Straw N A
Monks Wood Experimental Station, Institute of Terrestrial Ecology, Abbots Ripton, PE17 2LS, Huntingdon, Cambridgeshire, UK.
Oecologia. 1991 May;86(4):492-502. doi: 10.1007/BF00318315.
The intensity of resource exploitation by phytophagous insects is usually considered to reflect population size. For populations of two flowerhead-attacking tephritid flies, however, the resources utilised were not related to the numbers of searching adults. Tephritis bardanae Schrank attacked 11-13% of the total flowerheads each year, and Cerajocera tussilaginis (Fab) 17-65%, despite much wider and uncorrelated variation in adult numbers. Analysis of field data showed that the proportion of flowerheads used was not limited by poor flowerhead quality, but was restricted by (1) the synchronisation of adult activity with the appearance of flowerheads at the correct age for oviposition, and (2) by factors which influenced the ability of female flies to locate available heads. These restrictions were more severe in T. bardanae and explained its relatively low rate of infestation. Both tephritids tended to avoid flowerheads in open areas. The processes governing resource exploitation in each tephritid operated independently of the other, and a partial separation of the two species between flowerhead types and habitats arose simply because of their different timing of attack.
植食性昆虫的资源利用强度通常被认为反映了种群数量。然而，对于两种攻击花头的实蝇种群来说，所利用的资源与搜寻成虫的数量并无关联。每年，巴达纳实蝇（Tephritis bardanae Schrank）会攻击11%至13%的总花头，而款冬角实蝇（Cerajocera tussilaginis (Fab)）则会攻击17%至65%的总花头，尽管成虫数量存在更广泛且不相关的变化。对野外数据的分析表明，被利用的花头比例并非受花头质量差的限制，而是受到以下因素的制约：（1）成虫活动与适合产卵的花头出现的同步性；（2）影响雌蝇定位可用花头能力的因素。这些限制在巴达纳实蝇中更为严重，这也解释了其相对较低的侵染率。两种实蝇都倾向于避开开阔区域的花头。每种实蝇控制资源利用的过程相互独立，这两个物种在花头类型和栖息地之间的部分分离仅仅是由于它们不同的攻击时间所致。
