Ecologically relevant symbioses are widespread in terrestrial arthropods but based on recent findings these specialized interactions are likely to be especially vulnerable to climate warming. Importantly, empirical data and climate models indicate that warming is occurring asynchronously, with night‐time temperatures increasing faster than daytime temperatures. Daytime (DTW) and night‐time warming (NTW) may impact ectothermic animals and their interactions differently as DTW results in greater daily temperature variation and moves organisms nearer to their thermal limits, while NTW avoids thermal limits and may relieve constraints of cooler night‐time temperatures; a nuance that has largely been ignored in the literature. In laboratory experiments, we investigated how the timing of warming influences a widespread defensive mutualism involving the pea aphid Three aphid sublines were experimentally created from single aphid genotype susceptible to An increase of 2.5°C, as predicted to occur by the IPCC before 2100, was sufficient to disable the aphid defensive mutualism regardless of the timing of warming; a surprising result given that the daily maxima for control and NTW scenarios were identical. We also found that warming negatively impacted (a) symbiont‐mediated interactions between host and parasitoid more than symbiont‐free ones; (b) species interactions (host–parasitoid) more than each participant independently and (c) aphids more than parasitoids even though higher trophic levels are generally predicted to be more affected by warming. Here we show that 2.5°C warming, regardless of timing, negatively impacted a common microbe‐mediated defensive mutualism. While this was a laboratory‐based study, results suggest that temperature increases predicted in the near‐term may disrupt the many ecological symbioses present in terrestrial ecosystems.
Herbivorous ectothermic vertebrates are more diverse and abundant at lower latitudes. While thermal constraints may drive this pattern, its underlying cause remains unclear. We hypothesized that this constraint stems from an inability to meet the elevated phosphorus demands of bony vertebrates feeding on P‐poor plant material at cooler temperatures because low gross growth efficiency at warmer temperatures facilitates higher P ingestion rates. We predicted that dietary carbon:phosphorus (C:P) should exceed the threshold elemental ratio between carbon and P‐limited growth (TERC:P) for herbivores feeding at cooler temperatures, thereby limiting the range of herbivorous ectothermic vertebrates facing P‐limited growth. We tested this hypothesis using the Andean suckermouth catfishes Supporting our hypothesis, we found that dietary C:P was predicted to exceed the TERC:Pfor the grazer Our results suggest that, at least for Andean suckermouth catfishes, cool temperatures constrain herbivory at higher elevations. Increased gross growth efficiency at cooler temperatures evidently restricts the ability of P‐limited consumers to meet P demand. However, our survey of fish TERC:Pestimates suggests that some fishes are able to circumvent this constraint through behavioural and life‐history adaptations that reduce P demand or increase P use efficiency. The physiological trade‐offs underlying these functional shifts reveal that geographic dietary patterns can be predicted by stoichiometric theory, but variation in food quality and consumer traits that reduce P demand and/or increase P efficiency can create exceptions to these patterns.
A
- NSF-PAR ID:
- 10461379
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Functional Ecology
- Volume:
- 33
- Issue:
- 5
- ISSN:
- 0269-8463
- Page Range / eLocation ID:
- p. 913-923
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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