Delphinium L

CURRENT TAXONOMY OF THE GENUS DELPHINIUM L .

To better understand the taxonomy of Delphinium L. and based on seed morphology, Malyutin (1987) divided the genus Delphinium L. into subg. Staphisagria (J. Hill) Peterm. and subg. Delphinium, and further divided the latter one in sect. Anthriscifolium Wang and sect. Delphinium (confirming Wang’s (1979) classification for this subgenus). This classification was supported by a combination of morphological and cytological characters (Blanché 1990). Later, based on breeding systems, pollination ecology, cytology and isozyme variations, he proposed the division of the sect. Delphinium into four series Cossoniana C. Blanché, Molero & P. Simon, Balansae C. Blanché, Molero & P. Simon, Macropetala C. Blanché, Molero & P. Simon and Halterata B. Pawl. (Blanché et al. 1997). Integrating the results of molecular data, Jensen et al. (1995) placed Delphinium L. together with Consolida (DC.) Gray and Aconitum L. in the subtribe Delphiniinae Benth. (Delphinieae Warm., Ranunculoideae Hutch). Using 65 morphological characters combined with four plastid and nuclear DNA sequence data, Wang et al. (2009) placed the genera Delphinium L., Consolida (DC.) Gray and Aconitum L. within the tribe Delphinieae. Through a morphological analysis, Trifonova (1990) proposed to consider Consolida (DC.) Gray and Aconitella Spach as different genera based on morphological characters. However, this was challenged by Jabbour & Renner (2011a) who found that both genera were nested within Delphinium L. using molecular data and a large taxon sampling, leading them to proposed an extended genus Delphinium L. including both Consolida (DC.) Gray and Aconitella Spach. Based on the results of a molecular phylogenetic analysis, they decided to resurrect the genus Staphisagria J. Hill, including D. staphisagria L. (Jabbour & Renner 2011b). They recognized three genera in the tribe Delphinieae: Delphinium L., Aconitum L. and Staphisagria J. Hill. (Jabbour & Renner 2012a). The genus Aconitum L. was further split into Aconitum L. sensu stricto and the monotypic Gymnaconitum (Stapf.) Rapaics (Wang et al. 2013).

DESCRIPTION OF THE TYPICAL DELPHINIUM FLOWER

As seen in the above section, the genus Delphinium sensu lato (Jabbour & Renner 2011a) belongs to the tribe Delphinieae Warm. (Ranunculoideae Hutch, Ranunculaceae Juss.). This tribe is the only clade within the family Ranunculaceae with flowers that are bilaterally symmetrical.

Based on flowers of D. peregrinum L. (Fig. 2 B-b3), Delphinium typical flowers are composed of four categories of organs: sepals and petals composing the perianth (the diversity of terms used in the bibliography of these organs is reviewed in Jabbour & Renner 2012b), and the two types of sexual organs, stamens and carpels (Blanché 1990; Fig. 2 B-b3). From outside in, there are five free petaloid sepals quincuncially arranged: two ventral, two lateral and a spurred dorsal one, four free petals located in the dorsal half of the flower: two dorsal organs forming nectariferous spurs inserted into the spur of the dorsal sepal and with an exserted limb, and two lateral organs with a wide limb and a narrow claw. The other petals (corresponding to four ventral primordia) stop developing shortly after organogenesis (Payer 1857; Jabbour & Renner 2012b). The stamens are arranged in eight spiral series, and the gynoecium is composed of 3(-5) free carpels (Pawłowski 1964) turning into follicles after fertilization. In Delphinium, bilateral symmetry is established through two phenomena: 1) the development of dorsal spurs; and 2) the arrested development of the ventral petals (Jabbour et al. 2009).

However, as mentioned earlier (see Current taxonomy of the genus), the genus Delphinium L. includes species with floral morphological particularities that should be included in the description of Delphinium L. flowers. These exceptions will be presented in detail in the next section.

The inclusion of Consolida (DC.) Gray into Delphinium L. (Jabbour & Renner 2011a) implies an extension of the floral typical character states of the genus. The perianth of Consolida (DC.) Gray is bilaterally symmetrical and is composed of five petaloid sepals which arrangement and morphological characteristics are identical to those of Delphinium L. sepals. However, the inner perianth organs of Consolida (DC.) Gray consist of only two fused dorsal petals forming a single organ with a nectariferous spur inserted into the sepal spur (Fig. 2 A-a3). The other petals (in this case six primordia) stop developing shortly after initiation (Jabbour & Renner 2012b). Consolida (DC.) Gray flowers are bisexual, with five spirals of stamens, three less than the typical Delphinium L. flowers and, a single carpel, as opposed to the three carpels of the Delphinium typical gynoecium (Pawłowski 1964). Consolida (DC.) Gray flowers exemplify a case of reduction in floral organ numbers (petals, stamens and carpels) compared to the typical Delphinium L. flowers (Fig. 2 A-a3).

