Contemporary gene movement across landscapes
Dr. Rodney Dyer, associate professor in the VCU Department of Biology, and his graduate students are conducting research at the Rice Center focused on understanding and modeling the processes, mechanisms and consequences of the dispersal of genes across a landscape. The spatial patterning of gene movement within populations has several fundamental ecological and evolutionary consequences.
At the individual level, the genetic relationship between mating individuals can affect the fitness of offspring via the expression of inbreeding depression. Second, the distance and manner in which genes are dispersed interface with local demographic and ecological factors to influence the effective population size. Next, the rate at which selectively beneficial or even artificially introduced genetic variants are able to move through a population is dictated by the specific mechanisms that species have evolved to disperse genes. Finally, the recurrence of these ongoing processes percolates up, spatially and demographically, to ultimately determine the spatial granularity of intraspecific genetic variation.
For higher plant species, the movement of genes occurs in two phases separated in both space and time. Research from this laboratory is focusing on each of these phases.
- Contemporary pollen movement: Pollen is released from the paternal individual and, through various means, is deposited on the stigma of the maternal individual. For many plant species, the movement of pollen is facilitated by insects that move pollen grains in trade for nutrient or other rewards produced by the plant. Therefore, in order to understand how genes are dispersed across a natural landscape, one must examine how insects perform this pollen transport every spring. To address this issue, we are taking a two-pronged approach combining mathematical modeling (in conjunction with Dr. David Chan from the Department of Mathematics) and field studies at the Rice Center.
Using the understory tree species Cornus florida (flowering dogwood) and Aralia spinosa (devil’s walking stick) as study species, we are conducting a large scale “paternity analysis” to determine which fathers are pollinating which maternal individuals. From these data, we can construct landscape-level pollination networks that document how insects move pollen through the forest. Components of this study focusing on C. florida form a significant portion of the master’s research for Vicki Gardiakos.
- Dispersal and recruitment: Following the dispersal of pollen, ripe seeds must disperse and germinate for reproduction to be considered successful. By setting up arrays of seed traps, we have been able to quantify the distance and quantity of seeds dispersed by C. florida. Moreover, we can use the adult genetic data from the pollen studies to determine who the maternal individual is for each dispersed seed and thus gain insights into how far seeds move from the maternal individual. In spring 2006, we began testing germination success in alternate microenvironments at the Rice Center. A main component of the germination tests revolves around understanding how the dense cover created by the recently invading grass species, Microstegium vimineum (Japanese stilt grass), influences recruitment of forest tree species. This research is being conducted by Rebekha Archibald as a component of her master’s research project.
A quantitative understanding of how dispersal processes operate in natural systems is particularly important for ecological, evolutionary and conservation purposes. With the continued increase in anthropogenic habitat modification, invasive species introduction and the use of plant platforms for pharmaceutical and industrial protein production, understanding the dispersal process becomes paramount.
Learn more about Dyer’s research interests.