Status of the potentially invasive Asian species Sceliphron deforme in Europe, and an update on the distribution of S. curvatum (Hymenoptera: Sphecidae)

Abstract

We reviewed the distribution of the two Asian species of the genus Sceliphron Klug, introduced into Europe in the late 1970s to early 1980s: S. (Hensenia) curvatum (Smith) and S. (Hensenia) deforme (Smith). Both species are routinely considered as invasive in Europe, but the status and effects of their (eventual) invasiveness are yet to be documented and evaluated. We had a focus on two areas, the Balkan Peninsula and European Russia, based principally on the study of specimens collected over the last 15 years, but we also reviewed the extensive published evidence (including some very important internet-based records), and for S. curvatum we provided a concise overview of the entire European range. We confirmed that the latter recorded species, S. deforme, has been introduced into Europe at least twice, first in the central part of European Russia, and then in the SW Balkans, and we established that these introductions originated from different source populations, belonging to a geographically widely separated Asian subspecies. Based on the most recent evidence, we confirmed successful establishment of S. deforme in both areas, and documented its ongoing spreading: from central European Russia southwards/southeastwards, and most probably from the Balkans eastwards. We rectified several erroneous country records for S. deforme (France, Italy, Bulgaria, Greece, “central Europe”), which have been extensively perpetuated in several important publications about the invasive species in Europe in the last three years (n.b. – for Greece, we have positively documented its presence only now). For S. curvatum, we added a new country record (Georgia/Abkhazia), and provided a few important earlier records from the Balkans (Serbia, Greece, Croatia, Bulgaria), which shift the timing of the previously published “first appearance” dates in the area (for two years for N Serbia and C Greece), or otherwise modify the knowledge of its history of spread. Since the most recent evidence suggests the rapid eastward advancing of both introduced species towards their respective westernmost/northernmost native range limits in western to central Asia, we considered it important to briefly review the state of knowledge about their possible coexistence in that area. We also provided detailed maps of their allochtonous ranges in Europe (currently exceeding the longitudinal span of 4,000 km) and westernmost part of their native ranges in Asia. Finally, we very briefly commented on some ecological aspects of their existence within the allochtonous range (parasitism, sex ratio, phenology). KEY WORDS: Sceliphron deforme, Sceliphron curvatum, invasive Sphecidae, Europe, Balkans, Russia.