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Burmese Python Invasion Risk:
Bioclimatic and Physiological Models
Burmese Python, Python
molurus bivittatus
● Generalist snakes native to
Southern Asia
● Established in Southern Florida
via pet trade
● Great concern in the Everglades
○ 31 species at risk due to
python predation
Species Distribution
Two Models of Invasion Risk
Bioclimatic Envelope Model- uses
empirical data about species distribution to
inform model.
Physiological Model - uses empirical data
about a species’ physiological tolerance to
inform model.
Bioclimatic Models: Individual Suitability Maps
*
Annual Mean Temp.
Range: 19.6 - 24.5 C
Combined Quarterly Rainfall
Range: 124-661 mm
Bioclimatic Model: Combination of Annual Mean
Temperature and Precipitation
Weaknesses of Bioclimatic Models
● Doesn’t take into consideration:
○ biotic interactions
○ physiological limitations
○ evolutionary change
○ dispersal ability
● Invasive species are still spreading
○ not necessarily at equilibrium with their environment!
● Current distributions are not reliable in predicting future risk.
Literature Review: Dorcas et al.
● Monitored 10 wild-captured pythons
● Recorded air temp, water temp,
underground refuge temp
● Observed deaths during cold winter
temps
● Avg. min. temperature at death: 7.65 c
Physiological Model
Min Jan Temp
> 7.65
Weaknesses of Physiological Models
● Small samples sizes of studies
● Flawed experimental design (done on
captive snakes, etc.)
● Limited data
So...which is the optimal model?
Neither!
Ideal: integrated model including physiological
limitations, climatic of invaded and native
range, interactions, adaptations and dispersal
ability.
Sources
http://www.evergladeshub.com/lit/pdf09/Rodda09BioInvas-103-PythoNorth.pdf
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1859&context=icwdm_usdanwrc&seiredir=1&referer=http%3A%2F%2Fscholar.google.com%2Fscholar%3Fq%3Dburmese%2Bpython%2Bi
nvasive%26btnG%3D%26hl%3Den%26as_sdt%3D0%252C22#search=%22burmese%20python%20i
nvasive%22
http://usark.org/wp-content/uploads/2012/05/Cold%20pythons%20(2).pdf
http://link.springer.com/article/10.1007/s10530-010-9797-5/fulltext.html
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002931
Questions?