the timing of a female's egg laying and her tendency to later mate with other males. Some of these male-derived proteins also migrate from the female's reproductive tract to her brain.
Now, in a new study, scientists of the University of Oregon and Bowdoin College show that sexual conflicts can evolve rapidly in natural populations, driven by competition among males for mating success. The study was published online in BioMed Central's open-access journal BMC Evolutionary Biology.
Researchers in the UO biology lab of Patrick C. Phillips had just begun a set of experiments using the nematode Caenorhabditis remanei, when graduate student Colin Peden noticed that females that mated with males originally collected from New York die more quickly than those that mated to males from Ohio or Germany.
Females mated to New York males for even a single day lived only half as long as they did spending their lives as virgins. Even when they lived, Peden found, females mated to New York males produced half as many offspring as when their offspring were fathered by other males.
Phillips and colleagues then asked, in an evolutionary sense, how could the attributes of the New York males still exist when they lead to so few successful offspring in the next generation?
In seeking an answer, they put the different males together in a competition. The sperm of the New York males, the researchers found, easily outcompeted sperm from the Ohio and German males to successfully fertilize a female's eggs.
"Despite their small size, nematode sperm is actually much larger than human sperm, and it is thought that the sperm from different males literally battle it out inside the female for access to her eggs," said Phillips, who is a researcher in the UO's Institute of Ecology & Evolution. "So a reasonable evolutionary explanation would be that these males make bad mates but highly successful fathers."
To test this hypothesis more rigorously, Phillips turned to Michael Palopoli, an evolutionary biologist at Bowdoin College in Brunswick, Maine.
Palopoli and a group of undergraduate students used genetic tricks to transform the mating system of a closely related nematode Caenorhabditis elegans.
These roundworms usually exist as hermaphrodites that reproduce using sperm and eggs produced inside the same individual. Males also exist in C. elegans, but they are rare and wimpy compared to males from male-female species like C. remanei. Palopoli and his team used a genetic mutation that blocks sperm production in hermaphrodites, effectively turning them into females. They then mated these newly formed females with males and allowed them to evolve together for 60 generations.
Males in this highly competitive environment rapidly evolved larger sperm, as well as sperm that became much more competitive when compared to their female-free ancestors. Most importantly for the evolutionary story, these males also evolved such that females died more frequently when mated with them than when they were mated with males that had never been subjected to the high male-competition treatment.
"Overall, we were able to rapidly recapitulate the evolutionary pattern that we see in the male-female species by converting a hermaphroditic species to be male-female and then allowing them to evolve under these new circumstances," Palopoli said.
The mystery of why sexual conflict exists within these species is now replaced by the mystery of how the males are affecting the females. "It could be a change in the behavior of the males, or it could be something in the seminal fluid that they transfer during mating," Phillips said. "We are following up on this work to figure that out."
INFORMATION:
The National Science Foundation supported the research by grants (DEB-064-1066 and DEB-1120417) to Phillips. Additional funding was provided by the National Center for Research Resources (5P20RR016463-12), the National Institute of General Medical Sciences of the National Institutes of Health (8P20GM103423-12), the Howard Hughes Medical Institute's Undergraduate Science Program and Bowdoin College.
Coauthors with Phillips, Peden and Palopoli were Caitlin Woo and Ken Akiha of Bowdoin College. Other UO coauthors were Lori Cruze, a former UO research assistant now a professor in the Department of Obstetrics and Gynecology at the Medical University of South Carolina; former UO undergraduate student Megan Ary, now a mathematics teacher in the South Lane School District in Cottage Grove, Oregon; and former research assistant Jennifer L. Anderson, now a researcher at the National Institute of Agronomic Research in Rennes, France.
Sources: Patrick C. Phillips, UO professor of biology, currently on sabbatical at the Ecole Normale Superieure in Paris, pphil@uoregon.edu, and Michael F. Palopoli, professor of evolutionary biology, Bowdoin College, 207-725-3657, mpalopol@bowdoin.edu
Links:
Paper: http://www.biomedcentral.com/1471-2148/15/93
Phillips faculty page: http://ie2.uoregon.edu/people/phillips
Phillips lab: http://pages.uoregon.edu/pphil/
Palopoli: http://www.bowdoin.edu/faculty/m/mpalopol/
Department of Biology: http://biology.uoregon.edu/
Institute of Ecology and Evolution: http://ie2.uoregon.edu/
CHICAGO -- Researchers from the Abramson Cancer Center of the University of Pennsylvania and Penn's Perelman School of Medicine will present results from several clinical trials and other key studies during the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting from May 29 through June 2.
