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.