Release Recapture Experiments Research Articles

Alleviating the loss: A conical fish screen installation reduces native fish entrainment at a gravity‐fed water diversion

Abstract Each year, millions of fish are extracted from Australian waterways by the pumping and diversion of water into irrigation systems. Fish protection screens can help reduce these losses but are largely untested in Australian rivers. In this study, a large, gravity‐fed irrigation offtake on Gunbower Creek, Victoria, Australia, was investigated for fish and debris entrainment. Experiments were performed under screened and unscreened conditions across various river flows. Mark–release–recapture experiments were undertaken with fingerlings of two recreationally significant fish species, Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua), together with wild fish community assessments, to determine how effective the screen was at reducing fish entrainment into the irrigation channel. The mean percentage of recaptured fingerlings was significantly lower when the irrigation channel offtake was screened compared with unscreened. Entrainment of released fish into the irrigation channel was reduced by >98%. Similarly, wild fish entrainment was significantly lower when the irrigation channel was screened. When screened, fewer wild species dominated the sampled fish community, and entrained fish were generally <40 mm in length. Debris loads decreased significantly in the irrigation channel owing to the screen, indicating the economic benefits of fish screens. Implementing screens could aid in native fish conservation efforts in riverine environments.

Movement patterns and size distribution of little tunny (Euthynnus alletteratus) in the Eastern Central Atlantic Ocean: Insights from conventional tag release-recapture data

This study investigates the movements, patterns, and size distribution of little tunny (Euthynnus alletteratus) in the Eastern Central Atlantic Ocean. Data were collected as part of the ICCAT Atlantic Ocean Tuna Tagging Programme (AOTTP) through conventional tag release-recapture experiments. The study analyzed data from 7870 tagged fish, of which 452 were recaptured between 2016 and 2020. The results indicated that little tunny could travel long distances, with some fish covering up to 600 Nm between Mauritania and Côte d’Ivoire. The movement patterns of tagged fish varied, and there appeared to be some exchange of fish between Senegal-Mauritania and the Gulf of Guinea through the Côte d’Ivoire Exclusive Economic Zone (EEZ). The recapture rate was the highest within the first month after release, with half of the tagged fish recaptured within this period, then approximately 17 % and 11.5 % of tagged fish were recaptured within 60 and 90 days, respectively. The size distribution of tagged and recaptured little tunny varied by area with statistically significant differences between Côte d’Ivoire – Gulf of Guinea and those from Mauritania to Liberia. The recaptured fish were larger than the tagged fish in all areas studied, suggesting a significant growth of individuals (4.2 cm per quarter). In conclusion, this study highlights the extensive movements and migration patterns of little tunny in the Eastern Central Atlantic Ocean. These findings suggest that factors such as Anchored Fish Aggregating Devices (AFAD) may influence the mobility of fish in certain areas and that the size distribution varies significantly between different regions.

Exploring alternative insecticide delivery options in a “lethal house lure” for malaria vector control

The In2Care EaveTube is a house modification designed to block and kill malaria mosquitoes using an electrostatic netting treated with insecticide powder. A previous study demonstrated prolonged duration of effective action of insecticide-treated electrostatic netting in a semi-field setting. As part of a cluster randomized controlled trial (CRT) of the EaveTube intervention in Côte d’Ivoire, we investigated the residual efficacy of a pyrethroid insecticide deployed in EaveTubes under village conditions of use. We also explored the scope of using existing malaria control technologies including LLINs and IRS as alternative methods to deliver insecticides in the lethal house lure. The efficacy of beta-cyfluthrin was monitored over time using the “eave tube bioassay” method. Mortality of beta-cyfluthrin exposed pyrethroid resistant Anopheles gambiae mosquitoes was > 80% after 4 months. The impact (mosquito mortality) of PVC tubes coated with pirimiphos methyl was similar to that of beta-cyfluthrin treated insert (66.8 vs. 62.8%) in release-recapture experiments in experimental huts. Efficacy was significantly lower with all the LLINs tested; however, the roof of PermaNet 3.0 induced significantly higher mosquito mortality (50.4%) compared to Olyset Plus (25.9%) and Interceptor G2 (21.6%) LLINs. The efficacy of the alternative delivery methods was short-lived with mortality decreasing below 50% within 2 months in residual activity bioassays. None of the products tested appeared superior to the powder treatments. Further research is therefore required to identify suitable insecticide delivery options in EaveTube for malaria vector control.

