Host plant stimuli effects on survival and duration of dormancy of Rhagoletis zoqui, Rhagoletis completa (Diptera: Tephritidae) and associated parasitoids.

Tephritid fruit flies in the genus Rhagoletis bridge between predictable periods of fruit availability by becoming dormant. To cope with acyclic unpredictable events (e.g., frost, mast seeding, etc), a proportion of the population can undergo prolonged dormancy. In the case of walnut infesting Rhagoletis, host plant-derived cues such as juglone soil concentration vary seasonally in predictable patterns. Here, we examined the effects of host plant parts and derived compounds on emergence rates and dormancy duration of Rhagoletis completa (Cresson), Rhagoletis zoqui (Bush) (Diptera: Tephritidae), and associated parasitoids. Pupae of both species were exposed to walnut leaves, fruit, or fruit and leaves and compared to a control. In a second experiment, R. zoqui were exposed to 10 mg l-1 of juglone applied to pupation medium during four consecutive 4-week time periods under variable combinations of temperature and frequency of exposure. Overall, the presence of fruit resulted in greater overwintering survival of R. completa but had no effect on the duration of dormancy of either fly species. Application of juglone over two consecutive periods produced greater mortality of R. zoqui than the control. Three parasitoid species emerged from R. completa and one from R. zoqui. Duration of dormancy for parasitoids was longer than that of fly hosts. Regardless of treatment, 13.3-18.4% of R. completa pupae and 1.3-2.8% R. zoqui engaged in prolonged (>year) dormancy. Our results indicate that host plant derived cues have little or no effect on survival and duration of dormancy of walnut infesting Rhagoletis, and at the tested concentration juglone is toxic to R. zoqui pupae. Testing the effect of juglone at lower concentrations is necessary to rule out its role as an environmental cue for regulation of dormancy. So far, host plant fruiting phenology appears to play a greater role than host plant derived cues in selecting for fly eclosion times.

Differential Response to Photoperiod by Diverging Rhagoletis pomonella (Diptera: Tephritidae) Populations Exploiting Host Plants with Different Fruiting Phenology.

Photoperiod has been found to influence the proportion of non-dormant individuals and the duration of dormancy among North American populations of Rhagoletis pomonella (Walsh) (Diptera: Tephritidae). In particular, long days combined with high temperatures can produce a 100% non-dormant generation. There are several genetically distinct populations of R. pomonella in the highlands of Mexico, two of which occur at the same latitude, at different elevations, that exploit hawthorn plants with different fruiting phenology (early (summer-fall) and late (winter)). Flies exploiting such hosts might use day length in different ways as a cue to match adult emergence with fruit availability. Here, we compared responses of pupae from two Mexican populations of R. pomonella to a 12/12 L/D photoperiod, a long-day photoperiod 17/7 L/D, and continuous illumination. Experiments were performed under warm conditions (27°C). Day length had no effect on the proportion of adults emerged from the early-fruiting hawthorn population, while pupae extracted from late-fruiting hawthorns and exposed to long days emerged as adults in lower proportions and engaged in prolonged dormancy in greater proportions than those exposed to a short day. Photoperiod had no effect on the proportion from both Mexican populations foregoing dormancy. Dormancy duration was affected by photoperiod and was longer than previous reports for North American populations. Host plant fruiting phenology may be the driver of these differences. These findings, coupled with previous reports of genetic and biological differences, suggest that the Eje Volcanico Trans-Mexicano R. pomonella population may actually be a distinct species.

Phenotypic plasticity in clutch size regulation among populations of a potential invasive fruit fly from environments that vary in host heterogeneity and isolation.

