Geometric morphometrics and phylogenetic analysis of Delphinium taxa from south of Russia

Abstract

The leaf blade’s shape of 665 samples of 18 taxa from the genus Delphinium was analyzed using geometric morphometrics method. Within the subgenus Delphinastrum, D. elatum and, to a lesser extent, D. uralense were relatively well separated by canonical analysis, while D. litwinowii, D. pubiflorum, D. duhmbergii, and D. subcuneatumwere not actually separated. Within the subgenus Oligophyllon, D. caucasicum was well separated by this method. The scatter clouds of D. freynii + D. puniceum + D. sergii on the one hand, and D. fedorovii + D. gelmetzicum on the other hand, also separated. D. arcuatum, D. bracteosum, D. crispulum, D. flexuosum, and D. mariae did not separate from each other. The nature of such separation of species groups observed in the space of canonical variables and their relative proximity to each other can be associated with the habitat similarity of their populations driven by ecological or geographical conditions, as well as the influence of hybridization processes in the zone of secondary contact of species. The differences in leaf blade’s shape are mainly related to the width of the segments, the lengths of the central segment of the middle lobe and the undissected part of the leaf blade, the degree of its dissection, the shape of the base and the distance between the lower lobes. Based on the results of DNA sequencing of the intergenic transcribed spacer ITS2, the taxonomic independence of D. puniceum, D. macropogon, D. mariae, D. samurense, and D. pubiflorum is beyond any doubt. The synonymy of D. freynii and D. sergii is supported, with the priority name of D. schmalhausenii. D. cuneatum, D. subcuneatum, D. duhmbergii, and D. litwinowii should be considered as synonyms with the priority name of D. cuneatum. The taxonomic status of D. dictyocarpum, D. elatum, and D. uralense needs further clarification. This is probably related to their easy hybridization with D. cuneatum in sympatric populations within the overlapping areas. Delphinium arcuatum, D. bracteosum, D. caucasicum, D. crispulum, D. elisabethae, D. fedorovii, D. flexuosum, D. gelmetzicum, and D. speciosum are poorly separated, which can also be associated with hybridization processes. They need to be studied in more detail.