Aim Newly formed polyploids experience problems of establishment and spread similar to those faced by newly introduced alien species. To understand the significance of polyploidy in biological invasions, we mapped the distribution of ploidy levels in Solidago gigantea Aiton in its native range in North America, and in Europe and East Asia where it is invasive.
Location North America, Europe and East Asia.
Methods Flow cytometry was used to measure ploidy levels in a total of 834 plants from 149 locations. Together with data from contributors and a literature review, ploidy‐level data were assembled for 336 locations. Cytogeographical maps from North America and Europe were prepared, incorporating new and previously published ploidy‐level data.
Results In the native range, diploid, tetraploid and hexaploid plants were found, and also one triploid and one pentaploid plant (2n = 3x and 2n = 5x, respectively, each being new reports for this species). There was a high degree of geographical separation among the ploidy levels, and populations with mixed ploidy were rare. However, four zones were identified where plants of different ploidy could come into contact. In Europe and East Asia, only tetraploid plants were found.
Main conclusions The geographical pattern in North America suggests that the ploidy levels are ecologically differentiated, although further investigations are needed to identify the nature of these differences. Alien populations appear to be exclusively tetraploid, but it is not clear whether this is because tetraploids were selectively introduced or because diploids were unsuccessful. In any case, comparisons between native and introduced populations need to account for ploidy level.
Premise of the study:The ability to conduct species delimitation and phylogeny reconstruction with genomic data sets obtained exclusively from herbarium specimens would rapidly enhance our knowledge of large, taxonomically contentious plant genera. In this study, the utility of genotyping by sequencing is assessed in the notoriously difficult genus Solidago (Asteraceae) by attempting to obtain an informative single-nucleotide polymorphism data set from a set of specimens collected between 1970 and 2010.Methods:Reduced representation libraries were prepared and Illumina-sequenced from 95 Solidago herbarium specimen DNAs, and resulting reads were processed with the nonreference Universal Network-Enabled Analysis Kit (UNEAK) pipeline. Multidimensional clustering was used to assess the correspondence between genetic groups and morphologically defined species.Results:Library construction and sequencing were successful in 93 of 95 samples. The UNEAK pipeline identified 8470 single-nucleotide polymorphisms, and a filtered data set was analyzed for each of three Solidago subsections. Although results varied, clustering identified genomic groups that often corresponded to currently recognized species or groups of closely related species.Discussion:These results suggest that genotyping by sequencing is broadly applicable to DNAs obtained from herbarium specimens. The data obtained and their biological signal suggest that pairing genomics with large-scale herbarium sampling is a promising strategy in species-rich plant groups.
Chromosome numbers are reported here for the first time from 117 individuals of Solidago rugosa and S. fistulosa. Including 178 previously published reports for the two species plus S. latissimifolia, chromosome numbers have been determined from 295 individuals from 269 locations. Only diploids (2n = 18) were found throughout the range of S. fistulosa on the coastal plain in the eastern U.S.A. (44 counts). Diploids (2n = 18) were found in the northern portion of the range of S. latissimifolia, and tetraploids (2n = 36) and hexaploids (2n = 54) were found in the central and southern portions of the range (nine counts in total). Diploids (2n = 18) were found throughout the range of S. rugosa in much of eastern North America in four of the five varieties (northern var. rugosa, var. sphagnophila; southern var. aspera and var. celtidifolia). Tetraploids (2n = 36) were found in all four of these varieties and exclusively in var. cronquistiana in the southern high Appalachian Mountains. Hexaploids (2n = 54) were found in var. sphagnophila at scattered locations. One possible hexaploid in var. rugosa was found in the Allegheny Mountains. The diversity in ploidy levels was independent of the size of the range and the diversity of growing conditions among the three species of S. subsect. Venosae.
Chromosome number determinations were made from 227 populations of 43 taxa of Euthamia and Solidago. Nearly all were confirmations of previous reports. The majority of the populations sampled were from Ontario. First report: Solidago hispida Muhl. var. tonsa Fern., 2n = 18.
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