Phenotypic plasticity is thought to evolve in response to environmental unpredictability and can shield genotypes from selection. However, selection can also act on plastic traits. Egg-laying behaviour, including clutch size regulation, is a plastic behavioural trait among tephritid fruit flies. We compared plasticity in clutch size regulation among females of Anastrepha ludens populations stemming from environments that differed in the degree of predictability in egg-laying opportunities. Clutch size regulation in response to hosts of different sizes was compared among flies from (a) a wild, highly isolated population, (b) a wild population that switches seasonally from a small wild host fruit that varies greatly in abundance to an abundant large-sized commercial host, and (c) a laboratory population. Flies from all three populations adjusted clutch number and size according to host size. However, flies from the heterogeneous wild environment were more plastic in adjusting clutch size than flies from agricultural settings that also laid fewer eggs; yet both populations were more plastic in adjusting clutch size in line with host size when compared with laboratory females. When wild and orchard females encountered the largest host, clutch size was extremely variable and egg regulation did not follow the same trend. Heterogeneity in host availability in space and time appears to be as important as seasonal variation in host size in maintaining plastic clutch size regulation behaviour. In stable environments, there was a clear reduction in the plasticity of these traits.

Do mothers really know best? Complexities in testing the preference-performance hypothesis in polyphagous frugivorous fruit flies.

The preference-performance hypothesis (PPH) has widely been used to explain host exploitation patterns by phytophagous insects. However, this hypothesis often fails in the case of polyphagous species when compared with specialists. One explanation, validated by the information-processing hypothesis (IPH), considers that polyphagous insects are unable to process a large array of cues, which hinders females from distinguishing between high- and low- quality hosts. Here we analyzed Anastrepha ludens female host preference and offspring performance, and tested if neuronal limitations could possibly play a role in the incapacity of the polyphagous A. ludens to make 'accurate decisions' and therefore partially explain mismatches related to PPH. Results testing the PPH by correlating female preference to six naturally occurring hosts and its offspring outcomes show that A. ludens females oviposited greater proportions of eggs on fruit according to hierarchical preferences. Infestation level was low in white sapote, the preferential and seemingly putative ancestral host, likely due to sapote defence mechanisms. Pupal weight and adult size were lower when A. ludens larvae developed in guava (conditional host that was artificially infested) and peach, a lower ranked host compared with 'Marsh' grapefruit, white sapote, and 'Manila' mango (three preferred hosts). Larvae reared in 'Manzano' pepper, a low-ranked host, performed better than in peach and guava. Results testing the IPH, show that polyphagous A. ludens females were less accurate when discerning between a non natural host (guava) when compared with a preferred, natural host (grapefruit): error rate was significantly higher, number of oviposited fruit in a 6-h period was extremely low, time searching and ovipositing took longer, and pupae recovery was extremely low. Our findings indicate that both hypotheses tested are complementary and help better understand host use by A. ludens. However, we also discuss the complexity of polyphagy considering other factors such as plant resistance/defence mechanisms which are not fully addressed in both theories tested.

The effect of winter length on duration of dormancy and survival of specialized herbivorous Rhagoletis fruit flies from high elevation environments with acyclic climatic variability.

Dormancy can be defined as a state of suppressed development allowing insects to cope with adverse conditions and plant phenology. Among specialized herbivorous insects exploiting seasonal resources, diapause frequently evolves as a strategy to adjust to predictable plant seasonal cycles. To cope with acyclic and unpredictable climatic events, it has been found for some insects that a proportion of the population undergoes prolonged dormancy. We compared the response of three species in the Rhagoletis cingulata species group exploiting plants differing in fruiting phenology from environments varying in frequency and timing of acyclic climatic catastrophic events (frost during flowering and fruit set) and varying also in the time of the onset of the rainy season. Small proportions (10 months), and large proportions of pupae died without emerging as adults. The number of days elapsed from the end of artificial winter and adult eclosion was longer for R. cingulata exploiting late fruiting Prunus serotina in Northeastern Mexico than for flies recovered from earlier fruiting plants in the central Altiplano. Rhagoletis turpiniae and northeastern R. cingulata pupae suffered high proportions of parasitism. Large proportions of R. cingulata from central Mexico engaging in prolonged dormancy may be explained by the fact that flowering and fruit set for its host, P. serotina var capuli, driven by the timing of maximum precipitation, matches a period of highest probability of frost often resulting in large areas with fruitless trees at unpredictable time intervals. As a consequence of differences in host plant fruiting phenology, central and northeastern Mexican R. cingulata were found to be allochronically isolated. Prolonged dormancy may have resulted in escape from parasitism.

