Genetic integrity of four species of Leptidea (Pieridae, Lepidoptera) as sampled in sympatry in West Siberia

In southern West Siberia, as many as four Leptidea Billberg, 1820 species are present sympatrically: L. amurensis (Ménétriés, 1859), L. morsei (Ménétriés, 1859), L. sinapis (Linnaeus, 1758) and L. juvernica Williams, 1946. The two latter were recently recognised as nearly sibling species on morphological and molecular characters. Specimens intermediate as to their subtle diagnostic characters occurring in West Siberia and elsewhere were interpreted as resulted from limited introgression. This supposition was tested via populational morphological and molecular analysis of spring brood specimens of all the four species taken from a limited (4.5 × 0.2 km) area in the suburbs of Novosibirsk. The samples were analysed with respect to the genitalic morphology, external characters, three nuclear (CAD, H1 gene and ITS2) and one mitochondrial (COI) molecular markers, infection of the intracellular maternally inherited bacterial symbiont Wolbachia Hertig, 1836 and its wsp gene coding for a hypervariable surface protein. Interspecific variation of the nuclear CAD and ITS2 sequences and the mitochondrial COI gene in L. sinapis and L. juvernica turned out concordant. The absence of molecular evidence of introgression suggests genetic integrity of these two species and allows their reliable identification by molecular characters. The genitalic (lengths of the saccus and valva) and external characters (wing pattern) of males overlap in L. sinapis and L. juvernica, as identified by molecular markers and thus are not so helpful in actual species identification. Only the ductus bursae length showed no overlap and can be used for identification of females. The histone H1 gene appeared five times less variable over the four studied species than COI, and found to be identical in species L. sinapis and L. juvernica. Wolbachia infection was found in all studied species. We identified three wsp variants of Wolbachia: 1) wsp-10 allele in L. amurensis, L. sinapis, L. juvernica; 2) a very similar wsp-687 allele in L. sinapis; and 3) wsp-688, highly divergent to the previous ones, in L. morsei

Genetic Evidence of Broad Spreading of Lymantria dispar in the West Siberian Plain

Gypsy moth Lymantria dispar L. 1758 (Lepidoptera: Erebidae) is one of the most dangerous forest pests of the Holarctic region. Outbreaks of gypsy moth populations lead to significant defoliation of local forests. Within the vast territory of the West Siberian Plain, we noted the outbreak front movement of in the north-east direction with a speed 100-200 km per year. The reason for the outbreak’s movement is still unclear because L. dispar females are characterised by limited flight ability, which is not enough to support that movement per se. Herein, we analysed the mtDNA divergence pattern among L. dispar populations collected from the vast territory of the West Siberian Plain to determine the boundaries of populations and reveal the effect of the outbreak’s front movement on mtDNA patterns of populations. The 590-bp region of the cytochrome oxidase subunit I gene of the mitochondrial genome was sequenced for 220 specimens that were collected from 18 localities along a transect line (~ 1400 km). Our results clearly show that the gypsy moth populations of the vast Siberian territory are not subdivided. This result can be explained by extensive genetic exchange among local populations. Taking into account that the flight ability of L. dispar females is rather limited, we suggest that spreading occurs through ballooning of early instar larvae. This hypothesis was confirmed by the coincidence of the outbreaks’ movement direction with that of the dominant winds, complemented by the observation of ballooned larvae far from a forest edge

Genetic evidence of broad spreading of Lymantria dispar in the West Siberian Plain.

Gypsy moth Lymantria dispar L. 1758 (Lepidoptera: Erebidae) is one of the most dangerous forest pests of the Holarctic region. Outbreaks of gypsy moth populations lead to significant defoliation of local forests. Within the vast territory of the West Siberian Plain, we noted the outbreak front movement in the north-east direction with a speed 100-200 km per year. The reason for the outbreak's movement is still unclear because L. dispar females are characterised by limited flight ability, which is not enough to support that movement per se. Herein, we analysed the mtDNA divergence pattern among L. dispar populations collected from the vast territory of the West Siberian Plain to determine the boundaries of populations and reveal the effect of the outbreak's front movement on mtDNA patterns of populations. The 590-bp region of the cytochrome oxidase subunit I gene of the mitochondrial genome was sequenced for 220 specimens that were collected from 18 localities along a transect line (~ 1400 km). Our results clearly show that the gypsy moth populations of the vast Siberian territory are not subdivided. This result can be explained by extensive genetic exchange among local populations. Taking into account that the flight ability of L. dispar females is rather limited, we suggest that spreading occurs through ballooning of early instar larvae. This hypothesis was confirmed by the coincidence of the outbreaks' movement direction with that of the dominant winds, complemented by the observation of ballooned larvae far from a forest edge