Widespread plant specialization in the polyphagous planthopper Hyalesthes obsoletus (Cixiidae), a major vector of stolbur phytoplasma: Evidence of cryptic speciation

Abstract

The stolbur phytoplasma vector Hyalesthes obsoletus is generally considered as a polyphagous species associated with numerous wild and cultivated plants. However, recent research in southeastern Europe, the distribution centre of H. obsoletus and the area of most stolbur-inflicted crop diseases, points toward specific host-plant associations of the vector, indicating specific vector-based transmission routes. Here, we study the specificity of populations associated with four host-plants using mitochondrial and nuclear genetic markers, and we evaluate the evolution of host-shifts in H. obsoletus. Host-plant use was confirmed for Convolvulus arvensis, Urtica dioica, Vitex agnus-castus and Crepis foetida. Mitochondrial genetic analysis showed sympatric occurrence of three phylogenetic lineages that were ecologically delineated by host-plant preference, but were morphologically inseparable. Nuclear data supported the existence of three genetic groups (Evanno’s ΔK(3) = 803.72) with average genetic membership probabilities > 90%. While populations associated with C. arvensis and U. dioica form a homogenous group, populations affiliated with V. agnus-castus and C. foetida constitute two independent plant-associated lineages. The geographical signal permeating the surveyed populations indicated complex diversification processes associated with host-plant selection and likely derived from post-glacial refugia in the eastern Mediterranean. This study provides evidence for cryptic species diversification within H. obsoletus sensu lato: i) consistent mitochondrial differentiation (1.1–1.5%) among host-associated populations in syntopy and in geographically distant areas, ii) nuclear genetic variance supporting mitochondrial data, and iii) average mitochondrial genetic distances among host-associated meta-populations are comparable to the most closely related, morphologically distinguishable species, i.e., Hyalesthes thracicus (2.1–3.3%).

Relationships between Hyalesthes obsoletus, Its Herbaceous Hosts and Bois Noir Epidemiology in Northern Italian Vineyards

“…Adults of H. obsoletus originating from stinging nettle survived better on stinging nettle than on field bindweed and vice versa for adults from bindweed. These data confirm the results of previous studies [ 35 , 36 , 37 ] and support the hypothesis of cryptic speciation [ 38 , 39 ].…”

“…Hyalesthes obsoletus adult populations collected on field bindweed and stinging nettle showed a better survival and adaptation to the originating host [ 26 , 35 , 36 , 37 ]. The genetic differences between the populations associated with these two herbaceous plants suggested the occurrence of cryptic speciation [ 38 , 39 ].…”

Lavender Decline in France Is Associated with Chronic Infection by Lavender-Specific Strains of “Candidatus Phytoplasma solani”

“…According to microsatellite analyses, H. obsoletus populations collected in French lavenders differ from populations living on C. arvensis and U. dioica in Europe ( 30 ). H. obsoletus can locally adapt to new plant hosts, developing into plant-specialized ecotypes that can be morphologically identical but that have limited exchange with other populations living on different plants ( 31 , 32 ). It was recently shown that H. obsoletus populations developing on clary sage, a crop of the lavender plant family, had limited exchange with populations living on surrounding lavenders ( 33 ).…”

Symptomatology, (Co)occurrence and Differential Diagnostic PCR Identification of ‘Ca. Phytoplasma solani’ and ‘Ca. Phytoplasma convolvuli’ in Field Bindweed

“…Field bindweed is one of the major and most widely distributed natural hosts and plant reservoirs of ‘ Candidatus Phytoplasma solani’ (‘ Ca. P. solani’) and its planthopper vector Hyalesthes obsoletus (Hemiptera: Cixiidae) in agroecosystems and in natural habitats of the Euro-Mediterranean area [ 2 , 3 , 4 , 5 , 6 , 7 ]. ‘ Ca.…”

“…Given the epidemiological and ecological complexity of ‘ Ca. P. solani’-induced diseases [ 6 , 7 , 8 , 19 , 20 , 21 , 22 , 23 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ] and its evolutionary relatedness to ‘ Ca. P. convolvuli’, the focus of this study was to analyze the (co)occurrence of the two pathogens in shared host plant and related symptoms.…”