Development of a Low-Cost and Effective Trapping Device for Apple Maggot Fly (Diptera: Tephritidae) Monitoring and Control in Mexican Commercial Hawthorn Groves.

Few efforts have been made in Mexico to monitor Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) in commercial hawthorn (Crataegus spp.) crops. Therefore, the main objectives of this study were to evaluate infestation levels of R. pomonella in feral and commercial Mexican hawthorn and to assess the efficacy of different trap-lure combinations to monitor the pest. Wild hawthorn was more infested than commercially grown hawthorn at the sample site. No differences among four commercial baits (Biolure, ammonium carbonate, CeraTrap, and Captor + borax) were detected when used in combination with a yellow sticky gel (SG) adherent trap under field conditions. However, liquid lures elicited a slightly higher, although not statistically different, capture. Cage experiments in the laboratory revealed that flies tended to land more often on the upper and middle than lower-bottom part of polyethylene (PET) bottle traps with color circles. Among red, orange, green, and yellow circles attached to a bottle trap, only yellow circles improved fly captures compared with a colorless trap. A PET bottle trap with a red circle over a yellow background captured more flies than a similar trap with yellow circles. An SG adherent yellow panel trap baited with ammonium carbonate was superior to the improved PET bottle trap (red over a yellow background) baited with different liquid proteins, but a higher proportion of females and no differences in fly detection were measured in PET traps baited with protein lures. These trials open the door for future research into development of a conventional nonadherent trap to monitor or control R. pomonella.

The effect of winter length on survival and duration of dormancy of four sympatric species of Rhagoletis exploiting plants with different fruiting phenology.

Dormancy has been thoroughly studied for several species of economic importance in the genus Rhagoletis in temperate areas of North America and Europe. Much less is known on life history regulation for species inhabiting high-elevation areas in the subtropics at the southern extreme of their geographical range. Host plant phenology has been found to play a key role in generating allochronic isolation among sibling species and host races of Rhagoletis in the course of sympatric speciation, and has important implications for pest management. We compare the effect of winter length on survival to adult eclosion and dormancy duration among four species of Rhagoletis (three of them sympatric) exploiting hosts with different fruiting phenology in subtropical isolated highlands. Survival and duration of dormancy was found to be different among the four species. At 24°C, a very small proportion (<1%) of R. pomonella, R. turpiniae and R. zoqui completed development without becoming dormant, while in the case of R. solanophaga the majority of the population emerged after development within 40 days of pupation. Also, a large proportion of braconid parasitoids infesting Rhagoletis eggs and larvae emerged as adults without becoming dormant. Greatest survival after artificial winter was obtained for R. pomonella (50-60%) and R. zoqui (30%) after only four weeks at 5°C (a third of the time reported for studies on northern R. pomonella), while R. turpiniae, under identical environmental conditions experienced low adult emergence, and highest survival (11%) was recorded for flies exposed to 5°C during 10 and 12 weeks. For R. pomonella, there was a strong positive relationship between winter length and time to post-winter adult eclosion that was not observed for R. zoqui. In sum, for R. pomonella, mild winters in highland subtropical areas appear to select for flies better able to withstand longer periods of warm temperature before winter than flies exploiting late fruiting hosts and inhabiting northern latitudes. In the case of R. turpiniae and R. zoqui environmental cues such as fluctuations in humidity and/or different temperature thresholds (5°C) may play a more important role than winter length in life history regulation. Continuous host availability for R. solanophaga appears to have selected for non-diapausing flies. From an applied perspective our results are useful for handling flies in the laboratory to conduct research and suggest that non-diapausing strains of flies and parasitoids may be selected for SIT and innundative biological control programs.

