Genetic variation in time and space: the use of herbarium specimens to reconstruct patterns of genetic variation in the endangered orchid Anacamptis palustris
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Habitat alteration, fragmentation and destruction as a consequence of human impact are a global phenomenon. Here we document changes in genetic variation in the marsh orchid Anacamptis palustris as a consequence of such habitat changes. We examined historical specimens that were collected during the nineteenth and early twentieth centuries, prior to the most recent massive habitat changes affecting this species. Sequences of a hypervariable region in the plastid DNA, located in the tRNALEU intron, from herbarium vouchers were compared with those from a near-exhaustive survey of the extant A. palustris populations on the Italian peninsula. It was found that private haplotypes and alleles found in small, extant populations were once widespread and more common in historic populations and that alleles, once present in historic populations, have gone extinct. In addition, genetic differentiation among populations has increased over time and haplotype frequencies significantly differ among historic and extant populations. These results document that human induced habitat changes have reduced genetic diversity and increased the importance of random genetic drift in this species. It is concluded that the analysis of herbarium specimens may provide important insights into changes of genetic diversity over time and may be critical for correct inference of the evolutionary history of rare and endangered species.
KeywordsAnacamptis palustris Plastid DNA Herbarium specimens Historic haplotype diversity Temporal variation
The authors thank the herbarium institutions (NAP, FI, ROMA, TO, Z/ZT) for providing access to their historic collections and for permitting sampling of specimens. In particular we thank the herbarium curators, namely M. Baltisberger, P. Cuccuini, L. Guglielmone, A. Millozza, and A. Santangelo for their invaluable help in specimen identification, label translation, and sample shipment. The authors also thank three anonymous reviewers for their comment that contributed to improve the MS. The present study was supported by the PRIN program of the Italian Ministry of the University and Scientific research and by a Swiss Federal Institute of Technology (ETH) grant to AW.
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