Mitochondrial and microsatellite DNA markers reveal a Balkan origin for the highly invasive horse‐chestnut leaf miner Cameraria ohridella (Lepidoptera, Gracillariidae)

Abstract

Biological invasions usually start with a small number of founder individuals. These founders are likely to represent a small fraction of the total genetic diversity found in the source population. Our study set out to trace genetically the geographical origin of the horse-chestnut leafminer, Cameraria ohridella, an invasive microlepidopteran whose area of origin is still unkown. Since its discovery in Macedonia 25 years ago, this insect has experienced an explosive westward range expansion, progressively colonizing all of Central and Western Europe. We used cytochrome oxidase I sequences (DNA barcode fragment) and a set of six polymorphic microsatellites to assess the genetic variability of C. ohridella populations, and to test the hypothesis that C. ohridella derives from the southern Balkans (Albania, Macedonia and Greece). Analysis of mtDNA of 486 individuals from 88 localities allowed us to identify 25 geographically structured haplotypes. In addition, 480 individuals from 16 populations from Europe and the southern Balkans were genotyped for 6 polymorphic microsatellite loci. High haplotype diversity and low measures of nucleotide diversities including a significantly negative Tajima's D indicate that C. ohridella has experienced rapid population expansion during its dispersal across Europe. Both mtDNA and microsatellites show a reduction in genetic diversity of C. ohridella populations sampled from artificial habitats (e.g. planted trees in public parks, gardens, along roads in urban or sub-urban areas) across Europe compared with C. ohridella sampled in natural stands of horse-chestnuts in the southern Balkans. These findings suggest that European populations of C. ohridella may indeed derive from the southern Balkans.

Temporal and spatial variations in the parasitoid complex of the horse chestnut leafminer during its invasion of Europe

“…By contrast, the Balkans as the origin of the horse chestnut leafminer are supported by the theory that the only representative of the genus Cameraria in Europe may be a relict species, which survived the glacial cooling of the tertiary period together with its main host tree, A. hippocastanum (Deschka and Dimić 1986;Grabenweger and Grill 2000;Xiang et al 1998). This theory is more recently supported by a study based on mitochondrial and microsatellite DNA markers (Valade et al 2009). High genetic diversity found in C. ohridella populations of remote natural horse-chestnut stands in the mountains of the southern Balkans suggest that C. ohridella is native to this region.…”

Taxonomy, time and geographic patterns. Chapter 2

“…Th e horse-chestnut leaf miner, Cameraria ohridella, is illustrative of the diffi culty in identifying the native range of such species. Whereas this leaf miner was previously considered as an extra-European alien, recent genetic studies indicate that it originates from the southern Balkans (Valade et al 2009). …”

“…However, in the last 20 years, several exotic pests of economic concern, to name a few, the western corn rootworm (Diabrotica virgifera virgifera LeConte), the red palm weevil ( Rhynchophorus ferrugineus (Olivier)), the harlequin labybeetle (Harmonia axyridis (Pallas)), or the chestnut gall maker (Dryocosmus kuriphilus (Yasumatsu)), have invaded Europe, inducing more interest in the issue of alien arthropods. Th e horse-chestnut leaf miner, Cameraria ohridella Deschka and Dimić, an alien in Europe originating from the Balkans, has also raised much public concern because of its spectacular damage to urban trees in invaded areas of Central and Western Europe (Valade et al 2009). …”

Contrasted invasion processes imprint the genetic structure of an invasive scale insect across southern Europe

“…Harmful invasions of pests usually originate from native sources located further away, for example, in different continents (Ciosi et al, 2008;Lombaert et al, 2011), or follow the introduction of their host plant (for example, the oak gall wasp Andricus kollari, Stone et al, 2007). The rapid colonization of Europe by the horse-chestnut leafminer is one striking example of an invasive species that suddenly expanded from a geographically close region, namely the Balkans (Valade et al, 2009). In that particular case though, the expansion of the moth was due to the massive plantation of its preferred host as ornamental tree in European cities.…”