Submitted to: Aquatic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 20, 2003
Publication Date: June 20, 2003
Citation: Madeira, P.T., Jacono, C.C., Tipping, P.W., Van, T.K., Center, T.D. 2003. A genetic survey of salvinia minima in the southern united states. Aquatic Botany 76:127-139. Interpretive Summary: Salvinia minima, a non-native floating aquatic plant, has spread throughout the southeastern United States from Florida to Texas. In many areas it produces excessive surface growth which can restrict boating and block light to submersed aquatic vegetation. The oldest of the introduced populations are in Florida where this plant is seldom problematic, probably because of a small weevil, Cyrtobagous salviniae, which feeds exclusively on Salvinia. There has been a debate in the environmental community as to whether this insect should be introduced to the newer infestations in the other states. One of the questions asked is whether the Salvinia minima in the other states is genetically similar to the Florida plant. Since the native range of Salvinia ranges from south central Mexico to northern Argentina introductions from different sources could result in different genetic populations. This study used a molecular technique called RAPD to look at the genetic relationships among 68 samples from throughout Florida and the southeast. The study found some minor differences between populations but no significant differences between the Florida populations, as a group, and the populations in other states. This indicates that there is a reasonable chance that the Cyrtobagous weevil, if taken from Florida and introduced elsewhere, would succeed in reducing Salvinia densities.
Technical Abstract: The genetic relationships among 68 samples of Salvinia minima (Salviniaceae) were investigated using RAPD analysis. Neighbor Joining, Principle Components, and AMOVA analyses were used to detect differences among geographically referenced samples within and outside of Florida. Genetic distances (Nei and Li) range up to 0.48, although most are under 0.30, still relatively high levels for an introduced, clonally reproducing plant. Despite the diversity AMOVA analysis yielded no indication that the Florida plants, as a group, were significantly different from the plants sampled elsewhere in its adventive, North American range. A single, genetically dissimilar population probably exists in the recent (1998) horticultural introduction to Mississippi. When the samples were grouped into 10 regional (but artificial) units and analyzed using AMOVA the between region variance was only 7.7%. Genetic similarity among these regions may indicate introduction and dispersal from common sources. The reduced aggressiveness of Florida populations (compared to other states) may be due to herbivory. The weevil Cyrtobagous salviniae, a selective feeder, is found in Florida but not other states. The genetic similarity also suggests that there are no obvious genetic obstacles to the establishment or efficacy of C. salviniae as a biological control agent on S. minima outside of Florida.