Abstract

Although many non-native species negatively influence amphibian populations, non-native aquatic vegetation has been documented to have positive, negative, and neutral effects on anuran larvae. To evaluate the response of anurans to non-native plants, we exposed two frog species, Gray Treefrog (Hyla versicolor-chrysoscelis) and Southern Leopard Frog (Lithobates sphenocephalus), to detritus from either native hardwood trees, non-native purple loosestrife (Lythrum salicaria), or a mixture of both. Experiments were conducted in artificial ponds, and we recorded the survival, growth, and metamorphic size of larvae. Gray Treefrog survival was highest in tanks with native leaf litter. Developmental time did not differ among treatments, but tadpoles in tanks with purple loosestrife were significantly larger than those in tanks with native leaf litter. Southern Leopard Frog survival was lowest in the mixed vegetation treatment. As with Gray Treefrogs, developmental time was not influenced by treatment, but larvae from tanks with purple loosestrife were significantly larger than those from other treatments. Lower survival in the presence of purple loosestrife has been linked to secondary compounds in the plant, and the higher growth rates we observed are consistent with recent findings on response of anuran larvae to other non-native plants. Our results suggest the negative effects of purple loosestrife detritus on the species examined are manifest at the individual and (perhaps) population level. Because the fewer animals that did survive in tanks with purple loosestrife grew larger, overall ecosystem-level effects may not be present; however, larger scale experiments are needed to evaluate this hypothesis.