The spatial distribution of egg masses of the apple snail, Pomacea flagellata in a neotropical marsh (2008)

Undergraduates: Charlene Mangi, Kaity Mattos, Washington University in St. Louis

Faculty Advisor: Bob Goldstein
Department: Biology

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Due to the high cost of reproduction, oviposition site selection can be an important decision for females. The influence of many factors, such as predation, resource competition and habitat suitability can result in variety of the spatial distribution patterns of egg masses across available habitats. We surveyed Thalia geniculata stalks at the Palo Verde marsh for egg masses of a freshwater apple snail of the Pomacea genus to determine the spatial distribution of oviposition sites. Based on the visual search capabilities of its main predator, the snail kite (Rostrhamus sociabilis sociabilis) and the importance of humidity to egg development, we expected to find more eggs on the inside of clumps of T. geniculata then on the outside or on solitary stalks. However, the snail does not lay in the expected clumped pattern. Pomacea may exhibit random spatial distribution of egg masses due to the neutrality of the landscape with respect to these threats or may have other adaptations to deal with these pressures that do not involve egg spatial distribution.