Geography-dependent symbiont communities in two oligophagous aphid species.

Aphids and their diverse symbionts have become a good model to study bacteria-arthropod symbiosis. The feeding habits of aphids are usually influenced by a variety of symbionts. Most studies on symbiont diversity have focused on polyphagous aphids, while symbiont community patterns for oligophagous aphids remain unclear. Here, we surveyed the bacterial communities in natural populations of two oligophagous aphids, Melanaphis sacchari and Neophyllaphis podocarpi, in natural populations. Seven common symbionts were detected, among which Buchnera aphidicola and Wolbachia were the most prevalent. In addition, an uncommon Sodalis-like symbiont was also detected in these two aphids, and Gilliamella was found in some samples of M. sacchari. We further assessed the significant variation in symbiont communities within the two aphid species, geographical regions and host specialization using statistical and ordination analyses. Geography was an important factor in shaping the symbiont community structure in these oligophagous aphids. Furthermore, the strong geographical influence may be related to specific environmental factors, especially temperature, among different regions. These findings extend our knowledge of the significance of geography and its associated environmental conditions in the symbiont community structure associated with oligophagous aphids.

Diversity of bacterial symbionts associated with Myzus persicae (Sulzer) (Hemiptera: Aphididae: Aphidinae) revealed by 16S rRNA Illumina sequencing.

Aphids are known to be associated with a variety of symbiotic bacteria. To improve our knowledge of the bacterial diversity of polyphagous aphids, in the present study, we investigated the microbiota of the cosmopolitan agricultural pest Myzus persicae (Sulzer). Ninety-two aphid samples collected from different host plants in various regions of China were examined using high-throughput amplicon sequencing. We comprehensively characterized the symbiont diversity of M. persicae and assessed the variations in aphid-associated symbiont communities. We detected a higher diversity of symbionts than has been previously observed. M. persicae hosted the primary endosymbiont Buchnera aphidicola and seven secondary symbionts, among which Wolbachia was the most prevalent and Rickettsia, Arsenophonus, and Spiroplasma were reported for the first time. Ordination analyses and statistical tests revealed that the symbiont flora associated with M. persicae did not change with respect to host plant or geography, which may be due to frequent migrations between different aphid populations. These findings will advance our knowledge of the microbiota of polyphagous insects and will enrich our understanding of assembly of host-microbiome systems.

The Bacterial Flora Associated with the Polyphagous Aphid Aphis gossypii Glover (Hemiptera: Aphididae) Is Strongly Affected by Host Plants.

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.

Wolbachia Infection in Two Species: Novel Views on the Colonization Ability of Wolbachia in Aphids.

Wolbachia pipientis (Rickettsiales: Anaplasmataceae) is an intracellular symbiont residing in arthropods and filarial nematodes. Sixteen supergroups have been described from different host taxa. Four supergroups A, B, M, and N were found in aphids according to prior studies. The cotton aphid, Aphis gossypii, and the green peach aphid, Myzus persicae, are typical polyphagous species with global distributions. We conducted an extensive and systematic survey of Wolbachia infections in these aphids from China. High incidences of Wolbachia infection were detected. The total infection incidence was 60% in A. gossypii and 88% in M. persicae. Both aphid species were infected with supergroups A, B and M. Different incidences of infection were observed among the seven geographical regions in China, which suggested a positive relationship between Wolbachia infections and the geographical distribution of aphid species. Furthermore, multiple infection patterns (M, B, A&M, B&M, and A&B&M) were observed. Infection patterns M and B&M were detected in almost all populations. Patterns A&B&M and B showed geographical restriction in North China. Three factors can possibly influence the Wolbachia infection incidences and patterns: the geographical distribution, aphid species, and different supergroup types.

The genes expression difference between winged and wingless bird cherry-oat aphid Rhopalosiphum padi based on transcriptomic data.

