On the verge of extinction: genetics of the critically endangered Iberian plant species, Borderea chouardii (Dioscoreaceae) and implications for conservation management
Segarra-Moragues, J.G.; Palop-Esteban, M.; González-Candelas, F.; Catalán, P.. On the verge of extinction: genetics of the critically endangered Iberian plant species, Borderea chouardii (Dioscoreaceae) and implications for conservation management. Molecular Ecology. 2005, Vol. 14(4), p. 969-2005.
Borderea chouardii
is a relictual and dioecious, strictly sexually reproducing, long-living
geophyte of the Dioscoreaceae family. Previous biological and demographic studies have
indicated the existence of a uniformly distributed panmictic population of this taxon at the
southernmost Spanish pre-Pyrenean mountain ranges where it occurs in rather inaccessible
crevices of a single limestone cliff. However, individuals of
B. chouardii
are spatially subdivided
into two subpopulations located, respectively, on the upper and lower parts of the
cliff, and vertically separated 150 m. Because of its extreme rarity,
B. chouardii
was the first
Iberian taxon to have a specific conservation plan and has been included in several red lists
under the category of critically endangered (CR). However, no previous attempts have been
conducted to analyse the fine scale evolutionary mechanisms involved in its present microspatial
distribution. Genetic diversity and population structure have been investigated through
the analysis of neutral hypervariable markers such as simple sequence repeats (SSRs) and
randomly amplified polymorphic DNAs (RAPDs) to unravel the impact of life history traits
in the differentiation of the two subpopulations. Both types of molecular markers were
unequivocal in distinguishing two genetically distinct groups of individuals corresponding
to their spatial separation. However, SSRs detected a higher level of subpopulation differentiation
(
F
ST
= 0.35,
R
ST
= 0.32) than RAPDs (
F
ST
= 0.21). SSR data indicated significant
deviation from random dispersal of genes and genotypes between the two groups, suggesting
that mating occurs mainly among individuals within subpopulations, thus, favouring
the divergence between the two groups. This microevolutionary differentiation scenario
might have been caused by a coupled effect of past genetic drift and reproductive isolation,
as a result of strong glacial age bottlenecks and inefficient dispersal system of pollen and
seeds, respectively. The identification of such genetic structure in this narrow endemic
prompts a modification of the management strategies of its single extant population.
Borderea chouardii
is a relictual and dioecious, strictly sexually reproducing, long-living
geophyte of the Dioscoreaceae family. Previous biological and demographic studies have
indicated the existence of a uniformly distributed panmictic population of this taxon at the
southernmost Spanish pre-Pyrenean mountain ranges where it occurs in rather inaccessible
crevices of a single limestone cliff. However, individuals of
B. chouardii
are spatially subdivided
into two subpopulations located, respectively, on the upper and lower parts of the
cliff, and vertically separated 150 m. Because of its extreme rarity,
B. chouardii
was the first
Iberian taxon to have a specific conservation plan and has been included in several red lists
under the category of critically endangered (CR). However, no previous attempts have been
conducted to analyse the fine scale evolutionary mechanisms involved in its present microspatial
distribution. Genetic diversity and population structure have been investigated through
the analysis of neutral hypervariable markers such as simple sequence repeats (SSRs) and
randomly amplified polymorphic DNAs (RAPDs) to unravel the impact of life history traits
in the differentiation of the two subpopulations. Both types of molecular markers were
unequivocal in distinguishing two genetically distinct groups of individuals corresponding
to their spatial separation. However, SSRs detected a higher level of subpopulation differentiation
(
F
ST
= 0.35,
R
ST
= 0.32) than RAPDs (
F
ST
= 0.21). SSR data indicated significant
deviation from random dispersal of genes and genotypes between the two groups, suggesting
that mating occurs mainly among individuals within subpopulations, thus, favouring
the divergence between the two groups. This microevolutionary differentiation scenario
might have been caused by a coupled effect of past genetic drift and reproductive isolation,
as a result of strong glacial age bottlenecks and inefficient dispersal system of pollen and
seeds, respectively. The identification of such genetic structure in this narrow endemic
prompts a modification of the management strategies of its single extant population.