Larissa Guillén

Colonization and domestication of seven species of native New World hymenopterous larval-prepupal and pupal fruit fly (Diptera: Tephritidae) parasitoids

Abstract We describe the techniques used to colonize and domesticate seven native New World species of hymenopterous parasitoids that attack flies within the genus Anastrepha (Diptera: Tephritidae). All parasitoid species successfully developed on artificially reared Mexican fruit fly, Anastrepha ludens (Loew) larvae or pupae. The parasitoid species colonized were the following: Doryctobracon areolatus (Szépligeti), Doryctobracon crawfordi (Viereck), Opius hirtus (Fischer), Utetes anastrephae (Viereck) (all Braconidae, Opiinae), Aganaspis pelleranoi (Bréthes) and Odontosema anastrephae Borgmeier (both Figitidae, Eucoilinae) (all larval-pupal parasitoids), and the pupal parasitoid Coptera haywardi (Ogloblin) (Diapriidae, Diapriinae). We provide detailed descriptions of the different rearing techniques used throughout the domestication process to help researchers elsewhere to colonize local parasitoids. We also describe handling procedures such as number of hosts in parasitization units and compare optimal host and female age, differences in parasitism rate, developmental time, life expectancy and variation in sex ratios in each parasitoid species over various generations. In the case of D. crawfordi and C. haywardi we also provide partial information on mass-rearing techniques such as cage type, parasitization unit, larval irradiation dose and adult handling.

Developing diagnostic SNP panels for the identification of true fruit flies (Diptera: Tephritidae) within the limits of COI-based species delimitation

BackgroundRapid and reliable identification of quarantine pests is essential for plant inspection services to prevent introduction of invasive species. For insects, this may be a serious problem when dealing with morphologically similar cryptic species complexes and early developmental stages that lack distinctive characters useful for taxonomic identification. DNA based barcoding could solve many of these problems. The standard barcode fragment, an approx. 650 base pairs long sequence of the 5′end of the mitochondrial cytochrome oxidase I (COI), enables differentiation of a very wide range of arthropods. However, problems remain in some taxa, such as Tephritidae, where recent genetic differentiation among some of the described species hinders accurate molecular discrimination.ResultsIn order to explore the full species discrimination potential of COI, we sequenced the barcoding region of the COI gene of a range of economically important Tephritid species and complemented these data with all GenBank and BOLD entries for the systematic group available as of January 2012. We explored the limits of species delimitation of this barcode fragment among 193 putative Tephritid species and established operational taxonomic units (OTUs), between which discrimination is reliably possible. Furthermore, to enable future development of rapid diagnostic assays based on this sequence information, we characterized all single nucleotide polymorphisms (SNPs) and established “near-minimal” sets of SNPs that differentiate among all included OTUs with at least three and four SNPs, respectively.ConclusionsWe found that although several species cannot be differentiated based on the genetic diversity observed in COI and hence form composite OTUs, 85% of all OTUs correspond to described species. Because our SNP panels are developed based on all currently available sequence information and rely on a minimal pairwise difference of three SNPs, they are highly reliable and hence represent an important resource for developing taxon-specific diagnostic assays. For selected cases, possible explanations that may cause composite OTUs are discussed.

Understanding Long-Term Fruit Fly (Diptera: Tephritidae) Population Dynamics: Implications for Areawide Management

