Abstract
The genetic structure of <em>Dactylorhiza incarnata</em> var. <em>incarnata</em> populations is shaped not only by historical events such as recolonization after ice sheet retreat or limited seed and pollen dispersal, but also the bottleneck effect. During the last decade, <em>D. incarnata</em> var. <em>incarnata</em> has also experienced a strong decline in population numbers and sizes, due to habitat loss and fragmentation. In the present research genetic diversity was examined in eight populations located in northern Poland, using six nuclear microsatellites loci. At the species level our results showed a moderate mean level of genetic diversity (<em>A</em> = 4.67; <em>A</em><span><sub>e</sub></span> = 2.73; <em>R</em><span><sub>s</sub></span> = 4.48; <em>H</em><span><sub>o</sub></span> = 0.438; <em>F</em><span><sub>IS</sub></span> = 0.224), which varied among the studied populations (<em>A</em>: 2.17–3.67; <em>A</em><span><sub>e</sub></span>: 1.55–2.69; <em>R</em><span><sub>s</sub></span>: 1.31–1.61; <em>H</em><span><sub>o</sub></span>: 0.292–0.631; <em>F</em><span><sub>IS</sub></span>: −0.283–0.340). A considerable overabundance of homozygotes was detected in four populations (<em>F</em><span><sub>IS</sub></span> within the range of 0.067–0.340), and in the remaining populations an excess of heterozygotes was observed. The average apparent out-crossing rate was also calculated (<em>t</em><span><sub>a</sub></span> = 0.980), and primarily indicated a tendency to out-cross within the species. Moderate genetic differentiation was found among the studied populations (<em>F</em><span><sub>ST</sub></span> = 0.149; <em>R</em><span><sub>ST</sub></span> = 0.174; <em>p</em> &lt; 0.05). The differentiation of the populations corresponded to relatively low gene flow value (<em>N</em><span><sub>m</sub></span> = 0.426) among populations, which amounted to only one migrant every second generation.
Highlights
In recent decades the processes of the extinction of vascular plant species has accelerated considerably as a result of human activity causing disturbances within their natural habitats [1,2]
Naczk et al / Genetic diversity in Dactylorhiza incarnata identified as D. incarnata var. incarnata
Refugia for D. incarnata were presumably located in Southern and southwestern Europe, and previous studies of the genetic structure showed that these populations are characterized by the highest levels of genetic variation in Europe [12,17,45]
Summary
In recent decades the processes of the extinction of vascular plant species has accelerated considerably as a result of human activity causing disturbances within their natural habitats [1,2]. Habitat fragmentation had a great impact on the genetic variation of plant populations. Orchidaceae is a family of flowering plants which is vulnerable in Europe [4]. This is due to, inter alia, their unique reproductive strategies, specific interactions with symbionts, and often specific habitat requirements which make them very sensitive to changes in their habitat. Orchids usually form small populations that are vulnerable to such evolutionary processes as the bottleneck effect or inbreeding. The combination of these processes can lead to genetic erosion and, to the loss of genetic diversity [5].
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