Abstract
Aphids live in symbiosis with a variety of bacteria, including the obligate symbiont Buchnera aphidicola and diverse facultative symbionts. The symbiotic associations for one aphid species, especially for polyphagous species, often differ across populations. In the present study, by using high-throughput 16S rRNA sequencing, we surveyed in detail the microbiota in natural populations of the cotton aphid Aphis gossypii in China and assessed differences in bacterial diversity with respect to host plant and geography. The microbial community of A. gossypii was dominated by a few heritable symbionts. Arsenophonus was the most dominant secondary symbiont, and Spiroplasma was detected for the first time. Statistical tests and ordination analyses showed that host plants rather than geography seemed to have shaped the associated symbiont composition. Special symbiont communities inhabited the Cucurbitaceae-feeding populations, which supported the ecological specialization of A. gossypii on cucurbits from the viewpoint of symbiotic bacteria. Correlation analysis suggested antagonistic interactions between Buchnera and coexisting secondary symbionts and more complicated interactions between different secondary symbionts. Our findings lend further support to an important role of the host plant in structuring symbiont communities of polyphagous aphids and will improve our understanding of the interactions among phytophagous insects, symbionts, and environments.
Highlights
Aphids are well known for their symbiotic associations with bacteria
The bacterial community of A. gossypii was dominated by the primary endosymbiont Buchnera aphidicola, followed by the secondary symbiont Arsenophonus (1.11%) and the bacteria Acinetobacter (0.99%) (Fig. 1a, Table S3)
Along with Arsenophonus, they were infected with Rickettsia, Serratia symbiotica (0.07%), Wolbachia (0.04%), Hamiltonella defensa (< 0.005%), Regiella insecticola (< 0.005%), and Spiroplasma (< 0.005%) (Fig. 1b, Table 1)
Summary
Some are commonly studied, such as Arsenophonus, Fukatsuia symbiotica, Hamiltonella defensa, Regiella insecticola, Rickettsiella viridis, and Serratia symbiotica from the Gammaproteobacteria; Rickettsia and Wolbachia from the Alphaproteobacteria; and Spiroplasma from the Mollicutes [15,16,17,18,19,20,21]. These secondary symbionts reside in bacteriocytes, sheath cells, or hemocoel [22] and are transmitted maternally and horizontally [18, 23, 24]. Several facultative symbionts seem to have established coobligate associations along with Buchnera in certain aphid species, such as Serratia symbiotica, Erwinia haradaeae, Fukatsuia symbiotica, Hamiltonella defensa, and Sodalis in some Lachninae species [21, 47,48,49,50,51] and Wolbachia in Pentalonia nigronervosa [52, 53]
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