Genetic diversity and differentiation in narrow versus widespread taxa of Helianthemum (Cistaceae) in a hotspot: The role of geographic range, habitat, and reproductive traits

We thank the authorities of the Sierra Nevada National Park and the Junta de Andalucía (Andalusian Regional Government) for granting permission to collect samples even of species under protection. We also thank the Centro de Investigación Tecnología e Innovación de la Universidad de Sevilla (“Celestino Mutis” CITIUS-2 center) for facilities to use the Coulter Multisizer 3. This research was supported by grants from the Ministerio de Agricultura, Alimentación y Medio Ambiente (National Parks Authority ref. 296/2011) and by the Ministerio de Economía y Competitividad (CGL2014-52459-P and partially CGL2013-45037-P and CGL2017-82465-P). S. MartínHernanz was supported by a fellowship from the Spanish Secretaría de Estado de Investigación, Desarrollo e Innovación (FPI 2015, BES-2015-073314). All samples in this study were collected under permission by the Sierra Nevada National Park and the Andalusian Regional GovernmentUnraveling the relationships between ecological, functional traits and genetic diversity of narrow endemic plants provide opportunities for understanding how evolutionary processes operate over local spatial scales and ultimately how diversity is created and maintained. To explore these aspects in Sierra Nevada, the core of the Mediterranean Betic‐Rifean hotspot, we have analyzed nuclear DNA microsatellite diversity and a set of biological and environmental factors (physicochemical soil parameters, floral traits, and community composition) in two strictly endemic taxa from dolomite outcrops of Sierra Nevada (Helianthemum pannosum and H. apenninum subsp. estevei ) and two congeneric widespread taxa (H. cinereum subsp. rotundifolium and H. apenninum subsp. apenninum ) that further belong to two different lineages (subgenera) of Helianthemum . We obtained rather unexpected results contrasting with the theory: (a) The narrow endemic taxa showed higher values of genetic diversity as well as higher average values of pollen production per flower and pollen‐to‐ovule ratio than their widespread relatives; and (b) the two taxa of subg. Helianthemum , with larger corollas, approach herkogamy and higher pollen production than the two taxa of subg. Plectolobum , displayed lower genetic diversity and higher values of inbreeding. Altogether, these results disclose how genetic diversity may be affected simultaneously by a large number of intrinsic and extrinsic factors, especially in Pleistocene glacial refugia in mountains where the spatial context harbors a great ecological heterogeneity. On the other hand, differences in mating system and the significant effect of the substrate profile, both being highly diverse in the genus Helianthemum , in the genetic variability illustrate about the importance of these two factors in the diversification and species differentiation of this paradigmatic genus in the Mediterranean and open the field to formulate and test new hypotheses of local adaptation, trait evolution, and habitat diversification.Secretaría de Estado de Investigación, Desarrollo e Innovación, Grant/Award Number: BES-2015-073314; Ministerio de Economía y Competitividad, Grant/Award Number: CGL2013-45037-P, CGL2014- 52459-P and CGL2017-82465-P; Ministerio de Agricultura, Alimentación y Medio Ambiente, Grant/Award Number: 296/201