Bees and wasps inhabiting steppe formations are, according to recent red lists, among the most endangered species, quickly disappearing from local faunas of central European countries. Several species, which are specialised nesters in empty gastropod shells, show the opposite pattern. Based on their distribution maps, we found that these species are recently more common and widespread than in the past. In contrast, the bee species nesting in the ground showed clearly the opposite result. They are much rarer now than in the past. Climatic data suggest that the bees nesting in gastropod shells have expanded towards higher altitudes and/or areas of lower mean July temperature. The main reasons of these distributional shifts are (i) unfavourable nature conservation management practices during the twentieth century, resulting in the successional shifts of steppe formations towards shrubs and mesic grasslands, (ii) human-driven change of many sites towards wood plantations or crop fields, and (iii) the increase of the number of available gastropod shells (i.e. nesting resources for shell-nesting bees) in steppe habitats as the response to the mentioned successional changes.

中文翻译：

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与草原相关的野生蜜蜂的长期变化在壳筑巢物种和地面筑巢物种之间有所不同

根据最近的红色名录，栖息在草原地层的蜜蜂和黄蜂是最濒危的物种之一，它们迅速从中欧国家的当地动物群中消失。有几个物种是专门在空腹足动物壳中筑巢的，表现出相反的模式。根据它们的分布图，我们发现这些物种最近比过去更常见和分布更广。相比之下，在地下筑巢的蜜蜂物种明显显示出相反的结果。他们现在比过去少得多。气候数据表明，在腹足动物壳中筑巢的蜜蜂已经向更高的海拔和/或 7 月平均气温较低的地区扩张。这些分布变化的主要原因是 (i) 二十世纪不利的自然保护管理实践，