The Cryptic Bombus lucorum Complex (Hymenoptera: Apidae) in Austria: Phylogeny, Distribution, Habitat Usage and a Climatic Characterization Based on COI Sequence Data.

Silas Bossert, Barbara-Amina Gereben-Krenn, Johann Neumayer, Bernhard Schneller, and Harald W. Krenn (2016) The Bombus lucorum complex represents a group of three distinct but cryptic bumblebee species in Europe. With the advent of DNA-based identification methods, their species status was confirmed and the use of COI barcoding proved to be an especially useful tool for species identification within the group. Meanwhile, the identification based on morphology remains difficult and recent studies challenged the general distinguishability by revealing an important character to be unreliable. This has consequences for our understanding of the distribution and ecology of the species in Europe and aggravates our patchy knowledge of the situation in Austria and the whole area of the European Alps. In this study, we investigate the exact species composition and distribution of the Bombus lucorum complex in Austria based on the reliable species identification with COI sequence data. The habitat usage is studied and the first extensive investigation of altitudinal and climatic differentiation is provided. The results support three distinct genotypic groups in the Bombus lucorum complex. B. lucorum and B. cryptarum co-occur in several areas across the country, with B. lucorum being the most common and most widespread species. The study provides no evidence for the presence of B. magnus in Austria. The less common species, B. cryptarum, mainly occurs in the high mountains and is the predominant species of the complex above altitudes of 2100 m a.s.l. Further, B. cryptarum is almost absent from woodlands and is relatively more abundant in habitats with colder climate than B. lucorum in Austria. Additionally, the results indicate a very low intraspecific genetic variation within B. lucorum and B. cryptarum. This study confirms previous findings of three distinct species within the species complex. Based on reliable COI identification, the first coherent overview of the species complex in Austria can be achieved. The climatic data allows us to explain the differences in the distribution patterns. Moreover, the low intraspecific variation may indicate past bottleneck conditions for B. lucorum and B. cryptarum.