Plasticity in host utilization by two host-associated populations ofAphis gossypiiGlover

Abstract

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.

DNA Barcoding Subtropical Aphids and Implications for Population Differentiation

“…As an example of geography related differentiation in hemipteran insects in another continent, high COI genetic distances (highest 4.7%) were observed between populations of stink bug Chinavia hilaris from the west coast and east coast of the United States and indicated that geographical isolation may promote cryptic diversity [82]. However, population differentiation of phytophagous insects may be driven simultaneously by both host plant and geography factors, as discussed in some previous cases [106,107]. Thus, more detailed studies on the differentiation of subtropical aphid populations at fine scales are needed in the future.…”

No Evidence of Bacterial Symbionts Influencing Host Specificity in Aphis gossypii Glover (Hemiptera: Aphididae)

“…When the temperature is higher than 25 °C, the fecundity of A. gossypii is inhibited [ 39 ]. In addition, host-specialized biotypes from different regions may differ in the degree of host specificity [ 40 ].…”

Prospective Alternate Hosts of an Emerging Polerovirus in Cotton Landscapes in the Southeastern United States

“…A single nymph per cage was monitored throughout the life cycle. Fitness parameters such as aphid survival (nymph to adult), nymphal period, adult period (pre-reproductive, reproductive, and post-reproductive), total fecundity, and intrinsic rate of increase were evaluated [ 37 , 38 ]. The total number of nymphs laid by an adult in the subsequent generation was recorded and removed from the cage.…”