Costly Nutritious Diets do not Necessarily Translate into Better Performance of Artificially Reared Fruit Flies (Diptera: Tephritidae).

Protein, lipid, carbohydrate, and energy contents of three artificial diets (Xal2, Met1, and Met2) used for laboratory-rearing and mass-rearing the Mexican fruit fly, Anastrepha ludens (Loew), for a sterile insect technique program were measured. The larval survival, pupation, pupal weight, adult emergence, sex ratio, and flight capacity of the flies reared on each of these diets were also quantified. The diet with the highest nutrient and energy content was Xal2 followed by Met2 and Met1, but larval recovery and percent pupation was significantly higher in flies reared on either the Met1 or Met2 diets. A. ludens reared on Xal2 exhibited the highest proportion of adults capable of flight. No other response variable differed significantly among the three diets tested. This suggests that a high content of nutrients and multiple sources of protein (dried yeast and wheat germ in the case of the Xal2 diet) do not necessarily improve overall performance or fly quality. We conclude that nutritious diets for A. ludens can be modified to reduce their cost without compromising the performance of artificially reared flies.

Economic and Highly Effective Trap-Lure Combination to Monitor the Mexican Fruit Fly (Diptera: Tephritidae) at the Orchard Level.

Monitoring population levels of the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), at the orchard level prior and during the fruit ripening period can result in significant savings in the costs of managing this pestiferous insect. Unfortunately, to date, no highly effective and economically viable trap is available to growers. To move toward this goal, trap-lure combinations were evaluated in trials performed in citrus orchards in Veracruz, Mexico. CeraTrap, an enzymatic hydrolyzed protein from pig intestinal mucose, was 3.6 times more attractive to A. ludens than the most commonly used bait of Captor (hydrolyzed protein and borax) when using Multilure traps. When several commercial traps were evaluated, the efficacy of a simple and inexpensive transparent polyethylene (PET) bottle with 10-mm lateral holes was similar to that of the costly Multilure trap when baited with CeraTrap and significantly more effective than a Multilure trap baited with Captor. PET bottles filled with Cera Trap, rebaited at 8-wk intervals, and tested in trials encompassing 72 ha of citrus groves, were significantly more effective than Multilure traps baited with Captor that need to be serviced weekly. In addition to this relevant finding, CeraTrap baited traps detected A. ludens at lower population densities and attracted a significantly higher number of flies at all densities when compared with Captor-baited traps. We conclude that CeraTrap represents a cost-effective and highly efficient bait that will enable us to pursue the goal of developing economic thresholds, a badly needed management tool for A. ludens.

Limits to the host range of the highly polyphagous tephritid fruit fly Anastrepha ludens in its natural habitat.

Anastepha ludens (Diptera: Tephritidae) is a highly polyphagous fruit fly that is able to develop in a wide range of hosts. Understanding the limits of this pest's host range could provide valuable information for pest management and plant breeding for pest resistance. Previous studies have shown that guavas (Psidium guajava (Myrtaceae) L.), are not attacked under natural conditions by A. ludens. To understand this phenomenon, guavas were exposed to natural infestation by A. ludens and to other fruit fly species that infest guavas in nature (Anastrepha striata Schiner, Anastepha fraterculus (Wiedemann), Anastepha obliqua (Macquart)). Once the susceptible phenological stage of guavas was determined, fruit infestation levels were compared between A. ludens and A. striata. Choice and non-choice tests were performed under field-cage conditions. Under field conditions, guavas were susceptible to A. striata and A. fraterculus attack all the way from when fruit was undeveloped to when fruit began to ripen. No infestation by A. ludens was recorded under natural conditions. Similar results were obtained when forced exposures were performed, indicating that unripe guavas were preferred by A. striata over ripe fruit, and that infestation rates were higher at early fruit maturity stages. Under forced oviposition conditions, A. ludens larvae were unable to develop in unripe guavas but did so in fully ripe fruit. However, A. ludens fitness parameters were dramatically affected, exhibiting reduced survival and reduced pupal weight compared to conspecifics that developed in a natural host, grapefruit. We confirm that P. guajava should not be treated as a natural host of this pestiferous species, and suggest that both behavioral aspects and the fact that larvae are unable to adequately develop in this fruit, indeed represent clear limits to A. ludens's broad host range.

