|FLEMING, JONATHAN - University Of North Alabama|
|DIBBLE, ERIC - Mississippi State University|
|WERSAL, RYAN - Lonza Corporation|
Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2014
Publication Date: 5/1/2015
Citation: Fleming, J.P., Dibble, E.D., Madsen, J.D., Wersal, R.M. 2015. Investigation of Darwin’s naturalization hypothesis in invaded macrophyte communities. Biological Invasions. 17(5):1519-1531.
Interpretive Summary: Invasion ecology has two opposing, though not necessarily exclusive, schools of thought. One school emphasizes the importance of the characteristics of the specific species to invade a site (or “invasiveness”). The other school emphasizes the characteristics of the particular location to be susceptible to invasion (or “invasibility”). Charles Darwin hypothesized that species introduced to a new location would be less likely to establish if the area already contains closely-related species, the so-called Darwin’s Naturalization Hypothesis. This study was to test this hypothesis using two species of invasive aquatic plants, Eurasian watermilfoil (Myriophyllum spicatum) and curlyleaf pondweed (Potamogeton crispus). Both species have similar native congeneric species in North America. We used data from 29 lakes across the United States. Analysis indicated that the relationship between native congeneric species and the invasive species was positive, rather than negative. While these results do not support the Darwin’s Naturalization Hypothesis, they also indicate that at least that one aspect of invasibility, the presence of native plants, is not a deterrent to invasion.
Technical Abstract: Although native macrophytes are beneficial in aquatic ecosystems, invasive macrophytes can cause significant ecological and economic harm. Numerous studies have attributed invasiveness to species’ characteristics, whereas others attribute invasion to biotic and abiotic characteristics of the invaded community. It has been suggested that studying the link between invader and invaded community is key to understanding invasiveness, and that invasions can be understood through the framework of community ecology theory. Charles Darwin hypothesized that introduced species would be less likely to naturalize in areas containing closely related species (Darwin’s Naturalization Hypothesis; DNH), suggesting competition between closely related species could limit naturalization potential (phylogenetic repulsion). The goal of this research was to test DNH using two species of highly invasive aquatic plants, Myriophyllum spicatum L. and Potamogeton crispus L., and assess whether results were consistent at small and large scales. Twenty-nine lakes containing invasive macrophytes were surveyed between 1997-2011. Invasive P. crispus occurred in 15 lakes and M. spicatum occurred in 19 lakes. There were 15 native Potamogeton species and 4 Myriophyllum. We used generalized linear mixed models with congeneric species richness data to estimate probability of invasive P. crispus or M. spicatum occupying a given sampling location. Contrary to predictions of DNH, the relationship between congeneric richness and presence of P. crispus at point and lake scales was positive. Unlike models for P. crispus, native Myriophyllum genera richness was not a significant model parameter. These results do not support DNH (the expectation of a negative relationship); furthermore, models had relatively low determination coefficients indicating very little explained variation. Although this study found no evidence for DNH, there is still a need to investigate how community assembly processes influence species invasions.