A study of floral shape variation in Delphinieae (Ranunculaceae) using geometric morphometrics on herbarium specimens

Abstract

The variation in the shape of flowers, the reproductive structures of angiosperms, is generally investigated in a qualitative way, or using multivariate statistical analyses of distance data (i.e. traditional morphometrics). In this study, we evaluate the application of geometric morphometric methods to flowers of herbarium specimens, a material that is still being massively overlooked as far as these methods are concerned. Flowers of Delphinieae (Ranunculaceae) are synorganised: the spurred and nectariferous dorsal petals are nested within the spur or hood of the dorsal sepal. The study of synorganised structures is challenging, and geometric morphometric-oriented investigation may provide working hypotheses for an evo-devo exploration of such hyperorgan formation. We analyze here the floral shape of Delphinieae using geometric morphometric methods and demonstrate the effectiveness of these methods on dry and compressed flowers. We also show the diagnostic value of the dorsal half of the perianth of the Delphinieae flower, and suggest some trends to help design future studies on the evo-devo of spur formation and the co-evolution of Delphinieae flowers with their pollinators.

Judge it by its shape: a pollinator‐blind approach reveals convergence in petal shape and infers pollination modes in the genus Erythrina

“…Given the lack of three‐dimensional information, the predictive power obtained here with both random forests and the inference of convergence with evolutionary models is noteworthy, particularly given that the two‐dimensional shapes were extracted from pressed specimens in herbaria. This highlights the potential of natural history collections as a source for extracting large amounts of functional trait information (Holmes et al, 2016; Chen et al, 2018; Soltis et al, 2020).…”

“…In particular, it highlights convergence in the shape of the keel petals suggesting their importance in the pollination in Erythrina . The use of geometric morphometrics with herbarium material has proven particularly useful to reach these conclusions and indicates the great potential held in herbaria for detailed functional trait and evolutionary analyses (Chen et al, 2018). Moreover, the use of robust, field‐based pollinator data, in combination with the use of a pollination‐blind approach allowed us to test whether petal shape can be reliably used to infer pollination modes.…”

Herbarium-based science in the twenty-first century

“…Dentant, Lavergne, and Malécot (2018) conducted a thorough study of the taxonomy of rockjasmines (genus Androsace, Primulaceae), while Henning et al (2018) introduce a workflow currently implemented on the EDIT Platform for Cybertaxonomy, which improves use and sustainable handling of specimen data. In addition, we also present a short review about the techniques used to prepare herbarium specimens for morphological and anatomical studies (Espinosa and Pinedo Castro 2018), and, to our knowledge, the first study investigating the morphological diversity of herbarium flowers using geometric morphometrics (Chen et al 2018).…”

Floral Organogenesis and Morphogenesis ofStaphisagria(Ranunculaceae): Implications for the Evolution of Synorganized Floral Structures in Delphinieae

“…Synorganized floral parts have been described in a wide range of angiosperm lineages (Endress 1990(Endress , 2010b. In Ranunculales, the earliest-diverging order of eudicots (APG IV 2016), synorganization was briefly reported in the flowers of the tribe Delphinieae, in which the nectar spurs of the dorsal petals are nested within the hollow dorsal sepal (Chartier et al 2016;Chen et al 2018;Jabbour et al in press). The phylogenetic position of Delphinieae within Ranunculaceae, and the floral morphological evolution in the family were both clarified recently (Zhai et al 2019;Carrive et al 2020).…”