The Use of Multiple Unmanned Aircraft Systems as a Swarm to Release Sterile Mexican Fruit Fly (Diptera: Tephritidae) Into South Texas Citrus Groves.

Mexican fruit fly Anastrepha ludens (Loew) (Diptera: Tephritidae) is a key economic pest of citrus and represents a quarantine issue along the United States and Mexico Border. In order to respond to this threat, the United States Department of Agriculture produces approximately 175 million sterile Mexican fruit fly pupae per week and releases approximately 150 million adult flies per week via conventional fixed wing aircraft. Unmanned aircraft systems (UAS) offer a novel means of releasing sterile insects aerially, can be deployed on short notice in rapid response scenarios, require a small footprint to operate, and offer an alternative means to releasing sterile insects to traditional manned aircraft. UAS, however, are currently limited in two key areas, range and payload capacity. Swarm technology, flying multiple UAS at once, may increase the utility of UAS by distributing payloads and release patterns across multiple UAS. In order to test the viability of swarm technology in the release of sterile insects we conducted multiple mark release recapture experiments over south Texas citrus groves during 2017, 2018, and 2019. The results of this study demonstrate improved release rates from 89.9% (n = 5) of flies released with ca. 0.64% recapture during 2018, to 98.2% (n = 6) released with ca. 0.74% recapture during 2019. These results demonstrate that swarm technology is a viable technique for increasing aerial release capacity and flexibility of sterile insect technique (SIT) programs.

Mark-release-recapture of male Aedes aegypti (Diptera: Culicidae): Use of rhodamine B to estimate movement, mating and population parameters in preparation for an incompatible male program.

Rapid advances in biological and digital support systems are revolutionizing the population control of invasive disease vectors such as Aedes aegypti. Methods such as the sterile and incompatible insect techniques (SIT/IIT) rely on modified males to seek out and successfully mate with females, and in doing so outcompete the wild male population for mates. Currently, these interventions most frequently infer mating success through area-wide population surveillance and estimates of mating competitiveness are rare. Furthermore, little is known about male Ae. aegypti behaviour and biology in field settings. In preparation for a large, community scale IIT program, we undertook a series of mark- release-recapture experiments using rhodamine B to mark male Ae. aegypti sperm and measure mating interactions with females. We also developed a Spatial and Temporally Evolving Isotropic Kernel (STEIK) framework to assist researchers to estimate the movement of individuals through space and time. Results showed that ~40% of wild females captured daily were unmated, suggesting interventions will need to release males multiple times per week to be effective at suppressing Ae. aegypti populations. Males moved rapidly through the landscape, particularly when released during the night. Although males moved further than what is typically observed in females of the species, survival was considerably lower. These unique insights improve our understanding of mating interactions in wild Ae. aegypti populations and lay the foundation for robust suppression strategies in the future.

Low-oxygen hormetic conditioning improves field performance of sterile insects by inducing beneficial plasticity.

As part of sterile insect technique (SIT) programs, irradiation can effectively induce sterility in insects by damaging germline genomic DNA. However, irradiation also induces other off‐target side effects that reduce the quality and performance of sterilized males, including the formation of damaging free radicals that can reduce sterile male performance. Thus, treatments that reduce off‐target effects of irradiation on male performance while maintaining sterility can improve the feasibility and economy of SIT programs. We previously found that inducing a form of rapid, beneficial plasticity with a 1‐hr anoxic‐conditioning period (physiological conditioning hormesis) prior to and during irradiation improves male field performance in the laboratory while maintaining sterility in males of the cactus moth, Cactoblastis cactorum. Here, we extend this work by testing the extent to which this beneficial plasticity may improve male field performance and longevity in the field. Based on capture rates after a series of mark release–recapture experiments, we found that anoxia‐conditioned irradiated moths were active in the field longer than their irradiated counterparts. In addition, anoxia‐conditioned moths were captured in traps that were farther away from the release site than unconditioned moths, suggesting greater dispersal. These data confirmed that beneficial plasticity induced by anoxia hormesis prior to irradiation led to lower postirradiation damage and increased flight performance and recapture duration under field conditions. We recommend greater consideration of beneficial plasticity responses in biological control programs and specifically the implementation of anoxia‐conditioning treatments applied prior to irradiation in area‐wide integrated pest management programs that use SIT.

