Embed Size (px)
Citation preview
1
Evolutionary and biogeographical significanceof refugia for arctic-alpine plants
Wien, Mariabrunn, 16.3.2009
Andreas TribschAG Ökologie und Diversität der PflanzenFB Organismische BiologieUniversität Salzburg
2
- Introduction-) When and where did Arctic and Alpine species evolve?-) Where do new adapted species/genotypes evolve today?-) How fast do species evolve?-) What is a refugium?-) Inferring processes with genetic & species diversity data
- Examples-) Fossil data-) Biogeographical evidence-) Molecular evidence
- Conclusion -) Theoretical concept of refugia in evolutionary research-) Open questions
Overview
3
When and where did Arctic and Alpine species evolve?
Cooling and parallel onset of alpidic orogenesis (including uplift of Tibetan plateau) in Miocene and Pliocene
Pleistocene cycles; glacial / interglacials
Willis & Niklas 2004. Phil. Trans. R. Soc. Lond. B: 359.
→ Adaptive evolution started well before glaciations
4
Modified from Abbott & Brochmann 2003; Brochmannet al. 2004
Maximum ice extent ~20,000 years ago:One mainly glaciated area One mainly unglaciated area
ice sheets
’arctic’, treeless habitats
5
Svendsen et al., 2004Quat. Sci. Rev.
Strbske Pleso
6
7
8
9
Forestation and fragmentation of the Forestation and fragmentation of the Arctic tundra c. 6ka BPArctic tundra c. 6ka BP
Crawford et al., 2003, Ann. Bot. 91
10
When and where did Arctic and Alpine species evolve?
Speciation and formationAdaptation from (Tertiary) lowland taxaAllopatric differentiation of adapted speciesAdaptive radiations within/among mountainsPolyploidisation & hybrid speciationImmigration of adapted species and anagenetic evolution
(Reisigl & Keller, 1987)
Composition of the European mountain flora
Biogeographic elements:
- ”in situ”-element- Asian element- arctic-alpine element
11
Where do new adapted species/genotypes evolve today?
Higher speciation rates expected:
High levels of genetic drift (small & isolated populations)range marginsislands (isolated mountains)specialized species with disjunct distribution
High selection pressureecologically extreme habitatshigh competition
Hybrid evolution (intra/interspecific)secondary contact zonesunstable environments & high disturbance
Higher mutation rates
→ could be ”anywhere”, no a priori hypothesis suggested
12
Where do new adapted species/genotypes evolve today?
Hendrych 1981. Preslia 53
Endemic plant species in Europe
New plant species start as neo-endemics!
13
Where do new adapted species/genotypes evolve today?
Low levels of endemism in the North
Brochmann et al. 2003. Taxon 53
14
Diploids tend to unglaciatedareas, whereas polyploidsinhabit once glaciated Areas
(example: Asplenium ceterach)
© A. Mrkvicka, flora.nhm-wien.ac.at Trewick et al., 2002, Molec. Ecol. 11
15
Higher rates of polyploidy in once glaciated areas of the Arctic
Brochmann et al. 2004. Biol.J.Linn.Soc. 82
→ higher rates of polyploid evolution in once glaciated areas !?
16
Once glaciated areas host only few endemicsEndemics are almost exclusively (Allo)Polyploids
North Atlantic: Brochmann et al. 2004Eastern Alps: Tribsch 2004
How fast do new Arctic and Alpine plants evolve?
Almost no restricted diploid species that evolved postglacially, although the Holocene was a unusually long stable periode
→ 20.000 years are not enough for extensivespeciation (except for hybrid speciation)
17
As climatic cycles are too fast to allow for speciation at diploid level, do species evolve in refugia or do they just survive there?
As endemism of species is not randomly distributed, so can we explain biogeographic patterns found today with geography of refugia only?
Where did those genetically variable populations survive that were source for those living today? Only in refugia?
Where do plant species speciate and where do they and their genes survive climatic instabilities?
18
„We define a refugium as a geographical area of relative ecological stability that has provided habitats during cold and warm, wet and dry stages during climatic instabilities for survival of populations, more or less in situ. Thus, a refugium is (more or less) situated in the same place during all stages of the Quaternary, for example, in mountain ranges that never have been fully glaciated.“
A refugium must provide:- a buffer for climatic changes- stability throughout time, ideally throughout [e.g.] the Pleistocene- survival of large, genetically variable (diploid) populations thatwere the source for populations found today
Tribsch & Schönswetter 2003, TaxonModified after Haffer 1969 & Tallis 1991
What is a refugium?
