Abundance and population profile of Helicostyla daphnis (Stylommatophora: Bradybaenidae), an endemic snail of Cebu, Philippines
Journal Title: Journal of Biodiversity and Environmental Sciences (JBES) - Year 2014, Vol 5, Issue 1
Abstract
Helicostyla daphnis is a tree snail endemic to Cebu, Philippines. The study aimed to survey and compare the abundance and population profile (by age category) of Helicostyla daphnis in North Cebu and South Cebu in relation to season and other physicochemical factors. Sampling was done twice between April and September 2013. For snail sampling, a standardized direct search equivalent to a two-hour sampling effort in a total of eighteen quadrats in six sites was used. Elevation, air temperature, relative humidity, surface soil pH, and soil exchangeable calcium were measured on each quadrat. Independent t-test and Pearson correlation were used to relate abundance to the physicochemical variables. Snail abundance was significantly higher (p<0.01) during the dry season (dry=783 snails; wet=436). South Cebu had higher total abundance (dry = 477; wet = 284) compared to North Cebu (dry = 306; wet = 152). Adult snails dominated at 87% of total abundance during the dry season and 74% during the wet season. Neonates were present only during the wet season, contributing 5% to total abundance. The presence of eggs in both seasons could mean year-round reproduction; but increased egg abundance and significant presence of neonates imply higher reproductive activity during the wet season. Relative humidity and air temperature were the identified major determinants of abundance as they affect the species’ ability to avoid desiccation stress. The rate of harvesting of H. daphnis cannot also be ruled out as a factor affecting abundance between location.
Authors and Affiliations
Mary Joyce L. Flores
Keywords
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