Can secondary compounds of an invasive plant affect larval amphibians?

1. There is significant concern over the impacts of plant invasions on habitat quality for native fauna. Recent research suggests that non-native Purple Loosestrife (Lythrum salicaria) invasions may negatively affect the performance of larval American Toad tadpoles (Bufo americanus), and that compounds leached from L. salicaria leaves play a direct or indirect role in this effect. 2. We raised individual B. americanus and Gray Treefrog (Hyla versicolor) tadpoles on high-quality diets in aqueous extracts of senescent leaves from L. salicaria, native Broad-Leaf Cattail (Typha latifolia), and control water to determine whether loosestrife extracts directly affect anuran tadpole performance. 3. Even at high artificial food levels, B. americanus survival was significantly lower in L. salicaria extracts compared with T. latifolia extracts and a water control. Food level strongly affected B. americanus development, but tadpoles raised in L. salicaria extract were less developed compared with conspecifics raised in cattail extract or water. Unlike B. americanus, Hyla performance was not affected by exposure to any plant extract compared with the water control. 4. Our study implicates secondary plant compounds as a mechanism underlying the impact of an invasive plant on some but not all native fauna. We hypothesize that high tannin concentrations of L. salicaria leaves have the potential to create environments that are directly toxic to B. americanus tadpoles. We hypothesize that obligate gill breathers such as B. americanus tadpoles are highly sensitive to gill damage caused by high concentrations of phenolics. Other anuran species such as H. versicolor that develop well-functioning lungs early may be less affected by high tannin concentrations.