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.     

Effects of grazing intensity on pollinator abundance and diversity,and on pollination services

1. Pollinating insects provide important ecosystem services and are influenced by the intensity of grazing. Based on the Intermediate Disturbance Hypothesis (IDH), pollinator diversity is expected to peak at intermediate grazing intensities. However, this hump‐shaped relationship is rarely found. 2. The effect of grazing intensity was tested on flower cover, on the abundance and richness of bees, hoverflies and bee flies, and on pollination services to early‐flowering bee‐pollinated Asphodelus ramosus L. For that, we used data on 11 plant–pollinator phryganic communities from Lesvos Island (Greece) widely differing in grazing intensities. 3. Flower abundance and richness showed hump‐shaped relationships with grazing intensity. Grazing affected the abundance and richness of bees and hoverflies directly and also indirectly, through changes in the flower community. Grazing influenced directly the richness but not the abundance of bee flies. Overall, pollinator abundance and richness showed hump‐shaped relationships with grazing intensity, but variations in strength (hoverfly abundance) and direction (bee community) of the effect appeared along the season. Early in the season, grazing increased bee abundance but decreased richness, resulting in increased pollen limitation in A. ramosus. 4. The effects of grazing on pollinators vary with the intensity of the disturbance, generally supporting the IDH, and the timing of land‐use activities may influence pollination services. Management strategies should include moderate grazing levels to preserve overall diversity in this area, however, the conservation of particular early bee or bee‐pollinated species may benefit from reduced grazing in early spring.     

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.     

P53 Mutation and c-fos Overexpression Are Associated With Detection of the Antigen VLA-2 in Human Melanoma Cell Lines

In this study, we examined the expression of c-fos, c-myc, mutant c-Ha-ras and mutant p53 proteins in three normal human melanocyte cell lines and the following 12 melanoma cell lines: M5, Mewo, A375, Bro, Mel 2a, O-Mel II, IgR 39, SkMel-13, -19, -28 Mel-57 and NKI-4, using an immunohistochemical assay (APAAP). An effort was made to correlate oncogene expression with growth parameters, differentiation antigens (HMB-45, vla-2, k.1.2.58, HLA-DR, HLA-I), and pigmentation. All melanocyte cell lines were negative for the oncogenes examined, whereas six of the melanoma cell lines were found also positive (three for c-fos, two for c-myc, one for c-Ha-ras, and four for p53). Three melanoma cell lines expressed one oncogene and three the combination c-fos/p53. These three melanoma cell lines were positive for the “late” tumor progression marker A. 1. 43 (vla-2 adhesion molecule) and negative for the differentiation marker k. 1. 2. 58. Positivity for A. 1. 43 combined with negative staining for k. 1. 2. 58 was found in six out of the 12 cell lines. The observed oncogene expression correlated neither with growth parameters nor melanin content. The present findings revealed a coexpression of mutant p53 and c-fos proteins being associated with a highly malignant phenotype in melanoma cell lines. Further studies are necessary to clarify the significance of the above findings