Local site differences in survival and parasitism of periwinkles (Littorina sitkana Philippi, 1846)

• Published in: Ecology and evolution Vol. 7; no. 4; pp. 1021 - 1029
• Main Authors: Ayala‐Díaz, Mónica, Richardson, Jean M. L., Anholt, Bradley R.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.02.2017; John Wiley and Sons Inc
• Subjects: Barkley Sound; Bayesian analysis; Body size; Community composition; Environmental factors; Intertidal zone; Littorina sitkana; MARK; Mark‐Release‐Recapture; Mollusks; Original Research; Parasites; Parasitism; snail ecology; Snails; Subpopulations; Survival; WinBUGS; Canada, British Columbia; INE, Canada, British Columbia, Vancouver I., Barkley Sound; parasites; WinBUGS; Barkley Sound; MARK; Mark‐Release‐Recapture; snail ecology
• DOI: 10.1002/ece3.2708
• ISSN: 2045-7758

The periwinkle, Littorina sitkana, is found throughout the intertidal zone, often in isolated subpopulations. The majority of trematode parasites use snails as intermediate hosts, and decreased survivorship is often observed in snails infected with trematodes. Sampling L. sitkana from four sites in Barkley Sound, British Columbia, Canada, we test the effects of parasitic infection on snail survival using maximum likelihood and Bayesian approaches using the software MARK and WinBUGS. We found that survival of periwinkles and trematode community composition differed among sites, but survival and trematode prevalence were uncorrelated. WinBUGS performed better than MARK in two ways: (1) by allowing the use of information on known mortality, thus preventing survival overestimation; and (2) by giving more stable estimates while testing the effect of body size on snail survival. Our results suggest that snail survival depends heavily on local environmental factors that may vary greatly within a small geographical region. These findings are important because the majority of experimental studies on survival are done on snails from a single location. Subpopulations of the intertidal periwinkle Littorina sitkana have potential to show differential survival in a small geographical area. We show that four subpopulations of L. sitkana differ in survival and parasite communities, but survival does not seem to be related to parasite presence. We compare maximum likelihood (program MARK) and Bayesian (program WinBUGS) inference modes and state advantages and disadvantages of both statistical approaches.