Molecular Systematics of the Gymnadenia conopsea Complex (Orchidaceae)

Abstract

Gymnadenia conopsea s.l., the fragrant orchid is widely distributed over Europe and adjacent parts of Asia. It is frequently found in open grassland, woodland and rich fen habitats, particularly in calcareous regions. The species is characterized by a high variation in morphological and genetic characters including plant height, floral characters, flowering time, habitat preferences, allozymes and microsatellite markers. Traditionally, G. conopsea s.l. has been subdivided into intraspecific taxa on the basis of variation in size and flowering time, an early- to late-flowering, small to medium-sized type as G. conopsea sensu stricto, and a late-flowering broad-leaved and many-flowered type as G. conopsea var. densiflora. In this study, the three molecular data sets of plastid microsatellites, nuclear microsatellites and ITS were investigated to examine whether these data sets supported separation in morphology and flowering period. The correlations between data sets were also analyzed at different geographic scales over the European distribution range, in Sweden and within one major site on the island of Gotland. The results showed that early-flowering G. conopsea is far more genetically variable, having more alleles per locus and higher values of genetic diversity than the late-flowering types (late-flowering G. conopsea and G. conopsea var. densiflora). According to the combination of three molecular data sets, flowering period, distribution and morphology, I found at least six population groups in this study: (1) G. frivaldii, (2) G. odoratissima, (3) northern early-flowering G. conopsea, (4) southern early-flowering G. conopsea, (5) late-flowering G. conopsea and (6) G. conopsea var. densiflora. The study has approved that there was a strong genetic differentiation between early-flowering subgroups and late-flowering subgroups in G. conopsea s.l. based on three different molecular markers and that the three data sets reveal similar differentiation patterns.

Popular Abstract

Gymnadenia conopsea s.l., the fragrant orchid ("brudsporre"), is widely distributed over Europe and adjacent parts of Asia. It is found in open grassland, woodland and rich fen habitats, mostly on calcareous ground, but also in hay meadows and grasslands kept open by traditional land use. The genus Gymnadenia contains approximately 20 species. Traditionally, G. conopsea s.l. has been subdivided on the basis of variation in morphology, an early-flowering to late-flowering var. conopsea flowering from June into August and a late-flowering var. densiflora flowering in July and August. Whereas var. conopsea is characterized by being low-grown with narrow leaves up to 1 cm wide and lax inflorescenses, var. densiflora is tall with leaves up to 2 cm wide and with many-flowered and dense inflorescences. It is sometimes difficult to distinguish between them due to overlap in flowering time and a continuous variation in morphology, spanning the gap between the two typical varieties. In contrast, molecular studies of a nuclear gene region, ITS (Internal Transcribed Spacers) have revealed a primary subdivision of G. conopsea into plants flowering early and plants flowering late, and where the late-flowering group includes material in agreement with both varieties. Moreover, according to ITS, early-flowering G. conopsea is most closely related to G. odoratissima, a species with a distinct morphology, whereas the late-flowering G. conopsea are more closely similar to other members of the genus, including the SE European G. frivaldii and members of the genus Nigritella. Other molecular studies based on nuclear microsatellites agree on the primary divide in G. conopsea, but do not provide comparison with other species. Therefore, to clarify the patterns given by molecular markers, I conducted an analysis of both G. conopsea and related members of the genus, and I screened all material for three different types of molecular markers: ITS, nuclear microsatellites and plastid microsatellites. Moreover, I included multiple samples from each population, enabling estimates of within-population variability. Whereas particular emphasis was put on a single site on the Baltic island of Gotland, Lojsthajd, where both varieties of G. conopsea grow in sympatry with G. odoratissima, reference material was included from other European and Scandinavian sites as well.

Combining the three molecular data sets, my material could be subdivided into five molecularly defined groups: (1) G. frivaldii, (2) G. odoratissima, (3) northern early-flowering G. conopsea, (4) southern early-flowering G. conopsea, and (5) late-flowering G. conopsea. However, no molecular data supported the separation of var. densiflora from late-flowering var. conopsea. In addition, this late-flowering group contains much less genetic variation than early-flowering G. conopsea. The results of my study provide information on the genetic status of G. conopsea s.l. in different parts in Europe, especially in Sweden, where genetically divergent units require appropriate implementations for conservation. However, more population samples, especially from the southern part of the European distribution are required to clarify the precise genetic structure in G. conopsea s.l.


Supervisor: Mikael Hedrén
Master´s Degree Project - Plant Ecology and Systematics 30 credits, 2014
Lund University, Department of Biology

• author: Saenruen, Anupong
• supervisor: Mikael Hedrén
• organization: Degree Projects in Biology
• course: BIOM31 20141
• year: 2014
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 4882736
• date added to LUP: 2014-12-19 10:34:16
• date last changed: 2014-12-19 10:34:16