Biological Invasions and Herpetology 4/18/13 Chris Thawley
What are some invasive species? http://news.discovery.com/animals/videos/animals-jumping-carp-attack-explained.htm
What is an Invasive species? Outside its native range Transported by humans Destructive? Detrimental? Exotic? Non-native? Alien?
Why do we care? Economic consequences: >$120 BILLION/year Agriculture, forestry, healthcare, fisheries Cost of control Ecological consequences: 2 nd leading threat to biodiversity Capable of disrupting whole communities
Case Study: Burmese Python Native to SE Asia Introduced to S. Florida and ENP Probably due to Hurricane Andrew Expanding population
Python Effects on Community Find lots of incidental past datasets to study effects No one was looking to study effects before they knew about problem!
Burmese Pythons in FL Pythons tracked via radiotransmitter Found with dogs and on roads Very difficult to count/study in ENP
Python Patterns
A little more complexity Rodents may decline due to python predation BUT may prosper due to removal of predators Pythons kept in check in native range by predation Prospects in FL?
Common Characteristics of Invasive Species Generalists Quick reproduction/generation time Lots of offspring Mature quickly Less related to native taxa (Strauss et al 2006) Aggressive competitors Disperse easily
Which groups of herps might be most invasive and why?
How do Invasions Spread? Stowaways Cargo Vehicles People Ballast Water Feces Pet Trade Biocontrol Agents Deliberate Introduction
Difficulties Facing Invaders Many factors working against successful invasions Low density Hard to find mate Stochastic effects Low genetic diversity Bottleneck Inbreeding http://eattheinvaders.org/
Brown Anole Case Study Jason Kolbe (Kolbe et al 2004) Brown anole invasion of SE US
Brown Anole Invasion Native to Caribbean Generalist Lizard Relative of Green Anole More aggressive/larger Displace native anoles
Invasive Range Brown Anole Spread More variation within populations Alleles from different areas of the native range mixed in invasive range Newer invasion sites have higher diversity
Controlling/Managing Invasions Often nearly impossible People may want invaders Killing/removing very difficult By the time presence noticed, may be too late
Brown Tree Snake Case Study Native to Australia and Pacific islands Introduced to Guam via airplane during WWII One native snake:
Brown Tree Snakes on Guam 1950 s First detection 1968 Occupies island Late 1960 s Bird declines begin 1984 Most native birds extinct
Total Annihilation
Attempts to Control Populations
More Management
Areas Vulnerable to Invasions Islands Hawaii Caribbean Guam Disturbed Habitats S. Florida Why? Fewer Competitors Unfilled Niches Less chance native species will be preadapted Temperate climate Propagule pressure
Invasion as an Opportunity Each One Is An Incredibly Large, Unethical Experiment
Why do Invasions Succeed? Niche The biotic and abiotic conditions under which an organism can survive and reproduce Ecological Release The removal of a previously limiting condition which allows a population to grow larger/faster or expand its niche
Predicting Invasions Species distributions determined by: Physiography Climate Geographic barriers Ecology Long time-scale historical processes
Predicting Invasions Kolbe et al 2004??? Invasive species distributions also determined by:?? Location and number of introductions Vectors Dispersal time Genetic diversity Adaptation
Context Problem: Invasions depend on complex factors which may make predictions difficult Case Study Two species of anurans in Cuba and SE U.S. Source population is important Use ENMs to generate predictions of suitable habitat and ID source populations Use phylogeographic methods to identify source populations and patterns of diversity
Cuban Treefrog Osteopilus septentrionalis Native to Cuba, Caymans, and Bahamas Invasive in FL, Caribbean Often associated with human activity Major threat to native treefrogs James Harding
Greenhouse Frog Eleutherodactylus planirostris Native to Cuba Invasive in Coastal Plain, Caribbean, Hawai i, Guam Threat level probably low Often transported via nursery plants James Harding
E. planirostris - Invasion History in US 1964 1944 1939 1910 1875 1889 Georgia Savannah - 1998 Brunswick Co. 1998 Thomasville/Valdosta - 2007 Alabama Mobile 1982 Mississippi - 2004 Louisiana SE 1975 Hawai i 1999 Guam - 2003
Creating an ENM -Select environmental layers Precipitation Temperature -Add point locality data (GPS, NHC, etc.) -Run modelling process (Maxent, etc.)