Results of Phase II Trial Show Successful Antitumor Response Rate in Patients with Advanced BRCA-Related Ovarian Cancer
Olaparib, an experimental twice-daily oral cancer drug, produces significant antitumor responses in more than a third of patients with BRCA-related ...
An app to test eyesight easily and affordably using a smartphone is as accurate as traditional charts, according to a study published today.
Peek (the Portable Eye Examination Kit) is a unique smartphone-based system for comprehensive eye testing anywhere in the world which has been designed and developed by the London School of Hygiene & Tropical Medicine, the University of Strathclyde and the NHS Glasgow Centre for Ophthalmic Research.
Globally, 285 million people are visually impaired and 80% have diseases which could be cured or prevented. However, most live in ...
Researchers from around the world have worked together to try to measure the global burden of cancer and they estimate there were 14.9 million new cases of cancer, 8.2 million deaths and 196.3 million years of a healthy life lost in 2013, according to a Special Communication published online by JAMA Oncology.
The Global Burden of Disease study by the Global Burden of Disease Cancer Collaboration group provides a comprehensive assessment of new cancer cases (incidence), and cancer-related death and disability. Researchers relied on cancer registries, vital records, verbal ...
Taking the medication metformin hydrochloride was associated with reduced risk of developing the sight-threatening disease open-angle glaucoma in people with diabetes, according to a study published online by JAMA Ophthalmology.
Medications that mimic caloric restriction such as metformin can reduce the risk of some late age-onset disease. It is unknown whether these caloric mimetic drugs affect the risk of age-associated eye diseases such as macular degeneration, diabetic retinopathy, cataract or glaucoma.
Researcher Julia E. Richards, Ph.D., of the University of ...
Hearing impairment was more prevalent among men and older individuals in a study of U.S. Hispanic/Latino adults, according to a report published online by JAMA Otolaryngology-Head and Neck Surgery.
Hearing impairment is a common chronic condition that affects adults. Hearing impairment may lead to lower quality of life and is associated with an increased risk for dementia. Most hearing impairment is undiagnosed and untreated.
Karen J. Cruickshanks, Ph.D., of the University of Wisconsin, Madison, and co-authors determined the prevalence of hearing impairment among Hispanic/Latino ...
This news release is available in Spanish.
In the largest study to date of hearing loss among Hispanic/Latino adults in the United States, researchers have found that nearly 1 in 7 has hearing loss, a number similar to the general population prevalence. The analysis also looked at the differences between subgroups and found that Hispanics of Puerto Rican descent have the highest rate of hearing loss, while Mexican-Americans have the lowest. The study identified several potential risk factors for hearing loss, including age, gender, education level, income, noise exposure, ...
SEATTLE -- New cases of virtually all types of cancer are rising in countries globally - regardless of income - but the death rates from cancer are falling in many countries, according to a new analysis of 28 cancer groups in 188 countries.
Thanks to prevention and treatment, progress has been made in fighting certain cancers, such as childhood leukemia. But researchers found that of all the cancers studied, there was just one - Hodgkin lymphoma - where the number of new cases dropped between 1990 and 2013. Over the same period, age-standardized death rates for all cancers ...
DAVIS, Calif. - Even though the walnut twig beetle (WTB) is likely native to Arizona, California, and New Mexico, it has become an invasive pest to economically and ecologically important walnut trees throughout much of the Western and into the Eastern United States. Through genetic testing, researchers from the Pacific Southwest Research Station (PSW) and partners from the University of California, Riverside and U.S. Forest Service Forest Health Protection have characterized the beetle's geographic distribution and range expansion. Results were recently published in the ...
CHICAGO --- An innocent mistake made by a graduate student in a Northwestern Medicine lab (she accidentally used male mice instead of female mice during an experiment) has led scientists to a novel discovery that offers new insight into why women are more likely than men to develop autoimmune diseases such as multiple sclerosis (MS).
The finding, detailed in a paper published in The Journal of Immunology, focuses on a type of white blood cell, the innate lymphoid cell, that exhibits different immune activities in males versus females.
MS is a disease that affects the ...
If you're a musician, this sounds too good to be true: University of Chicago psychologists have been able to train some adults to develop the prized musical ability of absolute pitch, and the training's effects last for months.
Absolute pitch, commonly known as "perfect pitch," is the ability to identify a note by hearing it. The ability is considered remarkably rare, estimated to be less than one in 10,000 individuals. It has always been a very desired ability among musicians, especially since several famous composers, including Mozart, reportedly had it. The assumption ...
