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No abstract

Structures on the surfaces of leaves strongly affect phylloplane mites. Glandular trichomes defend against some plant parasites but can also mire predators. However, leaves with tomenta of nonglandular trichomes are often inhabited by large populations of predatory mites. Tufts of hairs and other minute structures in the vein axils are called leaf domatia. Comparative observations and experimental data demonstrate that leaves with domatia have enhanced levels of predatory mites. By accumulating predatory mites, leaf domatia act as a kind of constitutive defense against herbivores. Mites benefit from leaf domatia by securing a safe place for oviposition and molting. Like several other plant structures, leaf domatia are the manifestation of a long-term and mutually beneficial interaction between plants and arthropods.

Dichotomous keys that follow a single pathway of character state choices to an end point have been the primary tools for the identification of unknown organisms for more than two centuries. However, a revolution in computer diagnostics is now under way that may result in the replacement of traditional keys by matrix-based computer interactive keys that have many paths to a correct identification and make extensive use of hypertext to link to images, glossaries, and other support material. Progress is also being made on replacing keys entirely by optical matching of specimens to digital databases and DNA sequences. These new tools may go some way toward alleviating the taxonomic impediment to biodiversity studies and other ecological and evolutionary research, especially with better coordination between those who produce keys and those who use them and by integrating interactive keys into larger biological Web sites.