Hiding in the Atlantic Forest: Leaf geometric morphometrics redefines endangered Aristolochia (Aristolochiaceae) sibling species and allows conservation strategies

Abstract

Aristolochia hypoglauca and A. paulistana (Aristolochiaceae) are two species that inhabit the Brazilian Atlantic Forest. They highly resemble each other especially on the size and overall shape of the caudate perianth, which causes confusion in herbaria determinations. We applied geometric morphometrics (GM) to overcome this taxonomic uncertainty. GM was based on the landmark method applied to leaves of all specimens available mostly in Brazilian herbaria. The GM results supported the recognition of the two species, as the two principal components were responsible for 94.97% of the variation assessed through the principal component analysis (PCA). The Discriminant Function and the Cross-validation tests resulted in the maximum percentage of correctly classified cases (100%). The Procrustes distance (0.2252; p< 0.0001), and the Mahalanobis Distance (8.4473; p< 0.0001) provide statistical support for leaf shape differences with taxonomic significance. Thus, we revisit the taxonomy and comparative morphology of both species, and compare them with other Aristolochia species with caudate floral limb native to Brazil, and commented the phenology, distribution and habitat, and conservation status. Additionally, we proposed the epitypification of A. hypoglauca, given that the holotype does not fulfill the purpose of precise application of the name.