Integrating palaeocology and genetics to uncover stand ... · G. de Lafontaine, A. Ducousso, C.A. Amasifuen Guerra, S. Lefèvre, and R.J. Petit UMR BIOGECO, INRA / Univ. Bordeaux

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