Branson David H
USDA-ARS, Northern Plains Agricultural Research Laboratory, 1500 N Central Ave, Sidney, MT 59270, USA.
Environ Entomol. 2010 Apr;39(2):346-50. doi: 10.1603/EN08319.
Although most North American grasshopper species overwinter as eggs, some species hatch in late summer, overwinter as nymphs, and become adults in late spring. These species periodically reach outbreak densities, but it is unknown if they impact the population dynamics of later developing egg-overwintering grasshopper species. Two experiments were conducted in a northern mixed-grass prairie to examine the effects of herbivory by nymph-overwintering grasshoppers on survival of an egg-overwintering grasshopper, Ageneotettix deorum. When very high densities of nymph-overwintering grasshoppers reduced grass biomass by 80%, survival of A. deorum nymphs was significantly reduced. There was no effect of early season herbivory at a lower density of 16/m(2) on survival of A. deorum nymphs. The effects of early season herbivory appear consistent with exploitative competition. Although a strong reduction in peak grass biomass caused by early season herbivory negatively affected late season grass-feeding grasshopper densities, additional research is needed to examine the potential importance of early summer herbivory on population dynamics of later developing grasshoppers.
虽然大多数北美蚱蜢物种以卵越冬，但有些物种在夏末孵化，以若虫越冬，并在春末变为成虫。这些物种会周期性地达到爆发密度，但它们是否会影响后来发育的以卵越冬的蚱蜢物种的种群动态尚不清楚。在北方混合草草原进行了两项实验，以研究以若虫越冬的蚱蜢的取食对以卵越冬的蚱蜢Ageneotettix deorum存活的影响。当以若虫越冬的蚱蜢密度非常高，使草生物量减少80%时，A. deorum若虫的存活率显著降低。在较低密度16只/平方米时，早期取食对A. deorum若虫的存活没有影响。早期取食的影响似乎与剥削性竞争一致。虽然早期取食导致的峰值草生物量大幅减少对后期以草为食的蚱蜢密度产生了负面影响，但需要进一步研究来检验初夏取食对后来发育的蚱蜢种群动态的潜在重要性。
