Abstrakt
Polyploidization is generally considered a major evolutionary force that can alter the genetic diversity, morphology, physiology and ecology of plants. One striking example is the polyploid Urtica dioica complex, in which diploid taxa are often found in remote and partly relictual geographical ranges, in contrast to tetraploid individuals, which have an unknown evolutionary history and occur in a variety of synanthropic habitats.
We used a set of 279 plants, evenly representing the geographical and morphological variation of U dioica al. in Europe and Southwest Asia, and employed multivariate and geometric morphometrics and Hyb-Seq sequencing to estimate the extent of differentiation of diploid taxa and the ubiquitous tetraploid cytotype. Diploid subspecies form more-or-less separate clusters in morphological analyses, but our molecular evaluation did not reveal any structure.
Moreover, tetraploids coalesced with diploids in both morphological and molecular analyses. This disparity between morphological and molecular data might be driven by (1) local adaptation of the diploid cytotype that is mirrored in specific phenotypes, (2) only recent genetic diversification of the group and (3) homoploid and heteroploid hybridization events.