Climate change-driven northward expansion of the mediterranean orchid Ophrys apifera from genetic and ecological perspectives.

Ophrys apifera, commonly known as the bee orchid, is a species of orchid that has expanded its range northwards in recent decades. The present study focuses on its occurrence in Poland and analyses possible causes of this expansion, including climate change, autogamy and genetic diversity of new populations. Genetic analyses using nuclear microsatellite markers and plastid DNA revealed low overall population variability in Poland and neighbouring countries (the Czech Republic, Germany), probably caused by the founder effect and bottleneck, as well as the autogamous reproductive strategy of this species. STRUCTURE analysis identified three genetic clusters, with western populations forming a distinct, homogeneous cluster, while southern populations show a greater degree of genetic mixing. Plastid haplotype diversity was limited, with most populations dominated by a single haplotype. This confirms the scenario of recent colonisation through long-distance seed dispersal. Ecological niche modelling indicates that although O. apifera will continue to spread in regions with a suitable climate in northern and central Europe, habitat loss due to rising temperatures is predicted in the southern and western parts of its range. The combination of genetic and ecological data suggests that several independent colonisation events contributed to the recent spread of O. apifera. These findings highlight the importance of monitoring genetic variation in newly established populations and further investigating the role of climate change in the range shift of orchids.