One supervisor, Leland Yee, took umbrage at the notion that only native species should be kept, and exotic ones eradicated, comparing it to racial cleansing or “xenophobia.”
“Plants and trees without the proper pre-Mayflower lineage are called ‘invasive exotics’ and are wrenched from the soil to die,” Yee wrote in a local newspaper editorial. “How many of us are ‘invasive exotics’ who have taken root in the San Francisco soil, have thrived and flourished here, and now contribute to the diversity of the wonderful mix that constitutes present-day San Francisco?”
How does R2d2 escape natural selection? By cheating at female meiosis, the specialized type of cell division that produces eggs. Most animals and plants, including humans and mice, carry two alleles of every gene – one allele from each parent. When an organism reproduces, it passes along only one allele to each offspring. The “law of segregation,” posited by Gregor Mendel in 1865, suggests that there is an equal probability of transmission of either a maternal allele or paternal allele.
But in a previous paper, published in PLoS Genetics in 2015, Pardo-Manuel de Villena’s team showed that some alleles of R2d2 distort meiosis to promote their own transmission to offspring in a process called meiotic drive. This advantage comes with a cost.
“Female mice with distorted transmission of R2d2 also had fewer offspring,” said co-author Andrew Morgan, a graduate student in Pardo-Manuel de Villena’s lab. “This trade-off is what makes R2d2 selfish: if meiotic drive is strong enough, then it increases the frequency of alleles that decrease reproductive fitness.”