Systematics and evolution of the Dactylorhiza romana/sambucina polyploid complex (Orchidaceae)

Abstract

The European-Mediterranean-Oriental Dactylorhiza romana/sambucina polyploid complex was studied with regard to genetic and morphological variation patterns. Allozyme and morphometric data were collected from 24 and 19 populations, respectively, initially identified as D. flavescens , D. insularis , D. markusii , D. romana , D. sambucina , and an indeterminate taxon. Genetic distances were calculated and illustrated by an unweighted pair-group method using arithmetic averages (UPGMA) dendrogram, and principal components analyses (PCAs) were used to summarize morphological variation patterns. Another PCA was performed on combined allozyme and morphometric data. On the basis of the dendrogram and the PCA plots, main groups of populations were delimited, and the probability that each morphological character would distinguish correctly between these groups was estimated. After combining morphometric interpretations with studies of herbarium material and information from the literature, the following taxa were confidently accepted: D. romana ssp. romana , D. romana ssp. guimaraesii (comb. et stat. nov.) , D. romana ssp. georgica , D. sambucina , D. cantabrica (sp. nov.) , and D. insularis . Levels of genetic diversity suggest that D. romana s.s. is the least derived member of the complex. The evolutionary divergence of the diploid species, D. romana and D. sambucina , was probably the outcome of vicariant speciation, whereas D. romana ssp. georgica and D. romana ssp. guimaraesii appear to have evolved from D. romana s.s. through incomplete vicariantand peripheral isolate speciation events, respectively. In some populations of the diploid taxa, a significant deficiency in heterozygotes was found at one to three loci. It is proposed that this pattern may indicate a Wahlund effect, hypothesizing that local populations are subdivided into demes determined by the commonly sympatric occurrence of two distinct colour morphs combined with partial morph constancy of individual pollinators (bumblebees). Several pathways are possible for the origin of the allotriploid D. insularis and the apparently allotetraploid D. cantabrica . A taxonomic revision is provided.

Seed micromorphology in Dactylorhiza Necker ex Nevski (Orchidaceae)and allied genera

“…guimaraesii. However, in the triploid species D. insularis, with a hybrid origin (Bullini et al, 2001;Pedersen, 2006), the trabeculae are mainly transversal to the longitudinal axis. This pattern of ornamentation has been also observed in D. cantabrica, but we need to analyze more seeds and more populations to confirm it.…”

“…A particularly remarkable case is the so-called Gymnigritella runei Teppner & E. Klein -tetraploid Gymadenia conopsea × Nigritella nigra hybrids that form self-reproducing populations in northern Sweden (Hedrén et al, 2000). Based on data from diverse molecular markers, patterns of allopolyploidization have also been well documented within Nigritella (Hedrén et al, 2000) and Dactylorhiza (Hedrén, 1996;Pedersen, 2006;Hedrén et al, 2007;Pillon et al, 2007).…”

Biological flora of Central Europe: Dactylorhiza sambucina (L.) Soó

“…The inflorescences are ovoid (egg-shaped) or shortly cylindrical dense racemes (without a terminal flower), (3.7) 5-7.5 (10.5) × (2.7) 3.5-4.5 (5) cm in length. The lower bracts are longer, the upper ones equal to the flowers in length; young inflorescences are sheeted by 1-8 (11) cataphylls (Pedersen, 2006). The flowers are zygomorphic and either yellowish or purple-red.…”

“…The species epithet apparently refers to the floral scent of Sambucus nigra L. (Adoxaceae) (Delforge, 2005 (Pedersen, 2006). Pedersen (2006) provides color photos and a key to these taxa.…”

“…Pedersen (2006) provides color photos and a key to these taxa. Two of the D. romana subspecies, namely romana and georgica, have the same flower colour dimorphism as D. sambucina, while D. cantabrica, D. insularis, and D. romana subsp.…”