Leaf morpho-anatomical diversity in <em>Echeveria</em> aff. <em>gigantea</em> (Crassulaceae)

Abstract

Background. Distinguishing species and populations in Crassulaceae is challenging because of the morphological variability and inter-specific hybridization. Currently our understanding of the morphological and anatomical features in Echeveria is poor, and therefore it is difficult to delimit species, and morphotypes within the species. Question. Our objective was to describe the foliar anatomy and the shape of accessions in E. gigantea. We used E. gibbiflora, another species in the series as a comparison group. Comparing the two species allowed us to evaluate the relationship between anatomy and morphology in E. gigantea. Methods. We performed a survey of anatomical features in seven accessions of E. gigantea, and one accession of E. gibbiflora. We obtained epidermal prints, leaf sections, performed geometric and morphometric analyses. Results. We found that 65 % of the anatomical traits are heterogeneous among the taxonomic units. Our analysis showed that E. gibbiflora and some E. gigantea accessions share extensive anatomical similarities. There was variation within the E. gigantea, suggesting that at least one of the accessions is an independent taxonomic group. The traits with the largest contribution to variation between the groups were related to the epidermis, the hypodermis, the type of vascular bundles and the collenchyma associated to the vascular bundles. In addition we quantified the variation in leaf shape. Interestingly, we found correlations between the organ shape and anatomical traits. Conclusion. These analyses provide information about traits towards the morpho-anatomical definition of E. gigantea variation and suggest developmental correlation yet to be explained.

Keywords

• Developmental constraints
• evolution
• leaf anatomy
• leaf shape
• multivariate analysis
• natural variation