Global Ecology and Conservation (Jun 2021)
Significant habitat loss of the black vanilla orchid (Nigritella nigra s.l., Orchidaceae) and shifts in its pollinators availability as results of global warming
Abstract
The black vanilla orchid (Nigritella nigra s.l.) is a perennial plant found in the main European mountain ranges. It occurs in large numbers in the Alps, but it has become a rare and endangered species in Scandinavia. Two subspecies of N. nigra s.l are recognized by most authors – the nominal subspecies which is restricted in its distribution to Scandinavia and N. nigra subsp. austriaca which is found in the alpine region. Some taxonomists postulated that these two taxa should be considered as separated species. The N. nigra s.l. is pollinated mostly by Lepidoptera. As a mainly montane species it is especially fragile to global warming, however, some previously published reports indicated that the climate changes will not significantly affect northern populations of this species. The aim of this study was to evaluate the differences in the climatic niche preferences between Scandinavian and central European populations of the black vanilla orchid and to estimate the impact of global warming on the distribution of this species using (ENM). Additionally, the predicted future location and extent of suitable climatic niches of insects pollinating studied orchid was modeled in order to estimate the availability of pollinators for this montane plant. This approach was applied as the persistence of an orchid population depends on pollination and subsequent seed production. Our analyses showed that the northern and southern populations differ in bioclimatic preferences and geographical distribution of these orchids together with variations in their chromosomes number and morphological discrepancies, suggest that N. nigra in not homogenous taxon as postulated by some authors and this approach should be also applied in assessing conservation priorities in Europe. Both, northern and southern population of N. nigra, will face significant habitat loss as a result of the global warming. In the best case scenario (rcp2.6) only 31.7% and 60.5% of the currently suitable niches will be still available for N. nigra respectively. The most damaging rcp8.5 scenario will cause the extreme decline of the coverage of orchid and just 2.3% of the habitats will be still suitable for N. nigra in the North and 18% for N. nigra in the South. Within the future potential range of N. nigra and N. nigra subsp. austriaca some pollinators will be still available for orchids, mostly for the latter taxon. Considering that the flowering time of the orchid seems to overlap with the activity of pollinators for the last 70 years we not expect significant desynchronization of these events which could prevent pollen transfer. Noteworthy as the Scandinavian populations N. nigra is characterized by lower genetic diversity than in the alpine region of central Europe, species seems to be more endangered in the North (Moen and Øien, 2002) and the future loss of habitats predicted in our study together with limited availability of pollinators can led to loss of the unique gene pool of this orchid. In our opinion this fact should be considered in the establishment of nature protection projects and the conservation efforts should focus on areas which in the future will be still suitable for occurrence of this species and its pollen vectors.
