Data from: Population differentiation in common walnut (Juglans regia L.) across major parts of its native range - insights from molecular and morphometric data

Juglans regia is an economically highly important species for fruit and
wood production in the warm temperate and subtropical zones of the
Northern Hemisphere. Besides the natural influence of climatic and
geomorphological barriers, its genetic structure has been strongly
modified by humans and the population history is still unclear. For this
reason, we investigated mainly natural walnut populations across the
Eurasian continent on a molecular (44 populations, 581 trees) and
morphometric level (23 populations, 1391 ripe nuts). Population genetic
diversity and differentiation were examined by using 7 microsatellite
loci. Morphometric characteristics of the nuts (mainly roundness index and
nut density) were used to estimate trait variation and population
differentiation. Highest allelic richness Rs12 = 7.05 was observed in a
Pakistani and the lowest value Rs12 = 3.04 in a Kyrgyz population. The
genetic differentiation among populations was high (FST = 0.217; RST =
0.530) indicating a strong phylogeographic pattern. While variation of the
roundness index within single populations was high, this trait neither
differentiated geographical regions nor was it associated to genetic
clusters. Approximated QST based on this trait equalled FST, while
approximated QST based on nut density considerably exceeded FST,
indicating selection. Nut density was moderately correlated with altitude,
latitude, and longitude, and differentiated populations according to their
origin. Pakistani and Indian populations showed highest nut densities.
These South Asian populations contain putatively ancestral nut forms,
which probably have been lost in other populations as a consequence of
human selection.