Recently, Vural et al. (2012) described a new genus named Pseudodelphinium H.Duman, Vural, Aytaç & Adıgüzel, including the single species Pseudodelphinium turcicum H.Duman, Vural, Aytaç & Adıgüzel. The description of this new species is based on a single population reported since 1997 in central Turkey. Plants of this species are herbaceous with radially symmetrical flowers presenting a perianth composed of five tepals (corresponding to petaloid sepals but considered as petals by the authors), numerous stamens, and three free carpels turning into follicles (Fig. 2 D-d3). The authors noted its probable taxonomic affinity with the genus Delphinium L., but chose to establish a new genus based on the morphological particularities of the single population (no dorsal spurs, radial symmetry, perianth composed of a single type of organs) they decided to establish a new genus. Later, the genus was placed in Delphinium L. subg. Delphinium by Xiang et al. (2017) based on molecular data. Espinosa et al. (2017) found that in this species the perianth is exclusively composed of sepals, while petals seems to stop their development at a very early stage. By integrating lines of evidence from morphology, anatomy, palynology, and molecular phylogeny they further supported its inclusion in Delphinium L. and proposed the new combination Delphinium turcicum (H. Duman, Vural, Aytaç & Adigüzel) Espinosa (Espinosa et al. 2017). Floral characteristics of this species are very similar to those of the Chinese species D. ecalcaratum S.Y. Wang & K.F. Zhou presenting spurless actinomorphic flowers with an uniseriate perianth. Flowers of this species include fewer stamens than D. turcicum (H. Duman, Vural, Aytaç & Adigüzel) Espinosa (5 vs 15 respectively) but one additional carpel (Ding et al. 1981).

W.T. Wang (1964) published the new species Chienia honanensis W. T. Wang (Ranunculaceae), based on a single specimen bearing flowers with bilateral symmetry and a biseriate perianth. Calyx is composed by 5 free petaloid sepals quincuncially arranged and there are 5(-6) W2 organs, all in the dorsal half of the flower (Fig. 3A). The flowers present numerous stamens and the gynoecium is composed of three free carpels turning into follicles. Even if the author recognized the proximity of C. honanensis with the genus Delphinium, the higher number of petals (5-6 vs 4 in the typical Delphinium flower; Fig. 2b 3, 3A) and the absence of dorsal spurs led him to propose the new genus Chienia W.T. Wang (Wang 1964). The species was later considered as based on a single teratological specimen of Delphinium grandiflorum L. by Warnock (1993). The vegetative parts of this specimen, conserved at PE (http:// www.cvh.ac.cn/cvh6/view/spms/info.php?id=cb003d8d, Fig. 3B) match vegetatively with a specimen of Delphinium grandiflorum L. collected in the same province in the same year (http://www.cvh.ac.cn/cvh6/view/spms/info. php?id=cef539df and http://www.cvh.ac.cn/cvh6/view/ spms/info.php?id=cef53a7c; Fig. 3B, C). Since the floral organization observed on the type material of the Chienia honanensis appears to be restricted to a single individual, and was apparently not transferred to progeny (no other collection exists, leading to the assumption that no permanent population ever occurred), we consider this as a non-heritable teratological variation, unable to be fixed in a population. Such teratological variation may occur in selected horticultural plants but it is not usual to include such variation in the description of the common morphology of a genus.

Thus, as far as floral morphology is concerned, and considering that the former genus Consolida (DC.) Gray is now included in Delphinium L., we state that the Delphinium flower is zygomorphic and characterized by a perianth consisting of five spirally-initiated sepals (the dorsal one being spurred) and four (two lateral, two dorsal spurred) or one (spurred) petals, all in the dorsal half of the flower. The spurred dorsal petals are nectariferous, and their spurs are nested within the spur of the dorsal sepal. The gynoecium consists of a single carpel, or 3(5) carpels. The description of D. ecalcaratum (Ding et al. 1981) and the recent inclusion of Delphinium turcicum (Fig. 1D, d) into the genus Delphinium L. (Espinosa et al. 2017; Xiang et al. 2017) imply to amend the description of the genus, to indicate that there are exceptions to the typical floral morphology. The major diagnostic floral characters of D. ecalcaratum and D. turcicum are: 1) radial symmetry; 2) uniseriate perianth composed of tepals; and 3) the absence of spurs. More analyses relying on herbarium material and particularly living material are needed to better understand the origin of the morphological deviations. Regarding Delphinium turcicum, having access to seeds of this species would allow us to conduct a karyological analysis in order to identify possible recent hybridization events, and testing the stability of the phenotype on other substrates, as the only known population of this species grows in the basin of the hypersaline lake Tuz Gölü, known for high levels of plant endemism (Yaprak & Tug 2009; Vural et al. 2012; Espinosa et al. 2017; Xiang et al. 2017).