A study of the biotic and abiotic factors that affect the proliferation of Lythmus salicaria in differing levels of invasion and population density.

Abstract

Non-native invasive plants species originating from Europe and Asia have become a problem in the northern latitudes of North America as they are aggressively taking over natural habitats, and in turn reducing species diversity. Purple loosestrife, Lythrum salicaria (Lythraceae), is an example of an invasive plant that is devastating the wetland regions of southeastern North America. This study is designed to look at the abiotic (soil type and soil moisture) and biotic factors (morph frequency, herbivory, number inflorescences per stem, number of non-flowering stems, number of seedlings, and plant height) in high and low invasion levels in in differeing population densities. Results showed that L. salicaria was most dense in high invasion sites and damp and organic soil types. Also, plants on average grew taller in more saturated soils. There were weak correlations between population density and the proportion of seedlings per square meter, and between population density the proportion of plants with herbivory per square meter. There was no correlation between population density and plant height. Morph frequencies followed a 1:1:1 ratio in two of the high invasion sites, two of the low invasion sites, and at the total low invasion level. Same morph pair frequencies were higher than the expected frequency of 1/3, showing that more asexual, than sexual reproduction is occurring than expected. With this data much more was known about factors that stimulate and hinder population growth of L. salicaria, and how it reproduces in each level of invasion.