Workshop on “Invasive exotic species”
B
Bozen,
December
D
b 14th 2010
Alien and native plants
respond differently to human and
climatic pressures
L
Lorenzo
Marini
M i i
DAAPV, University of Padova
Co-authors:
Andrea Battisti, Alessio Bertolli, Enzo
Bona Germano Federici,
Bona,
Federici Kevin Gaston,
Gaston
Phil Hulme, Fabrizio Martini, Filippo
Prosser
Alien plant invasions in the Alps
● Alien plant invasions are recognized as a
major driver of biodiversity decline and
altered
lt
d ecosystem
t
services
i
worldwide
ld id
● Most studies of invasive alien species have
concentrated on lower elevations, with little
attention being directed to the most pristine
hi h l
high-elevation
ti
environments
i
t
● Relative isolation and harsh climatic
conditions may have allowed mountain
ecosystems to experience lower levels of alien
species invasions than have lowland areas
BUT
Something has changed
The constraining factors for invasion are now changing due
to globalization and climate change, increasing the chances of
plant invasions into high-elevation environments
CLIMATE CHANGE
LAND-USE CHANGE
Climate change
Increased temperature along the elevation gradients
Relaxation of
minimum temperature
constraints
Optimum elevation shifts for native species
Upward shift
Lenoir et al. (2008) Science
Published by AAAS
Climate change and alien plants
Elevatio
on optim
mum
Will alien plant species respond similarly?
Potential elevation
optimum
Realized elevation
optimum
Dispersal
p
limitation:
Time lags in tracking
climate change
(immigration credit)
Species B
Species A
Species temperature
requirements
Is current alien species
distribution more
related to propagule
pressures or climatic
constraints?
Land--use change dynamics
Land
Main processes
Ellevation (m)
Forest expansion
2000
Urbanization
500
0
Elevation-dependence of land use changes
Urbanization and alien plants
Alien spe
A
ecies richness
Will alien and native plant species respond similarly?
Alien
?
Native
Urbanization
Human population
Increased disturbance
and movement of people
Increased available niches and
propagule pressures
Research aim
i) We tested whether the drivers of species richness patterns
differ between native and alien plants
ii) We examine the responsiveness of alien and native plant
life-forms to human and climatic pressures
Try to disentangle the effects of climatic and human
pressures on the invasion of exotic plant in the Alps to
make
k predictions
di ti
off global
l b l change
h
effects
ff t
Methods: data
Study area: NE of Italy
36
km2
Species richness
Floristic inventories of provinces of TN, BS and BG
Elevational patterns of species richness
Natives
Aliens
Drivers:
Drivers:
Population density
Temperature
Calcareous bedrock
p g p
heterogeneity
g
y
Topographic
Population density
Temperature
Marini et al. (2008) Journal of Biogeography
Marini et al. (2010) Journal of Biogeography
Species--human
Species
human--energy relationships
N ti
Natives
Aliens
Different shapes of the
relationships
Natives
Aliens
The level of invasion
drastically increased both with
temperature and humans
Coincidence between areas
with large native extinctions
and large alien invasions
Marini et al. (2009) Global Ecology and Biogeography
Differential response of aliens and natives
Two complementary hypotheses:
i) Different composition life
life-history
history traits among alien and native species
pool alter species richness response to human and climatic factors
ii) Overwhelming effect of human pressures on alien species richness
which can mask any life-history trait effect mediating response to the
environment
The low altitude filter effect (Becker et al. 2005)
We tested if plant life-form modifies the species richness
response to temperature and humans
Marini et al. (submitted)
Plant lifelife-forms
Structures to survive during adverse season
Perennial herbaceous
Annuals
Trees
Phanerophytes
Hemicryptophytes
Geophytes
Therophytes
We know that different life-forms present typical response to
t
temperature
t
along
l
elevational
l
ti
l gradients
di t
Expected results
Temperature x Life-form (native)=Temperature x Life-form (alien)
Different composition of life-history traits among alien and native plants
alters
lt
species
i richness
i h
response tto h
human and
d climatic
li ti ffactors
t
Aliens=187
Natives=2301
Diffe ent life-form
Different
life fo m spectra
spe t a
Temperature x Life-form (native)≠Temperature x Life-form (alien)
An overwhelming
g effect of human p
pressures on alien species
p
richness can
mask any life-history trait effect mediating response to the environment
Species--temperature relationship
Species
Species riichness
S
N ti
Natives
Aliens
Native≠Alien
Mean annual temperature (°C)
Species--human relationship
Species
Species riichness
S
N ti
Natives
Aliens
Native≠Alien
Log(Human population)
Separate elevation belts
We remove the correlation
between temperature and
humans
We tested human x lifelife-form within subsets of cells with the
same temperature
t
t
Separate elevation belts
Tre
ees
Sta
andardized
d species riichness
Annuals
s
Perennial herbaceou
P
us
Aliens
Natives
Log(Human population)
Conclusions
● Alien species richness was higher in areas with the most rich and
diverse assemblages of native species
● Annual
A
l natives
ti
and
d all
ll aliens
li
will
ill b
be th
the winners,
i
native
ti
tree
t
and
d
perennial species will be the losers
● Native species richness showed complex responses to both human
population and temperature suggesting that life-form modifies the
sensitivity of native species to environmental changes
● Human pressures are the main drivers of alien plant invasions and
climatic conditions seem to have smaller direct effect on the CURRENT
distribution of alien species richness (no life-form effect)
● Current distributions of alien species and also certain native species
may reflect dispersal limitation rather than climatic limits and may exhibit
only limited tracking of future climate
..but we are probably accumulating an invasion credit
Future scenarios
An increased upwards movement of human activities such as agriculture
and urban development is expected under current global warming
Lev
vel of invasio
on (%)
70
60
Current
50
Future
In the short term we expect strong
biotic homogenization at low- and
mid-elevations and small changes at
hi h elevations
high
l
ti
40
30
20
In the long-term we will probably
cash the accumulated invasion credit
10
0
0
1000
2000
3000
Elevation (m)
Plantt conservation
Pl
ti agenda
d should
h ld probably
b bl ffocus more on llandd
use change effect than on climate change effect
Thank you for your attention
PRATIQUE information
i f
ti
https://secure.fera.defra.gov.uk/pratique/
Data owners:
Alessio Bertolli, Enzo Bona, Germano
Federici, Fabrizio Martini, Filippo Prosser
Contact details:
Lorenzo Marini, PhD http://www.biodiversity-lorenzomarini.eu/
E-mail: lorenzo.marini@unipd.it