Plants in danger: Floral and other plant traits as drivers of vulnerability in Mediterranean countries

Plants with complex floral morphologies are adapted to be pollinated by restricted pollinator assemblages and may suffer pollinator limitation. Understanding how floral traits and other variables relate to plant vulnerability can provide a powerful tool for predicting the conservation status and prioritizing the assessment of plants with scarce field data. Using circa 3000 records of rare and threatened (sensu IUCN) entomophilous plant taxa from seven Mediterranean countries, we evaluated how six floral traits and other eight intrinsic and extrinsic variables were related to plant vulnerability (less vs. more threatened plants). Besides, we analyzed 29 experts' opinions regarding the floral traits most related to floral complexity. Floral shape, reproductive unit, and flowering duration were good vulnerability indicators. Taxa with lip-and flag-shaped flowers were the most threatened, which agrees with the opinion of experts who considered lip-and flag-shaped flowers to have more complex morphologies. Also, plants with cylindrical inflorescences or solitary flowers were more threatened than those with flat-spherical inflorescences; and longer flowering durations reduced the probability of being threatened. Regarding extrinsic variables, coastal and freshwater habitats, i.e. habitats heavily impacted by human activities, had the highest percentage of highly threatened taxa. Yet, plant vulnerability decreased with maximum elevation and total distribution range. These results may serve as a basis for managers and practitioners when field data are scarce or unavailable, so that, depending on their traits, species could be provisionally listed in Red Lists as deserving priority for assessment to ascertain conservation status and actions.