ABSTRACT Fruit flies (Diptera: Tephritidae) are devastating agricultural pests worldwide but studies on their long-term population dynamics are sparse. Our aim was to determine the mechanisms driving long-term population dynamics as a prerequisite for ecologically based areawide pest management. The population density of three pestiferous Anastrepha species [Anastrepha ludens (Loew), Anastrepha obliqua (Macquart), and Anastrepha serpentina (Wiedemann) ] was determined in grapefruit (Citrus × paradisi Macfad.), mango (Mangifera indica L.), and sapodilla [Manilkara zapota (L.) P. Royen] orchards in central Veracruz, México, on a weekly basis over an 11-yr period. Fly populations exhibited relatively stable dynamics over time. Population dynamics were mainly driven by a direct density-dependent effect and a seasonal feedback process. We discovered direct and delayed influences that were correlated with both local (rainfall and air temperature) and global climatic variation (El Niño Southern Oscillation [ENSO] and North Atlantic Oscillation [NAO]), and detected differences among species and location of orchards with respect to the magnitude and nature (linear or nonlinear) of the observed effects, suggesting that highly mobile pest outbreaks become uncertain in response to significant climatic events at both global and local levels. That both NAO and ENSO affected Anastrepha population dynamics, coupled with the high mobility of Anastrepha adults and the discovery that when measured as rate of population change, local population fluctuations exhibited stable dynamics over time, suggests potential management scenarios for the species studied lie beyond the local scale and should be approached from an areawide perspective. Localized efforts, from individual growers will probably prove ineffective, and nonsustainable.

Effect of continuous rearing on courtship acoustics of five braconid parasitoids, candidates for augmentative biological control of Anastrepha species

The courtship acoustics of five species of parasitoid wasps (Hymenoptera: Braconidae), potential candidates for augmentative biological control of Anastrepha (Schiner) species (Diptera: Tephritidae), were compared between recently colonized individuals and those continuously reared 70–148 generations. During courtship, males of these parasitoid species fan their wings and produce a series of low amplitude pulses. The first series of 15 or more continuous courtship pulses was used to measure the pulse duration, frequency, and interpulse interval (IPI) from the beginning, middle, and end of the pulse series. Each parameter was compared between young and old colonies, and among species. Several differences in courtship acoustics were detected in colonies that had been continuously reared. The pulse duration at the end of the pulse series was longer in old colonies for Doryctobracon crawfordi (Viereck) (Hymenoptera: Braconidae), but shorter for old colonies of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). The IPI of the middle pulse was shorter in old colonies of Opius hirtus (Fischer) (Hymenoptera: Braconidae), and was also shorter at the last pulse for old colonies of both Utetes anastrephae (Viereck) (Hymenoptera: Braconidae) and D. longicaudata. The duration of the middle pulse distinguished the three native species, and separated the two introduced species from each other. We discuss our findings in light of their biological and applied implications, particularly those dealing with quality control of mass-reared parasitoids.

Xyleborus glabratus, X. affinis, and X. ferrugineus (Coleoptera: Curculionidae: Scolytinae): Electroantennogram Responses to Host-Based Attractants and Temporal Patterns in Host-Seeking Flight

ABSTRACT The redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is an exotic wood-boring insect that vectors the mycopathogen responsible for laurel wilt, a lethal vascular disease of trees in the Lauraceae, including avocado (Persea americana Mill.). Effective semiochemical-based detection and control programs for X. glabratus will require an understanding of the chemical ecology and host-seeking behaviors of this new invasive pest. This study 1) presents an electroantennography (EAG) method developed for assessment of olfactory responses in ambrosia beetles; 2) uses that new method to quantify EAG responses of X. glabratus, X. affinis, and X. ferrugineus to volatiles from three host-based attractants: manuka oil (essential oil extract from Leptospermum scoparium Forst. & Forst.), phoebe oil (extract from Phoebe porosa Mex.), and wood from silkbay (Persea humilis Nash); and 3) documents temporal differences in host-seeking flight of the sympatric Xyleborus species. Field observations revealed that X. glabratus engages in flight several hours earlier than X. affinis and X. ferrugineus, providing a window for selective capture of the target pest species. In EAG analyses with X. glabratus, antennal response to phoebe oil was equivalent to response to host Persea wood, but EAG response elicited with manuka oil was significantly less. In comparative studies, EAG response of X. glabratus was significantly higher than response of either X. affinis or X. ferrugineus to all three host-based substrates. Future research will use this EAG method to measure olfactory responses to synthetic terpenoids, facilitating identification of the specific kairomones used by X. glabratus for host location.

