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

QUIROGA MP; PREMOLI AC; GRAU ALFREDO; MALIZIA LUCIO

DARWINIANA

INSTITUTO DE BOTÁNICA DARWINION

Lugar: Buenos Aires; Año: 2016 vol. 4 p. 195 - 211

0011-6793

Congener species with incomplete reproductive barriers that coexist along environmental gradients maybe prone to ecological divergence, in spite of the potential for hybridization in sympatry. We analyzed distributionpatterns of isozymes, plastid, and nuclear DNA sequences at regional and local scales in three timberCedrela species of the subtropics in the northern Argentina (Cedrela angustifolia, C. balansae, and C.saltensis), to test whether populations of distinct species have diverged in montane habitats in relation totheir ecological characteristics. Cedrela balansae and C. angustifolia can be identified by diagnostic isozymealleles. Nuclear ITS sequences yielded intraindividual polymorphism; ambiguous bases were shared betweenC. balansae and C. saltensis while those of C. angustifolia were part of its intraspecific polymorphism. ChloroplastDNA consisted mainly of a low-elevation haplotype present in C. balansae and C. saltensis and otherfound in C. angustifolia which in turn was shared locally by all species in sympatry. Multivariate UPGMAanalysis of isozymes and Bayesian phylogeny of haplotype ITS yielded concordant patterns. Populations ofC. angustifolia clustered in one group and were separated from the rest whereas those of C. saltensis and C.balansae were grouped together in one cluster. This indicates that stronger reproductive barriers exist betweenC. angustifolia and the low-elevation taxa C. saltensis and C. balansae which seem to maintain continuousgene flow. Nonetheless, under particular environmental settings, i.e., the three species hybridized sometimein the past and later became differentiated through ecological divergence.