Eduardo Tadeo

Ongoing speciation within the Anastrepha fraterculus cryptic species complex : the case of the Andean morphotype

The Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) cryptic species complex is currently composed of seven taxonomically recognized morphotypes. Both, pre‐ and post‐zygotic isolation has been documented among four of these morphotypes, revealing that in fact they appear to be distinct biological entities. In order to progress in the full delimitation of species within the complex, we examined reproductive isolation between a Colombian population of the Andean morphotype and populations belonging to four other morphotypes spanning from Mexico to Argentina. Flies from the Andean morphotype exhibited strong pre‐zygotic mating isolation through temporal partitioning of mating activity. Post‐zygotic isolation was observed for crosses of males of all morphotypes and Andean morphotype females, yet most of the F1 hybrid ♂ × F1 hybrid ♀ self‐crosses showed normal levels of fertility, a finding suggesting a nuclear–cytoplasmic interaction according to previous studies. Overall, the Andean morphotype within the complex also appears to be a distinct biological entity. We discuss the implications of these findings for the understanding of speciation mechanisms in the Neotropical genus Anastrepha.

Invasive drosophilid pests Drosophila suzukii and Zaprionus indianus (Diptera: Drosophilidae) in Veracruz, Mexico

Summary The invasive drosophilid pests Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) were captured in traps baited with hydrolyzed protein lures during a trial aimed at monitoring Anastrepha flies infesting guava, Psidium guajava L. (Myrtales: Myrtaceae) in Xico, Veracruz, Mexico, during Sep 2014. This is the first record of these species in Veracruz State. These exotic species represented over 80% of the total drosophilid flies captured. Studies on the commercial impact of these pests in guava and in the production of other fruit species in the region should be considered a priority.

Alternative Mating Tactics as Potential Prezygotic Barriers to Gene Flow Between Two Sister Species of Frugivorous Fruit Flies

Rhagoletis completa Cresson and Rhagoletis zoqui Bush, are two sister species in the suavis group that were thought to occupy non-overlapping geographical ranges. Recent discovery of a contact zone in North Eastern México where natural interspecific hybrids with intermediate morphotypes can be found has led to laboratory studies in small enclosures that failed to identify the existence of reproductive barriers capable of maintaining the genetic integrity of both species. Because the experimental approach used in such studies could have interfered with natural behavior of flies, a series of additional mating compatibility tests under much less restrictive conditions were performed. Our observations, confirmed the fact that males and females of both species engage in interspecific matings. However, R. completa females were more reluctant to engage in heterospecific matings than R. zoqui females, revealing asymmetries in sexual isolation. Also, careful scrutiny of male guarding behavior and species specific partitioning of mating location unveiled subtle differences that could result in reproductive isolation if reinforced during secondary contact.

Fruit firmness, superficial damage, and location modulate infestation by Drosophila suzukii and Zaprionus indianus: the case of guava in Veracruz, Mexico

The exotic pestiferous flies Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) were recently identified in traps used for monitoring tephritid pests of guava, Psidium guajava L. (Myrtaceae), in Veracruz, Mexico. To determine whether both drosophilids were infesting guava, a previously unreported host, samples were taken from fruits on trees and fallen fruits on the ground. Overall, 74 and 36% of visually intact fruits attached to the tree were infested by D. suzukii and Z. indianus, respectively. Under laboratory conditions, small artificial punctures on the surface of ripe guavas did not result in increased oviposition by D. suzukii compared to undamaged fruit, whereas Z. indianus almost completely avoided oviposition, or were not capable of developing in fruit. Females of D. suzukii were capable of ovipositing in early ripe guavas in laboratory tests (23% of fruits were used for oviposition), although a high penetration force is required to pierce fruit (mean ± SEM = 89.0 ± 3.0 cN). Fully ripe and overripe guavas were softer (52.2–53.5 cN penetration force) and were more frequently infested (ca. 60% infestation). Numbers of females that developed in guavas were not influenced by ripeness/firmness, whereas male development was reduced in early ripe fruit compared to ripe and overripe fruit. In laboratory choice experiments with crushed fruits, D. suzukii adults were equally attracted to guava and blueberry, independent of gender and age. However, raspberry was more attractive than guava. This study demonstrates that D. suzukii is attracted to guava, is capable of ovipositing in fruit and, under field conditions, is more abundant in fruits still attached to the tree compared to fallen fruit that remain intact. In contrast, Z. indianus was not capable of developing in intact guavas and, although present in fruits attached to the tree, was most abundant in fallen damaged fruits.

