Biodemography of the Mediterranean fruit fly: aging, longevity and adaptation in the wild

Abstract

The purpose of this paper is to summarize recent research on longevity, aging and adaptation in wild medfly populations and in a close relative of the medfly. The key findings include a new life table identity that relates age structure and the distribution of deaths in stationary populations, seasonal variation in the post-capture longevity of trapped medflies of unknown age, greater longevity of once-wild (wild-caught) adult medflies relative to never-wild (laboratory-emerged) individuals, differences in age specificity of different medfly field capture methods, large variation in the sex-specific longevity of six medfly global biotypes (e.g. Kenya; Brazil; Greece), and the extraordinary longevity of the natal fruit fly - a sister species of the medfly. The discussion contains a listing of discoveries derived from this recent research that appear to be unique to the investigations on medfly aging in the wild. It is suggested that studies of aging in wild populations of Drosophila melanogaster have the potential to exploit this model organism in an entirely new aging research domain and thus complement the already deep literature on aging in this species.

Figure 1

Post-capture lifespans for 4,088 medflies (2653; 1435 males) trapped during the 2003–05 field seasons on Chios Island, Greece. The points (individual remaining lifespan) within each field season are connected by lines to depict both variation and seasonal trends. The running 30-day medians for each season are shown as the internal smoothed lines. The horizontal dashed lines show the 20-day (shorter-lived) and 100-day (longer-lived) post-capture age are included for reference (from Carey et al., 2008).

Figure 2

Expectation of remaining life at 60, 80, 100 and 120 days for medflies that emerged as adults in the laboratory from wild-collected hosts and for medflies of unknown ages that emerged in the field and were subsequently trapped as free-ranging adults.. ‘Chronological’ age applies known-aged flies that emerged in the laboratory and ‘post-capture’ age applies to the wild-caught flies and refers to the time that had elapsed since they were captured and brought to the laboratory (from Carey et al., 2008). The chronological age of known-age flies from the laboratory must have always been less than or equal to the post-capture age of wild-caught flies. Note that, with the exception of males at 60 days, remaining life expectancies in wild-caught flies for both sexes was always higher at all ages

Figure 3

Sex-specific post-capture longevity of wild medfly adults on Chios Island, Greece that were captured live on the same date (July 23, 2006) using either a food (protein-baited) trap (n= 211 and 268 for males and females, respectively, aspirator (n=233 and n=66 for males and females, respectively) or a pheromone (n=211 for males-only) (from Kouloussis et al., 2009). Means (±SD) for males were 59.9 (±35.4), 49.2 (±30.4), and 48.7 days (±27.6) for captures made by the food trap, the aspirator and the pheromone trap, respectively. Means for females were 49.1 (±30.7) and 41.1 days (±28.4) for captures made with the food trap and aspirator.

Figure 4

a,b. Estimated mean reproductive functions in the medfly biotypes for (1) the survival-unadjusted; and (b) the survival-adjusted samples (re-drawn from Müller, et al., 2009). Note the similarity of the adjusted rates (Fig. 4b) relative to the dissimilarity of the unadjusted rates (Fig. 4a).

Figure 4

a,b. Estimated mean reproductive functions in the medfly biotypes for (1) the survival-unadjusted; and (b) the survival-adjusted samples (re-drawn from Müller, et al., 2009). Note the similarity of the adjusted rates (Fig. 4b) relative to the dissimilarity of the unadjusted rates (Fig. 4a).

Figure 5

Comparative sex-specific life expectancy of two Ceratitis species— the natal fruit fly, C. rosa (from Duyck et al., 2010) and the medfly, C. capitata (from Carey et al., 2008).