Coping with an unpredictable and stressful environment: The life history and metabolic response to variable food and host availability in a polyphagous tephritid fly

The way energy resources are used under variable environmental conditions lies at the heart of our understanding of resource management and opportunism in many organisms. Here we sought to determine how a time-limited, synovigenic and polyphagous insect with a high reproductive-potential (Anastrephaludens), copes behaviourally and metabolically with environmental unpredictability represented by constant and variable regimes of host availability and variation in food quality. We hypothesized that an adaptive response to a windfall of nutritious food would be the rapid accumulation of energy metabolites (whole body lipids, glycogen and proteins) in the female. We also studied patterns of oogenesis as an indicator of egg-reabsorption under stressful environmental conditions. As predicted, patterns of energy metabolites were mainly driven by the quality and temporal pattern of food availability. In contrast, patterns of host availability had a lower impact upon metabolites. When given constant access to high quality nutrients, after an initial increase early in life, whole body lipids and glycogen were regulated downward to a steady-state level and somatic protein levels did not vary. In contrast, when food uncertainty was introduced, whole body lipid, glycogen and protein oscillated sharply with peaks associated with pulses of high-quality food. Production of eggs was highest when offered continuous access to hosts and high quality food. Importantly, females fully recovered their reproductive capacity when fruit became available following a period of host deprivation. With no evidence of egg resorption and high levels of egg dumping, it appears that egg dumping may favour the continuous production of eggs such that the females reproductive tissues are ready to respond to rapid changes in the availability of hosts. Our results exemplify the capacity of insects to maximize reproduction under variable and stressful environmental conditions.

Latitudinal variation in parasitoid guild composition and parasitism rates of North American hawthorn infesting Rhagoletis.

ABSTRACT Rhagoletis pomonella (Diptera: Tephritidae) populations in North America have diverged by exploiting host plants with varying fruiting phenologies in environments that differ markedly in temperature and humidity. As a result, four genetically and ecologically distinct R. pomonella populations that display partial reproductive isolation have evolved. Host shifting by Rhagoletis and similar evolutionary histories could have had cascading effects across trophic levels, influencing the diversity and distribution of associated parasitoid guilds. To establish the basis for a future understanding of the possible effect of divergence in R. pomonella populations on the parasitoids attacking these flies, we surveyed parasitoids from five different species of hawthorns distributed over 15 states in México and 2 states in the midwestern United States. Emerging parasitoids were identified, parasitism rates were calculated, and regional fly and parasitoid emergence schedules were determined. Parasitism rate, emergence schedules, Shannon-Weiner diversity indexes, and species accumulation curves were compared across three main geographical regions. Parasitism levels varied greatly among regions from an overall high of 27.2% in the United States to 5.5% in the Sierra Madre Oriental (SMO) mountains of Mexico, to as low as 0.19% in the Eje Volcánico Trans Mexicano (EVTM). Shannon-Weiner diversity indexes showed that parasitoid species diversity was similar across the distribution range of R. pomonella in Mexico and the United States because of the fact that total parasitism was dominated by only two species, one of them recovered across the whole North American range of hawthorn infesting Rhagoletis. Nevertheless, eight parasitoids were found attacking R. pomonella in Mexico compared with only four collected in the United States. Only two diapausing parasitoid species were shared between the U.S. and Mexican R. pomonella populations: Utetes canaliculatus and Diachasmimorpha mellea. Interestingly, many subtropical parasitoid species, usually associated to flies in the subtropical genus Anastrepha, were recovered in the SMO in low numbers. The wide distribution of U. canaliculatus and D. mellea offers an ideal opportunity to test for a shared biogeography and co-evolution between fly and parasitoids. In this regard, one factor contributing to the success of U. canaliculatus seems to be the wasps ability to modulate its eclosion time to track regional variation in hawthorn fruiting phenology and host (i.e., fly larvae) availability. Both R. pomonella and U. canaliculatus from southern sites emerged later than insects from northern populations, mirroring seasonal differences in hawthorn fruiting times across Mexico and the United States. These results suggest that molecular studies and crossing experiments could show, as they have for Rhagoletis, recent speciation events for parasitoid species of Nearctic origin that were found to be ecologically tracking environmentally driven divergence of their tephritid hosts.