Susceptibility of 15 mango (Sapindales: Anacardiaceae) cultivars to the attack by Anastrepha ludens and Anastrepha obliqua (Diptera: Tephritidae) and the role of underdeveloped fruit as pest reservoirs: management implications.

We evaluated the susceptibility of 15 mango cultivars to the attack of Anastrepha ludens (Loew) and Anastrepha obliqua (Macquart) (Diptera: Tephritidae), the main tephritid pests of this crop in Mexico. In a field experiment, bagged fruit-bearing branches were exposed to gravid females of both fly species. Infestation rates, developmental time, adult eclosion, and F1 adult longevity, fecundity, and fertility were recorded, ranking cultivars in terms of susceptibility to fly attack and development. We also compared the volatile profile in selected resistant and susceptible cultivars in search of possible correlations. In a second experiment, clutch size for A. ludens was determined in each cultivar. Infestation rates, developmental time, and F1 demographic parameters varied sharply among cultivars and between fly species for bagged fruit. Cultivars 'Vishi,' '74-82,' and 'Brooks' were most susceptible to A. ludens infestation while "Tommy,' 'Sensation,' and 'Ataulfo "niño"' (parthenocarpic fruit) were most susceptible to A. obliqua infestation. 'Edward,' 'Kent,' 'Brooks late,' 'Palmer, and 'Ataulfo' exhibited tolerance to attack of both fly species. Fruit of susceptible and resistant cultivars exhibited unique volatile profiles. Fly development and F1 adult demographic parameters varied significantly among cultivars. A. ludens females laid larger clutches in larger and harder fruit. We highlight the important role of Ataulfo "niño" as pest reservoir if fruit is left unharvested on trees. We discuss the possible use of highly resistant cultivars as trap crops or egg sinks.

Is the alpine divide becoming more permeable to biological invasions? - Insights on the invasion and establishment of the Walnut Husk Fly, Rhagoletis completa (Diptera: Tephritidae) in Switzerland.

The Walnut Husk Fly, Rhagoletis completa Cresson (Diptera: Tephritidae), is native to North America (Midwestern US and north-eastern Mexico) and has invaded several European countries in the past decades by likely crossing the alpine divide separating most parts of Switzerland from Italy. Here, we determined its current distribution in Switzerland by sampling walnuts (Juglans regia L.) in ecologically and climatically distinct regions along potential invasion corridors. R. completa was found to be firmly established in most low altitude areas of Switzerland where walnuts thrive, but notably not a single parasitoid was recovered from any of the samples. Infested fruit was recovered in 42 of the 71 localities that were surveyed, with mean fruit infestation rate varying greatly among sites. The incidence of R. completa in Switzerland is closely related to meteorological mean spring temperature patterns influencing growing season length, but not to winter temperatures, reflecting survival potential during hibernation. Importantly, areas in which the fly is absent correspond with localities where the mean spring temperatures fall below 7°C. Historical data records show that the natural cold barrier around the Alpine divide in the central Swiss Alps corresponding to such minimal temperatures has shrunk significantly from a width of more than 40 km before 1990 to around 20 km after 2000. We hypothesize on possible invasion/expansion routes along alpine valleys, dwell on distribution patterns in relation to climate, and outline future research needs as the incursion of R. completa into Switzerland; and, more recently, other European countries, such as Germany, Austria, France and Slovenia, represent an example of alien species that settle first in the Mediterranean Basin and from there become invasive by crossing the Alps.

