Virtual Issue: Nutritional Ecology

 

The field of nutritional ecology, which examines how an organism’s nutritional requirements, foraging behavior and utilization of ingested nutrients are linked to the environment has a long and rich history. For many years nutritional ecology focused heavily on understanding how foraging behavior and growth responses differed as food quantity, and occasionally food quality (although often loosely characterized), were varied in both the laboratory and the field. However, nutritional ecology has matured since these early days and there is now an appreciation that nutrition is multidimensional and complex, and animals must balance and regulate the intake of multiple nutrients simultaneously. It is also clear that nutrition often links and impacts populations, communities, and ecosystems in significant ways.

Journal of Animal Ecology has, over the years, published many papers that fall under the remit of nutritional ecology. This virtual issue highlights recent papers in Journal of Animal Ecology focused on nutritional ecology, and which span a range of scales and interactions, including the effects of nutrients on foraging behavior, animal life history traits and ecology, host-parasite/pathogen interactions, community ecology and ecosystems. This virtual issue also coincides with an up-coming nutritional homeostasis workshop that will be hosted at the LIMES Institute, at the University of Bonn (May 1-4).

Foraging behavior will always be a central tenet of nutritional ecology, and given the recent attention bee health has received, and the importance of bees as pollinators, there has been a surge in studies exploring how bees forage for pollen. Eckhardt et al. show that a generalist solitary bee practices pollen mixing as a mechanism that allows them to incorporate into their diets, a relatively high amount of pollen that alone would be unsuitable. Dramatic abiotic effects can also alter the nutritional landscape. For herbivores, fire is an important event in grasslands and savannas and is known to modify plant nutrient characteristics. However, fire also reduces vegetation height, which can increase visibility and risks to predation. Eby et al. show that fire increases leaf nitrogen, copper, potassium and magnesium content in leaves, and that smaller herbivores prefer burned areas more strongly than larger herbivores. They suggest that increased herbivore abundance on burned areas is driven by an increase in non-nitrogen nutrients. Body size, as well as ontogeny, and their link to nutrition has been recently investigated by Richman et al. Working with Canada and lesser snow geese, they show that smaller-bodied goslings are more negatively affected by low quality food (defined by protein and fiber content), and suggest that larger body size may provide some flexibility in dealing with low forage quality. Interestingly, nutrients can sometimes modify foraging behavior. Rodriguez-Pena et al. show that when nectar contains only sugar, a specialist nectarivorous bat prefers the most concentrated sugar-only nectar. However, this preference disappears when the nectar contains amino acids. For a generalist nectarivorous bat, supplementing nectar with an amino acid cocktail did not alter preferences.

Life history, and changes in food nutrient content and temperature, can also interact to impact how animals respond to food nutrient content. Providing supplemental food for garden birds is a growing trend, and Plummer et al. have investigated the carry-over effects of winter food supplementation on egg production in wild blue tits. They found that winter provisioning can have negative downstream consequences, but this was dependent on the combination of nutrients provisioned. Supplementing the diet with fat alone resulted in larger eggs with smaller relative yolk mass and reduced carotenoid concentrations. These negative effects were not observed when foods were supplemented with fat plus vitamin E. Animals adapted to short and cold summers also respond to changes in food quality and temperature. Liess et al. found that arctic tadpoles grew and developed faster on high-quality food and that rearing temperature affected their stoichiometric (and life history) responses. They suggest that increased temperature likely alters uptake and incorporation of nutrients, and may modify nutrient requirements and nutrient cycling.

We are now also beginning to better understand how nutritional status mediates an animal’s response to parasites. Cornet et al. infected canaries with Plasmodium parasites and then allocated them to control or supplemented diets. They then transferred parasites from these two environments (employing a factorial design) to new hosts reared on control or supplemented diets. They found that parasites from control hosts performed better in their subsequent hosts, and were more virulent. Using a somewhat similar approach, Lalubin et al. looked at how the nutritional status of mosquitos infected with Plasmodium affected fecundity and survival. They found that mosquitos infected with Plasmodium had lower starvation resistance, but only under low nutritional conditions. However, they observed no interactive effect of nutritional history and Plasmodium infection on fecundity. It is well established that animals challenged with pathogens and parasites can self-medicate, usually through consuming toxins or secondary metabolites. However, Povey et al. show that food nutrient content has important consequences for caterpillars following a viral challenge. In particular, caterpillars restricted to diets rich in protein but low in digestible carbohydrates show an increased probability of survival. Furthermore, caterpillars challenged with a virus modify their nutrient regulation. Compared to controls, virally challenged caterpillars self-select a diet rich in protein and low in carbohydrates. They do this by reducing their intake of carbohydrates, and in general eating less food.

