The importance of models —dynamics of extinction and their drivers from the Miocene to the last 40 years

Liliana M. Dávalos

National Science Foundation15 July 2016

!

Who am I? Evolution & Conservation

Our research mission

Biological diversityDiversification Extinction

Focus first part

Biological diversity

Colonization, speciation Extinctionincrease decrease

The debate: equilibrium

• Spp. richness ~ resource abundance

• Long-term spp. richness stable

• Diversity dynamics follow predictable course after perturbation

The debate: disequilibrium

• Communities are unsaturated

• Disturbance prevents communities from reaching equilibria

• Dispersal limitation slows reaching equilibrium

Elements of the equilibrium model MacArthur & Wilson 1963 Evolution

Most common application

Morgan & Woods 1986 Biol. J. Linnean Soc.

Extended application Dávalos & Russell 2012 Ecol. Evol.

Change in habitat ~ change in spp. Dávalos & Russell 2012 Ecol. Evol.

But larger Greater Antilles < spp. than expected Dávalos & Russell 2012 Ecol. Evol.

But what about the dynamics over time? Rabosky & Hurlbert 2015 Am. Nat.

Phylogenies and equilibrium

• Test of MW evolutionary equilibrium dynamics using phylogenies

Ricklefs & Bermingham 2001 Science

A model including speciation Valente et al. 2015 Ecol. Lett.

Key findings from model comparison

• Disequilibrium in most bird groups

• Tendency to equilibrium in Darwin’s finches

• Diversity-dependent

• Together, community dynamics are non-equilibrial

Valente et al. 2015 Ecol. Lett.

Rojas et al. 2016 Syst. Biol.

Rojas et al. 2016 Syst. Biol.

Figure 2

Ametrida Sphaeronycteris Centurio Pygoderma Ardops Ariteus Phyllops

† Phyllops silvai† Phyllops vetus

Stenoderma † Cubanycteris silvai

Artibeus (Artibeus)

† Artibeus anthonyiArtibeus (Koopmania)

Artibeus (Dermanura)

Ectophylla Enchisthenes Chiroderma Vampyressa (Vampyriscus)

Vampyressa (Metavampyressa)

Mesophylla

Vampyressa (Vampyressa)

Platyrrhinus Vampyrodes Uroderma

12 10 8 6 4 2 0

Mil l ion years before present

S A

M2.83

1.780.28

0.12

2.60

1.02

Founder-event dispersal(20% of cladogenetic events)

S A

M

1.13

0.32

6.465.04 0.68

0.73

Anagenetic dispersal(33% of cladogenetic events)

Miocene Pliocene

Tavares et al. in prep.

How old are the Greater Antilles? 35 Ma?

Iturralde-Vinent & MacPhee 1999 Bull. Am. Mus. Nat. Hist

Input data on Greater Antillean bats Valente, Etienne, Dávalos in review

Equilibrium dynamics! Valente, Etienne, Dávalos in review

Age Ma

λc μ γ λa

20 0.28 0.33 0.030 0.1945 0.32 0.41 0.036 0.16

What happens if no fossils? Valente, Etienne, Dávalos in review

Age Ma

λc μ γ λa

20 0.22 0.26 0.017 0.2745 0.26 0.35 0.021 0.27

Why are so many bats extinct? Climate? Humans?

It’s looking more and more like humans Stoetzel et al. 2016 Quat. Sci. Rev.

0 10 20 30 40

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How long to restore the species? Valente, Etienne, Dávalos in review

Conclusions part I

• First proposed in the 1960s, some evolutionary aspects of equilibrium theory can only be tested now

• Using phylogenies

• Longstanding questions remain to be answered, e.g.,

• is diversity predictable?

• relative contribution biotic vs. abiotic factors

Photo by Jon Flanders

More conclusions part I

• Need to include extinct species

• Underestimate extinction rate (obvious)

• Underestimate immigration rate (less obvious)

• Human effects large

• Long time to recovery

• Habitat change probably important Dávalos & Russell 2012 Ecol. Evol.

Focus second part

Biological diversity

Colonization, speciation

Land use changeincrease decrease

When the UN comes knocking The Special Session of 2016

But illicit crops are everywherePrevious focus on

Colombia

Why tropical deforestation? I

• 2 models

• Immiserization:

• poor growers bring marginal land into production

• external shocks (e.g., debt crisis)

• internal dynamics (e.g., demographic growth)

Rudel & Roper 1997 World Dev.

Why tropical deforestation? II

• Frontier:

• investors/government build roads

• roads bring colonization

• colonists clear land

• frontier stabilizes (development),

• or recedes (hollow frontier)

Rudel & Roper 1997 World Dev.

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Figure 2

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The closing of the forest frontier

• An example from Guaviare, Colombia

• Forest declines, pastures increase

• Forest fragments become smaller and more isolated

• New stable equilibrium loses forest almost completely

Dávalos et al. 2014 Biol. Cons.

Where do illicit crops grow?

• In 2000s Colombia

• Correspond to forest frontier

• Interface between settled land and forests

• Spatially clustered

Dávalos et al. 2011 Environ. Sci. Technol.

What happened in the 1960s? Etter et al. 2006 J. Environ. Manage.

Opening the frontier Denevan 1966 Geogr. Rev.

Roads and colonization projects

Brücher 1977 Geogr. Z. Schuurman 1978 Tijdschr. Econ. Soc. Ge.

Brazil

Bolivia

Peru

Colombia

Ecuador

Coca cultivation

Government-sponsored

before 1979

1990/1992

Projects

Coca cultivation

High

Low

2014

Percent forest Probability of coca

a b c

A remarkable spatial pattern

Dávalos, Sanchez, Armenteras in revision

Brazil

Bolivia

Peru

Colombia

Ecuador

Coca cultivation

Government-sponsored

before 1979

1990/1992

Projects

Coca cultivation

Percent forest

a b

Location of projects ~ C emissions Harris et al. 2012 Science

Coca cultivation

High

Low

2014

Percent forestHigh

Low

Probability of coca

b c

Is coca spatially clustered around projects? Dávalos, Sanchez, Armenteras in revision

High

Low

Probability of coca

c

~40 years later, Amazonia coca remains clustered Dávalos, Sanchez, Armenteras in revision

Parameter 2.5 Mean 97.5Intercept -1.2671 -1.1540 -1.0410Distance to nearest project

-0.6096 -0.5613 -0.5129

Precision municipality intercept

1.116 1.4582 1.910

Precision spatial

0.243 0.5211 1.079

Coca is spatially associated with the frontier UNODC 2016

Can coca explain some deforestation?

• Three independent studies say no

• Dávalos et al. 2011 Environ. Sci. Technol. no effect after including social factors

• Armenteras et al. 2013 Reg. Environ. Change no effect of coca in Amazon

• Sánchez-Cuervo et al. 2013 Ecosystems no effect any time or place Photo by Ana Luz Porzecanski

No relationship coca cultivation ~ deforestation

ratesUnpublished

Conclusions part II

• Actions from 4 decades ago have large effects

• Brought colonists to the Amazon

• Farmers turned to coca

• Landscapes transform following roads

• End point often minimal forest

Photo by OSITRAN, Peru

More conclusions part II

• Spatial patterns misleading without history

• History illuminates the opening of the frontier

• Frontier deforestation can be connected to poverty

• But actually requires investment, e.g.,

• Roads

• Development projects

Thanks!