Location, Location, Location: Location, Location, Location: Laboratory Experiment Shows Laboratory Experiment Shows Invasive Invasive P. insularum P. insularum Choose Choose

Elephant Ear as Oviposition SitesElephant Ear as Oviposition Sites

Colin H. Kyle, James P. McDonough and Romi L. Colin H. Kyle, James P. McDonough and Romi L. Burks, Burks,

Biology Department, Southwestern University, Biology Department, Southwestern University, Georgetown, TX. Georgetown, TX.

Process of InvasionTransported to New Area

Establish Reproducing Population

Spread to other areas

Ecological Impact Adapted from Sakai et al. 2001

Exotic

Invasive

Exotic Invasive Species:Global Threat on Many

FrontsBiological– Compete with native species– Reduce native biodiversity

Economic– EIS cost $120B in US alone –

Pimentel et al. 2005– $9B on aquatic EIS

Political– Legal issues about regulations

Social– Harmful to humans– Cost taxpayer money to control

Focus: Pomacea insularum• Native to temperate S. America• Established in bayous of

Houston• Threatens Gulf Coast

ecosystems (FL, GA)

•Closely related to P. canaliculata•Large size •Voracious consumer•High fecundity

What to do about the snails?

Transported to New Area

Establish Reproducing Population

Spread to other areas

Ecological Impact

P. insularum Currently

Long Term Implications of Research•Prevent Spread•Limit Ecological Impact

Introduced through the aquarium industry

The Source of the Problem

• Limit reproduction – control population growth

• Each clutch contains up to 4500 eggs (mean = 2064 eggs)

• Clutches hatch in 14 – 21 days

• Removing egg clutches before they can hatch

• Simple and undamaging to the environment

Finding the Eggs

• Determine where the snails will most likely oviposit

• Understand egg laying (oviposition) behavior and activity

Research Questions1. Does P. insularum show preferences

for the type of surface on which they lay eggs?

2. What behavior does P. insularum exhibit when reproducing?

Question 1 Methods

• Presented snails with 4 different surface types on which to oviposit– Elephant Ear stalk– Wood– Metal– Astroturf

• Astroturf possible control mechanism

• Poles of 1.9 cm diameter

• Recorded the number of clutches laid on each surface type

Elephant ear(Colocasia esculenta)

Question 1 Methods•Constructed a tank system to contain snails for experiment•12 microenvironments, each containing 2 female snails and 1 male•Deterred snails from ovipositing on the tank walls using water •Maintained for approximately 3 weeks•Analyzed preference using a Chi-Squared test

Microhabitat

Question 1 Results

•No clutches occurred on metal and Astroturf structures

•Significantly more clutches laid on elephant ear (chi-square, p<0.01) compared to other substrates.

Question 2 Methods

• Recorded location of each snail 3 times a day– Floor– Pole– Lettuce– Box– Wall

• Grouped different pole and box types

• Analyzed results using a Chi-Squared test

Pole

Box

Wall

Lettuce

Floor

Question 2 Results

• Significant difference in percentage of time spent by snails on different locations within the tanks (chi-square, p<0.001).

•Snails observed most either feeding on the lettuce or hanging onto the sides of the tanks.

Discussion of Results• Females preferred to lay their clutches on the

elephant ear more than on any other structure.• The use of Astroturf or metal as control

mechanisms in nature would be ineffective.• Snails observed significantly more either on

the walls of the tank or feeding on lettuce • Suggests that snails spend most time feeding

and searching banks for potential egg-laying surfaces than resting on the floor or boxes.

Results Mimic Field Observations

• Most clutches in field observed on elephant ear plants.

• Snails found in the field at the base of elephant ear stalks.

Conclusion• We now understand that P.

insularum egg clutches will more likely be found in stands of elephant ear than any other structure around their habitat.

• In future P. insularum invasions, removing egg clutches from plants near the banks should be an effective way of slowing their population growth.

Transported to New Area

Establish Reproducing Population

Spread to other areas

Ecological Impact

Acknowledgements• Texas Academy of Science• Southwestern University

(Funding)

• Dr. Burks (Advisor)

• Mark Kramer and George Regmond (Armand Bayou)

• James McDonough(Research Partner)

• Sarah Hensley (Current Research Student)

• Matt Barnes (Former Research Student)

• Abby Youens(Former Research Student)

• Brandon Boland(Former Research Student)