Seed and capsule morphology of Iranian perennial species ofEuphorbia(Euphorbiaceae) and its phylogenetic application

Abstract

Of the 480 species of Euphorbia subgenus Esula, c. 290 occur in the Mediterranean and Irano-Turanian regions. Turkey and Iran are the most species-rich countries in Asia with 83 and 74 species, respectively. Following our previous paper on annual species of Iranian Euphorbia, we studied the quantitative and qualitative macro- and micromorphological traits of seeds and capsules of 47 perennial species, including E. ferdowsiana sp. nov., E. sulphurea sp. nov. and E. glareosa, as a first report from Iran. A key for all Iranian perennial Euphorbia spp. based on seed and capsule morphology is provided. The phylogenetic relationships of Iranian species based on internal transcribed spacer (ITS) nuclear and ndhF plastid regions are updated and used for the characterization of the synapomorphies of each clade. Capsule shape, seed shape, seed surface and shape of the caruncle have been found to be homoplastic, whereas the presence or absence of granulate elements on seed surfaces represents a phylogenetically important trait for section delimitation. The capsule surface is synapomorphic for several sections, including Helioscopia (tuberculate-verrucose), Myrsiniteae (vesiculate) and Esula (granulate), and seed shape is synapomorphic for sections Helioscopia (ellipsoidal), Myrsiniteae (ovoid-quadrangular) and Herpetorrhizae (pseudo-hexahedral). Reversals have also taken place in some features, including capsule surface (E. mazandaranica, E. altissima) and seed shape (E. densa, E. aleppica). It seems that ecarunculate seeds are plesiomorphic in sections Helioscopia (E. eriophora) and Herpetorrhizae (E. consanguinea and E. turczaninowii).