Integrative Taxonomy and Synonymization of Aculus mosoniensis (Acari: Eriophyidae), a Potential Biological Control Agent for Tree of Heaven (Ailanthus altissima)

Abstract

The taxonomy of Aculus mosoniensis appears to be an unresolved question and its clarification is required, owing to the potential relevance of this mite species as a biological control agent of the tree of heaven. This paper is aimed at giving accurate details on a previously and shortly announced synonymization with Aculops taihangensis, using a morphological and molecular approach. A fusiform morph of A. mosoniensis was distinguished from a vermiform morph and this latter was recognized as deutogyne, which was herein documented. Phylogenetic relationships between Chinese Ac. taihangensis and all A. mosoniensis mites collected in twenty localities in Europe were examined through the analysis of the mitochondrial cytochrome c subunit I (CO1) protein and the nuclear ribosomal internal transcribed spacer 1 region (ITS1). CO1 sequences of Ac. taihangensis from the Shandong province in China and those from mites collected in Austria and Slovenia were 100% identical; the ITS1 sequence of an Ac. taihangensis paratype matched for 99.8% with those obtained from protogynes and deutogynes of A. mosoniensis collected in Italy. All these data supported the announced synonymization of A. mosoniensis with Ac. taihangensis. Aculusmosoniensis was found genetically variable, with five CO1 haplotypes in Europe (becoming eight along with those of Ac. taihangensis) clustering in two highly supported maternal lineages and eight ITS1 haplotypes (becoming nine along with those of Ac. taihangensis) distributed in four supported clades. No overlap between intra- and interspecies distances was observed for both markers and all studied A. mosoniensis populations clustered in one monophyletic mitochondrial clade, suggesting that only one single species might occur in Europe. However, more mite clades may be related to more tree of heaven biotypes with potential ecological differences, which might have potential effects on the biological control and should be investigated.

Keywords: Aculops taihangensis; CO1; ITS1; deutogyne; invasive plant species; molecular analysis.

Figure 1

Line drawings of a deutogyne of Aculus mosoniensis. AD: prodorsal shield; AL: lateral view of anterior body region; CG: female coxigenital region; em: empodium; IG: internal female genitalia; LO: lateral view of annuli; L1: leg I; PM: lateral view of posterior opisthosoma. Scale bar: 10 μm for AD, AL, CG, IG, and PM; 5 μm for LO and L1; 2.5 μm for em.

Figure 2

Scanning electron micrographs of deutogynes of Aculus mosoniensis: (A) dorsal view; (B) leg tarsal empodium and solenidion; (C) coxigenital region; (D) dorsal view of gnathosoma and frontal lobe. Scale bars: 10 μm for (A,B,D); 2 μm for (B).

Figure 3

Scanning electron micrographs of a protogyne (A) and a deutogyne (B) of Aculus mosoniensis. Prodorsal shield and part of dorsal opisthosoma. Scale bars: 10 μm.

Figure 4

Line drawing of the prodorsal shield of Aculops taihangensis paratype.

Figure 5

Maximum likelihood phylogenetic tree of CO1 sequences of Aculus mosoniensis, Aculops taihangensis, and two congeners, Aculus ichnocarpae and Aculus amygdali, used as outgroups. Only significant values of bootstrap support (>90%) and of Bayesian posterior probabilities obtained by MrBayes (>0.8) are shown at the nodes. Branch lengths represent expected substitutions per site. The scale bar indicates the expected number of substitutions per site. Tip labels refer to specimen IDs and haplotypes listed in Table 1.

Figure 6

Maximum likelihood phylogenetic tree of Aculus mosoniensis ITS1 sequences, Aculops taihangensis, and one congener, Aculus cercidis, used as outgroup. Only significant values of bootstrap support (>90%) and of Bayesian posterior probabilities obtained by MrBayes (>0.9) are shown at the nodes. The scale bar indicates the expected number of substitutions per site. Tips labels refer to specimen IDs and haplotypes listed in Table 1.