Maxent A machine-learning algorithm working on the principle of maximum entropy Essentially a maximum likelihood approach to modelling a niche Output: a continuous probability surface representing probability of occurrence/habitat suitability
ENM Construction Point locality data from field collections and online databases (GBIF, Herpnet) BioClim environmental layers 10 variables representing temperature and water availability Models created in Maxent with native or invasive locality data and trained over the extent of the southeastern U.S. and Cuba
O. septentrionalis Invasive Range Model 0.1612
E. planirostris Invasive Range Model 0.1612
Sequencing Overview O. septentrionalis 600 bp sequence of cyt b 38 locations in Cuba and Florida 66 individuals E. planirostris 700 bp sequence of cyt b 31 locations in Coastal Plain 69 individuals Native range data from Heinicke et al 2011
Sequencing O. septentrionalis 2 lineages 24 total haplotypes 8 in FL 5 unique to FL Pairwise divergence 2.9% - FL 1% - W. Cuba 1.7% - Mainland Cuba 2 introductions
Sequencing E. planirostris 4 lineages in Cuba 2 lineages in SE US 5 haplotypes in SE US Pairwise divergence 0.3 1.1% across Cuba 0.3% - SE US 2 introductions Heinicke et al 2011
Source Populations O. septentrionalis
Source Populations E. planirostris
Results Summary Both species show phylogenetic structure in native but not invasive ranges Both methods identify the same source populations Source populations are in the north of Cuba and close to Havana, suggesting that human trade may be a vector
Future Spread? E. planirostris seems to be approaching northern limit of range but may become continuous across the southern Gulf Coast O. septentrionalis may continue expanding northward along Atlantic Coast, but spread along the Gulf Coast seems limited Is adaptation taking place?
Is Physiological Adaptation Occurring? A A B C B C A B C Physiology Thawley, Unpublished Data
Invasion and Climate Change 2009
Predicted Range of Burmese Pythons (2100) (Current/2010)
Cane Toad Invasion and Evolution Introduced intentionally in 1935 Biocontrol of cane beetle Huge effect on many animals in Oz Uneradicable
Evolution of Predators
Evolution of Cane Toads Physiology Dispersal Morphology Phillips et al 2006 Older populations have shorter legs Invasion has sped up
Evolution of Cane Toads Spatial Sorting Shine et al 2011
Red Imported Fire Ant Invasion Predicted to occupy >50% of Earth s surface Major human and agricultural pest Introduced in Mobile, AL in 1920s Significant threat to native species Alex Wild alexanderwild.com
Fence Lizard/Fire Ant System Both predator and prey of lizards Do not alter habitat use in presence of fire ants
Fence Lizard/Fire Ant System Behavior mediates survival via anti-predator adaptations Uninvaded Lizards Freeze response to predators Invaded Lizards Increase in flee behaviors Increase in hind limb length Juvenile Lizards Act like invaded Langkilde, 2009, Ecology
Fence Lizard/Fire Ant System Behavior mediates survival via anti-predator adaptations Invaded Lizards Increase in twitch behaviors Removes ants BUT Predators such as birds and snakes? Langkilde, 2009, Ecology
Research Questions How do fire ants exert pressure on fence lizard populations? Direct Effects: Predation Indirect Effects: Growth, Body Condition, Behavioral Changes
Treatments Adults vs. Juveniles Vulnerability to venom Prey differences Behavior Invaded vs. Uninvaded populations Fire ant Presence vs. Absence
Enclosures 520 m 2, Aluminum flashing Supplemental cover/perch objects Natural habitat, plenty of food
Experimental Setup Transplant juvenile and adult lizards 6 sites 2 weeks in paired enclosures Fire ants removed from two enclosures Lizards observed daily for survival No Fire Ants Inv n=10 Inv n=10 Fire Ants UnInv n=10 UnInv n=10 N=240
Survival Summary of Exps Daily observations parametric survival analysis Body Cond/Growth Measure SVL and Mass before and after enclosures Body Condition
Results Survival Analysis - Juveniles Uninvaded lizards have significantly lower survival
Results Survival Analysis - Adults Fire ants decrease survival in adults Difference based on origin?
Survival Conclusions No difference in absolute survival between adults and juveniles Juveniles Effect of Origin Adults FA cause mortality Origin effect?
Growth/Body Condition Differences in Mass, SVL, and Body Condition GLMs Body Condition as residuals from OLS regression of lntransformed values Before placement in enclosures Juveniles Lower size and body condition at uninvaded sites Adults No differences No differences by sex No differences for survival
Results-Growth-Juveniles Juveniles in FA enclosures grow less A B B C Lower mass and SVL gain in FA enclosures A AB AB B Mass: FA: F=15.392, p<0.001 Inv: F=21.329, p<0.001 SVL: FA: F=15.229, p<0.001 Inv: F=10.312, p=0.002
Results-Growth-Adults Interaction effect for Mass Difference No change in SVL (no surprise) Mass: FA*Inv: F=7.275, p=0.011 SVL: NS
Results-Body Condition Adults Interaction effect for difference in body condition Juveniles No sig effect Body Condition Difference: FA*Inv: F=5.434, p=0.025
Immediate vs. Delayed Consequences Predation Trade-offs: Adults: Avoidance behaviors alter susceptibility to different predators Juveniles: avoiding fire ant consumption reduces envenomation and energy intake Body Condition: Overwintering Survival Reproductive Output
Conclusions FA cause increased mortality in adult lizards FA reduce body condition in juvenile lizards May recover quickly in non- FA environment Interaction between origin and FA in adults Escape behavior: exposed to predation? Change in diet?
Arthropod surveys Does prey community vary with FA presence? Fecal samples Do lizards eat FA and how many? Future Work Do lizards eat more/ less in presence of FA? Extensions: Stress Population modeling Epigenetics