Fatty Acid Profile as an Indicator of Larval Host for Adult Drosophila suzukii.

Simple SummarySpotted-wing drosophila, Drosophila suzukii, is an invasive pest of soft-skinned fruits. Adult female flies oviposit, or lay eggs, into fruits where the larvae develop, making infested fruit unmarketable. The flies rely on alternative hosts, both cultivated and wild, to survive and maintain populations throughout the year. Better understanding of how the flies migrate between different hosts could be beneficial to improving management of the pest in crops. This study demonstrates potential to discriminate larval host of adult flies by analysis of fatty acids carried from the larvae to the adult stage in the body using a machine learning algorithm as an alternative to linear discriminant methods. Our study shows that fatty acids in adult flies can be used to determine larval host and that the machine learning algorithm can perform the discriminant analysis without making any assumptions about the data.Drosophila suzukii is a severe economic invasive pest of soft-skinned fruit crops. Management typically requires killing gravid adult female flies with insecticides to prevent damage resulting from oviposition and larval development. Fruits from cultivated and uncultivated host plants are used by the flies for reproduction at different times of the year, and knowledge of D. suzukii seasonal host plant use and movement patterns could be better exploited to protect vulnerable crops. Rearing and various marking methodologies for tracking movement patterns of D. suzukii across different landscapes have been used to better understand host use and movement of the pest. In this study, we report on potential to determine larval host for adult D. suzukii using their fatty acid profile or signature, and to use larval diet as an internal marker for adult flies in release-recapture experiments. Fatty acids can pass efficiently through trophic levels unmodified, and insects are constrained in the ability to synthesize fatty acids and may acquire them through diet. In many holometabolous insects, lipids acquired in the larval stage carry over to the adult stage. We tested the ability of a machine learning algorithm to discriminate adult D. suzukii reared from susceptible small fruit crops (blueberry, strawberry, blackberry and raspberry) and laboratory diet based on the fatty acid profile of adult flies. We found that fatty acid components in adult flies were significantly different when flies were reared on different hosts, and the machine learning algorithm was highly successful in correctly classifying flies according to their larval host based on fatty acid profile.

Dispersal behaviour of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae) in avocado groves and estimation of lure sampling range

Abstract Invasive ambrosia beetles in the Euwallacea nr. fornicatus species complex (Coleoptera: Curculionidae: Scolytinae) threaten avocado production in multiple countries. These pests are currently monitored with lures containing quercivorol; α‐copaene was also recently discovered to be an effective attractant. We investigated dispersal behaviour of female E. nr. fornicatus in two Florida avocado groves using mark–release–recapture experiments and laboratory flight mills. Additionally, we estimated the sampling range of quercivorol and α‐copaene lures deployed alone and in tandem. The two‐component lure recaptured 31.2% of marked beetles, which was significantly more than quercivorol (11.2%) or α‐copaene (8.8%) alone. Contour analysis indicated that wind speed and direction can influence the number of females that disperse, as well as the direction and distance of their flight. Two methods were used to estimate sampling range and both of them indicated comparable effective ranges for the three lure treatments, with 80% of marked beetles being recaptured within 30–35 m of the release point. Average total flight distance in laboratory tests was 81.0 m in 24 h, with a maximum distance recorded at 400 m. The combination of quercivorol and α‐copaene lures provides the best detection of pest E. nr. fornicatus in Florida, with a recommended trap spacing of approximately 30 m in surveillance programmes for this pest in avocado groves.

Avoiding Unwanted Vicinity Effects With Attract-and-Kill Tactics for Harlequin Bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae).

