Invasive Plant and Experimental Venue Affect Tadpole Performance |
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Authors: | Carrie J Brown Bernd Blossey John C Maerz Steve J Joule |
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Institution: | (1) Department of Natural Resources, Cornell University, Fernow Hall, Ithaca, NY 14853, USA;(2) Ft. Drum Military Installation, 85 First Street West, Ft. Drum, NY 13602, USA;(3) Present address: New York Department of Environmental Conservation, Bureau of Wildlife, 21 South Putt Corners Road, New Paltz, NY 12561, USA |
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Abstract: | Introductions of non-native predators and competitors appear to contribute to worldwide amphibian declines; however, potential
negative impacts of invasive plants on habitat quality and amphibian populations have not been examined. Loss of diversity
and alterations in ecosystem function associated with plant invasions may disrupt food webs, potentially leading to further
declines of already threatened amphibian populations. We used a combination of small bins, mesocosms, and field experiments
to examine the impacts of Eurasian purple loosestrife (Lythrum salicaria) replacing native cattails (Typha latifolia) in North American freshwater wetlands on survival, developmental rate, and diet (freshwater algae) of American toad (Bufo americanus) tadpoles. Tadpoles developed slower in L. salicaria compared to tadpoles developing in T. latifolia. This effect was consistent across experimental venues, although mesocosms showed this effect only in the second year of
our study. Survival and development rates were always more variable in purple loosestrife than in cattail. In bins, tadpoles
showed significantly reduced survival when raised in purple loosestrife extract and addition of leaf litter exacerbated this
negative effect. Tadpole survival rates in mesocosms and field cages were not significantly different between plant species,
most likely an effect of high variability among replicates. We suspect a combination of direct toxicity of high tannin concentrations
in L. salicaria leaves and their indirect negative impacts on aquatic food webs are responsible for these results. Tadpole gut analyses revealed
differences in algal communities among venues and between L. salicaria and T. latifolia suggesting that alterations in tadpole food quality and quantity contribute to the observed reduced tadpole performance.
The replacement of native wetland plant species by L. salicaria does not represent a simple exchange of ecological equivalents and the function of invaded habitats for native species has
clearly changed. While we were investigating only a single amphibian species, our results suggest that the impact of L. salicaria on ecosystem processes and aquatic food webs may be more general and likely to negatively affect other wetland species. The
threats non-indigenous plants represent for amphibian populations and food webs may be underestimated, and warrant further
investigation. |
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Keywords: | amphibian declines food web effects freshwater algae invasion mesocosms |
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