Aphids produce wing and wingless morphs, depending on the environmental conditions during their complex life cycles. Wing and wingless variations play an important role in migration and host alternation, affecting the migration and host alternation processes. Several transcriptional studies have concentrated on aphids and sought to determine how an organism perceives environmental cues and responds in a plastic manner, but the underlying mechanisms have remained unclear. Therefore, to better understand the molecular mechanisms underlying the wing polyphenism of this fascinating phenomenon, we provide the first report concerning the wing development of aphids in bird cherry-oat aphid Rhopalosiphum padi with comparative transcriptional analysis of all the developmental stages by RNA-Seq. We identified several candidate genes related to biogenic amines and hormones that may be specifically involved in wing development. Moreover, we found that the third instar stage might be a critical stage for visibility of alternative morphs as well as changes in the expression of thirty-three genes associated with wing development. Several genes, i.e., Wnt2, Fng, Uba1, Hh, Foxo, Dpp, Brk, Ap, Dll, Hth, Tsh, Nub, Scr, Antp, Ubx, Asc, Srf and Fl, had different expression levels in different developmental stages and may play important roles in regulating wing polyphenism.

A new species of Mollitrichosiphum Suenaga from Taiwan Island (Hemiptera, Aphididae), based on morphological characteristics and DNA sequences.

A new species of Mollitrichosiphum Suenaga, Mollitrichosiphum tumorisiphum Qiao & Jiang, sp. n., from Fagus longipetiolata in Taiwan island is described. Siphunculi of Mollitrichosiphum tumorisiphum in alatae are distinctly swollen on the distal part, unlike those of the other known species in the genus. Updated keys to apterous and alate viviparous females of all known Chinese species of Mollitrichosiphum are provided. The specimens studied are deposited in the National Zoological Museum of China, Institute of Zoology, Chinese Academy of Sciences, Beijing, China and the Natural History Museum, London, United Kingdom.

The fern-feeder aphids (Hemiptera: Aphididae) from China: a generic account, descriptions of one new genus, one new species, one new subspecies, and keys.

Fern-feeder aphids (Hemiptera: Aphididae) in China are represented by 13 species in 10 genera, including a new genus, Vietaphis gen nov., a new species, Vietaphis aliquantus sp nov., from Guizhou and Tibet on Plagiogyria japonicum, and a new subspecies, Amphorophora scabripes galba ssp nov., from Guizhou on Pentarhizidium intermedium. Two genera, Amphorophora Buckton and Idiopterus Davis, and four species or subspecies, Amphorophora ampullate ben-galensis Hille Ris Lambers and Basu, Idiopterus nephrelepidis Davis, Micromyzodium polypodii Takahashi, and Myzus filicis Basu, are reported for the first time in China. Apterae and alatae of Myzus filicis are redescribed herein, and with host plant notes. The fern-feeder aphid genus Ne-omacromyzus Lee is considered a junior synonym of Idiopterus. Furthermore, Neomacromyzus cyrtomicola Lee is transferred to the genus Idiopterus, as Idiopterus cyrtomicola (Lee), comb nov., which is herein considered a junior synonym of Idiopterus nephrelepidis Davis. Keys to Chinese fern-feeder species are provided. Morphological figures and biometrical data of Vietaphis aliquantus sp nov., Amphorophora scabripes galba ssp nov., and Myzus filicis are presented.

Species differentiation of Chinese mollitrichosiphum (Aphididae: greenideinae) driven by geographical isolation and host plant acquirement.

The impact of both the uplift of the Qinghai-Tibetan Plateau (QTP) and the separation of the Taiwan and Hainan Islands on the evolution of the fauna and flora in adjacent regions has been a topic of considerable interest. Mollitrichosiphum is a polyphagous insect group with a wide range of host plants (14 families) and distributions restricted to Southeast Asia. Based on the mitochondrial Cytochrome C Oxidase Subunit I (COI) and Cytochrome b (Cytb) genes, the nuclear elongation factor-1α (EF-1α) gene, and the detailed distribution and host plant data, we investigated the species differentiation modes of the Chinese Mollitrichosiphum species. Phylogenetic analyses supported the monophyly of Mollitrichosiphum. The divergence time of Mollitrichosiphum tenuicorpus (c. 11.0 mya (million years ago)), Mollitrichosiphum nandii and Mollitrichosiphum montanum (c. 10.6 mya) was within the time frame of the uplift of the QTP. Additionally, basal species mainly fed on Fagaceae, while species that fed on multiple plants diverged considerably later. Ancestral state reconstruction suggests that Fagaceae may be the first acquired host, and the acquisition of new hosts and the expansion of host range may have promoted species differentiation within this genus. Overall, it can be concluded that geographical isolation and the expansion of the host plant range may be the main factors driving species differentiation of Mollitrichosiphum.