Population Genetics of Invasive
Invasive plant species offer special opportunities
to study population genetics as their populations are often very dynamic
in terms of population size, colonization ability and genetic composition.
My special interest is to determine how the breeding system of invasive
species affects their ability to colonize new sites and to rapidly expand
their population sizes.
(mimosa; Mimosoideae) - Mimosa is an introduced, early-successional, weedy
tree that has become widespread in the southeastern US. Dr. M. J. Godt
and I are examining spatial and temporal variation in mimosas reproductive
biology to elucidate the population genetic processes that contribute
to its ability to invade new habitats, establish populations and disperse
to new sites. Multilocus allozyme data are being combined with ecological
and demographic data to address a series of questions: Are isolated trees
predominantly selfed or outcrossed? Do the number and frequency of pollen
donors differ between isolated trees and trees within established populations?
How do small, growing populations acquire genetic diversity? What proportion
of the new recruits in growing populations are progeny of the initial
founder? Does the breeding structure of populations change as they grow
or senesce? Does gene flow differ between isolated trees and established
populations? Has this introduced species adapted to different climatic
regimes? Several characteristics of mimosa allow detailed analyses if
its reproductive biology including abundant annual seed production, early
maturity, high allozyme polymorphism and singly sired fruits. The identification
of isolated trees and paired trees in nearby populations coupled with
seven years of stored seed collections from these sites permit unprecedented
insights into the spatial and temporal dynamics of the breeding structure
of populations of this invasive tree during colonization and population
establishment. Common gardens are being used to determine the degree of
geographic variation that has evolved.
Godt, M. J. W. and J. L. Hamrick. 1997. Estimation
of mating system parameters of Albizia julibrissin (Fabaceae).
Forest Genetics 4:217-221.
Irwin, A.J., J.L. Hamrick, M.J.W. Godt and P.E. Smouse.2003. A multiyear
estimate of the effective pollen donor pool for Albizia julibrissin.
Lee, J. M. and J. L. Hamrick. 1983. The demographic characteristics of
two natural populations of musk thistle (Carduus nutans L.). Journal
of Ecology 71:923-936.
Smyth, C. A. and J. L. Hamrick. 1987. Realized gene flow via pollen in
artificial populations of Carduus nutans. Evolution 41:613-619.