INTRODUCTION Glacial refugia usually refer to broad regions where boreal and temperate taxa persisted through the Last Glacial Maximum (LGM) (Bennett et al. 1991). Traditionally, such regions were defined by regional scale pollen analysis or transcontinental phylogeographical surveys. The scale at which refugia are defined might be irrelevant to determine specific stand-scale ecological or evolutionary processes. REFERENCES Bennett et al. 1991. J Biogeog 18:103–115; de Lafontaine & Payette. 2011. Quat Sci Rev 30:867–875; de Lafontaine & Payette. 2012. Holocene 22:191–201; Lefèvre et al. 2012. Mol Ecol Res 12:484–491; Timbal & Ducousso. 2010. Bull Soc Linn Bordeaux 145:127–137; Magri et al. 2006. New Phytol 171:199–221; Svenning et al. 2008. J Ecol 96:1117–1127. ACKNOWLEDGEMENTS Experiments were funded by DGPAAT Convention E30/08, CRPF Nord-Pas de Calais-Picardie, FEDER, INTERREG IVA 2 mers, MEDDE, Conseil Général des Pyrénées Orientales, Région Languedoc- Roussillon, INRA-EFPA Projet Innovant, GdL benefited from a FQRNT postdoctoral fellowship, CAAG benefited from Erasmus Mundus BAPE and Labex fellowships. Integrating palaeocology and genetics to uncover stand-scale glacial beech refugium G. de Lafontaine, A. Ducousso, C.A. Amasifuen Guerra, S. Lefèvre, and R.J. Petit UMR BIOGECO, INRA / Univ. Bordeaux 1, Bordeaux, France OBJECTIVES Macrofossil soil charcoal analysis (de Lafontaine and Payette 2011, 2012) and SSR markers (Lefèvre et al. 2012) were used to uncover stand-scale history of isolated Fagus sylvatica (beech) populations at its low-elevation rear edge in Landes de Gascogne and Entre-deux-Mers, Southwestern France (Timbal and Ducousso 2010). Predictive models linked to estimates of LGM climate indicated that beech could have found suitable climatic conditions in this area during the LGM (Svenning et al. 2008). ? ? Beech (Fagus sylvatica L.) stands in ‘Landes de Gascogne’ and surrounding areas Timbal & Ducousso 2010 Tentative broad-scale beech refugia and postglacial migration pathways of current french lineages, following Magri et al. 2006. Distribution of F. sylvatica in France. Note the few, highly remote beech stands in southwestern France, at the low-elevation rear edge. Modelled potential distribution of F. sylvatica during the LGM, from Svenning et al. 2008. BROAD-SCALE GENETIC STRUCTURE REGIONAL-SCALE ANALYSIS Genetic structure analysis including only sites from Landes de Gascogne. STRUCTURE K = 7 groups within Landes de Gascogne. High genetic structure within the Landes de Gascogne refugium. Reminds of the ‘refugia within refugia’ phylogeographical pattern (Gómez and Lund 2007), albeit at a finer scale here. REGIONAL-SCALE ANALYSIS Soil macrofossil charcoal analysis including only sites from Landes de Gascogne. •Forest history since 44,000 cal yr BP (43,930 to 13 BP cal yr BP) •Six fire periods; beech is present in 5 of 6 •Hiatus between 30,000 & 14,000 cal yr BP (during LGM) … but more dates are coming! STAND-SCALE ANALYSES Ciron A Ciron B Ciron C The largest beech stand in the area, the Ciron valley stand, was subsampled in three study sites (CIRON A, B, and C) spaced by c. 1 km along the Ciron river (whereas average pairwise distance between stands in the area is 45 km) CONCLUSION At CIRON B, radiocarbon dating of beech at c. 44,000, c. 33,000 cal yr BP and after the LGM, suggested in situ persistence of beech through Late Pleistocene but direct macrofossil charcoal evidence from the LGM are still needed to ascertain this inference. Genetic structure analyses showed a strong differentiation between CIRON B and all the other populations in the area, including the proximate CIRON A and CIRON C. Together, results of this integrated research at increasingly refined scales suggested that beech persisted through the Last Glacial Maximum in situ in at least one stand-scale refugium (CIRON B) within a regional cryptic refugium as defined by a more broad-scale analysis (Landes de Gascogne and Entre-deux- Mers). CIRON A CIRON B CIRON C 4.5 km 44,000 3800 900 33,000 STRUCTURE K = 2 groups Beech stand at CIRON B is genetically different from nearby stands CIRON A (upstream) and CIRON C (downstream) SOIL MACROFOSSIL CHARCOAL ANALYSIS At CIRON B, beech dates back to 44,000 cal yr BP. By contrast, beech presence on upstream (CIRON A) and downstream (CIRON C) sites along the same valley was more recent, dated at 3800 and 900 cal yr BP, respectively. Sampling KOH 1% Wet sieving Sorting Drying Weighting Taxonomic identification 14 C dating SOIL MACROFOSSIL CHARCOAL ANALYSIS: a method to uncover stand-scale history of forest communities through botanical identification and radiocarbon dating of wood charcoal Indicates a fire period with regional presence of beech BAPS K = 10 groups Evidence for a regional cryptic glacial refugium in Landes de Gascogne and Entre-deux-Mers area. •2510 individuals •65 populations •16 microsatellite loci Following protocol by Lefèvre et al. 2012
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INTRODUCTION
Glacial refugia usually refer to broad regions where boreal and
temperate taxa persisted through the Last Glacial Maximum
(LGM) (Bennett et al. 1991). Traditionally, such regions were
defined by regional scale pollen analysis or transcontinental
phylogeographical surveys. The scale at which refugia are
defined might be irrelevant to determine specific stand-scale
ecological or evolutionary processes.
