Maurine Neiman, Ph.D

Research in Evolutionary Biology

Professional Interests:

My research is centered in evolutionary biology, with a particular focus on the advantages provided by sexual reproduction and genetic recombination. All else equal, asexual females will produce twice as many daughters as sexual females, which make both male and female offspring. Because only females can contribute directly to the rate of population growth, the production of males by sexual females creates a two-fold cost of sexual reproduction that should logically result in the selective elimination of sex. However, biological reality shows that sex dominates among eukaryotes. Why sex remains so common despite these advantages of asexual reproduction has been termed the “queen of problems in evolutionary biology.”

Much of my research to date has utilized Potamopyrgus antipodarum, a freshwater snail native to New Zealand. This snail is of particular interest to evolutionary biologists because populations vary in the frequency of obligately sexual and obligately asexual individuals, which sets the stage for empirical investigation into the benefits of sex. Potamopyrgus antipodarum has been the focus of research into the maintenance of sex for close to 20 years, and is now the best-characterized natural system available for studying why sexual reproduction is so common. My current research endeavors and plans for the future are focused around using techniques from population and molecular genetics, ecological stoichiometry, cellular biology, and behavioral ecology to study the maintenance of sex in natural populations. These broad areas of research are amenable to student participation at a variety of levels.

  Link to PDF of Dr. Neiman's CV

Current Projects

The predominance of sex is only paradoxical if asexuals and sexuals truly are equal apart from their mode of reproduction. This means that the two-fold cost of sex can be negated if asexuals experience fitness disadvantages directly linked to asexuality. Accordingly, my research into the maintenance of sex is focused around determining ways in which asexual and sexual P. antipodarum differ.

• Mutation accumulation. Theory predicts that asexual lineages are doomed to extinction via the inevitable accumulation of deleterious mutations. This is because genetic recombination (the essence of sex) is required for organisms to produce offspring that have fewer mutations than they do themselves. I am using DNA sequence data to determine whether increased mutation accumulation in asexual P. antipodarum may in fact help to explain the persistence of sex in this species.

• Ecological stoichiometry. Another way in which sexual and asexual P. antipodarum may differ is in their requirements for certain elemental nutrients. In particular, because asexual P. antipodarum are triploid, they may have higher requirements for phosphorus than the diploid sexual P. antipodarum due to the high phosphate concentration of DNA. Phosphorus is a limiting resource in many aquatic systems, and may plausibly help to explain some of the distributional differences between sexual and asexual snails. In collaboration with Dr. Adam Kay, I am using techniques from ecological stoichiometry to determine whether phosphorus requirements do in fact differ in sexual and asexual P. antipodarum and could thus facilitate the maintenance of sex in this species.
• Mitochondrial performance. In collaboration with Dr. Jennifer Cruise, I am using cellular biology techniques to determine whether mutation accumulation in asexual lineages has detectable negative effects. Mitochondrial genomes are an appropriate focus for this study because 1) they are important to organismal fitness, 2) they can easily be isolated and their performance (e.g. ATP production) assayed), and 3) the proteins they produce interact with proteins produced by the nuclear genome, so mutations afflicting the nuclear genome can be indirectly assayed along with mutations in mtDNA. We are comparing mitochondrial genome performance in sexual and asexual lineages as well as in asexual lineages of varying time since derivation from sexual ancestors, since mutational degradation of asexual lineages is expected to increase with time since recombination (and mutational clearance) last occurred.
• Population dynamics of asexuals. I have used laboratory experiments to demonstrate that asexual females have a negative impact on one another's reproduction. This finding is interesting in light of the fact that P. antipodarum is an invasive species in Europe, Australia, and North America. Almost all of these invading populations are comprised entirely of asexual females. Ongoing research into why and how asexual females affect one another's reproduction, in collaboration with Dr. Adam Kay may provide insight into snail reproductive physiology and invasion dynamics and control.