19
A potential refugium offering longterm stability is most likely found in ”southern” mountaneous regions
20
Climate 1: species is widespread
21
Climate 2: species range is restricted
22
If there is evidence that in a potential refugium stable populations have lived throughout climatic cycles it should be called realized refugium
Climate 3: species spreads again
23
All populations originate from refugia, where they survived effectively
24
realized realized refugiumrefugium
potentialpotentialrefugiumrefugium
25
Potential peripheral refugia of mountain plants in the European Alps during the Last GlacialMaximum (20,000 years ago). Blue areas: refugia on calcareous bedrock; red areas siliceousbedrock. Broken black line: maximum extent of the ice sheet, white broken line: snow line.
Schönswetter, Stehlik, Holderegger & Tribsch 2005. Mol. Ecol. 14
Potential refugia in the Alps(based on palaeo-environmental and geological information)
26
Potential ‘Arctic’ refugia
European MountainsCentral Asian MountainsRocky Mount.& CascadesBeringia
Potential source areas of ‘arctic lineages’
? Taymyr, Ural, Putorana? Northeast. N-America?
??
??
27
Inferring historical patterns from species distributions and genetic diversity data
Conclusions on refugia based on:
Distribution patterns of species, biogeographical & phylogenetical analysisSpecies richnessPatterns of endemism
Phylogeographic patternsGenetic variation of populations within speciesDistribution of endemic (private, unique, rare) alleles
28
Inferring historical patterns from species distributions and genetic diversity data
Conclusions on refugia based on:
Distribution patterns of species, biogeographical & phylogenetical analysisSpecies richnessPatterns of endemism
Phylogeographic patternsGenetic variation of populations within speciesDistribution of endemic (private, unique, rare) alleles
29
Hypothesis: same processes shape genetic and species diversity
Vellend & Geber, Ecol. Lett. (2005)
Localitycharacteristics
AreaIsolationspatial/temporal
heterogeneityenvironment, etc.
immigration
driftselection
Genetic diversitywithin populations
Species diversitywithin communities
[local floras]
immigrationdriftselection
parralleleffects
causaleffects
30
high variation low variationGenetic diversityindex
rare marker Rarity index
Population 1 Population 2 Genetic variation
31
bottlenecks due to long-distance dispersal,single immigration
high gene flow among populations,multiple immigration,no refugium
low divergence(few rare / endemic alleles)
bottlenecks/drift in small,isolated populations,in situ survival in isolated real refugium/a
limited gene flow, but large populations,in situ survival in large real refugium/a
high divergence(many rare / endemic alleles)
low genetic diversityhigh genetic diversity
Genetic diversity patterns and history of species
low divergence(few rare / endemic alleles)
high divergence(many rare / endemic alleles)
low genetic diversityhigh genetic diversity
32
Species diversity & patterns(3 areas/local floras)
highhigh
lowlow
Species richness
highhigh
RarityRarity indexindex
lowlow
33
bottlenecks due to long-distance colonisation,recent immigration to remote areas
high species flow among areas,massive immigrationfrom various sources, no refugium
not peculiar floristic compositionfew rare/endemic taxa
bottlenecks/drift in small,isolated floras, small isolated refugium
limited species flow, but rich floras,large long-term refugium
peculiar floristic compositionmany rare/endemic taxa
low species richnesshigh species richness
Species diversity patterns and history of regional floras
34
Diversity & divergenceand
population/species/flora histories
35
Testing hypotheses of potential refugia to discover realized refugia of general importance
-) Evidence from fossil data-) Biogeographical evidence-) Molecular evidence
36
Willis & Niklas 2004. Phil. Trans. R. Soc. Lond. B: 359.