Response of the sapote fruit fly, Anastrepha serpentina (Diptera: Tephritidae), to commercial lures and trap designs in sapodilla orchards

Abstract Anastrepha serpentina (Wiedemann) (Diptera: Tephritidae) is one of the least studied of the pestiferous Neotropical tephritid flies despite its propensity to attack several commercial fruit crops, mainly in the Sapotaceae (Ericales). Few studies have been performed to improve monitoring traps and lures specifically targeted at this species. Management currently is achieved by using the hydrolyzed protein lure (Captor® with borax) and a Multilure® trap in combination with chemical control measures. Here, we aimed to evaluate the efficacy of other commercial lures and traps for monitoring purposes in sapodilla orchards. The efficacies of 3 commercial lures, namely, Captor (chemically hydrolyzed protein) + borax, CeraTrap® (enzymatically hydrolyzed protein), and Biolure® (dry lure based on ammonium acetate and putrescine), were compared in 2 independent experiments. In a 1st experiment, CeraTrap caught twice as many A. serpentina flies per trap per day as Captor + borax. In a 2nd experiment, trapping efficacy of CeraTrap and Biolure was similar, and both lures caught more A. serpentina flies per day per trap than Captor + borax. No significant differences in the capture of A. serpentina were observed among a Multilure trap, a Tephi Trap®, or a simple polyethylene bottle trap, when baited with CeraTrap. This study contributes with additional information on the response of A. serpentina to commercial lures, showing that CeraTrap could represent an effective alternative to monitor this pest using simple and cheap polyethylene bottle traps.

Divergence and evolution of reproductive barriers among three allopatric populations of Rhagoletis cingulata across eastern North America and Mexico

Geography is often a key factor facilitating population divergence and speciation. In this regard, the geographic distributions of flies in the genus Rhagoletis (Diptera: Tephritidae) in temperate North America have been affected by cycles of Pleistocene glaciation and interglacial periods. Fluctuations in climatic conditions may have had their most dramatic effects on geographically isolating Rhagoletis flies in the central highland region of Mexico. During past periods of allopatry, a degree of post‐zygotic reproductive isolation appears to have evolved between hawthorn‐infesting populations of Rhagoletis pomonella (Walsh) in the central Eje Volcanico Trans Mexicano (EVTM) and those from the Sierra Madre Oriental Mountains (SMO) of Mexico, as well as hawthorn flies from the eastern USA. Here, we investigate the generality of this finding in the genus Rhagoletis by testing for reproductive isolation among populations of Rhagoletis cingulata (Loew) (Diptera: Tephritidae) collected from infested domesticated sweet cherry (Prunus avium L.) in the USA and black cherry [Prunus serotina Ehrh. (both Rosaceae)] from the SMO and EVTM. We report evidence for marked post‐mating reproductive isolation among certain R. cingulata populations. The high levels of reproductive isolation were observed between R. cingulata flies from populations in the USA and SMO differed from the pattern seen for R. pomonella, primarily involving the EVTM. In addition, egg hatch was significantly reduced for crosses between SMO males and EVTM females, but not greatly in the opposite direction. We discuss potential causes for the different patterns of post‐mating reproductive isolation among Rhagoletis flies.

Elucidating the function of ejaculate expulsion and consumption after copulation by female Euxesta bilimeki

Postcopulatory processes can influence male reproductive success in several animal species. Females can use different mechanisms to bias male paternity after copulation. One of such mechanisms consists in expelling all or part of the ejaculate after copulation. Euxesta bilimeki is an Ulidiid fly whose females not only frequently expel ejaculates after mating but also consume the ejaculate after expulsion. In order to understand the significance of these behaviors we examined video recordings of courtship, copulatory, and postcopulatory behaviours. The presence of sperm in female storage organs was confirmed after mating with males of different sizes and was correlated with duration of courtship, copulation, and the period from the end of copulation to ejaculate expulsion. The effect of ejaculate consumption on female fitness (fecundity and longevity) was compared among females held under different dietary treatments: a rich diet consisting of protein, sugar and water, an intermediate diet composed of sugar and water, a poor diet of only water and females that were completely deprived of food and water. All of the observed females expelled ejaculates after mating. The probability of storing sperm in the two spermathecae and the ventral receptacle was correlated with interactions between the duration of all behaviours examined and male size. Except for starved females, who lived longer when allowed to consume ejaculates, ejaculate consumption had no effect on fitness. Results suggest that females can bias sperm storage according to male mating effort, while the consumed ejaculate had some nutritional value only evident when females were completely starved.

