A COMPARATIVE STUDY OF THE REPRODUCTIVE TRAITS AND FLORAL MORPHOLOGY OF A GENUS OF GEOPHYTIC CACTI

作者：Martinez Peralta Concepcion; Molina Freaner Francisco; Golubov Jordan; Vazquez Lobo Alejandra; Mandujano Maria C^*

来源：International Journal of Plant Sciences, 2014, 175(6): 663-680.

DOI：10.1086/676302

• breeding system
• Cactaceae
• comparative method
• floral morphology
• mating system
• phylogenetically independent contrasts

Premise of research. Plant sexuality evolves in response to genetic and ecological pressures that shape mating systems and floral traits. Comparing such systems and traits within phylogenies can show evolutionary trends in reproduction and floral morphology without the problems posed by the nonindependence of species. We compared sexual systems in seven species of the monophyletic genus Ariocarpus to elucidate major differences in floral morphology and potential relationships between biogeographic rarity and reproductive traits. We hypothesized that floral morphology would be linked to outcrossing rates and that deviations from strict outcrossing and reduced fertility would be present in rare species.
Methodology. In one population per species, floral biology was detailed to characterize breeding systems, and mating systems were determined through pollination treatments. Discriminant analysis was used to identify floral traits that separate flowers into species. Phylogenetically independent contrasts were obtained to search for phylogenetic correlations between floral traits, and we inferred ancestral characters of floral traits across the phylogeny, using a maximum likelihood approach.
Pivotal results. Breeding systems are uniform across Ariocarpus species, according to Cruden's outcrossing index and pollen-to-ovule ratios. The outcrossing index obtained from pollination experiments showed that five Ariocarpus species are predominantly outcrossers but that selfing can occur in two species. Most floral traits differed among species, and those related to male function separated flowers into species. Floral traits showed a conservative pattern of evolution within clades.
Conclusions. Breeding systems are uniform across Ariocarpus species, with floral traits that promote outcrossing. The mating system in A. agavoides and A. kotschoubeyanus departed from strict outcrossing; A. kotschoubeyanus flowers were smaller and had the least herkogamy. A conservative pattern of evolution in floral traits between sister species suggests that floral divergence in Ariocarpus is restricted, but deviations from strict outcrossing can occur.

• 出版日期2014-7