Spatial genetic structure of an endangered orchid Cypripedium calceolus (Orchidaceae) at a regional scale: limited gene flow in a fragmented landscape

Julita Minasiewicz,Joanna M. Znaniecka,Adam Kawiński,Marcin Górniak

doi:10.1007/s10592-018-1113-4

Julita Minasiewicz, Joanna M. Znaniecka + Show 2 more

Open Access

https://doi.org/10.1007/s10592-018-1113-4

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Abstract

Plant species that are capable of propagating clonally are expected to be less vulnerable to habitat fragmentation due to their long life span. Cypripedium calceolus L. is a rare, clonal, long-lived orchid species. It has suffered marked decline because of habitat loss and fragmentation and over-collection, yet an IUCN report on this species does not regard fragmentation as a major threat to the species. We applied 13 nuclear microsatellites and cpDNA sequences to identify the patterns of population structure, genetic diversity and connectivity of six remnant local populations of C. calceolus in highly fragmented Gdańsk Pomerania region (N Poland). Despite severe (80%) loss of localities in the studied area we found that the local populations retain high levels of clonal (R 0.86–1) and genetic diversity (He = 0.572). However, their differentiation is relatively high (FST = 0.132 for nuclear SSR and FST = 0.363 for cpDNA) despite close geographic proximity (0.6–57 km). Bayesian clustering classified populations according to their geographic origin with little admixture. Low genetic connectivity between the remnant populations shows that the current gene flow is too low to serve as a cohesive force in a fragmented habitat, which may impede a quick response to environmental change. The species’ ability to retain ancestral variation may help withstand fragmentation, but in the light of observed extirpation rate it should be rather considered as a factor that only delays local populations’ extinction. This leads to the conclusion that habitat loss and fragmentation should be regarded as a real threat to stability of C. calcelolus populations.

Highlights

Human-induced habitat loss and fragmentation are serious threats to the viability of plant populations that may lead to their decline and extinction (Young et al 1996; Young and Clarke 2000; Lienert 2004; Reed 2004; Ouborg et al 2006; Aguilar et al 2006, 2008; Vranckx et al 2012)
Reduced sexual reproduction resulting from environmental changes may lead populations to shift towards a predominately clonal reproductive strategy (Barrett 2015; Lin et al 2016)
In this study we investigated the genetic diversity and fine-scale patterns of population genetic structure of six, highly fragmented populations of rhizomatous orchid C. calceolus within a narrow geographic area in Gdańsk Pomerania

Summary

Introduction

Human-induced habitat loss and fragmentation are serious threats to the viability of plant populations that may lead to their decline and extinction (Young et al 1996; Young and Clarke 2000; Lienert 2004; Reed 2004; Ouborg et al 2006; Aguilar et al 2006, 2008; Vranckx et al 2012). Erosion of genetic variation due to random genetic drift and inbreeding in populations of reduced size compromises their ability to respond to environmental changes and increases their risk of extinction (Reed 2004). Sensitivity to this process largely depends on a plant’s life history characteristics (Herault and Honnay 2005; Honnay and Jacquemyn 2007; Lindborg 2007; Lindborg et al 2012). Due to a low frequency of seed production and dispersal, clonal plants may be less effective in spreading into new habitat patches and respond more slowly to habitat change than non-clonal species, which may result in local extinction (Buckley and Frecleton 2010; Zobel et al 2010; Wiberg et al 2016)

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