Life history evolution in a globally invading tephritid: patterns of survival and reproduction in medflies from six world regions

Comparisons among populations from different localities represent an important tool in the study of evolution. Medflies have colonized many temperate and tropical areas all over the world during the last few centuries. In a common garden environment, we examined whether medfly populations obtained from six global regions [Africa (Kenya), Pacific (Hawaii), Central America (Guatemala), South America (Brazil), Extra-Mediterranean (Portugal) and Mediterranean (Greece)] have evolved different survival and reproductive schedules. Whereas females were either short-lived [life expectancy at eclosion (e₀) 48–58 days; Kenya, Hawaii and Guatemala] or long-lived (e₀ 72–76 days; Greece, Portugal and Brazil], males with one exception (Guatemala) were generally long-lived (e₀ 106–122 days). Although males universally outlived females in all populations, the longevity gender gap was highly variable (20–58 days). Lifetime fecundity rates were similar among populations. However, large differences were observed in their age-specific reproductive patterns. Short-lived populations mature at earlier ages and allocate more of their resources to reproduction early in life compared with long-lived ones. In all populations, females experienced a post-reproductive lifespan, with this segment being significantly longer in Kenyan flies. Therefore, it seems plausible that medfly populations, inhabiting ecologically diverse habitats, have evolved different life history strategies to cope with local environmental conditions.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 106–117.     

Female philopatry in coastal basins and male dispersion across the North Atlantic in a highly mobile marine species, the sperm whale (Physeter macrocephalus)

The mechanisms that determine population structure in highly mobile marine species are poorly understood, but useful towards understanding the evolution of diversity, and essential for effective conservation and management. In this study, we compare putative sperm whale populations located in the Gulf of Mexico, western North Atlantic, Mediterranean Sea and North Sea using mtDNA control region sequence data and 16 polymorphic microsatellite loci. The Gulf of Mexico, western North Atlantic and North Sea populations each possessed similar low levels of haplotype and nucleotide diversity at the mtDNA locus, while the Mediterranean Sea population showed no detectable mtDNA diversity. Mitochondrial DNA results showed significant differentiation between all populations, while microsatellites showed significant differentiation only for comparisons with the Mediterranean Sea, and at a much lower level than seen for mtDNA. Samples from either side of the North Atlantic in coastal waters showed no differentiation for mtDNA, while North Atlantic samples from just outside the Gulf of Mexico (the western North Atlantic sample) were highly differentiated from samples within the Gulf at this locus. Our analyses indicate a previously unknown fidelity of females to coastal basins either side of the North Atlantic, and suggest the movement of males among these populations for breeding.     

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

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 , 426–437, 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 50–75 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.