Data from: Population clustering and clonal structure evidence the relict state of Ulmus minor Mill. in the Balearic Islands

Field elm (Ulmus minor) is a riparian tree that grows in rare, small
populations scattered along temporary watercourses in the Balearic
Islands, nowadays mostly covered with Mediterranean vegetation.
Agriculture and farming on the fertile land along the periodically flooded
plains have reduced the elm populations to sparse tree lines along the
creek beds. The presence of field elm in this very anthropic landscape has
led some authors to consider it as an introduced species in the Balearics.
However, pollen data suggest these elms may be the remains of larger
populations experiencing continuous population shrinkage during the
Holocene, and hence be native to the isles. In this paper, we apply
genetic markers to assess whether field elm is or is not indigenous to the
Balearic Islands. We compare the genetic variation in nine nuclear
microsatellites of six Balearic populations (three in each of the largest
islands, Majorca and Minorca) with that of three natural Iberian
populations located in two regions, one geologically (Baetic mountains, SE
Iberia) and another historically (Catalonia, NE Iberia) related to the
islands. Principal coordinates analysis and Bayesian clustering methods
reveal a strong genetic differentiation of the Balearic populations from
the Iberian ones, and even among islands, which support their native
origin. Genotypic variation in the islands is very low and clonal
reproduction is very high compared with the mainland, as it is frequently
observed in populations of clonal species where sexual reproduction is
limited. We discuss the practical implications of these findings for the
conservation of elm genetic resources of these findings.