In the development of an attract-and-kill approach for the management of harlequin bug (HB), Murgantia histrionica (Hahn), we evaluated attraction and retention of HB by pheromone-baited traps in the field. In release-recapture and on-farm experiments, traps with collard plants with lures-containing HB aggregation pheromone (murgantiol = 10,11-epoxy-1-bisabolen-3-ol) arrested and retained more HB than traps with either plant or lure. In order to avoid unwanted vicinity effects (increased feeding injury to neighboring crop plants due to halo or spillover effects), we also investigated two methods of retaining HB that were attracted to traps: a systemic toxicant (neonicotinoid applied to the trap plant as a drench) and a contact toxicant (long-lasting insecticidal netting [LLIN] with incorporated pyrethroid). More HB adults and more HB-feeding injury were observed on collard plants in the vicinity of lures compared with those neighboring lures in combination with a systemic toxicant. This difference indicates that improvements to trap retention acted to mitigate spillover effects, thereby avoiding unwanted vicinity effects. We also conducted laboratory assays in order to estimate the length of exposure to LLIN necessary to knock down HB adults and nymphs, calculating a knockdown time (KDT50) of 78.3, 2.6, and 2.1 s for females, males, and nymphs, respectively.

Caught in transit: offshore interception of seafaring propagules from seven mangrove species

AbstractMany organisms are transported passively and make use of the energy of natural phenomena or other organisms to disperse. However, not all species are equally likely to disperse over long distances. In mangroves, which possess seafaring propagules, it is largely unknown which species are more likely to reach the ocean and contribute to long‐distance dispersal. This is because dispersal has been mainly studied under reductionist laboratory conditions and via localized release–recapture experiments. Direct interceptions of propagules at sea have hardly been attempted because of the high labor intensity. Here, we set up a local citizen‐science network and engaged local fishermen to collect floating mangrove propagules over a period of 27 months. By comparing the dispersing community of propagules from the local stands in which they were produced, the open water of the bay, and the open ocean beyond the coral reef barrier, we could study the transition between local and long‐distance dispersal. The composition of the dispersing community changed from the local stands toward the ocean, suggesting that this transition imposes an important selective filter for leaving the local system. With the exception of three rare species (Lumnitzera racemosa, Pemphis acidula, and Xylocarpus moluccensis), we intercepted dispersing propagules of every mangrove species occurring in the East African region. Most intercepted propagules were produced by Rhizophora mucronata and Ceriops tagal, followed by Bruguiera gymnorrhiza and Avicennia marina, which also represent the most abundant species in the nearby mangrove forest. A larger number of propagules were intercepted during the wet season, with fewer propagules recovered during the dry season. Overall, our study indicates that differences in the dispersal capacity of mangrove propagules are not straightforward and that some species may better disperse at local scales within an estuary or embayment, while others might be more suitable for dispersal over longer distances. The presence of such trade‐offs may help explain why current attempts to use mangrove traits to predict mangrove species distributions at different scales have remained only moderately successful.

Estimating Monitoring Trap Plume Reach and Trapping Area for Drosophila suzukii (Diptera: Drosophilidae) in Michigan Tart Cherry

Central-monitoring trap, multiple point release-recapture experiments were used to interpret Drosophila suzukii (Diptera: Drosophilidae) catch in a monitoring trap baited with a Scentry Biologicals commercial D. suzukii lure deployed in Michigan tart cherry orchards. The plume reach was found to be short (<3 m), while the maximum dispersive distance for 95% of the released D. suzukii was projected to be ca. 90 m, so as to yield a trapping area of 2.7 ha. These data were consistent across two growing seasons and provide the first information about the dispersal distance and monitoring trap efficacy in a fruit crop setting for D. suzukii. Catch data per single monitoring trap can now be used to estimate absolute pest density in cherries. Alarmingly, catching one D. suzukii in a monitoring trap translates to approximately 192 D. suzukii per trapping area of 2.7 ha (26 per acre). Thus, by the time D. suzukii catch becomes detectable, it is very probable that the population is already above the tolerable damage threshold, suggesting control measures should immediately be taken if the fruit is in a vulnerable stage. Caution should be taken when extrapolating these results from cherry because the measured values may differ in other crop systems.

Isotropic and anisotropic processes influence fine-scale spatial genetic structure of a keystone tropical plant.

