1 p.-5 fig. IBC 2024 XX International Botanical Congress July 21st-27th, P.0485, p.259 (2024), The Mediterranean Basin is a biodiversity hotspot harbouring numerous plant lineages that have undergone rapid in situ diversification. The Baetic Mountains, in the western Mediterranean, are a particularly rich centre of plant diversification associated with high topographic, climatic and edaphic heterogeneity. A plant lineage that has radiated in this region is the tribe Antirrhineae (Plantaginaceae), and particularly the genus Linaria.
Interestingly, this genus displays a floral key innovation potentially driving diversification, the nectar spur. The pair of recently-diverged sister species formed by L. becerrae and L. clementei,endemic to neighbouring areas of the Baetic Mountains (Málaga, Spain), is an ideal system to investigate the interplay of factors driving plant
speciation. These species occur on calcareous substrates and display a striking difference in spur length. They interbreed under nursery conditions,but this does not seem to happen in nature,most likely because of ecological isolating factors, potentially including biotic interactions and small-scale differences in climate and soil.To disentangle the factors driving speciation and population differentiation in this species pair,we generated genotyping-by-sequencing (GBS)data and investigated climatic and edaphic variables, accompanying plant communities and pollinator interactions. The GBS analyses revealed strong genetic isolation between species
despite their geographical proximity (<5 km for the closest population pair). According to pollinator censuses and discriminant analyses of ecological variables, pollination interactions or climatic differences alone do not seem to explain this genetic pattern. Remarkably, both species inhabit edaphic islands on distinct calcareous lithologies:calcarenite for L. becerrae and marble for L. clementei. We propose that these edaphic differences have been a primary driver of speciation in these species, possibly in combination with climatic and biotic factors. These results are congruent with a major role of the edaphic factor as driver of plant diversification in the western Mediterranean biodiversity hotspot., This work has been supported by Fellowship PRE2022-102456, funded by MCIN/AEI/10.13039/501100011033 and ESF+HISPAPHYLO project PID2021-124234NA-I00, fundedMCIN/AEI /10.13039/501100011033/ERDF, EU Fellowship IJCI-2015-23459, funded by Ministerio de Economía y Competitividad, Spain LINARIA-SPECIATION project FP7-PEOPLE-2013-IEF, reference 624396, funded by European Commission, EU., Peer reviewed