What makes species

The researchers use genetic markers to track segments of the X chromosome that they move from one species of Drosophila fruit fly into a different species in order to find X-linked genes that cause male sterility.

Genetic markers that affect eye color are located on the X chromosome, so the researchers start with Drosophila mauritiana that have two genetic markers—giving them dark red eyes, left—and cross them to white-eyed Drosophila simulans.

Chromosomes are divided into two types: sex chromosomes and autosomes. Sex chromosomes are the XY chromosomes that denote a male in both fruit flies and humans and the XX that denote a female. When the researchers mapped the factors that cause hybrid males to become sterile, they found that there were many more incompatibility factors on the X sex chromosome compared to on the autosomes. This means that sex chromosomes become functionally different between species much faster than non-sex chromosomes, Presgraves says.

But what is it that makes sex chromosomes evolve genetic incompatibilities faster than the rest of the genome? In general, selfish genes are parasites of the genome—they propagate themselves at the expense of other genes. Meiotic drive elements in particular subvert the rules of typical inheritance: in normal Mendelian inheritance, a gene is transmitted to half of the offspring. Meiotic drive elements, however, manipulate reproduction so they can transmit themselves to greater than 50 percent—more than their fair share.

In a twist, however, the researchers also found that if meiotic drive elements have the opportunity for gene flow between species, they can also help bring species together. Materials provided by University of Rochester. Note: Content may be edited for style and length. Science News. Story Source: Materials provided by University of Rochester.

Gene flow mediates the role of sex chromosome meiotic drive during complex speciation. The role of selfish genes in distinguishing a species. ScienceDaily, 3 January University of Rochester. What makes two species different? Retrieved November 10, from www. A team of It shows that gene flow, or gene As a result of this research, ScienceDaily shares links with sites in the TrendMD network and earns revenue from third-party advertisers, where indicated. Print Email Share.

Boy or Girl? Also, many plants, and some animals, form hybrids in nature. Hooded crows and carrion crows look different, and largely mate within their own groups — but in some areas, they hybridize. Should they be considered the same species or separate species? If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species?

There are lots of other places where the boundary of a species is blurred. Read about the biological species concept and other species concepts. Learn more about the evolution of the happy face spider species: Aloha, spider style! The work of Rosemary Gillespie , a research profile.