Abstract
The island of St Helena in the South Atlantic Ocean has a rich endemic flora, with 10 endemic genera and 45 recognised endemic species. However, populations of most endemic species have undergone dramatic reductions or extinction due to over-exploitation, habitat destruction and competition from invasive species. Consequently, endemic species are likely to have lost genetic variation, in some cases to extreme degrees. Here, the entire extant wild populations and all planted trees in seed orchards, of two critically endangered species in the endemic genus Commidendrum (Asteraceae), C. rotundifolium and C. spurium, were sampled to assess levels of genetic variation and inbreeding. Six new microsatellite loci were developed from next-generation sequence data, and a total of 190 samples were genotyped. Some seed orchard trees contained alleles from both wild C. rotundifolium and C. spurium indicating they could be hybrids and that some backcrossing may have occurred. Some of these trees were more similar to C. rotundifolium than C. spurium both genetically and morphologically. Importantly, allelic variation was detected in the putative hybrids that was not present in wild material. C. rotundifolium is represented by just two individuals one wild and one planted and C. spurium by seven, therefore the seed orchard trees comprise an important part of the total remaining genetic diversity in the genus Commidendrum.
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References
Courchamp F, Hoffmann BD, Russell JC, Leclerc C, Bellard C (2014) Climate change, sea-level rise, and conservation: keeping island biodiversity afloat. Trends Ecol Evol 29:127–130
Cronk QCB (1986) The decline of the St Helena gumwood Commidendrum robustum. Biol Conserv 35:173–186
Cronk Q (1995) A new species and hybrid in the St Helena endemic genus Trochetiopsis. Edinburgh J Bot 52:205–213
Eastwood A (2003) Use of molecular tools in the conservation biology of the St Helenan flora. University of Edinburgh, Edinburgh
Eastwood A, Gibby M, Cronk QCB (2004) Evolution of St Helena arborescent Astereae (Asteraceae): relationships of the genera Commidendrum and Melanodendron. Bot J Linn Soc 144:69–83
Ellstrand NC, Elam DR (1993) Population Genetic Consequences of Small Population Size: implications for Plant Conservation. Annu Rev Ecol Syst 24:217–242
Ellstrand NC, Schierenbeck KA (2000) Hybridization as a stimulus for the evolution of invasiveness in plants? Proc Natl Acad Sci USA 97:7043–7050
Emerson BC, Kolm N (2005) Species diversity can drive speciation. Nature 434:1015–1017
Emms SK, Arnold ML (1997) The effect of habitat on parental and hybrid fitness: transplant experiments with louisiana irises. Evolution 51:1112–1119
Faircloth B (2008) MSATCOMMANDER: detection of microsatellite repeat arrays and automated, locus-specific primer design. Mol Ecol Res 8:92–94
Fant JB, Banai A, Havens K, Vitt P (2010) Hybridization between the threatened plant, Lespedeza leptostachya Englem. and its co-occurring congener Lespedeza capitata Michx.: morphological and molecular evidence. Conserv Genet 11:2195–2205
Glen A, Atkinson R, Campbell K, Hagen E, Holmes N, Keitt B, Parkes J, Saunders A, Sawyer J, Torres H (2013) Eradicating multiple invasive species on inhabited islands: the next big step in island restoration? Biol Invasions 15:2589–2603
Kohn DD, Hulme PE, Hollingsworth PM, Butler A (2009) Are native bluebells (Hyacinthoides non-scripta) at risk from alien congenerics? Evidence from distributions and co-occurrence in Scotland. Biol Conserv 142:61–74
Kothera L, Ward SM, Carney SE (2007) Assessing the threat from hybridization to the rare endemic Physaria bellii Mulligan (Brassicaceae). Biol Conserv 140:110–118
Levin DA, Francisco-Ortega J, Jansen RK (1996) Hybridization and the extinction of rare plant species. Conserv Biol 10:10–16
Myers N, Mittermeier RA, Mittermeier CG, da Fonseca GAB, Kent J (2000) Biodiversity hotspots for conservation priorities. Nature 403:853–858
Peakall R, Smouse PE (2006) GENALEX 6: genetic analysis in excel population genetic software for teaching and research. Mol Ecol Notes 6:288–295
Peakall R, Smouse PE (2012) GenAlEx 6.5: genetic analysis in excel. Population genetic software for teaching and research—an update. Bioinformatics 28:2537–2539
Rhymer JM, Simberloff D (1996) Extinction by hybridization and introgression. Annu Rev Ecol Syst 27:83–109
Rieseberg LH, Ellstrand NC, Arnold M (1993) What can molecular and morphological markers tell us about plant hybridization? Crit Rev Plant Sci 12:213–241
Rozen S, Skaletsky H (2000) Primer3 on the WWW for general users and for biologist programmers. In: bioinformatics methods and protocols: Methods in Molecular Biology (eds. Krawetz S, Misener S). Humana Press, Totowa, NJ
Stace C (1975) Hybridization and the flora of the British Isles. Academic Press Inc, London
Stebbins G (1950) Variation and evolution in plants. Columbia University Press, New York
Whiteley AR, Fitzpatrick SW, Funk WC, Tallmon DA (2015) Genetic rescue to the rescue. Trends Ecol Evol 30:42–49
Acknowledgments
We would like to thank Katrine Herian, Lourens Mallen, Matti Niissalo, Neil Henry, Jeremy Henry and David Francis who all collected samples in the field. We also thank Sadie Barber, Fiona Inches, Greg Kenicer and Suzanne Cubey from RBGE for facilitating and granting access to the living collections of C. spurium at RBGE. We would like to acknowledge the financial support from St Helena Agriculture and Natural Resources Department and the Natural Environment Research Council. Finally we would like to the editor and the anonymous reviewers for comments and suggestions that greatly improved the manuscript.
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Gray, A., Perry, A., Cavers, S. et al. Hybrid plants preserve unique genetic variation in the St Helena endemic trees Commidendrum rotundifolium DC Roxb. and C. spurium (G.Forst.) DC. Conserv Genet 18, 241–246 (2017). https://doi.org/10.1007/s10592-016-0884-8
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DOI: https://doi.org/10.1007/s10592-016-0884-8