Local climate and latitude affect flower form of Ophrys fuciflora (Orchidaceae): evidence for clinal variation

The widely accepted approach – the use of morphometrics – often reveals gradients without clear morphological discontinuities, which can be explained as clinal variability. The Ophrys fuciflora complex from South-eastern Europe (Slovenia and Croatia) was morphologically evaluated. Classical morphology was performed on specimens from 18 populations. Each individual plant is represented with a set of 19 floral characters obtained from a single flower. Altogether, 221 flowers were measured. According to PCA results, a high proportion of specimens shows intermediate character values, specimens belonging to different morphological entities overlap. The first morphological principal component was considered as a flower form (size and shape) vector. Correlation tests were performed based on 19 bioclimatic variables and the first morphological principal component. Nine bioclimatic variables show statistically significant, strong correlation with the flower form. Results indicate that the observed floral continuous quantitative characters, traditionally utilized to differentiate taxa in the Ophrys fuciflora complex are affected by the local climatic conditions and latitude, and exhibit clinal variability. An integrative taxonomical approach to the genus Ophrys should also take into account site-specific ecological conditions, to investigate and prove possible clinal variability first, but also taxa-specific phenology.