Phytogeographical Analysis Of Euphorbia Subgenus Esula (Euphorbiaceae)

Abstract

Euphorbia subg. Esula is one of four major clades within the genus. A geographical analysis of the 466 species in the subgenus is reported here. Every species was assigned to one of 29 geographical elements clustered in ten groups of elements. This geographical analysis showed that the Tethyan group (comprising nine geographical elements) clearly dominates the subgenus and contains 260 species (55.79% of the total number of species). The most numerous geographical elements are Irano-Turanian (105 species) and Mediterranean (85). Other significant groups of elements are Boreal (91 species, 19.54%), East Asian (40 species, 8.58%), Madrean (26 species, 5.58%), Paleotropical (23 species, 4.94%) and South African (16 species, 3.43%). The area of the Tethyan floristic subkingdom is the center of the modern diversity of E. subg. Esula. It is likely that such diversity is the result of intensive speciation that took place during the Eocene–Miocene.