Time and the Number of Herbivore Species: The Pests of Sugarcane

Abstract

Previous analyses have established that host species range in the most important determinant of plant— and animal—associated parasite species richness, and that the age of a host species within a region is, at most, much less important in determining this richness. However, these previous analyses were not able to completely rule out age as a cause, because the available host age estimations were crude and few host groups were available for comparison. This paper examines the arthropod pests of sugarcane (Saccharum officinarum) in 51 regions for which dates of introduction, areas in cultivation, and associated pest data are available. The sugarcane data are more complete and extensive than those for previously investigated host—parasite associations, and they make possible a more detailed analysis of the causes of species richness. Multiple regression analyses of these data cannot identify time to have any measurable influence upon the species richness of sugarcane pests. This implies pest species accumulation to reach an asymptote within, at most, a few hundred years. The asymptote is set by the geographic range of host species. The results of this study are consistent with those of four other analyses of host—parasite associations. We suggest sufficient evidence has accumulated to justify abandoning nonasymptotic species accumulation models (the "time) and "stability—time" hypotheses), at least for parasite communities. We caution against invoking "time" hypotheses for the explanation of diversity variation in other ecological systems where the influence of area and immigration rates cannot be dealt with. The "time" hypothesis also often involves virtually untestable assumptions about habitat constancy over very long periods of time.

Novel chemistry of invasive exotic plants

“…A plant species introduced to a new habitat can be colonized rapidly by herbivores that recognize it as potential food and have the physiological capability to detoxify its secondary constituents (Strong 1974;Strong et al 1977;Singer et al 1993). Herbivores of native plants often shift onto novel hosts that are phytochemically similar to, but not necessarily related to, their traditional hosts (Strong et al 1984).…”

Taxonomic isolation and the accumulation of herbivorous insects: a comparison of introduced and native trees

“…Strong and co-workers (Strong, 1974a, b , c;Strong & Levin, 1975Strong et al, 1977) interpret the 'rapid asymptotic' accumulation of herbivores onto introduced plants t o imply that biogeographic speciesrichness patterns of phytophagous insects are determined largely independently of time, after an initial period for colonization (up t o 300 years). Our results are consistent with this interpretation.…”

Rapid adaptation of insect herbivores to an invasive plant

“…A release from enemy attack may benefit invasive plants relative to native plants both through phenotypic responses to benign conditions (Mack et al 2000;Maron & Vila 2001;Keane & Crawley 2002) and by evolutionary shifts in allocation from defence to growth and reproduction (Blossey & Nö tzold 1995;Bossdorf et al 2005). Yet, studies of crop plants and introduced trees have shown that they have a diversity of insect herbivores comparable to native species within 350 years of their introduction (Strong 1974a,b;Strong et al 1977;Leather 1986;Andow & Imura 1994). Together these findings suggest a complex interaction of native herbivores and introduced plants in which low levels of herbivory at first may promote invasion success but then accumulation of herbivores over a period of centuries eventually equalizes invasive and native plant performance (defined here as naturalization).…”