Regional climate oscillations and local topography shape distribution and persistence of drylands in the tropical Andes: genetic and ENM evidence on the columnar cactus Echinopsis terscheckii

QUIPILDOR, V.; KITZBERGER, T.; ORTEGA-BAES, P.; QUIROGA, M.P.; PREMOLI, A.C.

JOURNAL OF BIOGEOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017

0305-0270

Aim: Currentfragmentary distribution of tropical drylands are considered relic of a previouslywidespread range during cold and dry phases of the Last Glacial Maximum (LGM).We analyzed present and past distribution patterns of the columnar catus Echinopsis terscheckii combiningecological niche models (ENM) with molecular polymorphisms by isozymes and DNAsequences to disentangle current and historical signals.Location: Tropicaland subtropical dry ecotonal areas of northern and central Andes of Argentina. Methods: Wecollected samples from 30 individuals from each of 24 locations for geneticanalysis covering a wide environmental range of conditions. We resolved 15 isozymeloci. We sequenced the nuclear ITS and three non-coding regions of the chloroplastDNA. Potential distribution was modeled using 88 E. terscheckii presence trainingrecords and a reduced set of 10 modern bioclimatic variables. LGM and the Mid-Holocenedistributions were derived by projecting the model onto bioclimatic data derivedfrom CCSM4 and MIROC-ESM GCM models.Results:We detected high genetic diversity that significantly increased towards the south.Populations were genetically structured. The multivariate cluster analysisyielded two groups of populations that were geographically concordant to theDNA haplotypes located north and south of a divide at 27°S. Currentdistribution modeling shows two areas separated by a gap of low suitability.During the LGM we found a strong reduction in suitability in the northern area.In contrast, Mid-Holocene bioclimatic conditions where relatively unsuitable inthe southern area of E. terscheckii distribution. Main conclusions: Ourresults suggest that the divergence of north and south groups of E.terscheckii populations reflect long-lasting persistence through climaticcycles that were reinforced by the presence of a divide at mid-latitudes.Species inhabiting drylands of tropical mountains are affected by regionalclimates and also by the heterogeneity of the landscape that has a greatinfluence on conditions for survival.