Abstract:

Objective: The bark beetles in the genus Ips (Coleoptera: Scolytinae) are severe stem borers of conifers, and widely distributed in the Northern Hemisphere. The purpose of this paper is to identify the species in genus Ips in China and provide DNA data based on a nationwide investigation. Method: In this study, a total of 12 062 Ips adult specimens were collected from 39 sites in the coniferous forests in 9 provinces (autonomous regions) in Northeast, Northwest and Southwest China. Based on the first preliminary identification of species level with the morphological characters recorded in literature, fifty-two representative samples were selected for mtDNA COⅠ gene sequencing and sequence alignment. Phylogenetic trees containing all species in the genus and Chinese samples were constructed based on maximum likelihood, maximum parsimony and Bayesian methods. Result: A total of 10 Ips species were identified based on their morphological characteristics. The molecular identification based on sequence comparisons further verified the morphological identification results, namely I. chinensis, I. duplicatus, I. hauseri, I. nitidus, I. schmutzenhoferi, I. sexdentatus, I. shangrila, I. stebbingi, I. subelongatus and I. typographus. In the phylogenetic analysis of all known 37 Ips species worldwide, the Chinese samples were clustered in the same branch with the same reference species, which further supported the results of morphological and molecular identifications. At the same time, phylogenetic analysis further showed that I. duplicatus and I. hauseri were sibling species. There was obvious genetic differentiation between the samples of I. chinensis and the known northern and southern populations of the species, and the samples were independently classified into the third subclade within the species. The I. typographus samples from Xinjiang, Northeast-Far East and Europe were divided into three separate subbranches. The I. schmutzenhoferi samples from China and those from Nepal and Pakistan were divided into two subbranches. The I. duplicatus and I. sexdentatus samples were divided into two subclades with their corresponding European samples. There was no genetic differentiation in I. subelongatus from Xinjiang and northeast China. Conclusion: The species of Ips are abundant and widely distributed in China. The morphological characteristics of many sibling species are very similar, and difficult to distinguish solely based on morphology. Joint methods based on morphological characters and mtDNA COⅠ gene sequence alignment and phylogenetic analysis can accurately identify Ips species. Among the 10 Ips species in this study, I. schmutzenhoferi is a new record species in China. In addition, the identification of I. chinensis was amended, and seven Ips species were found with subspecific genetic differentiations.

Key words: bark beetles, Ips, mtDNA COⅠ gene, phylogenetic analysis, morphological characteristics, coniferous forest