Population variation in the Oncocyclus irises along a geographical gradient in Israel

The section Oncocydus of the genus Iris L.comprises eight species in Israel, which are among the most beautiful and important plants for conservation. Three of the dark-coloured species (7. honey. I. atrofusca and I. petrana) are distributed along the North-South climatotogical gradtenr in Israel. Although many taxonomists have dealt with this section in (he last century, no quantitative research has been done. Many transitional forms between species or populations are known from the field. The purpose of the current reaearch was to test quantitatively, by using inter and intrapopulation variation, the relationship among those species, and to examine whether morphological traits changed along the ecogeographical North-South gradient. Morphological traits were measured in eleven populations along this gradient. Intrapopulati¯on variation is significantly higher than variation between each nearest population for most characters. Morphological distance was calculated using the Pearson distance coefficient, and is significantly correlated with geographical distance. Regression of all traits against latitude revealed that diagnostic characters, especially flower size, stem height and leaf characters, change along the aridity gradient.