Fossil evidence for refugia
37
Fossil evidence for refugia
Magri et al. 2006, New Phytol. 171
© Thomas StützelSpezielle Botanik Ruhr-Universität Bochum
38
Good quality of fossil records necessary
Restricted to certain plants, usually common species
Difficult to proof continuous presence of populations in an area
! Increasingly support for ”Northern Refugia” also for boreal and nemoral species
Fossil evidence for refugia
→ Fossils alone cannot proof presence of realized refugia
39
Testing hypotheses of potential refugia to discover realized refugia
-) Evidence from fossil data-) Biogeographical evidence-) Molecular Evidence
40
Verlaque et al. 1997, Geobios 21
Realized refugia for species in the Southern Europe – Centres of Endemism are mainly in mountain ranges
41
Diversity Diversity (species numbers(species numbers846 species) 846 species)
Rarity (weighted)Rarity (weighted)
Biogeographic patterns in the Alps(Data from IntraBioDiv)
Niklfeld, H., et al. & IntraBioDiv Consortium. in prep. Distribution Altas of the High-Mountain Flora of the Alps and Carpathians
42
(Tribsch et al., in press)
43
Diversity & History Diversity & History
44
Realized refugia for species only in E, S, SW
Potential refugiaPotential refugia
WWüürmrm ice sheetice sheet
WWüürmrm glaciationglaciation cetrescetres
Species diversity s.l.
45
Biogeographical evidence for refugia for floras
Summary:
AlpsSW, S, E-Alps host realized refugia for vascular plant species assemblagesNo realized refugia in Central and Northern Alps
Eurasia (see introduction)new analyses needed, but mountains and Beringiahost doubtlessly realized refugiaNo refugia north of Alps/Carpathians/Pyrenees
46
Testing hypotheses of potential refugia to discover realized refugia
-) Evidence from fossil data-) Biogeographical evidence-) Molecular Evidence
47Sotiropolos 2007, Molec.Phylogenet.Evol. Schmitt 2007, Frontiers in Zoology 4
Examples from molecular data
Refugia of Mesotriton alpestris(Salamandridae)
Refugia of Erebia epiphron
(c) Ken Willmott, www.butterfly-conservation.org© Mysliwietz Rainer,
48
Schönswetter, Stehlik, Holderegger & Tribsch 2005
Realized refugia – phylogeographical evidence in the Alps
Summary of phylogeographic data of 10 taxa of alpine vascular plants
Rumex nivalis; northern refugia(c) Ivana Stehlik
Eritrichium nanum, nunatak survivor
49
AlpsRanunculus alpestris s.l.Carex curvula
EurasiaGentiana verna s.l.Thalictrum alpinumPedicularis oederi
Study taxa & results: AFLP fingerprinting
patterns of genetic diversity (& phylogeographic patterns)
50
high variation low variationGenetic diversityindex(Nei 1972)
rare marker
Rarity index(Schönswetter & Tribsch 2005, frequency down-weighted marker values, calculated for eachpopulation)
Population 1 Population 2 Genetic patterns
AFLP marker
51
AlpsAlpsRanunculusRanunculus alpestrisalpestris s.ls.l..CarexCarex curvulacurvulaIntraBioDivIntraBioDiv--data with 40 data with 40 taxataxa (see (see GugerliGugerli et al. 2009, PPEES)et al. 2009, PPEES)
52
Carex curvula s.l.(Tribsch et al., ined.)
53
Carex curvula s.l.(Tribsch et al., ined.)
data from IntraBioDiv
diversity diversity
rarityrarity
54
Carex curvula s.l.(Tribsch et al., ined.)
rarityrarity
diversity diversity
55
RanunculusRanunculus alpestrisalpestris s.ls.l..((PaunPaun et al., et al., MolecMolec. Ecol., 2008). Ecol., 2008)
56
Ranunculus alpestris s.l.(Paun et al., Molec. Ecol. 2008)
rarityrarity
diversity diversity
57
Ranunculus alpestris s.l.(Paun et al., Molec. Ecol. 2008)
some evidence for Northern refugia
58
(Tribsch et al., in press)
59
genetic diversity & historygenetic diversity & historyIntraBioDiv data set with 40 taxa IntraBioDiv data set with 40 taxa
60
EurasiaEurasiaGentianaGentiana vernaverna s.ls.l..ThalictrumThalictrum alpinumalpinumPedicularisPedicularis oederioederi
61
GentianaGentiana vernaverna s.ls.l..(Karin (Karin MoosbruggerMoosbrugger, master thesis), master thesis)
62
GentianaGentiana vernaverna s.ls.l..(Karin (Karin MoosbruggerMoosbrugger, master thesis), master thesis)
rarityrarity
diversity diversity
63
GentianaGentiana vernaverna s.ls.l..(Karin (Karin MoosbruggerMoosbrugger, master thesis), master thesis)
64
PedicularisPedicularis oederioederi & P. & P. flammeaflammea(Tribsch et al., (Tribsch et al., inedined.).)
