, Volume 293, Issue 1-4, pp 197-205
Date: 24 Mar 2011

Discordant patterns of morphological and genetic divergence in the closely related species Schizanthus hookeri and S. grahamii (Solanaceae)

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Abstract

In this study I have examined the patterns of morphological and genetic differentiation between two species of the Andean genus Schizanthus that differ in their pollination and mating systems. Schizanthus hookeri has a bee pollination syndrome and is strongly dependent on pollinators for seed set. In contrast, S. grahamii has a hummingbird pollination syndrome and exhibits late autonomous selfing. Southern populations of the latter species have red flowers (reddish morph), while northern populations have yellow (yellowish morph) or pink flowers (pinkish morph). I used two noncoding chloroplast DNA (cpDNA) regions to investigate the genetic affinities between S. hookeri and the three morphs of S. grahamii. I also performed intra- and interspecific crosses to assess whether gene flow between species was possible. Phylogenetic analyses supported the existence of two differentiated clades that did not match currently accepted taxonomic classification. Accordingly, genetic distance did not correlate significantly with morphological distance. No fruits were produced from interspecific crosses, and there were no individuals with intermediate morphology that could indicate current and frequent hybridization events between species. I propose that the discordance between cpDNA data and conventional taxonomy could be explained by parallel evolution, or alternatively, by a very sporadic hybridization.