Pollen and floral morphology of Androsace brevis (Hegetschw.) Ces. (Primulaceae), a vulnerable narrow endemic plant of the Southern European Alps

Androsace brevis (Hegetschw.) Ces. (Primulaceae) is a narrow endemic plant of the Southern Central European Alps that lives only above 2000 m asl and flowers immediately after snowmelt for a very short period during which the plant must guarantee successful sexual reproduction. Despite the vulnerability of this species, mainly due to increasing temperature, competition with plant communities shifting to higher altitudes, and possible mismatches with pollinators, nothing is known about its pollen and floral morphology. In this study we aim to provide a detailed description of these traits and to investigate how they might be related to possible pollination strategies and vectors. Pollen and flower samples were collected from the Lepontine and Orobic Alps (Northern Italy) populations. The pollen grains are small (polar axis: 19.17 µm ± 0.09; equatorial axis: 10.84 µm ± 0.1) with a prolate shape. The morphology of the flower, with the location of both stamens and pistil inside the corolla tube, and the coloured corolla mouths, ranging from yellow to purple, suggest that A. brevis requires insect-mediated pollination. Moreover, floral morphology does not show a particular insect-selective pattern in that the presence of both stamens and pistil less than 1 mm below the corolla mouth (Ø: 0.76 mm ± 0.05) might allow many high-altitude flower-visiting insects to reach both nectar and pollen. A generalist pollination strategy could be fundamental in contests characterized by harsh environmental conditions as it could counteract potential plant-pollinator mismatches due to increase in temperatures.