Population structure of a native and an alien species of snail in an urban area of the Atlantic Rainforest

Abstract

Native Megalobulimus paranaguensis was identified on Brazil's Ilha Porchat promontory, an area that Achatina fulica commonly populates. The population structures of these species were investigated for interactions. Spatial distribution, niche overlap and mark-recapture analysis were conducted. The outer lip of M. paranaguensis and environmental variables were measured. One and two abundance peaks were observed for A. fulica and M. paranaguensis, respectively. Survivorship was higher in A. fulica. Distribution was aggregate for M. paranaguensis, whereas for A. fulica it varied from random to aggregate. Both species aggregate as abundance increases. The lifespan of M. paranaguensis in this location is shorter than its lifespan in a nearby location. Achatina fulica was affected by soil temperature and humidity; M. paranaguensis was influenced by humidity. Niche overlap was random. The results show that M. paranaguensis can keep its natural activity and abundance in the presence of A. fulica, but environmental degradation impacts M. paranaguensis and should be evaluated.

Population dynamics of Megalobulimus paranaguensis (Gastropoda: Pulmonata) in the southeast coast of Brazil

“…Recruitment also occurs in the same period as found by MIRANDA et al (2015), but in their study only one recruitment peak during a period of six months was found. Aestivation in this study was found from November to February, consistent with MIRANDA et al (2015).…”

“…Recruitment also occurs in the same period as found by MIRANDA et al (2015), but in their study only one recruitment peak during a period of six months was found. Aestivation in this study was found from November to February, consistent with MIRANDA et al (2015). Aestivation, a state of dormancy where there is a lot of heat or dryness (BOSS 1974), is relatively common among terrestrial and freshwater mollusks (CÁCERES 1997).…”

“…Furthermore, according to RIZZATTI & ROMERO (2001), body hydration increases heart rate in M. mogianensis, and since heart rate indicates activity, precipitation is also an important factor modulating activity in M. paranaguensis. MIRANDA et al (2015), in a nearby location of this study, showed that the abundance of M. paranaguensis increases with increasing environmental humidity, and that humidity decreased in the period when evapotranspiration and temperature increased in this study.…”

“…MIRANDA et al (2015) estimated the survival rate of M. paranaguensis at 73% in Porchat Island, São Vicente. Three factors seem to have played a role in the higher survival rate found in our study: 1) there are no predators to control the population in Parque Zoobotânico Orquidário Municipal de Santos; 2) the Orquidário has a deeper layer of plant litter, is more densely covered with vegetation and is less impacted than the Porchat Island.…”

Variación génica intrapoblacional del caracol gigante africano (Achatina fulica) en el Valle del Cauca

“…Lo anterior es el reflejo de la escala utilizada en ambos estudios, pues aunque se mantiene un tamaño de muestra similar, las muestras utilizadas en el estudio anterior (16) provienen de países en continentes diferentes, mientras que la escala en el presente trabajo es regional, además de que los loci descritos aún no habían sido registrados en individuos de Latinoamérica. Sin embargo, considerando la naturaleza de A. fulica como especie invasora, es de esperar que el polimorfismo del marcador disminuya con la escala geográfica debido a los altos niveles de endogamia en el que suelen encontrarse sus poblaciones (1,20,21).…”