Leaf Geometric Morphometrics as a Tool to Differentiate the Cyrtandra villosissima Group

Abstract

The Cyrtandra villosissima group is an artificial group of morphologically similar species consisting of C. argentii, C. ferruginea, C. hirtigera, and C. villosissima. These species independently evolve but share characteristics such as an erect, suffrutescent habit and slightly falcate, densely hirsute, large leaves. Due to their similarities, herbarium specimens of this group with missing reproductive parts are often misidentified. Leaves are a good source of taxonomic information for species identification because they are present all year, have generally conserved and stable characteristics, and are not as fragile during handling and transportation as flowers. In the present study, we obtained leaf geometric morphometric data from herbarium specimens of the Cytandra villosissima group to determine if morphologically distinct groups exist using Principal Component Analysis and Linear Discriminant Analysis. Results showed no morphologically distinct groups within the C. villosissima group based on leaf shape. These results may be due to phenotypic plasticity, as similar environments and microenvironments may cause plants to develop similar morphological characteristics, such as leaf shape, despite coming from different genetic lineages and geographic locations. Our results suggest that the differentiation of C. villosissima group members using leaf shape is only possible in combination with other parts, such as the reproductive parts. Future geometric morphometric studies may look into using fresh specimens and pressing them into herbarium sheets themselves, as recently pressed herbarium specimens may have a more accurate representation of the original leaf outlines than old herbarium sheets that have degraded over time.