Effect of cold storage on larval and adult Anastrepha ludens (Diptera: Tephritidae) viability in commercially ripe, artificially infested Persea americana 'Hass'.

Commercially ripe 'Hass' avocados, Persea americana Mill, artificially exposed to wild Anastrepha ludens (Loew) (Diptera: Tephritidae) females 24 h after harvest were placed in a cold storage facility to determine the effect of low temperature on larval survival and adult viability. Fruit were left for 3, 6, 9, and 12 d in a cold room at 5 degrees C followed by a 20-25-d period at ambient temperature to allow for larval development and pupation. Hass avocados and grapefruit, Citrus paradisi Macfadyen, maintained at ambient temperature served as controls. Overall, only 0.23% of the Hass avocados and 19.30% of the grapefruit were infested. The number of infested fruit increased with decreasing exposure time to cold. Puparia from cold-treated Hass avocados were significantly smaller than those stemming from cold-treated grapefruit. Hass avocados exposed for 12 d to 5 degrees C yielded no puparia, and those exposed for 6 and 9 d yielded 22 and two puparia, respectively, but no adults. Although Hass avocados exposed to cold temperature for 3 d yielded adults that reached sexual maturity (N = 16), females laid inviable eggs. Grapefruit exposed to cold for 12 d yielded normal-sized puparia (but no adults), whereas those exposed over 9 d yielded females able to lay viable eggs. We conclude that exposing fruit to cold storage after packing and during transport represents an effective risk-mitigating procedure in the highly improbable event that a gravid A. ludens female might lay eggs in a commercially ripe Hass avocado that had been left unprotected in a packinghouse.

Male and female condition influence mating performance and sexual receptivity in two tropical fruit flies (Diptera: Tephritidae) with contrasting life histories.

Recent recognition of widespread polyandry in insects has generated considerable interest in understanding why females mate multiple times and in identifying factors that affect mating rate and inhibit female remating. However, little attention has been paid to understanding the question from both a female and male perspective, particularly with respect to factors that may simultaneously influence female remating rates. Here, we report on a study aimed at ascertaining the possible interactive effects that male and female size and diet, and female access to a host could have on mating latency, probability, and duration and female refractory period using two tropical fruit fly species with contrasting life histories. Of all factors tested, adult diet played the most significant role. Both Anastrepha ludens and Anastrepha obliqua males which had constant access to protein and sucrose mated more often, had shorter copulations and induced longer refractory periods in females than males fed a low quality diet (sucrose offered every third day). Female size and the interaction with male diet determined how quickly female A. ludens mated for the first time. Smaller females mated sooner with low quality fed males than with high quality fed males while there was no difference for large females, suggesting that male choice may be at play if high quality fed males discriminate against smaller females. Copulation duration also depended on both male and female nutritional condition, and the interaction between male diet and female size and diet. Large and high quality fed females had shorter copulations regardless of male condition. Importantly, for A. ludens, female refractory period depended on male size and the nutritional condition of both males and females, which could indicate that for this species, female receptivity does not depend only on the condition of the male ejaculate. For A. obliqua refractory period was associated with the interaction between male size and diet and male diet and host presence. We discuss our results in terms of male ability to inhibit female remating and the relative contribution of female condition to this behavior. We also address the importance of studying effects simultaneously on species with contrasting life histories.

Random mating among Anastrepha ludens (Diptera: Tephritidae) adults of geographically distant and ecologically distinct populations in Mexico.

