Abstract
Knowing the phylogeographic structure of invasive species is important for understanding the underlying processes of invasion. The micromoth Phyllonorycter issikii, whose larvae damage leaves of lime trees Tilia spp., was only known from East Asia. In the last three decades, it has been recorded in most of Europe, Western Russia and Siberia. We used the mitochondrial cytochrome c oxidase subunit I (COI) gene region to compare the genetic variability of P. issikii populations between these different regions. Additionally, we sequenced two nuclear genes (28S rRNA and Histone 3) and run morphometric analysis of male genitalia to probe for the existence of cryptic species.The analysis of COI data of 377 insect specimens collected in 16 countries across the Palearctic revealed the presence of two different lineages: P. issikii and a putative new cryptic Phyllonorycter species distributed in the Russian Far East and Japan. In P. issikii, we identified 31 haplotypes among which 23 were detected in the invaded area (Europe) and 10 were found in its putative native range in East Asia (Russian Far East, Japan, South Korea and China), with only two common haplotypes. The high number of haplotypes found in the invaded area suggest a possible scenario of multiple introductions. One haplotype H1 was dominant (119 individuals, 67.2%), not only throughout its expanding range in Europe and Siberia but, intriguingly, also in 96% of individuals originating from Japan. We detected eight unique haplotypes of P. issikii in East Asia. Five of them were exclusively found in the Russian Far East representing 95% of individuals from that area. The putative new cryptic Phyllonorycter species showed differences from P. issikii for the three studied genes. However, both species are morphologically undistinguishable. They occur in sympatry on the same host plants in Japan (Sendai) and the Russian Far East (Primorsky krai) without evidence of admixture.
Highlights
The number of non-native terrestrial arthropods established in Europe has increased exponentially during the second half of the 20th century [1]
We studied P. issikii samples from 10 different Tilia host plant species, six species in East Asia (T. mandshurica, T. maximowicziana, T. amurensis, T. japonica, T. taquetii and T. mongolica) and four species in Europe, Western Russia and Siberia (T. cordata, T. sibirica, T. platyphyllos and T. dasystyla); 13 lime trees surveyed in the Russian Far East and in Europe have not been identified to the species level
The analysis of 377 DNA barcodes of Tilia leaf miners collected in the Palearctic revealed a deep split with two clades: one formed by 334 specimens belonging to P. issikii and a second clade formed by 43 specimens which could represent an undescribed species from the genus Phyllonorycter (Fig 3)
Summary
The number of non-native terrestrial arthropods established in Europe has increased exponentially during the second half of the 20th century [1]. Most of these alien species introduced to Europe originate from Asia [1, 2] and can cause significant ecological impact [3]. Micromoths of the family Gracillariidae are an important group of herbivores with several species that are pests of agricultural crops, orchards and ornamental woody plantations worldwide [2, 7]. The lime leaf miner Phyllonorycter issikii Kumata, 1963, the plane leaf miner P. platani Staudinger, 1870, the firethorn leaf miner P. leucographella (Zeller, 1850), the horse-chestnut leaf miner Cameraria ohridella Deschka & Dimić, 1986, the locust digitate leaf miner Parectopa robiniella Clemens, 1863, Macrosaccus robiniella (Clemens, 1859)–all these micromoths have colonized many European countries attacking woody plants of ornamental value [11]
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