Limited seed or pollen dispersal enhances spatial genetic relatedness between individuals (fine-scale spatial genetic structure, FSGS), which usually decreases as a function of physical distance. However, such isotropic pattern of FSGS may not always occur when spatially asymmetric processes, for instance, wind direction during dispersal, are considered in wind-pollinated and -dispersed plants. This study assessed the pattern of FSGS in the keystone tropical wetland plant Cyperus papyrus (papyrus) as a function of these isotropic and anisotropic processes. We tested the hypothesis that the FSGS would be influenced by predominant wind direction during pollen and seed dispersal, as well as by the physical distance between individuals. We genotyped a total of 510 adults and 407 juveniles from three papyrus swamps (Ethiopia) using 15 microsatellite markers. In addition, the contemporary directional dispersal by wind was evaluated by seed release-recapture experiments and complemented with parentage analysis. Adults and juveniles differed in the strength of isotropic FSGS ranging from 0.09 to 0.13 and 0.12 to 0.16, respectively, and this suggests variation in dispersal distance. Anisotropic FSGS was found to be a function of asymmetric wind direction during dispersal/pollination that varied between sites. Historical gene dispersal distance was astoundingly low (<4 m), possibly due to localized seed rain. According to our contemporary dispersal estimates, mean pollen dispersal distances were longer than those of seed dispersal (101 and <55 m, respectively). More than two-thirds of seeds and half of pollen grains were locally dispersed (≤80 m). The difference in historical and contemporary dispersal distance probably resulted from the asymmetric wind direction due to change in vegetation cover in the surrounding matrix. We further concluded that, in addition to wind direction, post-dispersal processes could influence gene dispersal distance inferred from the FSGS.

Bidirectional gene flow on a mangrove river landscape and between-catchment dispersal of Rhizophora racemosa (Rhizophoraceae)

Understanding how landscape structure shapes the genetic structure of populations of keystone species is important for their long-term management. We tested the unidirectional dispersal hypothesis on the linear river landscape of the Wouri River and the one catchment-one gene pool hypothesis on red mangrove (Rhizophora racemosa) populations of the Cameroon Estuary complex. Therefore, we conducted release–recapture experiments in the field, and sampled 649 adult trees for plant material for genetic analyses. This allowed for estimating genetic diversity and structure, as well as dispersal directionality. Genetic diversity in populations downstream did not differ significantly from upstream populations and the molecular variance of populations did not correlate with their position on the linear landscape. Contemporary and historical migration estimates indicated bidirectional dispersal, i.e. in both the downstream and the upstream direction along the Wouri River. This was confirmed by the propagule dispersal directions derived from our field experiments. Bayesian clustering analysis assigned all individuals of this estuary into one cluster, suggesting high inter-catchment connectivity. River flow currents, tides, and wind plausibly operate together to ensure the high genetic connectivity within this complex estuary.

Comparative Responses of Anastrepha ludens and Anastrepha obliqua (Diptera: Tephritidae) to the Synthetic Attractant BioLure.

The responses of wild and sterile Anastrepha ludens (Loew) and Anastrepha obliqua (Mcquart) fruit flies to the synthetic attractant BioLure were determined by electroantennography (EAG), in field cage tests using MultiLure traps, and by release-recapture field experiments using sterile flies. In EAG bioassays, no differences were found between species, sexes, sterile and wild flies. There were only specific differences and interactions in dose responses. More A. ludens than A. obliqua individuals were captured in multilure traps in field cage test. In A. ludens, there was not significant difference between the number of females and males captured, whereas in A. obliqua more females than males were caught. Age showed a bimodal response in both species and both sexes, with peaks at 4 and 14 d old. In the release-recapture experiments, there were significant differences between species, sexes, and orchards and among the days after release. More individuals of A. ludens than A obliqua were recaptured. Only in A. obliqua the difference between the sexes was significant, with a 3.60:1 female:male ratio. Orchard conditions affected the recapture rate, but in both orchards the largest number of flies recaptured occurred during the first day after release (46 and 88% in each orchard). Our results show that the response to this synthetic lure is species-specific and contribute to better interpret trapping data.

