Invasion consequences and ecology: evaluation of community and environment interactions of an exotic, invasive plant, garlic mustard (Alliaria petiolata).
Abstract: Globally, exotic, invasive species are the second leading cause of
native species decline. I aimed in this thesis to explore first the resource ecology of a
"strong invader" of New England forests, the exotic weed garlic mustard (Alliaria
petiolata). Particularly, I aimed to understand to what extent performance
differences among populations were explained by limitations impos... read moreed by soil nutrient
abundance and availability. Secondly, I aimed to understand the potential of a native
herbivore () to adapt to community disturbances
following garlic mustard and exotic parasitoid invasion to escape an evolutionary trap.
Specifically, I focused on the adaptation of larvae to complete development to pupation on
the novel host plant that has previously caused population decline. With regards to the
first aim, I surveyed several populations of garlic mustard from a variety of habitats in
Massachusetts and measured a variety of variables related to soil nutrient availability and
plant performance. Overall, soil variables have limited explanatory and predictive power
with regards to plant performance. There is some evidence of stronger relative effects of
soil pH and potassium availability on performance, however it does not resolve much of the
variation among populations. It is likely that other environmental factors, such as light
or soil moisture, impose greater limits on performance. To address the second aim, I
modified an existing stochastic simulation model to generate a subpopulation of adapted
individuals. I applied treatments addressing two issues: (1) the source of genetic
variation for the adaptive trait, and (2) the role of top-down regulation by exotic
parasitoids in limiting adaptation. Results show that even under high rates of mutation,
persistence of adapted individuals is low, and any adaptation observed in natural
populations is likely due to residual variation. Secondly, parasitism significantly
decreased the likelihood of adaptation, and persistence of adapted individuals was possible
at substantial levels only under conditions of enemy free space. Cumulatively, my research
shows that for garlic mustard, the abiotic soil environment imposes little limitations on
performance and likely this plant can successfully colonize a variety of environments,
provided there is a suitable availability of light and water. When it comes to
understanding the effect of such colonization and invasion on native community members, my
research shows that the community context, particularly the third trophic level, influences
greatly predictions for native species persistence and adaptation.
Thesis (M.S.)--Tufts University, 2012.
Submitted to the Dept. of Biology.
Advisor: Colin Orians.
Committee: Frances Chew, and J. Michael Reed.
Keyword: Biology.read less