LOCAL HIBRIDIZATION IN SUBTROPICAL MOUNTAIN HABITATS: CAN CEDRELA (MELIACEAE) MAINTAIN SPECIES? IDENTITY IN SYMPATRY?

PREMOLI, A.C.; GRAU, A.; QUIROGA, M. P.; MALIZIA, L.

DARWINIANA

INSTITUTO DE BOTÁNICA DARWINION

Lugar: Buenos Aires; Año: 2016

0011-6793

Congener specieswith incomplete reproductive barriers that coexist along environmentalgradients may be prone to ecological divergence, in spite of the potential forhybridization in sympatry. We analyzed distribution patterns of isozymes,plastid, and nuclear DNA sequences at regional and local scales in three timberCedrela species of the subtropics inthe northern Argentina (Cedrelaangustifolia, C. balansae, and C. saltensis), to test whetherpopulations of distinct species have diverged in montane habitats in relation to their ecological characteristics. Cedrela balansae and C. angustifolia can be identified bydiagnostic isozyme alleles. Nuclear ITS sequences yielded intraindividualpolymorphism; ambiguous bases were shared between C. balansae and C. saltensis whilethose of C. angustifolia were part ofits intraspecific polymorphism. Chloroplast DNA consisted mainly of alow-elevation haplotype present in C.balansae and C. saltensis and otherfound in C. angustifolia which inturn was shared locally by all species in sympatry at high-elevations.Multivariate UPGMA analysis of isozymes and Bayesian phylogeny of haplotype ITSyielded concordant patterns. Populations of C.angustifolia clustered in one group and were separated from the restwhereas those of C. saltensis and C. balansae weregrouped together in one cluster. This indicates that stronger reproductivebarriers exist between C. angustifoliaand the low-elevation taxa C. saltensis and C. balansae whichseem to maintain continuous gene flow. Nonetheless, under particularenvironmental settings, i.e. high-elevation, the three species hybridizedsometime in the past and later became differentiated through ecologicaldivergence.