Premise
The genetic structure between plant populations is facilitated by the spatial population arrangement and limited dispersal of seed and pollen. Saxifraga acerifolia, a local endemic species in Japan, is a habitat specialist that is confined to waterfalls in riparian environments. Its sister species, Saxifraga fortunei, is a generalist that is widely distributed along riverbanks. Here, we examined sympatric populations of the two Saxifraga species to test whether the differences in habitat preference and colonization process influenced regional and local genetic structures.
Methods
To reveal genetic structures, we examined chloroplast microsatellite variations and genome‐wide nucleotide polymorphisms obtained by genotyping by sequencing. We also estimated the gene flow among and within populations and performed landscape genetic analyses to evaluate seed and pollen movement and the extent of genetic isolation related to geographic distance and/or habitat differences.
Results
We found strong genetic structure in the specialist S. acerifolia, even on a small spatial scale (<1 km part); each population on a different waterfall in one river system had a completely different predominant haplotype. By contrast, the generalist S. fortunei showed no clear genetic differentiation.
Conclusions
Our findings suggest that the level of genetic isolation was increased in S. acerifolia by the spatially fragmented habitat and limited seed and pollen dispersal over waterfalls. Habitat differentiation between the sister taxa could have contributed to the different patterns of gene flow and then shaped the contrasting genetic structures.
Premise
Saxifraga fortunei
(Saxifragaceae) includes several infraspecific taxa that are ecologically and morphologically distinct. To investigate the evolutionary history of phenotypic polymorphisms in this species, we developed expressed sequence tag–simple sequence repeat (
EST
‐
SSR
) markers for
S
.
fortunei
.
Methods and Results
We developed 26 polymorphic markers based on transcriptome data obtained from Illumina HiSeq 2000. Within three populations of
S
.
fortunei
var.
incisolobata
, the number of alleles ranged from four to 25, and the levels of observed and expected heterozygosity ranged from 0.200 to 0.847 and from 0.209 to 0.930, respectively. Furthermore, all 26 loci showed transferability for
S
.
fortunei
var.
obtusocuneata
and
S
.
fortunei
var.
suwoensis
, and 18 loci were also successfully amplified in
S
.
acerifolia
.
Conclusions
These newly developed
EST
‐
SSR
markers will prove useful to infer the evolutionary history of
S
.
fortunei
var.
incisolobata
and its relatives in population genetic studies.
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