Niche models of invasive seaweed
species: predicting spread and areas
at risk of suffering blooms
Heroen Verbruggen, Klaas Pauly, Lennert Tyberghein
Ghent University, Belgium
Frédéric Mineur, Christine Maggs
Queen’s University, Belfast
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Marine macroalgae: seaweeds
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Invasive nature
• Beijing olympics:
Qingdao green tide
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Introduced and invasive macroalgae
macroalgal dispersal potential
hull fouling
estimated mean dispersal distance
based on genetic isolation-by-distance slopes
Kinlan & Gaines (2003) Ecology 84: 2007-2020
wakame
→ 277 introduced macroalgal species reported in literature
Williams & Smith (2007) Annu. Rev. Ecol. Evol. Syst. 38: 327-359
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
oyster farming
Ecological niche modeling
Definition
characterization of associations between environmental variables
and known species’ occurrence localities to define abiotic conditions
within which populations can be maintained
Distinction
ENM ↔ SDM (species distribution modeling)
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Niche models for invasion biology
• retroactive: niche models of introduced species
– predict spread (expected distribution range) in region where it
has been introduced
– caveat: occurrence data must be taken from the distribution of a
species in equilibrium
– generate model of introduced species from its native range and
extrapolate to the region of interest
• proactive: niche models to inform legislature
– identify species that are likely to be successful invaders
– identify high risk source countries or ecoregions
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Case studies
• Codium fragile ssp. fragile
native in Japan
introduced in many places
first observation in Europe 1845
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Case studies
• Sargassum muticum
native in Japan, Korea, Yellow Sea
introduced in many places
first observation in Europe 1971
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Case studies
• Caulerpa racemosa var. cylindracea
native in SW Australia
introduced in Mediterranean Sea
first observation in Europe 1990
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Datasets: sampling localities
Codium fragile ssp. fragile: 11
Sargassum muticum: 54
Caulerpa racemosa var. cylindracea: 5
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Datasets: macroecological data
AquaMODIS
SeaWiFS
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Datasets: macroecological data
• layers derived from satellite imagery
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CHL
PAR
SST
DA
CAL
ED
chlorophyll A: proxy for nutrient status
photosynthetically active radiation
sea surface temperature
diffuse attenuation
calcite
euphotic depth
yearly average
minimum month
maximum month
CHL
PAR
SST
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Modeling algorithm: maxent
Maximum Entropy (maxent)
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Gibbs
distribution
f
weight
feature
linear
env. var.
f
quadratic
env. var.
f
hinge
env. var.
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
f
threshold
env. var.
Modeling algorithm: quality assessment
use thresholds
0.80
receiver operating characteristic
0.70
contingency
table
fraction correctly predicted
(true positive rate)
0.75
ROC
AUC
area under the curve
(false positive rate)
fraction of predicted sites
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Codium fragile ssp. fragile
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Codium fragile ssp. fragile
ROC curves
AUCtrain = 0.989
AUCtest = 0.987
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Codium fragile ssp. fragile
ROC curves
– training
– test
AUCtrain = 0.989
AUCtest = 0.987
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Codium fragile ssp. fragile
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Codium fragile ssp. fragile
– training
– INVASIVE
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Sargassum muticum
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Sargassum muticum
– training
– INVASIVE
AUCtrain = 0.992
AUCinvas = 0.995
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Sargassum muticum
1. Moroccon coast
2. Bay of Genoa
3. Baltic Sea
3
2
1
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Caulerpa racemosa v. cylindracea
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Caulerpa racemosa v. cylindracea
– training
– INVASIVE
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Caulerpa racemosa v. cylindracea
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Caulerpa racemosa v. cylindracea
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Model for Caulerpa racemosa v. cylindracea
– training
– INVASIVE
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Conclusions and perspectives
• plusses and minuses
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ENM in marine environment at global scale
very good model performance for marine macroalgae
macroecological tolerances of organisms
perform risk assessment for management of introduced species
aliens at home (thanks to Satoshi Shimada)
macroecological data limited
intrinsic modeling limitations
identify high-risk source regions
evolutionary pathway
climate change
ocean acidification
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
Coming up ...
High risk source regions for the British Isles
AL-BC
CT-NS
S Chile
N Japan
YS
S Arg
Thanks to FWO, Satoshi Shimada, AlgaeBase
Niche models of invasive seaweed species ― Heroen Verbruggen ― VLIZ 2009
S NZ