Barman A K, Gadhave K R, Dutta B, Srinivasan R
Department of Entomology,University of Georgia,2360 Rainwater Road,Tifton,GA 31793,USA.
Department of Plant pathology,University of Georgia,2360 Rainwater Road,Tifton,GA 31793,USA.
Bull Entomol Res. 2018 Jun;108(3):360-369. doi: 10.1017/S0007485317000852. Epub 2017 Sep 12.
Biological and morphological plasticity in polyphagous insect herbivores allow them to exploit diverse host plant species. Geographical differences in resource availability can lead to preferential host exploitation and result in inconsistent host specialization. Biological and molecular data provide insights into specialization and plasticity of such herbivore populations. In agricultural landscapes, Aphis gossypii encounters several crop and non-crop hosts, which exist in temporal and spatial proximity. We investigated the host-specialization of two A. gossypii host-associated populations (HAPs), which were field collected from cotton and squash (cotton-associated population and melon-associated population), and later maintained separately in the greenhouse. The two aphid populations were exposed to seven plant species (cotton, okra, watermelon, squash, cucumber, pigweed, and morning glory), and evaluated for their host utilization plasticity by estimating aphid's fitness parameters (nymphal period, adult period, fecundity, and intrinsic rate of increase). Four phenotypical characters (body length, head capsule width, hind tibia length and cornicle length) were also measured from the resulting 14 different HAP × host plant combinations. Phylogenetic analysis of mitochondrial COI sequences showed no genetic variation between the two HAPs. Fitness parameters indicated a significant variation between the two aphid populations, and the variation was influenced by host plants. The performance of melon-aphids was poor (up to 89% reduction in fecundity) on malvaceous hosts, cotton and okra. However, cotton-aphids performed better on cucurbitaceous hosts, squash and watermelon (up to 66% increased fecundity) compared with the natal host, cotton. Both HAPs were able to reproduce on two weed hosts. Cotton-aphids were smaller than melon-aphids irrespective of their host plants. Results from this study suggest that the two HAPs in the study area do not have strict host specialization; rather they exhibit plasticity in utilizing several hosts. In this scenario, it is unlikely that host-associated A. gossypii populations would evolve into host-specific biotypes.
多食性昆虫食草动物的生物学和形态可塑性使它们能够利用多种寄主植物物种。资源可用性的地理差异会导致对寄主的优先利用，并导致寄主专一性不一致。生物学和分子数据为这类食草动物种群的专一性和可塑性提供了见解。在农业景观中，棉蚜会遇到几种作物和非作物寄主，它们在时间和空间上相邻。我们调查了从棉花和南瓜上田间采集的两个棉蚜寄主相关种群（HAPs）（棉花相关种群和甜瓜相关种群）的寄主专一性，随后将它们分别饲养在温室中。将这两个蚜虫种群暴露于七种植物物种（棉花、秋葵、西瓜、南瓜、黄瓜、藜和牵牛），并通过估计蚜虫的适合度参数（若虫期、成虫期、繁殖力和内禀增长率）来评估它们对寄主利用的可塑性。还从产生的14种不同的HAP×寄主植物组合中测量了四个表型特征（体长、头壳宽度、后胫节长度和腹管长度）。线粒体COI序列的系统发育分析表明，这两个HAPs之间没有遗传变异。适合度参数表明这两个蚜虫种群之间存在显著差异，并且这种差异受寄主植物影响。甜瓜蚜虫在锦葵科寄主棉花和秋葵上的表现较差（繁殖力降低高达89%）。然而，与原生寄主棉花相比，棉花蚜虫在葫芦科寄主南瓜和西瓜上的表现更好（繁殖力提高高达66%）。两个HAPs都能够在两种杂草寄主上繁殖。无论寄主植物如何，棉花蚜虫都比甜瓜蚜虫小。这项研究的结果表明，研究区域内的这两个HAPs没有严格的寄主专一性；相反，它们在利用多种寄主方面表现出可塑性。在这种情况下，与寄主相关的棉蚜种群不太可能进化成寄主特异性生物型。