Improved capture of Drosophila suzukii by a trap baited with two attractants in the same device

The improvement of trap-lure combinations is an important part of integrated pest management programs that involve monitoring pests for timely insecticide applications, or for their use in control strategies such as mass trapping or bait stations. In this study improvements in the capture of Drosophila suzukii were not observed following the inclusion of different color stimuli with respect to a red-black stripe cup trap. This red-black stripe trap with a hemispherical dome-shaped lid had a significantly improved physical retention of flies compared to traps fitted with a flat lid. Retention was further improved when an additional tube device, which could be baited with a supplemental attractant, was introduced through the dome-shaped lid. Under laboratory conditions, this trap, in which apple cider vinegar + 10% ethanol was present as the drowning solution and the additional tube device was baited with a fermenting mixture of sugar and yeast, was significantly more effective in catching D. suzukii flies than other conventional attractants or a commercial lure. The capture rate of this trap-lure combination remained higher than that of a commercial lure, even after 20 days of use under laboratory conditions. In a guava orchard this trap was 15-fold more effective in catching D. suzukii flies than similar traps baited with apple cider vinegar alone, 4 to 7 fold more effective than similar traps baited with a commercial lure, and 1.7-fold more effective than a fermenting mixture of yeasts and wheat flour. In commercial blackberry orchards, this trap was 6-fold more effective in trapping D. suzukii flies than the clear trap baited with apple cider vinegar used by growers. The efficacy of this trap presents a promising line of future research for monitoring and control of D. suzukii and likely other drosophilid pests.

Experimental hybridization and reproductive isolation between two sympatric species of tephritid fruit flies in the Anastrepha fraterculus species group

Among tephritid fruit flies, hybridization has been found to produce local adaptation and speciation, and in the case of pest species, induce behavioral and ecological alterations that can adversely impact efficient pest management. The fraterculus species group within Anastrepha (Diptera: Tephritidae), is a rapidly radiating aggregate, which includes cryptic species complexes, numerous sister species, and several pest species. Molecular studies have highlighted the possibility of introgression between A. fraterculus and A. obliqua. Reproductive isolation has been studied among morphotypes of the A. fraterculus species complex as a tool for species delimitation. Here we examined the existence and strength of prezygotic and postzygotic isolation between sympatric populations of two closely related species within the highly derived fraterculus group (A. fraterculus and A. obliqua), coexisting in nature. Although adults of both species showed a strong tendency for assortative mating, a small proportion of hybrid pairings in both directions were observed. We also observed asymmetric postzygotic isolation, with one hybrid cross displaying a strong reduction in fecundity and F1 egg fertility. Survival was greater for the progeny of homotypic and hybrid crosses in the maternal host. There was a marked female biased sex ratio distortion for both F1 hybrid adults. Hybridization between A. fraterculus and A. obliqua in nature may be difficult but possible; these two species display stronger reproductive isolation than all pairs of species previously examined in the A. fraterculus species complex. Asymmetric postzygotic isolation is suggestive of Wolbachia mediated cytoplasmic incompatibilities that may be exploited in area‐wide pest management.

Precopulatory mating and postzygotic isolation between two walnut-infesting species of Rhagoletis from Mexican highlands

Pleistocene glacial and postglacial cycles producing contraction and expansion of temperate habitats have resulted in substantial diversification among several plant and animal taxa of Neararctic origin undergoing periods of isolation and secondary contact in high‐elevation areas of Mexico. One of such groups are walnut‐infesting fruit flies in the genus Rhagoletis (Diptera: Tephritidae), comprised of six recently derived species among which phylogenetic relationships have been difficult to unravel using conventional molecular methods. Here, we examined pre‐ and postzygotic isolation between two genetically similar and morphologically distinct species which are currently parapatric in central Mexico. Local adaptation driven by differences in host plant phenology between Rhagoletis zoqui Bush and Rhagoletis ramosae Hernández‐Ortíz resulted in allochronic isolation. Despite the existence of precopulatory mating isolation, there was a substantial number of hybrid matings in field cages where conspecific and heterospecific males and females were simultaneously released. The bulk of mating activity took place on host fruit. Rhagoletis zoqui females were more reluctant to mate with R. ramosae males than with males of their own species. Distinctive behavioral differences were observed between males during contests, fruit guarding, and approach to conspecifics on fruit. There was also some asymmetric postzygotic isolation, with the hybrid combination of R. zoqui males and R. ramosae females resulting in lower egg hatch than other mating combinations. Results were consistent with those of a phylogenetic study suggesting recent divergence of R. ramosae from Rhagoletis completa Cresson and R. zoqui in the Sierra Madre Oriental and the Mexican Trans Volcanic Belt.