Ground cover and native ant predation influence survival of metamorphic amphibians in a southeastern pine savanna undergoing restoration

Abstract

Longleaf pine savannas historically supported abundant ground cover maintained by frequent fire but little other disturbance. Ground cover creates microclimates with lower temperatures, higher humidity, and increased soil moisture that may benefit wildlife, particularly small vertebrates such as amphibians. Today, most historical pine savannas have had extensive soil disturbance and altered fire regimes resulting in reduced ground cover and altered soil fauna communities including predatory invertebrates. We used a factorial terrestrial cage study to test the effects of native wiregrass (Aristida spp.) cover and the exclusion of a native predatory ant (Dorymyrmex smithi) on the survival of post‐metamorphic Ornate chorus frogs (Pseudacris ornata) and Gopher frogs (Rana capito). Although we were unable to achieve full ant exclusion, ant reduction in exclusion treatments and plant cover had an interactive effect on metamorph survival. Ant exclusion tended to increase Gopher frog survival and this effect was more pronounced when wiregrass was present. Within ant treatments, survival of Gopher frogs increased slightly with increasing wiregrass cover. Ornate chorus frogs had a high probability of survival (>95%) in all ant exclusion treatments regardless of wiregrass cover; however, in treatments without ant exclusion, survival increased with increasing wiregrass cover. Our results demonstrate that high abundances of a native ant species and low coverage of native wiregrass, which are legacies of historical soil disturbance and altered fire regimes, interact to elevate mortality of juvenile amphibians. Minimizing soil disturbance and restoring native ground cover are likely important for amphibian habitat management within historical southeastern pine savannas.

How plants affect amphibian populations

“…For example, Burrow et al . (2021) found that high groundcover availability increased juvenile survival in a southeastern USA pine savanna undergoing restoration. Further, they demonstrated that legacies of historical disturbance can interact with current conditions to influence juvenile amphibian survival (Burrow et al ., 2021).…”

“…Differences in ecosystem productivity and heterotroph community structure are often traceable to variations in leaf litter chemistry and associated effects on water chemistry, clarity, and decomposition (Stoler & Relyea, 2011Earl & Semlitsch, 2013;Stoler, Burke & Relyea, 2016;Burrow & Maerz, 2021). Both variation in plant nutrient (i.e.…”

“…First, the growing body of research demonstrating the potentially strong control of plants on larval amphibian performance in aquatic habitats has important management implications. Generally, maintenance of emergent, herbaceous vegetationparticularly within open-canopy ponds and wetlandsis likely to increase larval amphibian survival, shorten time to metamorphosis, and increase size at metamorphosis (Williams et al, 2008;Earl et al, 2014;Burrow & Maerz, 2021). These are all effects demonstrated to have positive impacts on amphibian population growth (reviewed in Marsh & Trenham, 2001).…”

“…Many studies report that higher nitrogen or phosphorus content in plant detritus leads to larger larval size at metamorphosis, faster development, and increased survival (Maerz et al, 2010;Cohen et al, 2012Cohen et al, , 2014Stephens et al, 2013;Stoler & Relyea, 2013b;Earl et al, 2014;Martin, Rainford & Blossey, 2015;Burrow & Maerz, 2021). However, larval amphibian responses to litter nutrient content can depend on the range of nutrient concentrations examined, the amount of leaf litter input, and litter identity (Maerz et al, 2005b;Stephens et al, 2013;Earl et al, 2014;Burrow & Maerz, 2021). In particular, some studies show that high amounts of nutrients leached from large amounts of decomposing plant litter might result in rapid microbial and filamentous algae growth that can reduce dissolved oxygen levels and increase larval amphibian mortality (Rubbo et al, 2008;Rittenhouse, 2011).…”

“…In particular, some studies show that high amounts of nutrients leached from large amounts of decomposing plant litter might result in rapid microbial and filamentous algae growth that can reduce dissolved oxygen levels and increase larval amphibian mortality (Rubbo et al, 2008;Rittenhouse, 2011). Amphibian species may also differ in their responses to variation in litter nutrient content (Maerz et al, 2005b;Williams et al, 2008;Earl et al, 2011;Stephens et al, 2013;Cohen et al, 2014;Burrow & Maerz, 2021). For example, in common garden experiments, wood frog tadpoles performed better than spring peeper tadpoles on deciduous leaf litter from closed-canopy ponds because wood frogs, but not spring peepers, showed a propensity for increased foraging activity (Skelly et al, 2002;Skelly & Golon, 2003).…”