Estimating changes in mean population age using the death distributions of live-captured medflies

Abstract

1. A simple, low-cost approach to estimating population ageing was introduced based on a modified version of the captive cohort method a technique developed earlier (Carey et al., Aging Cell, 7, 426437, 2008) in which information on the remaining lifespans of live-captured medflies of unknown age is used to estimate the overall population age structure. 2. To test this approach approximately 1200 medflies near Volos, Greece were live captured from daily sampling over a 3-month field season. 3. This simplified method reported: (i) an extraordinary post-capture longevity of wild medflies in early season (>200 days in longest lived); (ii) a decrease of 5075 days in the mean longevity from early-season to late-season flies; (iii) seasonality of frailty as indicated by the shorter-lived flies in late autumn; (iv) cessation of fly emergence in late season as indicated by the absence of long-lived individuals (indicating newly emerged at capture) sampled in the autumn; and (v) increase in mean age from about 20 days in early season to approximately 60 days in late season. 4. The applications of this simplified captive cohort method are discussed, including its use in the analysis of insect vector populations, Drosophila ecology and ageing in the wild, demographic toxicology, and age bias in sampling.