Abstract
Species range expansions are crucial for understanding niche formation and the interaction with the environment. Here, we studied the bumblebee Bombus haematurus Kriechbaumer, 1870, a species historically distributed from northern Serbia through northern Iran which has very recently started expanding northwestward into Central Europe without human-mediated dispersal (i.e., it is a natural spread). After updating the global distribution of this species, we investigated if niche shifts took place during this range expansion between newly colonized and historical areas. In addition, we have explored which climatic factors may have favored the natural range expansion of the species. Our results indicated that Bombus haematurus has colonized large territories in 7 European countries outside the historical area in the period from the 1980s to 2018, a natural expansion over an area that equals 20% of the historical distribution. In addition, this bumblebee performs generalism in flower visitation and it occurs in different habitats, although a preference for forested areas clearly emerges. The land-use associated with the species in the colonized areas is similar to the historical distribution, indicating that no major niche shifts occurred during the spread. Furthermore, in recently colonized localities, the range expansion was associated with warming temperatures during the winter and also during both queen overwintering and emergence phases. These findings document a case of natural range expansion due to environmental change rather than due to niche shifts, and specifically they suggest that warmer winters could be linked to the process of natural colonization of new areas.
Highlights
During their spread, species can suddenly startThe distribution of species’ populations are being utilizing environmental components that do not influenced by the climatic change and/or by entirely resemble the conditions of historical accidental or deliberate introduction events, and occurrences
After updating the global distribution of this species, we investigated if niche shifts took place during this range expansion between colonized and historical areas
Our results indicated that Bombus haematurus has colonized large territories in 7 European countries outside the historical area in the period from the 1980s to 2018, a natural expansion over an area that equals the 20% of the historical distribution
Summary
The distribution of species’ populations are being utilizing environmental components that do not influenced by the climatic change and/or by entirely resemble the conditions of historical accidental or deliberate introduction events, and occurrences. In other cases, it seems European countries as result of natural spread that bumblebee species are expanding naturally, northwards from the central Balkanic area In. Circle, probably favoured by climate warming addition, we have updated the distribution of the (Martinet et al 2015), while the opposite route has species both in the historical and newly colonized been taken by the Taiga bumblebee B. areas and listed the plants this bumblebee is semenoviellus which is expanding westwards interacting with.
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