The Mexican fruit fly Anastrepha ludens (Loew) (Diptera: Tephritidae) is a polyphagous pestiferous insect with a geographical range encompassing highly variable environmental conditions. Considering that cryptic species have been recently found among South American representatives of the same taxonomic group as A. ludens, we tested whether or not some populations of A. ludens have evolved assortative mating as an isolating mechanism that maintains intrapopulation genetic differences and behavioral adaptations to local conditions. Males and females stemming from widely separated locations with similar environmental conditions and males and females stemming from populations within individual-flight range, but collected in different hosts (a native and an exotic one), mated randomly amongst themselves when placed in a field cage. Despite the fact that sibling males and females from two distinct populations also mated randomly amongst themselves, siblings engaged in significantly longer copulations than non-siblings, indicating that perhaps adults discriminated mates with similar genetic compositions. Our results have important practical implications as A. ludens is the most devastating pest of citrus in Mexico and Central America, and large-scale releases of sterile flies are used to control it.

Radiation and divergence in the Rhagoletis pomonella species complex: inferences from DNA sequence data.

Here, we investigate the evolutionary history and pattern of genetic divergence in the Rhagoletis pomonella (Diptera: Tephritidae) sibling species complex, a model for sympatric speciation via host plant shifting, using 11 anonymous nuclear genes and mtDNA. We report that DNA sequence results largely coincide with those of previous allozyme studies. Rhagoletis cornivora was basal in the complex, distinguished by fixed substitutions at all loci. Gene trees did not provide reciprocally monophyletic relationships among US populations of R. pomonella, R. mendax, R. zephyria and the undescribed flowering dogwood fly. However, private alleles were found for these taxa for certain loci. We discuss the implications of the results with respect to identifiable genetic signposts (stages) of speciation, the mosaic nature of genomic differentiation distinguishing formative species and a concept of speciation mode plurality involving a biogeographic contribution to sympatric speciation in the R. pomonella complex.

Understanding differences between phylogenetic and pedigree-derived mtDNA mutation rate: a model using families from the Azores Islands (Portugal).

We analyzed the control region of the mitochondrial DNA (mtDNA) from maternally related individuals originating from the Azores Islands (Portugal) in order to estimate the mutation rate of mtDNA and to gain insights into the process by which a new mutation arises and segregates into heteroplasmy. Length and/or point heteroplasmies were found at least in one individual of 72% of the studied families. Eleven new point substitutions were found, all of them in heteroplasmy, from which five appear to be somatic mutations and six can be considered germinal, evidencing the high frequency of somatic mutations in mtDNA in healthy young individuals. Different values of the mutation rate according to different assumptions were estimated. When considering all the germinal mutations, the value of the mutation rate obtained is one of the highest reported so far in family studies. However, when corrected for gender (assuming that the mutations present in men have the same evolutionary weight of somatic mutations because they will inevitably be lost) and for the probability of intraindividual fixation, the value for the mutation rate obtained for HVRI and HVRII (0.2415 mutations/site/Myr) was in the upper end of the values provided by phylogenetic estimations. These results indicate that the discrepancy, that has been reported previously, between the human mtDNA mutation rates observed along evolutionary timescales and the estimations obtained using family pedigrees can be minimized when corrections for gender proportions in newborn individuals and for the probability of intraindividual fixation are introduced. The analyses performed support the hypothesis that (1) in a constant, tight bottleneck genetic drift alone can explain different patterns of heteroplasmy segregation and (2) in neutral conditions, the destiny of a new mutation is strictly related to the initial proportion of the new variant. Another important point arising from the data obtained is that, even in the absence of a paternal contribution of mtDNA, recombination may occur between mtDNA molecules present in an individual, which is only observable if it occurs between mtDNA types that differ at two or more positions.

Genetic structure of Flores island (Azores, Portugal) in the 19th century and in the present day: evidence from surname analysis.