Dispersal of Monochamus galloprovincialis (Col.: Cerambycidae) as recorded by mark–release–recapture using pheromone traps

AbstractThe spread of the pine wood nematode (PWN), Bursaphelenchus xylophylus (Nematoda; Aphelenchoididae), the causal agent of the pine wilt disease, is greatly constrained to the dispersal of its vectors, long‐horned beetles of the Monochamus genus. Disease spread at global and regional scales has been mainly caused by human‐mediated transport, yet at a local scale, the short‐ and long‐distance dispersal behaviour of the beetles determine colonization dynamics. Three mark–release–recapture experiments using commercial traps and lures allowed the parameterization of the dispersal kernel under two landscape fragmentation scenarios for the only known European PWN vector, Monochamus galloprovincialis. The respective release of 171 and 353 laboratory‐reared beetles in continuous pine stands in 2009 and 2010 resulted in 36% and 28% recapture rates, yet, at a fragmented landscape in 2011, only 2% of the released 473 individuals could be recaptured. Recaptures occurred as soon as 7–14 days after their release, in agreement with the requirement of sexual maturation to respond to the pheromone–kairomone attractants. Data from the first two experiments were fitted to one mechanical and two empirical dispersal models, from which the distance dispersal kernels could be computed. Derived estimated radii enclosing 50% and 99% of dispersing M. galloprovincialis under continuous pine stands ranged between 250–532 m and 2344–3495 m depending on the replicate and choice of model. Forecasted recaptures in 2011 resulted in a moderate underestimation of long‐distance dispersal, probably influenced by the high degree of habitat fragmentation. In addition, trapping parameters such as the effective sampling area (0.57–0.76 ha) or the seasonal sampling range (426–645 m) could be derived. Observed results, derived dispersal kernels and trapping parameters provide valuable information for the integrated pest management of PWD. Furthermore, estimated dispersal distances indicate that ongoing clear‐cut measures for eradication in the European Union are likely ineffective in stopping the vectors dispersal.

Attraction of wild‐like and colony‐reared Bactrocera cucurbitae (Diptera:Tephritidae) to cuelure in the field

AbstractThe attraction of wild tephritids to semiochemical‐based lures is the ideal basis for trap network design in detection programmes, but in practice, mass‐reared colony insects are usually used to determine trap efficiency. For Bactrocera cucurbitae Coquillett, a lower response by wild males compared with colony‐derived individuals, usually used to estimate attraction parameters, could mean that the sensitivity of detection networks targeting this pest is reduced. We describe the results of mark–release–recapture experiments with wild‐ and colony‐derived B. cucurbitae males in a grid of cuelure‐baited traps within a macadamia nut orchard in Hawaii Island designed to quantify the attraction of cuelure to each fly type. For colony males, we estimate a 65% probability of capture at 27 m, intermediate with previous estimates on the attraction of methyl eugenol to Bactrocera dorsalis Hendel (36 m) and trimedlure to Ceratitis capitata Wiedemann (14 m) at the same site. Results suggest similar response over distance by wild‐derived B. cucurbitae compared with colony in the field, but there may be qualitative differences in response between wild and colony based on very low response of wild males in a standard bioassay of attraction. For both fly types, the estimates of attraction in the smaller of two grid sizes tested were lower than for the larger spacing, suggesting trap competition was a factor at an intertrap distance of 75 m. Dispersal patterns within the grid were generally to the south for the colony‐derived males and more variable for the wild‐derived males. In neither case was the direction of recapture correlated with the prevailing direction of the wind.

Seasonal variation in size estimates of Aedes albopictus population based on standard mark–release–recapture experiments in an urban area on Reunion Island

The implementation of the sterile insect technique for area-wide vector control requires that natural population density be accurately estimated to determine both the appropriate time to treat and the adequate number of sterile males for release. Herein, we used mark–release–recapture (MRR) to derive seasonal abundance estimates of Aedes albopictus population sizes within a delimited geographical area in Reunion Island. Population size of Ae. albopictus was estimated through four mark–release–recapture experiments carried out separately in different seasons. Marked males and females were released each time, and recaptured using BG sentinel traps for six consecutive days. Data were used to estimate the population size using a conceptual model that incorporates the variation in daily mortality rates. The likely influence of environmental factors on the magnitude of catches and on population fluctuation was analyzed. A total of 2827 mosquitoes (1914 males and 913 females) were marked and released on four occasions during dry and wet seasons. After release, 138 males (7.21%) and 86 females (9.41%) of the marked specimens were recaptured in subsequent samplings. The effectiveness of the daily captures of wild and released mosquitoes was significantly influenced by meteorological conditions such as temperature, rainfall, wind speed and light intensity. The estimates of Ae. albopictus population size obtained with our model estimator ranged from 298 to 1238 males and 604 to 2208 females per ha, with seasonal variability – higher population size in the humid season. The presented results will be essential in designing more effective sterile male release strategies for long-term suppression of wild Ae. albopictus populations.