REFERENCES Bennett et al. 1991. J Biogeog 18:103–115; de Lafontaine & Payette. 2011. Quat Sci Rev 30:867–875; de Lafontaine & Payette. 2012. Holocene 22:191–201; Lefèvre et al. 2012. Mol Ecol
Res 12:484–491; Timbal & Ducousso. 2010. Bull Soc Linn Bordeaux 145:127–137; Magri et al. 2006. New Phytol 171:199–221; Svenning et al. 2008. J Ecol 96:1117–1127. ACKNOWLEDGEMENTS
Experiments were funded by DGPAAT Convention E30/08, CRPF Nord-Pas de Calais-Picardie, FEDER, INTERREG IVA 2 mers, MEDDE, Conseil Général des Pyrénées Orientales, Région Languedoc-
Roussillon, INRA-EFPA Projet Innovant, GdL benefited from a FQRNT postdoctoral fellowship, CAAG benefited from Erasmus Mundus BAPE and Labex fellowships.
Integrating palaeocology and genetics to uncover
stand-scale glacial beech refugium
G. de Lafontaine, A. Ducousso, C.A. Amasifuen Guerra, S. Lefèvre, and R.J. Petit
UMR BIOGECO, INRA / Univ. Bordeaux 1, Bordeaux, France
OBJECTIVES
Macrofossil soil charcoal analysis (de Lafontaine and Payette
2011, 2012) and SSR markers (Lefèvre et al. 2012) were used to
uncover stand-scale history of isolated Fagus sylvatica (beech)
populations at its low-elevation rear edge in Landes de Gascogne
and Entre-deux-Mers, Southwestern France (Timbal and
Ducousso 2010). Predictive models linked to estimates of LGM
climate indicated that beech could have found suitable climatic
conditions in this area during the LGM (Svenning et al. 2008).
?
?
Beech (Fagus sylvatica L.) stands in ‘Landes de Gascogne’ and surrounding areas
Timbal & Ducousso 2010
Tentative broad-scale beech refugia and
postglacial migration pathways of current
french lineages, following Magri et al. 2006.
Distribution of F. sylvatica in
France. Note the few, highly remote
beech stands in southwestern France,
at the low-elevation rear edge.
Modelled potential
distribution of F. sylvatica
during the LGM, from
Svenning et al. 2008.
BROAD-SCALE GENETIC STRUCTURE
REGIONAL-SCALE ANALYSIS
Genetic structure analysis including only sites from Landes de
Gascogne.
STRUCTURE K = 7 groups within Landes de Gascogne.
High genetic structure within the Landes de Gascogne refugium.
Reminds of the ‘refugia within refugia’ phylogeographical pattern
(Gómez and Lund 2007), albeit at a finer scale here.
REGIONAL-SCALE ANALYSIS
Soil macrofossil charcoal analysis including only sites from
Landes de Gascogne.
•Forest history since 44,000
cal yr BP (43,930 to 13 BP
cal yr BP)
•Six fire periods; beech is
present in 5 of 6
•Hiatus between 30,000 &
14,000 cal yr BP (during
LGM) … but more dates are
coming!
STAND-SCALE ANALYSES
Ciron A Ciron B
Ciron C
The largest beech stand in the
area, the Ciron valley stand,
was subsampled in three study
sites (CIRON A, B, and C)
spaced by c. 1 km along the
Ciron river (whereas average
pairwise distance between
stands in the area is 45 km)
CONCLUSION
At CIRON B, radiocarbon dating of beech at c. 44,000, c. 33,000
cal yr BP and after the LGM, suggested in situ persistence of
beech through Late Pleistocene but direct macrofossil charcoal
evidence from the LGM are still needed to ascertain this
inference. Genetic structure analyses showed a strong
differentiation between CIRON B and all the other populations in
the area, including the proximate CIRON A and CIRON C.
Together, results of this integrated research at increasingly
refined scales suggested that beech persisted through the Last
Glacial Maximum in situ in at least one stand-scale refugium
(CIRON B) within a regional cryptic refugium as defined by a
more broad-scale analysis (Landes de Gascogne and Entre-deux-
Mers).
CIRON A CIRON B CIRON C
4.5 km
44,000
3800
900
33,000
STRUCTURE K = 2 groups
Beech stand at CIRON B is genetically
different from nearby stands CIRON A
(upstream) and CIRON C
(downstream)
SOIL MACROFOSSIL CHARCOAL
ANALYSIS
At CIRON B, beech dates back to
44,000 cal yr BP. By contrast, beech
presence on upstream (CIRON A) and
downstream (CIRON C) sites along the
same valley was more recent, dated at
3800 and 900 cal yr BP, respectively.
Sampling KOH 1% Wet sieving Sorting Drying Weighting Taxonomic identification 14C dating
SOIL MACROFOSSIL CHARCOAL ANALYSIS: a method to uncover stand-scale history of
forest communities through botanical identification and radiocarbon dating of wood charcoal
Indicates a fire period with regional presence of beech
BAPS
K = 10 groups
Evidence for a regional cryptic glacial
refugium in Landes de Gascogne and
Entre-deux-Mers area.
•2510 individuals
•65 populations
•16 microsatellite loci
Following protocol by Lefèvre et al. 2012
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