Abstract
ABSTRACT In temporary ponds, submerged plants have adapted to recurrent periods of drought. These ponds often lack the impact of large herbivores but can harbor large numbers of herbivorous tadpoles. Tadpoles of the Iberian spadefoot toad (Pelobates cultripes) may reach large body size and consume large quantities of macrophytes during their long larval period, which is shortened with risk of pond drying. We conducted a mesocosm experiment to analyze the interplay between hydroperiod and impact of herbivorous tadpoles on the abundance and life history of 3 species of submerged plants common to temporary ponds. We observed differences in growth among plant species resulting in lags in timing of maximum cover, probably related to interspecific competitive interactions. Some plants responded to pond drying with a remarkable increase in the production of flowers. Tadpoles greatly reduced the plant cover, although their impact varied across plant species. Differential plant consumption by these large tadpoles can substantially modify the internal structure and complexity of temporary ponds, and tadpoles can also interfere with plant responses to shortened hydroperiod.
Highlights
Submerged plants are important components of freshwater ecosystems and modify the physical and chemical environment (e.g., Carpenter and Lodge 1986, Lodge 1991)
In the case of 3 macrophyte species; (b) generalized linear mixed models with binomial error distribution on flower production; (c) generalized linear models with negative binomial error distribution on the time to the first flower of Myriophyllum alterniflorum and Ranunculus peltatus; (d) generalized linear models, with Gaussian error distribution, on the length of the flowering period of M. alterniflorum and R. peltatus; (e) generalized linear mixed models on survival of individually monitored plants using a binomial error distribution
We observed broad changes in the composition of the plant assemblage in our experimental setup caused by the herbivory by spadefoot toad tadpoles and due to pond drying
Summary
Submerged plants are important components of freshwater ecosystems and modify the physical and chemical environment (e.g., Carpenter and Lodge 1986, Lodge 1991). They provide structural complexity that serves as refuge, food, and support for other aquatic organisms (Cronk and Fenessy 2001). Waterfowl and many fish are important herbivores, grazing large quantities of aquatic plants and affecting the structure of these habitats. Taking into account the proportion of aquatic macrophytes consumed by vertebrates, Lodge et al (1998) considered that this group could have a higher impact on vascular plants than any other taxonomic group, even though the impact of amphibians was not considered in their study
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