4.2 Conservation status and strategies for Androsace cantabrica
Our results support classifying Androsace cantabrica as Vulnerable (VU) based on the IUCN Red List framework, proposed under criteria B1ab(ii,iii) + 2ab(ii,iii), which accounts for its restricted distribution, ongoing declines in area of occupancy, and quality of habitat. Our research indicates that the estimated extent of occurrence (EOO) is below 20,000 km², with an area of occupancy (AOO) under 2,000 km², thus meeting the spatial thresholds for Vulnerable status. This is similar to the reasoning to categorise A. hemisphaerica Ludlow as Endangered due to a very limited distribution range (i.e., EOO of 1,008 km2; Bhutan Endemic Flowering Plants Workshop, 2017). Furthermore,A. cantabrica populations are restricted to fewer than ten isolated locations, each experiencing habitat encroachment from shrub expansion and ongoing degradation due to human activities, consistent with criteria B1ab(ii,iii) + 2ab(ii,iii). One notable limitation of our IUCN assessment is the potential underestimation of population size due to the species’ association with dense shrub margins, making locating individuals challenging. The ongoing shrub expansion reduces the visibility of A. cantabrica and exacerbates competition for light and space, threatening population stability across its range. Additionally, while the current distribution data meets IUCN’s ”Vulnerable” criteria, further decline in shrub-controlled habitats could eventually lead to ”Endangered” status.
Our revised population estimates (see Table 4) underscore the challenges of accurately assessing population sizes, as we observed potential discrepancies with past reports, especially in highly disturbed areas like Tres Mares (TM). For instance, TM showed a marked decline in population size compared to previous counts, likely due to human disturbances from ski resort expansions, hiking trail use, and trampling. Such disturbances, combined with the environmental pressures from global warming, drive shrub expansion into alpine zones. In the TM region, this shrub encroachment and diminished herbivory and fire threaten the remaining open meadow habitats essential for A. cantabrica survival. These disturbances significantly affect the species’ distribution and resilience, as reflected in the observed population declines and limited recruitment in this location.
Our results demonstrate the strengths of Angiosperms353 as an effective tool for refining the conservation status of polyploid species likeA. cantabrica . The population genetic analysis divides A. cantabrica populations into two genetic conservation units: Group W, comprising western populations with lower genetic diversity, and Group E, which includes eastern populations showing relatively higher genetic diversity (H E values as high as 0.184). While the genetic data confirms low inbreeding and healthy population structure across regions, they also reveal low genetic diversity within smaller populations (Group W), suggesting that some populations’ habitat fragmentation and small sizes could increase genetic vulnerability over time. For Group W, in-situ conservation measures should focus on bolstering genetic diversity by translocating individuals from genetically diverse populations within this group. The Peña Prieta population has an estimated population of approximately 1,600 individuals fragmented into smaller subpopulations, such as the LL population near Peña Prieta, with approximately 100 individuals. Future work should involve gathering complementary genetic data from HC and Peña Prieta localities to identify potential donor populations with higher genetic diversity within the same genetic group and conducting translocations to strengthen the population size and genetic diversity in the EP population. Although the TM population exhibits the highestH E, translocating individuals from TM (i.e., Group E) to Group W is not advisable due to the potential risk of outbreeding depression (Lynch, 1991). Avoiding translocations between genetically differentiated populations is crucial without experiments investigating the risk of outbreeding depression, as it can reduce fitness through adverse breeding effects (Liu & Zhao, 1999). After any translocation efforts, if necessary, establishing a monitoring program to track fruiting rates, seed setting, and seedling survival will be essential for assessing population health and adaptability (Liu & Zhao, 1999). Despite the relatively high H E of the TM population, it is still lower than that of other non-threatened taxa (e.g., A. halleri subsp. nuria ), emphasizing the importance of mitigating anthropogenic disturbances in the TM area to preserve its genetic diversity. As an overall recommendation, conservation practices should focus on the genetic group W by reducing threats where appropriate and feasible, for example, reducing shrub competition to improve habitat suitability or collaborating with ski resorts near Peña Prieta to develop conservation and sustainable practices that mitigate human impact on surrounding habitats.
Conversely, for Group E, conservation efforts should emphasize mitigating ecological threats by managing shrub encroachment to maintain habitat openness essential for A. cantabrica ’s survival. Shrub encroachment poses a significant threat to the TM area, with impacts particularly severe at higher altitudes where open habitats are more vulnerable to invasive shrub growth. This underscores the need for targeted interventions, such as controlled burning or grazing, where shrubs colonize high-altitude habitats and limit suitable growing spaces for A. cantabrica . Additionally, we recommend long-term monitoring of all known populations alongside efforts to locate and characterize additional populations.
Ex-situ conservation approaches are efficient for the long-term conservation of threatened species (e.g., Schoen and Brown, 2001; Wambugu et al., 2023). In 2021, more than 2,000 seeds were collected as part of the PRIOCONEX project (https://sites.google.com/aranzadi.eus/prioconex) to be stored at the Seed Bank in Gipuzkoa, Spain (Accession number 52/2020). Seeds from more than 50 mother plants were collected from the TM area to preserve most of its genetic diversity, and several morphometric measurements and germination protocols were conducted (Tejero et al., 2022). Ex-situ conservation of seeds from the western group is also recommended, but due to the scarcity of the species in the area, this task might be demanding in time and prospection.
Micro-reserves might be very efficient for conservation of cryptic populations of endangered plant species without a strong impact in local land use (Laguna, 2000; Médail et al., 2021). We recommend the creation of a micro-reserve in a specific locality in TM area (ETRS89 UN 86101 65592; 2058 MASL) which hosts the most conspicuous and dense known population and with the highest heterozigosity values. Additionally, it seems valuable to initiate high-altitude reintroductions given the projected habitat loss by 2070 (MITECO, 2011). Such measures align with PRIOCONEX, which focuses on ex-situ conservation in response to climate impacts on alpine habitats (Yuste et al., 2021). Notably, A. cantabrica produces larger seeds than most Androsace species, likely indicative of a K-selected reproductive strategy to adapt to harsh environmental conditions (Sam, 2013). However, seed production is limited (3–4 seeds per flower), and A. cantabrica exhibits cold-dependent germination (Tejero et al., 2022), complicating in-situ population expansion. Further research to investigate the effects of environmental changes on germination and the survivability of seedlings will provide essential knowledge for the long-term conservation of this species.