The genusTrifolium(Fabaceae) in south Europe: a critical review on species richness and distribution

Abstract

This paper deals with the diversity and biogeography of Trifolium in the Mediterranean Region. Data on 104 species, including 37 Mediterranean endemics and two established aliens, were gathered for 13 south European territories of seven countries: Portugal, Spain, France, Italy, Croatia, Albania and Greece. Species richness, frequency, endemism rate, chorological traits and ecological preferences were studied. The study area encompasses 85% of the Mediterranean Trifolium with 82% of the Mediterranean endemics (sensu Med‐Checklist), most of them restricted to a few localities. Among the rarest species, mainly Mediterranean endemics, seven occur only in one phytogeographical region of Greece (T. andricum, T. argutum, T. caudatum, T. dolopium, T. mesogitanum, T. michaelis, T. phitosianum) and one in Sicily, T. bivonae. The unique Mediterranean endemic reported exclusively for the Iberian Peninsula is T. gemellum, also occurring in Algeria and Morocco. Only 17% of the species occur in all the examined territories: T. campestre, T. repens, T. arvense and T. fragiferum are the most widespread. Multivariate analysis emphasized the connection among the territories with respect to the main centre of diversity and the main geographical east–west gradient of species richness. Greece is the richest country in south Europe with 89 wild species and 30 Mediterranean endemics, whereas Portugal has the lowest number of species (45) and only 6.7% of endemics. Over 60% of the species belong to Mediterranean s.l. chorotypes and 75% are therophytes, living mainly in grasslands, agricultural and ruderal habitats. Trifolium richness is consistent with species–area patterns known for each territory. Some species are still insufficiently studied and additional taxonomical and distributive analyses would be of great interest.

Genetic diversity of microsymbionts nodulating Trifolium pratense in subpolar and temperate climate regions

“…is one of the most important genera of the Fabaceae family, with more than 255 species spread across the world. These plants occur particularly frequently in the temperate and sub-tropical regions of North and South America, Europe, and Africa 33 , 34 . However, some Trifolium spp.…”

Variation in Ribosomal DNA in the Genus Trifolium (Fabaceae)

“…The genus Trifolium is distributed across both the Northern and Southern hemispheres, except for Southeast Asia and Australia. More than half of its species originated in the Mediterranean region [ 6 , 7 ], which still has the largest number of endemic species [ 8 , 9 ]. The genus’ origin was estimated by Ellison et al [ 3 ] to be in the Early Miocene (Tertiary Period), 16–23 million years ago.…”

Chromosome and Genome Diversity in the Genus Trifolium (Fabaceae)

“…The genus's origin has been estimated to have occurred in the Early Miocene, 16-23 million years ago, and its center of origin was first assumed to be in California with its subsequent spread into Asia and hence to Europe and Africa [4]. Later, a new hypothesis was proposed of clovers originating in the Mediterranean region due to their species diversity, including the diversity in their chromosome numbers, and because the greatest occurrence of their endemic species is found in this area, with a secondary center of distribution in North America and East Africa [3,[5][6][7]. By contrast, native clovers are absent from Australia and Southeast Asia.…”