65
rarityrarity
diversity diversity
PedicularisPedicularis oederioederi & P. & P. flammeaflammea(Tribsch et al., (Tribsch et al., inedined.).)
66© http://www.plant-identification.co.uk/skye; © Carl Farmer
ThalictrumThalictrum alpinumalpinum(Tribsch et al., (Tribsch et al., inedined.).)
67diversity diversity
ThalictrumThalictrum alpinumalpinum(Tribsch et al., (Tribsch et al., inedined.).)
rarityrarity
68
69
?
?
?
?
?
xxx
x
?
Realized refugia in Europe of general significanceRealized refugia in Europe of general significance““NorthernNorthern”” refugia common for:refugia common for:
populations of alpine taxapopulations of alpine taxaalpine vascular plant assemblagesalpine vascular plant assemblagesboreal and/or temperate forestsboreal and/or temperate forestssteppe communities?steppe communities?
?
?
x x x
x
x ?
x
x
??
??
x
x
70
Realized refugia in Asia of general significanceRealized refugia in Asia of general significance
Arctic refugia common for:Arctic refugia common for:populations of alpine taxapopulations of alpine taxaalpine vascular plant assemblages (incomplete?)alpine vascular plant assemblages (incomplete?)boreal and/or temperate forests (highly incomplete)boreal and/or temperate forests (highly incomplete)steppe communities?steppe communities?
x
xx
xx x ??
????
????
71
The term ”refugium” should be used in a defined way, discriminating between: potential refugia and realized refugia
It has to be defined for which group(s) of organisms a refugium (species or genes/alleles) is expected or real
Refugia accumulate rare alleles but not necessarily heterozygouspopulations, therefore genetic diversity s.str. is NOT a good predictor for refugial populations
Conclusions 1
Theoretical concept of refugia in evolutionary research
72
There are molecular data that support a longterm (?) refugium in Northern Siberia and longterm refugia in Central Europe in the mountains
So far strong evidence for longterm refugia of evolutionary significance in areas north of the Alps and Carpathians are missing, e.g. in the periglacial areas of the ice sheets (exceptions may be for freshwater organisms, wetland species?)
The ’out of the European mountains’-colonisation of Northern Europe and the amphi-atlantic Arctic is a common phenomenon with many examples already published
Speciation on the diploid level appears to be restricted to refugia
Evolution of newly adapted genotypes/species (including hybrid speciation) may be more likely outside refugia, but only if refugia are reached through range expansion a successful speciation could happen
Conclusions 2significance of refugia in evolutionary research
73
How fast can populations adapt and finally speciate during migration or in isolation?
Evolve species in refugia or do they just survive there?
Is refugial survival and limitation of geneflow really enough to explain phylogeographic and genetic diversity patterns?
Is allopatric differentiation in disjunct refugia at least sometimes associated with adaptive evolution of phylogroups/sister taxa or with reticulate evolution?
How is biodiversity in refugia affected by Global Change?
Open related questions
Many thanks to:those, who have collected samples in remote placesthose, who helped to reach remote places in RussiaDorothee Ehrich (Oslo), Peter Schönswetter (Oslo & Vienna), and others from
the NCB in Oslo for discussions especially about methodological issuesVirginia Mirré (Oslo) for help in the lab (AFLPs of Pedicularis oederi)Karin Moosbrugger (Salzburg) for her enthusiasm in GentiansIntraBioDiv floristic consortium for the excellent dataOvidiu Paun and the IntraBioDiv consortium for efforts related to the
Ranunculus alpestris studyChristian Brochmann and the National Centre for Biosystematics, Natural
History Museums, University of Oslo, for providing a motivating working environment during my postdoc stay and financial support (Strategic University Programme grant 146515/420 from the Research Council of Norway)
the Austrian Science Fund (FWF, Erwin Schrödinger-Stipendium J2303-B03) and the European Commission (FP6) for financial support
SYNTHESYS (European Union-funded Integrated Infrastructure Initiative grant; TAF-798, TAF-844) for financial support for travel grants to Virginia Mirre and Andreas Tribsch
