Pathways of introduction of the invasive aquatic plant Cabomba caroliniana

• Published in: Ecology and evolution 2013-06, Vol.3 (6), p.1427-1439
• Main Authors: McCracken, Andrée, Bainard, Jillian D., Miller, Michelle C., Husband, Brian C.
• Format: Article
• Language: English
• Subjects: Alleles; Aquatic plants; Cabomba; Cabomba caroliniana; Colonization; Deoxyribonucleic acid; DNA; Fanwort; genome size; Genomes; haplotype network; Haplotypes; Introduced species; Invasive plants; invasive species; molecular variation; Natural resources; Nonnative species; Nucleotide sequence; Original Research; polyploidy; Population; Population genetics; Populations; Range extension; Researchers
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.530

The pathway and frequency of species' introductions can affect the extent, impact, and management of biological invasions. Here, we examine the pathway of introduction of the aquatic plant Cabomba caroliniana (fanwort) into Canada and the northern United States using plastid DNA sequence (intergenic spacers atpF‐atpH, trnH‐psbA, and trnL‐trnF) and DNA content analyses. We test the hypothesis that the spread of fanwort is a result of commercial trade by comparing a Canadian population (Kasshabog Lake, ON) to native populations from southern U.S., introduced populations in northern U.S., and plants from commercial retailers. Thirteen plastid haplotypes were identified throughout North America, including one dominant haplotype, which was present in all C. caroliniana populations. Several rare haplotypes were used to infer shared colonization history. In particular, the Canadian population shared two rare alleles with a population from Massachusetts, suggesting range expansion of C. caroliniana from the northern U.S. However, the possibility of a commercial introduction cannot be excluded, as common alleles were shared between the Canadian population and both commercial and southern U.S. sources. Variation in C. caroliniana genome size was bimodal and populations were classified into “high” and “low” categories. The Canadian population had DNA contents similar to several northern U.S. populations (low DNA content). This may provide additional support for range expansion from these introduced populations rather than from commercial sources or populations in the southern U.S., which had high DNA content. Cabomba caroliniana is considered an aggressive aquatic invasive species, and there is much interest in determining the source of introduced populations. Using chloroplast DNA sequences and genome size variation, our research presents evidence to suggest that the movement of C. caroliniana into Canada is from populations in the northeastern United States, and less likely to be from commercial sources. We discuss several possible pathways of introduction for C. caroliniana across North America.