Finally, on a larger scale, nutrition can impact communities and ecosystems. Johnson et al. show that a root-feeding weevil changes the nutritional composition of the plant they are feeding on in such a way that it significantly benefits phloem-feeding aphids on the same plant, but feeding above-ground. In contrast, there was a significant drop in the population of an above ground leaf-feeder (sawfly larvae). Phosphorus content dropped in above ground vegetative tissues, which may affect the leaf-feeders. Changes in phloem nutrient profiles were not measured but increased aphid densities could have been tied to reallocation of nutrients as a function of root damage. Ultimately the increase in aphid numbers attracted predators. Thus root damage by weevils had both bottom-up and top-down effects. At the ecosystem level, Mischler et al. show how a trematode parasite in aquatic snails can impact nutrient excretion. They speculate that parasites might be playing a wide-spread but currently underappreciated role in nutrient cycling, especially in ecosystems where parasite and host abundance is high.

The future of nutritional ecology has much more to offer. In particular, new technological approaches will allow researchers interested in nutritional ecology to explore and understand the important nutritional contributions microbes provide. It is an exciting time to be thinking about nutritional ecology. As the current highlighted paper show, the Journal of Animal Ecology is positioned to be a leader publishing on this topic.

Spencer Behmer Associate Editor,
Journal of Animal Ecology

Pollen mixing in pollen generalist solitary bees: a possible strategy to complement or mitigate
Michael Eckhardt, Mare Haider, Silvia Dorn and Andreas Müller

The effect of fire on habitat selection of mammalian herbivores: the role of body size and vegetation characteristics
Stephanie L. Eby, T. Michael Anderson, Emilian P. Mayemba and Mark E. Ritchie

Ecological implications of reduced forage quality on growth and survival of sympatric geese
Samantha E. Richman, James O. Leafloor, William H. Karasov and Scott R. McWilliams

Nitrogen and amino acids in nectar modify food selection of nectarivorous bats
Nelly Rodríguez-Peña, Kathryn E. Stoner, Jorge Ayala-Berdon, Cesar M. Flores-Ortiz, Angel Duran and Jorge E. Schondube

Fat provisioning in winter impairs egg production during the following spring: a landscape‐scale study of blue tits
Kate E. Plummer, Stuart Bearhop, David I. Leech, Dan E. Chamberlain and Jonathan D. Blount

Hot tadpoles from cold environments need more nutrients - life history and stoichiometry reflects latitudinal adaptation
Antonia Liess, Owen Rowe, Junwen Guo, Gustaf Thomsson and Martin I. Lind

Impact of host nutritional status on infection dynamics and parasite virulence in a bird‐malaria system
Stéphane Cornet, Coraline Bichet, Stephen Larcombe, Bruno Faivre and Gabriele Sorci

Natural malaria infection reduces starvation resistance of nutritionally stressed mosquitoes
Fabrice Lalubin, Aline Delédevant, Olivier Glaizot and Philippe Christe

Dynamics of macronutrient self‐medication and illness‐induced anorexia in virally infected insects
Sonia Povey, Sheena C. Cotter, Stephen J. Simpson and Kenneth Wilson

Downstairs drivers ‐ root herbivores shape communities of above‐ground herbivores and natural enemies via changes in plant nutrients
Scott N. Johnson, Carolyn Mitchell, James W. McNicol, Jacqueline Thompson and Alison J. Karley

Parasite infection alters nitrogen cycling at the ecosystem scale
John Mischler, Pieter T.J. Johnson, Valerie J. McKenzie and Alan R. Townsend

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