Biomass export of salamanders and anurans from ponds is affected differentially by changes in canopy cover

Abstract

1. Previous research shows that canopy-associated shifts from an algal to a detritus-based food web can affect anuran tadpoles negatively. This may not be true of salamander larvae, however, because they are predators. 2. To investigate the influence of canopy cover on the survival and growth of salamanders, and on the subsequent export of biomass from ponds, we conducted a mesocosm experiment examining effects of shading (high or low) and litter (leaves or grass) on Ambystoma maculatum (a forest specialist) and A. texanum (a habitat generalist). Additionally, we reanalysed data from Williams, Rittenhouse & Semlitsch (2008) to examine the effects of shading and litter on biomass export of three anurans: Rana sphenocephala, Pseudacris crucifer and Hyla versicolor. 3. In contrast to previous studies, we found that salamanders performed better in mesocosms with the characteristics of closed canopy ponds (high shade and leaf litter), which resulted in a greater export of biomass. Salamanders grew larger under closed canopy conditions, probably because of differences in prey abundance among treatments. Anurans responded differently to canopy cover than caudates. The biomass export of R. sphenocephala and P. crucifer was reduced under closed canopy conditions (although differently affected by litter and shading), while the biomass of H. versicolor was not affected. 4. This and other studies suggest that changes in canopy cover may induce a shift in the amphibians emerging from ponds, from primarily anurans in open canopy ponds to primarily salamanders in closed canopy ponds. Additional multispecies studies will determine whether these trends hold true for more diverse amphibian assemblages. Further investigation into the effects of canopy cover on salamanders will be important for understanding aquatic-terrestrial linkages.

Mind the gap: treefalls as drivers of parental trade‐offs

“…In contrast, a recent work demonstrated that the predacious larvae of two species of salamanders, grew larger in closed forest conditions (Earl et al. ). However, the authors indicate that these results are presumably due to differences in prey abundance between ponds in closed and open canopy, rather than to differences in canopy cover per se (Earl et al.…”

Modelling nutrient transport and transformation by pool‐breeding amphibians in forested landscapes using a 21‐year dataset

“…Movement of amphibians between aquatic and terrestrial habitats in the forest–wetland matrix may generate a substantial flow of nutrients and energy between breeding pools and adjacent terrestrial ecosystems (Regester & Whiles, ; Earl et al ., ; Earl & Semlitsch, ). However, the flow of energy via dispersing amphibians has been quantified only for a few species (e.g.…”

Detritus Quality and Locality Determines Survival and Mass, but Not Export, of Wood Frogs at Metamorphosis

“…In wood frogs, phenotypic variation of size in post-metamorphic individuals exists at local scales and growth of larval wood frogs does differ across a latitudinal gradient (greater in northern latitudes) and temperature regimes [45], and it appears these variations can lead to differences in export biomass and standing crop of nutrients. Variations in biomass export of anurans has been shown to be influenced by canopy cover and plant litter input [31,32], but our study shows export may be influenced by phenotypic variation of post-metamorphic anuran size.…”

“…For example, a particular plant with high phenolics and high nutrient quality could reduce survival of anuran larvae, but produce larger larvae in return–thus creating a net zero or net gain in anuran biomass. Several studies have found direct relationships between higher leaf and grass detritus quality and increased anuran biomass export [30,31]. Most recently, Earl et al [32] showed high nutrient content and high secondary compounds of white oak ( Quercus alba ) resulted in measurable and distinct increases in larval anuran size, but decreases in survival.…”

“…variation in plant quality) to terrestrial systems. Larval anurans raised in environments with varying resource quality (e.g., variation in nutrient content and secondary compound concentrations) provide different quantities of subsidies (biomass and nutrient) to the surrounding upland environment via metamorphosis [29,30,31]. For example, Earl et al [32] found that survival, size and biomass export of gray treefrogs ( Hyla versicolor ) was strongly affected by leaf litter species and associated plant traits.…”