Self-compatible sympatric Chamaecrista (Leguminosae-Caesalpinioideae) species present different interspecific isolation
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ORIGINAL ARTICLE
Self-compatible sympatric Chamaecrista (LeguminosaeCaesalpinioideae) species present different interspecific isolation mechanisms depending on their phylogenetic proximity Cristiana B. N. Costa • Jorge A. S. Costa • Luciano P. de Queiroz • Eduardo L. Borba
Received: 20 August 2012 / Accepted: 20 December 2012 / Published online: 30 January 2013 Ó Springer-Verlag Wien 2013
Abstract The mating system of seven sympatric taxa of Chamaecrista occurring in the Chapada Diamantina Mountains, northeastern Brazil, was studied to determine the occurrence of self-incompatibility and interspecific genetic isolation mechanisms within the group. Self- and cross-pollination experiments and inter-taxon bidirectional crosses were performed. All of the populations were selfcompatible and showed high percentages of spontaneous seed abortion on both self- and cross-pollinated fruits. The inter-incompatibility among the taxa of Chamaecrista is directed by different mechanisms depending on their degrees of phylogenetic proximity. In the crosses between closely related taxa (same clade), seed inviability was observed in the crossing pairs C. desvauxii var. graminea 9 C. desvauxii var. latistipula, and C. chapadae 9 C. glaucofilix. Inter-compatibility between species of the same clade occurred in C. blanchetii and C. confertiformis, with the formation of viable seeds. Pre-zygotic gametophytic reproductive isolation was observed among taxa of
C. B. N. Costa (&) J. A. S. Costa Instituto de Cieˆncias Ambientais e Desenvolvimento Sustenta´vel, Colegiado de Cieˆncias Biolo´gicas, Universidade Federal da Bahia, Rua Prof. Jose´ Seabra, Barreiras, Bahia 47805-100, Brazil e-mail: [email protected] L. P. de Queiroz Departamento de Cieˆncias Biolo´gicas, Laborato´rio de Sistema´tica Molecular de Plantas, Universidade Estadual de Feira de Santana, Rodovia BR116 Km 03, Feira de Santana, Bahia 44031-460, Brazil E. L. Borba Centro de Cieˆncias Naturais and Humanas, Universidade Federal do ABC, Rua Santa Ade´lia 166, Bangu, Santo Andre´, Sa˜o Paulo 09210-170, Brazil
different clades, without penetration of the pollen tube into the ovule, or post-zygotic isolation through embryo or endosperm inviability, with abortion of the seeds. Interincompatibility represents an important factor in reproductive isolation and thus in the maintenance of the genetic identity of sympatric taxa that flower in synchrony and share pollinators. Keywords Campo Rupestre Chamaecrista Post-zygotic barriers Reproductive isolation Sympatric species
Introduction Studies of plant reproductive systems aid our understanding of the taxonomic complexity of certain species and patterns of gene flow, and are of basic importance in studies of the genetic evolution of those populations, in the elucidation of speciation processes, and the genetic relationships between species (Stace 1989; Richards 1997). A full understanding of the processes of speciation will involve determining what reproductive barriers are involved in reducing gene flow between populati
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