Distribución potencial y evolución de cuatro endemismos ibéricos de Gypsophila (Caryophyllaceae) en función de los cambios climáticos

Abstract

Goal, Loca.on and Studied Species : The Gypsophila (Caryophyllaceae) genus includes a set of plants gypsophytes of particular biogeographic, ecological, evolucionary and biochemical interest. In the Iberian Peninsula this genus contains 9 taxa included in 8 species (López González, 1990), of which 5 are endemics for Spain: G. Montserratti Fernández Casas, G. struthium subsp strutihum L., G. struthium subsp hispanica (Willk.) G. López, G. bermejoi G. López, G. tomentosa L.. The last four can be found on gypsum soils which determines their ecological behavior. This research has focused on them. The goal of the present work is to study of the climatic niches of the set of chosen taxa, their influence on the potential distributions and the effect of past and future climatic changes in these distributions and in the evolutionary processes. Methods: Our work is based on the modeling of ecological niches by comparing the current distributions of these plants with a series of climatic variables. Bioclimatic variables from Worldclim were used. Subsequently, the modeled niches have been projected to the geographic space of these variables (Iberian Peninsula), both in current climate and at other climatic moments by means of species distribu6on models (Maxent). This tool has allowed us to study the changes in the potential distribution of these taxa at different eras: the Last Glacial Maximum (LGM), the Middle Holocene (Mid Holocene, MH) and the present. The niche shiX among these taxa was assessed using ecological niche modelling and ordination techniques, adopting a niche overlap approach to compare the similarity and equivalency of the ecological niches. For the case of G. bermejoi, a method to locate its poten6al cradles is proposed. Our approach is based on the recurrent observation of differences in polyploid and diploid distributions, with polyploid taxa especially abundant in harsh environments. Thus, the narrow bioclimatic niche and the endemic nature of this plant could make this species particularly vulnerable to climate change. We used the MaxEnt to study the potential distribution of this taxon under four different scenarios of climate change, pin-pointing relevant changes in the potential distribution of this plant and enabling possible future areas of refuge to be assessed. Results: We present evidence of a possible repression on the process of G. bermejoi speciation by climatic factors. This plant is an allopolyploid species derived from the parental taxa G. struthium subsp. struthium and G. tomentosa. during the LGM certain bioclimatic factors could possibly repress the processes by which this species was formed. Accordingly, we favor a recent origin (post glacial) of the current populations of G. bermejoi. We also located several potencial centers of formation for this species that are consistent with its observed current distribution. Our results seem to indicate that niche shiX can occur over very different timespans. In the case of G. bermejoi, speciation may have produced significant niche shiXing in one or two generations. By contrast, G. struthium subsp. struthium and G. struthium subsp. hispanica seem to have undergone a more gradual process. Both these processes are rela6vely recent and they will have been strongly influenced by the climate change at the end of LGM. In the case of these last two subspecies, the clima6c models point to a more ancestral character of G. struthium subsp. struthium with respect to G. struthium subsp. hispanica. Our models suggest that the populations of G. struthium living in the Ebro valley during the LGM were very similar to the current G. struthium subsp. struthium. We believe that it was mostly climatic differences caused by geographical barriers that favored their genetic differentiation towards G. struthium subsp. hispanica after the LGM. Also, the potential distributions obtained with MaxEnt for G. bermejoi indicate that these could vary significantly under some climate change scenarios. This could cause potential climatic areas to not overlap, or to a lesser extent, with the suitable soils for this plant. Main conclusions: All these results point to a crucial rol of the quaternary climatic oscilaciones in the changes of the potencial areas and the evolution of the Iberian Gypsophila taxa. During the last 25,000 years, climatic factors have repressed or favored the formation of hybrid species, could have determined the centers of formation of some species and have driven genetic differentiation and ecological niche shifting in sister taxa. We believe that current climate change can have especially significant effects on endemic plant species on special soils. Changes in potential climatic areas may not coincide with edaphic suitability zones, or to a lesser extent. However, each particular case must be studied due to the unique adaptations shown by these plants.