A pre‐Miocene Irano‐Turanian cradle: Origin and diversification of the species‐rich monocot genus Gagea (Liliaceae)

Abstract

The Irano‐Turanian (IT) floristic region is considered an important center of origin for many taxa. However, there is a lack of studies dealing with typical IT genera that also occur in neighboring areas. The species‐rich monocot genus Gagea Salisb. shows a center of diversity in IT region and a distribution in adjacent regions, therefore representing a good study object to investigate spatial and temporal relationships among IT region and its neighboring areas (East Asia, Euro‐Siberia, Himalaya, and Mediterranean). We aimed at (a) testing the origin of the genus and of its major lineages in the IT region, (b) reconstructing divergence times, and (c) reconstructing colonization events. To address these problems, sequences of the ribosomal DNA internal transcribed spacer (ITS) region of 418 individuals and chloroplast intergenic spacers sequences (psbA‐trnH, trnL‐trnF) of 497 individuals, representing 116 species from all sections of the genus and nearly its entire distribution area were analyzed. Divergence times were estimated under a random molecular clock based on nrITS phylogeny, which was the most complete data set regarding the representation of species and distribution areas. Ancestral distribution ranges were estimated for the nrITS data set as well as for a combined data set, revealing that Gagea most likely originated in southwestern Asia. This genus first diversified there starting in the Early Miocene. In the Middle Miocene, Gagea migrated to the Mediterranean and to East Asia, while migration into Euro‐Siberia took place in the Late Miocene. During the Pleistocene, the Arctic was colonized and Gagea serotina, the most widespread species, reached North America. The Mediterranean basin was colonized multiple times from southwestern Asia or Euro‐Siberia. Most of the currently existing species originated during the last 3 Ma.

Biogeography of Rhaponticoides, an Irano-Turanian element in the Mediterranean flora

“…alpina/ruthenica complex with disjunct populations in different mountains: from the Tian Shan in central Asia to the Caucasus, Balkans, European Alps and the Iberian Peninsula 41 , 42 . Similar results have been obtained in other steppe taxa originated in the Irano-Turanian Region 28 , 29 , 51 .…”

“…Steppe flora and vegetation are present in the Mediterranean basin (comprised Western Europe) since the Paleogene and gained relevance throughout the Neogene, especially during the Miocene 10 , 20 . The geographical origin of the main steppe lineages that colonized the Mediterranean basin is Central and Western Asia 15 , 30 , 51 and this is also the case for Rhaponticoides (Fig. 4 ) because Turkey appears as the most probable ancestral area.…”

“…Considering the environmental variations throughout the late Cenozoic, vicariance could explain, at least partially, the origin of lineages and species of Rhaponticoides. However, speciation by dispersal events seems to be a lot more frequent than vicariance in steppe taxa located in the Mediterranean and Irano-Turanian regions 15,29,30,51 . In our analyses, BayArea + J was selected as the best model, and this model embraces cladogenesis and sympatry as well as anagenesis and dispersion whereas vicariance has no relevance 60 .…”

Phylogeny and Comparative Analysis for the Plastid Genomes of Five Tulipa (Liliaceae)

“…Tulips ( Tulipa L.) are famous ornamental and cut flowers due to their beautiful and colorful corolla [ 14 – 16 ]. Tulipa is a member of Liliaceae sensu APG IV [ 17 ], subfamily Lilioideae, tribe Tulipeae Kostel [ 18 , 19 ]; the tribe Tulipeae including Gagea Salisbury, Amana Honda, Erythronium L., and Tulipa [ 20 ] is sister to the tribe Lilieae [ 21 ]. The close relationship between Gagea and Tulipa , Amana , and Erythronium is generally accepted; however, the phylogenetic relationships among Tulipa , Amana , and Erythronium have remained controversial due to inconsistencies across studies and lack of strong support [ 22 , 23 ].…”

The twelve blooms of Christmas

“…This is a member of the Liliacae family, with a wide geographic distribution and beautiful yellow flowers in early spring. Looking at the ribosome and chloroplast DNA of 116 species of the genus Gagea has shown that the group originated in southwestern Asia, where it began its diversification in the early Miocene 6 .…”