| |
Intrigued that there might be a "Berkeley" group and a "Santa Monica Mountains" group we were curious about the distribution of genetic variation. |
|
|
| |
Chris Conroy
Staff Curator of Mammals, UC Berkeley Museum of Vertebrate Zoology |
|
| |
California voles (Microtus californicus) are common grassland rodents distributed from Oregon to Baja California. They are frequently found in oak woodlands and grasslands, but can be found from sea level to about 6,000 feet. Earlier workers have classified them into about 13 different geographic groups based on their size, shape and color. When I began my position as staff curator of mammals at UC Berkeley´s Museum of Vertebrate Zoology in 2001, I was searching for topics to research. I had previously studied other voles, so this species made practical sense.
This work on California voles actually began with laboratory work starting in the early 1980s (Gill 1984). Ayesha Gill studied vole genetics at UC Berkeley as a student and later became a professor at UCLA. She expanded her student research by attempting to breed voles from Berkeley and the Santa Monica Mountains in the lab, but found several odd things. 1) Pairs made up of parents from different areas were overly aggressive to each other. She had previously bred voles in the Berkeley area and knew what typical
behavior was like. 2) Of those voles that were born, there was reduced fertility in the females. 3) Perhaps most importantly, the male hybrids were sterile. Their testes did not
produce any sperm. These three points suggest that these two groups are beginning to lack recognition of each other as the same species, and when they mate, incompatibilities in
the genetic makeup might be causing a hybrid breakdown (reduced fertility and sterility).
If they were completely sterile, these would meet most definitions of different species.
But, since they were only partially sterile, it suggests they are only part way in that
process. Gill only carried her experiment two generations and never studied them in the
wild.
|
|
| |
 |
A bewildered vole caught in a trap with some beetles on May 11, 2009,
near Refugio State Beach. Courtesy of Chris Conroy. |
|
|
We have taken a different approach. Intrigued that there might be a "Berkeley" group and
a "Santa Monica Mountains" group we were curious about the distribution of genetic
variation. We began by determining the distribution of the groups by sequencing DNA
from voles from throughout their range and locating an area where the genes suggest that
they overlap (Conroy and Neuwald 2008). We found as Gill predicted that there are two
main groups within the species. |
|