Aganaspis alujai (Hymenoptera: Figitidae: Eucoilinae), a New Species Attacking Rhagoletis (Diptera: Tephritidae) in the Neotropical Region

Abstract A new neotropical species of Aganaspis (Hymenoptera: Figitidae, Eucoilinae) is described and compared to other Aganaspis species occurring in the Neotropical Region. This thelytokous species was reared from pupae of 2 species of fruit flies in the genus Rhagoletis (Diptera: Tephritidae), both in the suavis species group, and collected from 2 species of native walnuts in Mexico. Evidence of host specialization through diapause timing and notes on basic biology are provided.

Pest management through tropical tree conservation

Tropical trees can provide various ecological services to adjacent agricultural environments, including maintaining and amplifying the numbers of beneficial insects. In Mexico, certain tree species harbor a diverse guild of hymenopteran parasitoids that attack pest fruit flies (Diptera: Tephritidae) and are at the same time sources of valuable hardwood timber. Indigenous trees and their associated fauna are slowly disappearing due to forest clearance and the expansion of crop monocultures. Here we explore the relationship among pest and non-pest fruit flies, their fruit-hosts and parasitoids in the context of mango orchards and surrounding patches of uncultivated vegetation and propose a novel mechanism to use these associations in favor of conservation purposes and pest management. Trees of conservation biological control interest are classified as: (1) parasitoid multiplier plants, species that serve as alternate hosts for key fruit fly pests when their commercial hosts are not available, but in which they are unusually vulnerable to parasitism; (2) parasitoid reservoir plants, native or introduced trees in whose fruits non-pest fruit flies serve as hosts to generalist parasitoids that are able to attack pest tephritids in other species of commercially grown fruit; and (3) pest-based parasitoid reservoir plants, native or introduced species that are not economically important locally, but which harbor fruit flies that would be pests in other circumstances and that serve as hosts for parasitoids of the important pests in the vicinity. Protection, multiplication and dissemination of such tree species has the potential to increase the number of naturally produced fruit fly parasitoids and could assist in the management of tephritid pests in areas where destruction of forests has impoverished the historical sources of fruit fly natural enemies. Tropical forest conservation may help resource-poor farmers reduce crop losses, increase biodiversity within fruit-growing regions and conserve native forests for both conservation purposes and commercial use of native hardwoods.

Comparison of the host searching and oviposition behaviors of the tephritid (Diptera) parasitoids Aganaspis pelleranoi and Odontosema anastrephae (Hymenoptera: Figitidae, Eucoilinae).

We compared the host-searching and oviposition behaviors of two Neotropical figitid parasitoids (Hymenoptera) that exploit the same resource: ripe fruit infested by fruit fly larvae (Tephritidae) that have fallen to the ground. Sexually mature Aganaspis pelleranoi (Brèthes) and Odontosema anastrephae Borgmeier females were exposed individually, under no choice conditions, to four types of fruit: 1) Clean, intact guavas, Psidium guajava L. (no fruit fly larvae, no perforations); 2) clean, with artificial perforations; 3) artificially infested (with larvae), no perforations; 4) infested with artificial perforations. A behavioral transition matrix and sequence diagram of the following behaviors was constructed: walking on fruit, detection of larvae via the antennae, tarsi or aculeus, fruit perforation and penetration, and oviposition. Overall, we found that infested fruit (intact and with artificial perforations) elicited the most activity in the females of both species and that A. pelleranoi females exhibited a significantly more diverse behavioral repertoire (i.e., more transitions) and were significantly more active than O. anastrephae females. Females of both species penetrated the fruit in search of larvae by biting through the epi- and mesocarp, but O. anastrephae remained inside for significantly longer periods (up to eight hours). A. pelleranoi females used both their antennae and tarsi to detect larvae but the use of these structures varied depending on context: in infested fruit tarsi were used preferentially (usually while standing still) while in uninfested fruit, antennae were mainly used (usually while walking). In the case of O. anastrephae females the reverse pattern was usually observed with antennae most commonly used to detect larvae in infested fruit. We discuss our findings in light of their evolutionary, ecological and practical implications.