Evolution and Climate Change
Robin Allaby

Aim of lecture
• To provide a temporal dimension to understanding biodiversity
• To see biodiversity as the result of the history of the changing biosphere
• To understand how biota cope when change happens

Lecture outline
• How the bioshphere as changed over the long term
• How organisms have adapted: mass extinctions and radiations
• Some long term evolutionary adaptations – the leaf
• More recent biosphere change – the last glaciation
• Biodiversity is a result of recent (and ancient) environmental change
• Refugia
• Some examples.

Biodiversity then and now
Current global biodiversity glacial maximum

Palaeontological record

The 5 mass extinctions
There have been lots of mass extinctions, but we usually just think of the 5 biggest ones.
They occur at era boundaries

Ordovician extinction

Devonian extinction

Permian extinction (the big one)

Triassic extinction

Cretaceous extinction

Mass extinction causes
1. Ordovician Ice age (unknown)
2. Devonian Ice age (biotic probably)
3. Permian Global warming (unknown cause)
4. Triassic Global warming (volcanic activity possibly)
5. Cretaceous Asteroid impact (ouch)

What types of organism did mass extinctions wipe out?
• Large organisms (e.g. dinosaurs)
• Specialized organisms (e.g. climax community of Carboniferous forests, such as lycopod trees Lepidodendron; e.g. no entirely carnivorous or herbivorous fauna after the
Cretaceous event)

Radiations followed extinctions

Possible responses to stress induced by environmental change
• Reduce fecundity:
– ensure better chance of survival for offspring e.g. Parus major (Boyce &
Perrin 1987 Ecology 68:142-153), but at a cost in good environments.
– Reduce metabolism: reduces resources needed good for drought or toxic environments, increases longevity, decreases fecundity (Hoffmann & Parsons
1989 Biol. J. Linn. Soc. 37 117-36)
• Increase dormancy
( Cohen 1966 J. Theor. Biol 12:119-29)
• Saltatory change;
– e.g. retrotransposon activity (McClintock 1984 Science 226:792-801),
– single genes (Macnair 1991 Genetica 84:213-9)
– developmental genes (Markow 1995 Ann. Rev. Ecol. Syst. 40:105-120)

First land plants 480-360Mya
• cuticles & stomata
• archegonium & sporopollenin walled spores
• vascular systems
Circa 415 Mya Cooksonia paranensis (Gerrienne et al 2006)

Oldest seed plant by 385Mya salpinx megasporangium
Integument does not fully enclose ovule
Runcaria heinzelinii (Gerrienne et al 2004)

The late arrival of leaves by 360 Mya – end of Devonian
Leaf evolution associated with falling CO
2 levels (first plants evolved in a CO
2 rich atmosphere)
(Beerling 2005)

Ficus sp.
Leaf morphology indicates climate
Asimina sp.
Campsis sp.
Fraxinus sp.
(JA Wolfe 1990 Nature 343:153)
Acacia sp.

Climate Change since the Tertiary

The current Ice Age

Current Ice Age: Pleistocene -
Holocene

The end of the Devensian

Late glacial extinctions of megafauna
Hofreiter and Stewart 2009 Current Biology 19:R584-94

Holocene temperature variation

glacial and post-glacial refugia

Postglacial refugia – sky islands
Melanoplus oregonensis
Knowles & Richards 2005
Mol. Ecol. 14:4023-4032

Biodiversity seen through the postglacial transition
Hewitt 2000 Nature
405:907-913

Mitochondrial gene tree for UK bats
Barbastelle
Brandt’s
Whiskered
Natterer’s
Greater Mouse Eared
Bechstein’s
Daubenton’s
Brown Long Eared
Grey Long Eared
Serotine
Common Noctule
Lesser Noctule
Nathusius’ Pipistrelle
Soprano Pipistrelle
Common Pipistrelle
Lesser horseshoe bat
Greater horseshoe bat

Pipistrelles come in two flavours
Barratt et al 1997 Nature 387:139

UK Pipistrellus genus is a result of postglacial expansion

Brown bear recolonization
Barnes et al 2002 Science 295:2267-70
Ancient DNA shows that bears did NOT recolonate from southern refugia, but came from
Siberia (discovery of cryptic refugia) - we can distinguish what would otherwise look like similar bone remains.

Brown bears in Europe
Pleistocene Iberian bears moved to Italy, and Pleistocene Italian bears moved to
Iberia!
Complex movements revealed.
Valdiosera et al 2008 Proc. Natl. Acad. Sci.
USA 105:5123-5128

Arctic foxes did not contract with glaciers
Dalén et al 2007 Proc. Natl.
Acad. Sci USA 104:6726-9