Evaluating adaptive, carry‐over, and plastic antipredator responses across a temporal gradient in Pacific chorus frogs

Abstract

The development of antipredator traits is dependent on the frequency and intensity of predator exposure over evolutionary and ecological time. We hypothesized that prey species would respond with increasing accuracy when exposed to predators across generational, ontogenetic, and immediate time scales. We assessed larval Pacific chorus frog (PSRE; Pseudacris regilla) individuals that varied in population sympatry, embryonic conditioning, and immediate exposure to stocked populations of rainbow trout (Oncorhynchus mykiss). Using PSRE populations from sites with and without resident rainbow trout, we conditioned embryos to trout odor, PSRE alarm cues, trout odor in combination with alarm cues, or control water. After being hatched and reared in control water, individuals were exposed to the four predator cue treatments using a fully factorial design. Tadpoles from populations with resident rainbow trout did not behave or develop differently than tadpoles originating from fishless sites. However, we found evidence that PSRE reduced predation risk with a combination of carry‐over effect (i.e., transfer of information across life history stages) and within‐life stage phenotypically plastic mechanisms. We found both developmental and behavioral carry‐over effects: tadpoles conditioned with trout odor as embryos grew more slowly and took refuge more often than control animals. Within‐life‐stage behavioral plasticity was observed in tadpoles from all treatment groups, responding to predator cues with increased refuge use. Potentially additive effects of predator exposure on prey response should be considered when predicting the ability of prey to recognize novel threats.

A systematic review of the direct and indirect effects of herbivory on plant reproduction mediated by pollination

“…In this systematic review, we examined the relative frequencies and the extent that these important processes are studied in concert. While the effect of herbivores on plants have long been studied, and it has been well shown that herbivores can directly and indirectly impact plant reproduction, growth, and population dynamics (Hawkes & Sullivan, 2001;Ohgushi, 2005;Boivin, Doublet & Candau, 2019;Garcia & Eubanks, 2019), the small number of studies that were located within this review indicate how infrequently the effects of herbivores on pollination are studied. These studies were also heavily biased towards damage done by insects, temperate biomes, and the effects of a single herbivore species on a single plant species.…”

“…Complete florivory has been shown to have direct impacts on floral abundance. The net outcome of this form of direct damage is dependent on the strategy of the plant (Juenger & Bergelson, 1997;Wise, Cummins & De Young, 2008;Garcia & Eubanks, 2019). In some cases, plants will over-produce flowers as a defense against florivory creating more flowers than the plant is able to bring to seed (Huth & Pellmyr, 1997).…”

“…Therefore, florivory frequently results in no net loss in reproductive output for the plant. In other cases, plants are able to compensate or overcompensate for herbivory, replacing the flowers lost (sometimes producing more flowers than initially), delaying phenology (Wise, Cummins & De Young, 2008;Garcia & Eubanks, 2019), or changing mating system (i.e., shifting to self-pollination) (Penet, Collin & Ashman, 2009). If the plant is able to completely compensate (reproduce flowers of equal or greater quality and quantity) then the net effect of complete florivory is neutral or even positive.…”

“…These flowers may be less attractive to pollinators (Mothershead & Marquis, 2000) or theoretically be less fertile, producing fewer seeds. While plants are also able to compensate for vegetative damage, resources are often allocated to regrowth instead of reproduction and so vegetative damage can still decrease fitness (Pratt et al, 2005;Garcia & Eubanks, 2019). Root herbivory can also change how the plant interacts with aboveground herbivores and mutualists (Barber et al, 2015).…”

“…The net outcome is mediated by plant responses (Santangelo, Thompson & Johnson, 2019) in terms of resistances, allocation strategies, and defenses (see Hawkes & Sullivan, 2001). Plants can overproduce in preparation for herbivory or compensate for herbivory received by producing more structures or switching to self-pollination, reducing the overall impact (Garcia & Eubanks, 2019). Plants can also deter herbivores through defenses including constitutive (e.g., thorns) or inducible (e.g., volatile release) defenses that can be both mechanical or chemical (Chen, 2008).…”