Insect herbivore species often specialize on the host plants that they
eat, evolving adaptations to use a plant’s unique set of resources.
However, specialization doesn’t come without costs.
"A lot of evolutionary ecologists have pondered the advantages of
being a specialist, and there are presumably tradeoffs," says Michael
Singer of Wesleyan University. "Specialists have a smaller resource
base, but they might be better adapted to their niche."
Singer and his colleagues wondered if there could be other advantages
to specialization than better utilization of host plants as food.
Specialists might also be more adept than generalists, he postulated, at
using their host plants for defense or refuge from predation,
specifically by birds.
The team tested this idea by excluding birds from experimental plots
in a temperate forest in Connecticut and surveying the density of
generalist and specialist caterpillar species inside and outside the
exclosures. In the exclosures, his team observed a surge in generalist
density compared to natural areas. The number of specialists, however,
only increased slightly. These results suggest that the bird predators
were preferentially targeting generalists.
The difference is likely due to the specialists’ ability to take
better advantage of their host plants, says Singer. Many specialists use
chemicals from their host plant’s tissue to make themselves toxic.
Others, like Singer’s specialist caterpillars, might be more adept at
camouflaging themselves by finding the best places to hide or to blend
Singer’s experiment is the first to quantify bird predation on
specialist and generalist herbivores, and he hopes it will spark further
research. He says that the interactions among the three trophic levels –
plants, herbivores and predators – are the key to understanding the
species’ ecology and evolution.
"Food webs are complex, and that complexity is fundamental to
understanding ecological specialization and diversity in natural
ecosystems," he says.
Animals and plants communicate with one another in a variety of ways:
behavior, body patterns, and even chemistry. In a series of talks at
the Ecological Society of America’s annual meeting, to be held August
3-7 in Albuquerque, New Mexico, ecologists explore the myriad
adaptations for exchanging information among living things.
Source : Ecological
Society of America