Search for: All records

Most insect herbivores specialize on a few host plants; however, there are a minority of highly generalized species capable of feeding on hundreds of hosts. Generalism could emerge as a property of the species as a whole, while individuals would still exhibit greater specialization at more specific organizational levels. Yet, we lack studies with generalist insect herbivores directly testing this prediction. Here, we test if the highly generalized fall webworm (Hyphantria cunea) maintains its broad diet through specialization at the population, maternal genotype, or individual level. We reared two populations and multiple matrilines on either a static or rotating diet of four host plants. We found that both populations survived and pupated on all hosts, suggesting population-level generalization. We found evidence for generalization at the genotype level, as maternal genotypes did not vary in performance rankings across host plants. Finally, we found generalism at the individual level, as individuals reared on a rotating diet had no difference or showed intermediate performance to those reared on static diets. Overall, we found support for the maintenance of generalism across all levels, suggesting that generalist species need not be locally specialized to maintain their extremely broad diet. 

A long-standing problem in the study of mutualism is to understand the effects of non-mutualistic community members that exploit the benefits of mutualism without offering commodities in exchange (i.e., ‘exploiters’). Mutualisms are continually challenged by exploiters and their persistence may depend on the costliness of exploitation or on adaptations that allow mutualists to avoid the negative effects of exploiters. Coevolution could lead to changes in mutualists and exploiters that allow mutualisms to persist. Although coevolution is considered essential for mutualism persistence and resistance to disturbance, we have yet to obtain direct experimental evidence of the role of coevolution in resistance to exploitation. Additionally, resistance to exploitation via coevolutionary processes might vary with the degree of dependency between mutualistic partners, as facultative mutualisms are thought to be under weaker coevolutionary selection than obligate mutualisms. Here, we conducted an experimental evolution study using a synthetic yeast mutualism to test how coevolution in facultative and obligate mutualisms affects their resistance to exploitation. We found that naïve facultative mutualisms were more likely to breakdown under exploitation than naïve obligate mutualisms. After 15 weeks of coevolution, both facultative and obligate evolved mutualists were more likely to survive exploitation than naïve mutualists when we reassembled mutualist communities. Additionally, coevolved exploiters were more likely to survive with mutualists, whereas naïve exploiters frequently went extinct. These results suggest that coevolution between mutualists and exploiters can lead to mutualism persistence, potentially explaining why exploitation is ubiquitous but rarely associated with mutualism breakdown. 

Standardized protocols are an essential asset for research requiring the maintenance of live organisms. Ecological studies often involve collaborations between multiple teams that are spread across locations, and these collaborations benefit from sharing successful laboratory procedures. Our research team is studying the ecology of the fall webworm moth (Hyphantria cunea, hereafter FW) in North America for >10 years, during which time we have established reliable procedures for starting and maintaining FW colonies under laboratory conditions. FW is a North American species that has been introduced to Europe and Asia where it is a major pest. Here, we present a detailed review of the methods we use to find and collect FW caterpillars in the field, house and rear caterpillars in the laboratory, handle pupae, and initiate diapause for overwintering. We also describe how to end diapause the following summer, care for emerging adult moths and mate them, and tend to eggs. Lastly, we test the effectiveness of some of our protocols related to mating adult moths to determine whether fertile eggs are produced. FW is becoming a model study system for ecological and evolutionary studies related to diet breadth. As more researchers begin studying the ecology and management of FW, laboratory colonies will play an important role for these projects. Our protocols will provide guidance to inform the successful study of this important insect. 

Mutualisms, or reciprocally beneficial interspecific interactions, constitute the foundation of many ecological communities and agricultural systems. Mutualisms come in different forms, from pairwise interactions to extremely diverse communities, and they are continually challenged with exploitation by nonmutualistic community members (exploiters). Thus, understanding how mutualisms persist remains an essential question in ecology. Theory suggests that high species richness and functional redundancy could promote mutualism persistence in complex mutualistic communities. Using a yeast system (Saccharomyces cerevisiae), we experimentally show that communities with the greatest mutualist richness and functional redundancy are nearly two times more likely to survive exploitation than are simple communities. Persistence increased because diverse communities were better able to mitigate the negative effects of competition with exploiters. Thus, large mutualistic networks may be inherently buffered from exploitation.