Data from: Maintenance of genetic and morphological identity in two sibling Syrrhopodon species (Calymperaceae, Bryopsida) despite extensive introgression

Bryophytes are a group of land plants wherein the role of hybridization
has long been challenged. Using Genotyping by Sequencing to circumvent the
lack of molecular variation at selected loci previously used for phylogeny
and morphology, we determine the level of genetic and morphological
divergence and reproductive isolation between the sibling Syrrhopodon
annotinus and S. simmondsii (Calymperaceae, Bryopsida) that occur in
sympatry but in different habitats in lowland Amazonian rainforests. A
clear morphological differentiation and a low (0.06), but significant Fst
derived from the analysis of 183 SNPs were observed between the two
species. Conspecific pairs of individuals consistently exhibited higher
average kinship coefficients along a gradient of geographic isolation than
interspecific pairs. The weak, but significant genetic divergence observed
is consistent with growing evidence that ecological specialization can
lead to genetic differentiation among bryophyte species. Nevertheless, the
spatial genetic structures of the two species were significantly
correlated, as evidenced by the significant slope of the Mantel test based
on kinship coefficients between pairs of interspecific individuals and the
geographic distance separating them. Interspecific pairs of individuals
are thus more closely related when they are geographically closer,
suggesting that isolation-by-distance is stronger than the interspecific
reproductive barrier and pointing to interspecific gene flow. We conclude
that interspecific introgression, whose role has long been questioned in
bryophytes, may take place even in species wherein sporophyte production
is scarce due to dioicy, raising the question as to what mechanisms
maintain differentiation despite weak reproductive isolation.