Herbivore Offense

Abstract

Herbivore offense describes traits that allow herbivores to increase their feeding and other uses of host plants when these uses benefit the herbivores. We argue that ecological interactions and coevolution between plants and herbivores cannot be understood without an offense-defense framework. Thus far, plant defense theory and data have far outpaced knowledge of herbivore offense. Offensive tactics include feeding and oviposition choices, enzymatic metabolism of plant compounds, sequestration, morphological adaptations, symbionts, induction of plant galls, and induced plant susceptibility, trenching, and gregarious feeding. We propose that offensive tactics can be categorized usefully depending upon when they are effective and whether they are plastic or fixed traits. The advantages of offensive traits have not been adequately described in terms of herbivore fitness. Similarly, a more complete understanding of the costs and limitations of offensive traits will help put the herbivore back in plant-herbivore interactions and coevolution.

Ecological consequences of phenotypic plasticity

“…Although this research program has been motivated largely by evolutionary questions, studies of adaptive plasticity such as inducible defenses and inducible offenses [4,10,11] (Box 1) also have clear ecological implications. For example, in East Africa, herbivory by elephants and giraffes induces longer and more numerous protective spines on Acacia drepanolobium trees [8], which enhances the survivorship and competitive ability of A. drepanolobium when subsequent herbivores arrive.…”

Herbivore pressure increases toward the equator

“…Herbivore pressure is expected to increase with greater tissue loss when damage reduces growth and reproduction (quantitatively) (9) but also with changes in the identity of the herbivore species (qualitatively) (7). Increased number of species attacking a given plant host should result in a qualitatively different set of selective pressures compared with attack by fewer species because each herbivore reacts idiosyncratically to the defensive arsenal of a plant and may, therefore, influence plant fitness in different ways (10)(11)(12)(13). From the point of view of the plant, each combination of traits embodied by a specific herbivore species may represent an additional and potentially unique evolutionary hurdle that the plant may need to overcome and may be manifested as a tradeoff in defense allocation.…”

Propuesta de muestreo para Neohydatothrips signifer (Thysanoptera: Thripidae) en el cultivo de maracuyá

“…Siguiendo con esta tendencia, el máximo pico poblacional se registró en el estado de desarrollo R1, en que se evidenció el incremento de la población con la llegada de la fase reproductiva. Karban & Agrawal (2002) mencionan que los insectos, para optimizar su alimentación, pueden identificar las plantas que contienen mejor contenido nutricional y, dentro de estas sus órganos vegetales, para alimentarse; las plantas en floración son las más atacadas, por presentar moléculas fáciles de digerir como aminoácidos, los cuales se encuentran mayormente disponibles en las plantas en fase de brotamiento y floración. Además, la alta densidad poblacional del trips, en la etapa de floración, también coincidió con periodos de alta temperatura.…”