Unraveling the biogeographic origins of the Eurasian watermilfoil (Myriophyllum spicatum) invasion in North America.

Premise Of The Study: Using phylogeographic analyses to determine the geographic origins of biological invaders is important for identifying environmental adaptations and genetic composition in their native range as well as biocontrol agents among indigenous herbivores. Eurasian watermilfoil (Myriophyllum spicatum) and its hybrid with northern watermilfoil (M. sibiricum) are found throughout the contiguous United States and southern Canada, forming one of the most economically costly aquatic plant invasions in North America, yet the geographic origin of the invasion remains unknown.

Chemically mediated host-plant selection by the milfoil weevil: a freshwater insect-plant interaction.

The milfoil weevil Euhrychiopsis lecontei is a specialist aquatic herbivore that feeds, oviposits, and mates on the invasive freshwater macrophyte Myriophyllum spicatum. We characterized the weevil's preference for M. spicatum, and through bioassay-driven fractionation, isolated and identified two chemicals released by M.

Top-down control in a detritus-based food web: fish, shredders, and leaf breakdown.

We tested the hypothesis that fish decrease shredder abundance in leaf packs, thereby reducing leaf breakdown rates. Our goal was to test for the occurrence of a trophic cascade in a detritus-based food web. Willow leaves (Salix spp.

Variation in hostplant preference and performance by the milfoil weevil, Euhrychiopsis lecontei Dietz, exposed to native and exotic watermilfoils.

Exotic plants often displace native plants and thus alter the availability of native hostplants for specialist herbivorous insects. The submersed aquatic weevil Euhrychiopsis lecontei Dietz is endemic to North America, but there are now source populations on the exotic Eurasian watermilfoil (Myriophyllum spicatum L.) as well as on the weevil's ancestral host, northern watermilfoil (Myriophyllum sibiricum Komarov).

Oviposition specificity and behavior of the watermilfoil specialist Euhrychiopsis lecontei.

Eurasian watermilfoil (Myriophyllum spicatum L.) is a nuisance aquatic weed, exotic to North America. The freshwater weevil Euhrychiopsis lecontei (Dietz) is a potential control agent of Eurasian watermilfoil and is a fully submersed aquatic specialist herbivore.

The watercress glucosinolate-myrosinase system: a feeding deterrent to caddisflies, snails and amphipods.

Watercress (Nasturtium officinale) possesses the glucosinolate-myrosinase system. This system is regarded as a classic example of chemical defense for terrestrial crucifers. Damage of watercress initiates myrosinase-mediated hydrolysis of phenylethyl glucosinolate to a toxic endproduct, phenylethyl isothiocyanate.