Diverse Insect Communities Shape Host-Plant Defenses
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Martin Volf and his colleagues collaborate on interdisciplinary projects focusing on eco-evolutionary dynamics driving formation of plant defenses and insect diversity. Their recent work has been published in the prestigious journal, Ecology Letters. (http://onlinelibrary.wiley.com/doi/10.1111/ele.12875/full)
Herbivorous insects and vascular plants represent two of the most numerous groups of multi-cellular organisms. They owe their diversity to their mutual interactions. Herbivory pressure by diverse communities of insect herbivores has led to an arms-race between plants and insects, supporting escalation of plant defenses over evolutionary time. Martin and his colleagues studied the defenses and caterpillars associated with 21 sympatric New Guinean figs. Their results show that the structure of generalist and specialist insect communities correlates with traits that have evolved in different ways. Herbivore generalists were concentrated on hosts with low activity of escalated and highly toxic defenses. This illustrates how escalating traits may provide a good protection against non-adapted insects. On the other hand, highly specialized Asota moths used alkaloid rich plants. These aposematic, brightly colored moths are probably able to sequester alkaloids and use them for their own defense, showing how highly toxic defenses can be overcome by adapted herbivores. In turn, most specialists responded mainly to traits, which diverged among closely related Ficus hosts. Such an increase in trait divergence probably helps closely related hosts to escape from herbivory by specialized herbivores with conservative host-use. These results suggest that the evolution of defenses in Ficus can be driven towards both escalation and divergence in individual traits, in combination providing protection against a broad spectrum of herbivores.
Volf M., Segar S. T., Miller Scott E., Isua Brus, Sisol Mentap, Aubona Gibson, Šimek P., Moos M., Laitila Juuso, Kim Jorma, Zima J., Rota Jadranka, Weiblen George D., Wossa Stewart, Salminen Juha-Pekka, Basset Y. F., Novotný V. (2017) Community structure of insect herbivores is driven by conservatism, escalation and divergence of defensive traits in Ficus. Ecology Letters, in press. DOI:10.1111/ele.12875