The island of Flores is the most westerly of the Azores archipelago (Portugal). Despite its marked geographic isolation and reduced population size, biodemographic and genetic studies conducted so far do not support the idea that its population constitutes a genetic isolate. In this study we conducted a surname analysis of the Flores population for two time periods: the second half of the 19th century and the present day. Our main purposes were (1) to biodemographically and genetically characterize the island, taking into account the strong reduction in population observed from the middle of the 19th century to the present day; and (2) to analyze the influence that the effective population size and geographic distance have on the genetic structure of populations. For both periods analyzed, all indicators of diversity revealed a high level of surname diversity. Our results are in accordance with the diversity estimates obtained from both monoparental genetic markers located in the Y chromosome and frequencies of mtDNA haplogroups. Contrary to what could be expected, considering the strong reduction of population in the last 150 years, we observed that diversity was maintained and that microdifferentiation decreased. Both observations support a higher openness of parishes as a consequence of the increase in communication routes. From the first to the second period analyzed, a change in surname composition is evident, although the more frequent surnames in Flores are almost the same for both periods and some of them are reported to be surnames present in the first settlers of Flores. This result testifies to the impact of founders on the present-day gene pool of Flores island and allows us to infer that the genetic characterization of the present-day population of Flores could provide reliable information about the history of the peopling of the Azores.

Morphometric analysis of Mexican and South American populations of the Anastrepha fraterculus complex (Diptera: Tephritidae) and recognition of a distinct Mexican morphotype.

Discriminant function and cluster analyses were performed on 19 morphometric variables of the aculeus, wing and mesonotum to determine whether populations of Anastrepha fraterculus (Wiedemann) from different parts of Mexico could be distinguished from populations from South America. Samples were collected from seven localities across Mexico, two from Brazil, and one each from Colombia and Argentina. Results showed there were statistically significant differences between Mexican and South American populations with respect to the aculeus (tip length, length of serrated section, mean number of teeth) and wing (width of S-band and connection between S- and V-bands). The degree of morphological variation observed among Mexican populations was extremely low, and as a consequence, the Mexican populations were identified as a single morphotype by discriminant analysis. The 'Andean morphotype'consisting of the Colombian population, and the 'Brazilian morphotype'consisting of the two Brazilian populations plus the single Argentinian population were also distinguished. It was concluded that the macro-geographical morphotypes from Mexico, Colombia, and Brazil plus Argentina correspond to three distinct taxonomic entities. Comparisons of results with those obtained from behavioural, karyotypic, isozyme and DNA studies suggest that sufficient evidence now exists to name a new Mexican species from within the A. fraterculus complex. This will be done in a separate publication. A provisional key to the morphotypes of A. fraterculus studied is provided.

Determination of human caucasian mitochondrial DNA haplogroups by means of a hierarchical approach.

In this paper we propose a hierarchical approach that allows the screening of mitochondrial DNA (mtDNA) haplogroups in populations that have essentially West Eurasian mtDNA backgrounds but that could have some non-West Eurasian contributions. To develop and validate this scheme, we used data on 18 coding region polymorphisms (17 analyzed by RFLP analysis and 1 by sequencing) and sequences of hypervariable segment I (HVSI) of the mtDNA control region from the Azores Islands (Portugal) population. The proposed scheme allows the characterization of almost all West Eurasian and African major clusters by means of RFLPs. Furthermore, the scheme includes information on situations in which sequencing is pertinent to defining a particular haplogroup. The validity of the scheme is ensured by (1) using relatively stable polymorphic positions, (2) screening more than one position to define a specific haplogroup, and (3) typing confirmatory positions. Dubious samples can be resolved by sequencing. The robustness of this approach was assessed by sequencing all samples for HVSI, taking advantage of the previously established relationships between RFLPs and control region sequence polymorphisms. The use of this hierarchical approach avoids the screening of unnecessary control region polymorphisms and therefore results in a more rapid and cost-efficient screening than one in which all polymorphic positions are analyzed. Even if this approach leads to a lower level of phylogeographic resolution than the sequencing of all samples, it allows us to define population movements on a continental level and can be applied, unlike sequencing all samples, with a low cost in any laboratory.