Butterfly dispersal across Amazonia and its implication for biogeography

Spatial movement is fundamental to ecological and evolutionary processes because of its role in habitat colonization and diversification. This study examines the dispersal potential of two Neotropical butterflies, Morpho achilles and Bia actorion, to estimate the time necessary to expand into their current geographical distribution in the Amazon Forest. To do so, we use life history data, dispersal rates estimated from mark–release–recapture experiments, and reaction‐diffusion or integro‐difference equations to calculate an annual speed for the wave of dispersal across suitable unoccupied habitat. We show that times required for these butterflies to disperse across Amazonia are orders of magnitude smaller than phylogenetic estimates of the species ages. We compare dispersal rates of Morpho and Bia to other Neotropical butterflies, including taxa that could have moved relatively rapidly through Central America and Mexico. Our findings demonstrate that butterflies (and possibly many other organisms) have tremendous potential for rapid colonization of suitable habitats. Our results also suggest that dispersal can easily increase local diversity in areas where speciation has been attributed mostly to vicariance (such as the eastern slope of the Andes).

Age-based life cycle traits of the broadclub cuttlefish Sepia latimanus confirmed through release−recapture experiments

To understand the age-based life cycle traits of the broadclub cuttlefish Sepia lati- manus, we obtained biological information about the species through releaserecapture experi- ments, where 166 345 hatchlings with markings in their cuttlebones were released into their nat- ural habitat of Ishigaki Island, southern Japan, and 96 adult cuttlefish were recaptured over 2 successive years. Age groups were determined based on 3 indices: the number of lamellae in the cuttlebone, dorsal mantle length (DML), and the collection date of wild cuttlefish. The length- frequency data of DML, reconstructed from 4340 cuttlebones collected from either a fish market or coastal beaches, were analysed over a period of 3 yr. The cuttlefish consisted of 2 age groups (0 yr and 1 yr), and each group is thought to die after maturation at the end of the spawning season, indicating that they are different breeding groups. The ratio of 1 yr cuttlefish to total cuttlefish was highest at the beginning of the breeding season (November) and gradually de - creased throughout the breeding season. Abundance, maturation, and mating conditions of each breeding group and the estimated hatching season of cuttlefish in the wild suggest that the 0 yr and 1 yr groups contribute equally to production of offspring early in the hatching period, while the contribution of 0 yr cuttlefish is larger later in the hatching period. Offspring hatched later may return as recruits to breed as 1 yr cuttlefish the following year. Our analysis highlighted that the population of broadclub cuttlefish is composed of 2 breeding groups with alternative short and long life spans. This is the first study in which the life cycle traits of a Sepia species have been successfully clarified with releaserecapture experiments.

Dispersal of the leafhoppers Matsumuratettix hiroglyphicus and Yamatotettix flavovittatus (Homoptera: Cicadellidae), vectors of sugarcane white leaf disease

Sugarcane white leaf disease is a serious problem in many Asian Countries. The leafhoppers Matsumuratettix hiroglyphicus (Matsumura) and Yamatotettix flavovittatus Matsumura are the main vectors of sugarcane white leaf disease phytoplasma. Gaining a better understanding of the dispersal behavior of such insect vectors is essential for both disease epidemiology and vector control. The dispersal distances of M. hiroglyphicus and Y. flavovittatus in a sugarcane field were estimated by means of mark–release–recapture experiments. Adult leafhopper vectors collected from the fields were marked using fluorescent dye powder and released at a central release point in a sugarcane field. The marking method did not have a significant effect on the survival or flight activity of the leafhopper vectors. The overall release–recapture rates of M. hiroglyphicus and Y. flavovittatus within 50 m were 10.1 and 13.4 %, respectively. The estimated natural mean dispersal distances for M. hiroglyphicus and Y. flavovittatus were 162.1 and 387.5 m, respectively. Wind appears to be the main factor influencing the leafhopper dispersal direction.