The conservation significance of natural hybridisation in Mediterranean plants: from a case study onCyclamen(Primulaceae) to a general perspective

Abstract

Hybridisation plays a prominent role in plant evolution due to its influence on genetic diversity, fitness and adaptive potential. We identify a case of on-going hybrid evolution of floral phenotypes in disjunct populations of Cyclamen balearicum and C. repandum subsp. repandum on Corsica and Sardinia. Hybrid populations on the two islands contain similar patterns of variation in flower colour and size but are probably at different stages in the evolutionary process of hybridisation, and differences in the frequency of floral types and flower size suggest hybrid vigour that may contribute to the dynamics and maintenance of hybrid forms. In a review of cases of hybridisation in Mediterranean plants we found an equivalent number of cases for the contemporary occurrence of mixed hybrid populations, as there are cases of homoploid hybrid species differentiation. We argue for the development of a conservation strategy for Mediterranean plants that integrates the need to protect not just pure endemic species (some of hybrid origin) but also mixed populations where adaptive variation and new species are evolving due to contemporary hybridisation.

Is population genetic structure of vascular plants shaped more by ecological or geographic factors? A study case on the Mediterranean endemic Centaurea filiformis (Asteraceae)

“…This has also been highlighted for other taxa having complex genetic structures and showing evidence of hybridisation between ancient lineages in the Corsican–Sardinian system (Thompson et al . , ), thus similar to Centaurea in this aspect.…”

“…In fact, the association between genetic substructure of the populations and their geographic peculiarity makes it possible that each genetic cluster possesses high 'geography-driven' adaptive potential. This has also been highlighted for other taxa having complex genetic structures and showing evidence of hybridisation between ancient lineages in the Corsican-Sardinian system (Thompson et al 2010(Thompson et al , 2018, thus similar to Centaurea in this aspect.…”

Ecological niche differentiation in peripheral populations: a comparative analysis of eleven Mediterranean plant species

“…Using resources to protect widespread species in regions where they are rare, what Hunter and Hutchinson (1994) named 'parochialism' conservation, may be inefficient (due to their rarity, small population size and marginality) unless peripheral populations show genetic distinctiveness or have some form of cultural value (Lesica andAllendorf 1995, Leppig andWhite 2006). Indeed, peripheral populations may contain unique gene combinations that result from either isolation (Lesica andAllendorf 1995, Petit et al 1998) or hybridization with closely related species (Thompson et al 2010(Thompson et al , 2018. However, the lack of precise knowledge regarding the ecology of plant species at their range periphery compared to elsewhere in their distribution has limited a more fuller understanding of the evolutionary significance of peripheral populations (Woodward 1987, Crawford 2010.…”

Islands as a crossroad of evolutionary lineages: A case study of Centaurea sect. Centaurea (Compositae) from Sardinia (Mediterranean Basin)

“…In conclusion, our work stresses the urgent need to develop a dynamic approach for the conservation of plant diversity, based not only on the distribution of taxa (static approach) but by focusing mainly on understanding and preserving genetic diversity. The role of islands as "melting pots" for genetic diversification of terrestrial vascular plants has already been emphasized for other angiosperms in the Corso-Sardinian system [98][99][100]. The endemic Sardinian Centaurea represents a clear example of the need to focus conservation efforts on populations and gene pools rather than just 'species'.…”

“…Furthermore, we suggest that C. ×forsythiana originated by homoploid hybridization [30], and there is active introgression between C. filiformis and C. ferulacea. Because the processes of hybridization and introgression have great evolutionary potential in driving differentiation, speciation, and perhaps extinction, of endemic Centaurea taxa from Sardinia, the protection of hybrid zones remains urgent and critical for the conservation of biodiversity [98,99].…”