Table 1.
Overview of the study species Hieracium pilosella L. and Echium vulgare L. and the number of examined herbaria specimens in their native and alien ranges.
Fig 1.
Map of sampling locations of analyzed herbarium specimens.
Fig 2.
Measurements of herbarium specimens based on digital scans (resolution: 500 dpi).
(a) Hieracium pilosella L. (here: specimens from ALLAN Herbarium (CHR), New Zealand); (b) Echium vulgare L (here: specimens from Herbarium Hausknecht Jena (JE), Germany); (c) Measurements of hair density and length within a 10 x 10 mm square in the middle of the upper leaf surface on a H. pilosella specimen; (d) Measurement of hair density within two 5 x 10 mm squares placed left and right of the midrib on the upper leaf surface on a E. vulgare specimen.
Fig 3.
Most important UV-B/bioclimatic variables (predictors) to explain leaf hair trait data (response) based on the Boosted Regression Tree (BRT) analysis.
All variables having more than 0% relative influence are shown. UV-B of Highest Month accounts for most variation in hair length for Hieracium pilosella (a; rel. influence 67.1%) and leaf hair density for Echium vulgare (c; rel. influence 66.2%). Maximum Temperature of Warmest Month accounts for most variation in hair density for Hieracium pilosella (b; rel. influence 62.6%). See text for full list of variables used in the BRT analysis.
Fig 4.
Relationship between Mean UV-B radiation of Highest Month (a,c) and Maximum Temperatures of the Warmest Month (b) and phenotypic expressions of leaf hair traits represented by (a) foliar hair length, (b) foliar hair density in Hieracium pilosella and (c) foliar hair density in Echium vulgare. Records from the Northern Hemisphere are denoted by open circles, records from the Southern Hemisphere are denoted by black triangles. Lines with p-values represent fitted linear regression models. Vertical boxplots with p-values from t-tests show the differences in hair traits between the hemispheres. Horizontal boxplots with p-values from t-tests compare the tested environmental variables between the hemispheres. Panel (d) shows boxplots comparing leaf area [cm2] and estimated number of hairs per leaf between specimens collected in the Northern versus the Southern Hemisphere. Abbreviations: NH = Northern Hemisphere, SH = Southern Hemisphere.