Biology Reference
In-Depth Information
3.4 Genetic Variation Is Necessary for Evolution
Genetic variation is the grist of the mill of natural selection, grinding
out evolutionary change. Evolution is a process. Within a population
there is variation for phenotypic traits. A phenotype is what you see. It
can be simple, such as eye color, or complex, like an entire eye. It is a re-
sult of the genes and regulatory networks that af ect the trait, the devel-
opmental processes that build it, and the environment, a partner with
the genome in the determination of the phenotype. Natural selection is
simply the consequence of dif erential reproductive success. Individu-
als with some traits survive and reproduce more than those with alter-
native traits. If there is a correlation in a trait between parents and
of spring (the trait is heritable), then the favored trait will increase in
representation in the next generation. It evolves.
Without genetic variation for traits af e c t i n g s o c i a l o r g a n i z a t i o n ,
there can be no evolution of colony traits such as nest architecture, food
storage, reproduction, and defense. Variation can af ect social signaling
networks, such as pheromones produced by workers and queens or the
stimulus-response systems of individuals.
3.5 Genetic Variation for Worker Behavior
In 1986, Nick Calderone, Kim Fondrk, Gene Robinson, and I began
looking at the ef ects of genetic variation on individual worker behav-
ior within colonies. Calderone was my i rst doctoral student, Robinson
was the i rst postdoctoral fellow in my lab, and Fondrk was my i rst
technician. When we began our experiments, the general belief in the
social insect community was that genetic variation among workers
within a colony had no ef ect on individual behavior and that observed
variation was a consequence of experience and colony need.
Genetic variation in a population is distributed within colonies and
among colonies. If individuals within colonies are highly related, as
when a queen mates with one male, then the genetic variation within
colonies is relatively low, and variation among colonies is relatively high.
If, however, relatedness within colonies is low, as when queens mate
