The new kid on the block: immigrant males win big whereas females pay fitness cost after dispersal

Dispersal is nearly universal; yet, which sex tends to disperse more and their success thereafter depends on the fitness consequences of dispersal. We asked if lifetime fitness differed between residents and immigrants (successful between‐population dispersers) and their offspring using 29 years of monitoring from North American red squirrels (Tamiasciurus hudsonicus) in Canada. Compared to residents, immigrant females had 23% lower lifetime breeding success (LBS), while immigrant males had 29% higher LBS. Male immigration and female residency were favoured. Offspring born to immigrants had 15–43% lower LBS than offspring born to residents. We conclude that immigration benefitted males, but not females, which appeared to be making the best of a bad lot. Our results are in line with male‐biased dispersal being driven by local mate competition and local resource enhancement, while the intergenerational cost to immigration is a new complication in explaining the drivers of sex‐biased dispersal.     

Factors influencing and consequences of breeding dispersal and habitat choice in female grey seals (<Emphasis Type="Italic">Halichoerus grypus</Emphasis>) on Sable Island,Nova Scotia

Selection of breeding location can influence reproductive success and fitness. Breeding dispersal links habitat use and reproduction. This study investigated factors affecting breeding dispersal and its reproductive consequences in grey seals (Halichoerus grypus) on Sable Island, Nova Scotia. Breeding dispersal distance was determined in 692 individually marked, known-age female grey seals observed from 2004 to 2014. We used generalized linear mixed-effects models to test hypotheses concerning environmental and demographic factors influencing breeding dispersal distance and the consequences of dispersal distance on offspring weaning mass. Grey seal females rarely exhibited fidelity to previous breeding sites. Median dispersal distance between years was 5.1 km. Only 2.9% of females returned to a previous breeding site. Breeding dispersal distance was affected by parity and density, but effects were small and are presumably of no biological significance. Variation in dispersal distance among adult females was large. Dispersal distance had no significant influence on offspring weaning mass; however, as previously found, pup sex and maternal age did. Although breeding location was not important, heavier pups were born in habitats with no tidal or storm-surge influence indicating that breeding habitat type did influence offspring size at weaning. The lack of site fidelity in grey seals on Sable Island is associated with an unpredictable and changing landscape (sand dunes) that could make it difficult for females to locate previous breeding locations. Although breeding location within habitat type had small consequences on offspring weaning mass, we detected no evidence that breeding site selection within the habitat had consequences to females.     

Life table studies on the paddy field population of the green rice leafhopper,Nephotettix cincticeps Uhler (Hemiptera: Cicadellidae), with special reference to the mechanism of population regulation

The population growth of the green rice leafhopper, Nephotettix cincticeps, in the paddy field was analyzed based on the life table data accumulated for six years. The paddy field population, which stems from the invading adults of the first generation (G-I), repeats two complete generations, and the hatchlings of the fourth generation (G-IV) enter diapause and overwinter as the fourth instar nymphs in fallow paddy fields. It was clarified that the density dependent reduction in the mean longevity and oviposition rate of adult females in G-II and III played a primary role in stabilizing the annual population densities. The annual average of the mean longevity of G-II females (3.9 days) was much shorter than that of G-III ones (7.7 days) and thus the density dependent reduction in the mean longevity induced a more prompt regulatory effect on the oviposition of G-II females compared with G-III ones. As the result, two equilibrium densities of eggs were obtained, e.g., ca 100 and 700 eggs per hill in G-III and IV, respectively. Density dependent decrease in the proportion of mature females in the adult population was especially conspicuous in G-II, and this was closely associated with the density dependent reduction in the mean longevity and fecundity. Thus, the density dependent dispersal (emigration) of the adult females by flight in G-II and III was the most convincing factor in the process of population regulation. The density dependent dispersal of the adult females is effective in avoiding the deleterious effects of nymphal crowding in a breeding habitat unit (a paddy field), and may result in a more even distribution of the population over a continuous habitat units in a locality than otherwise.     

Short and flat grass preferred by adults of the endangered dragonfly <Emphasis Type="Italic">Sympetrum pedemontanum elatum</Emphasis> (Odonata: Libellulidae)

Sympetrum pedemontanum (Müller in Allioni) (Odonata: Libellulidae) is widely distributed across the Eurasian continent and its neighboring islands. However, the populations of its subspecies S. pedemontanum elatum (Selys) in Japan have been rapidly decreasing with the loss of habitats in rural and suburban areas since the 1970s. For the conservation of this subspecies, which is now listed as endangered in many prefectures, it is important to understand the habitat preferences of the adults. Previous studies indicate that adult males of this species tend to fly on the flat surface of rice paddy fields. Thus, we hypothesized that they preferred short and flat grass. Field experiments in the Sakasegawa River, Hyogo Prefecture, Japan, showed that adult S. p. elatum significantly preferred the trimmed grass of Phragmites japonicus to untreated shaggy grass, regardless of sex. Our results indicate the importance of grass management for the conservation of this species, not only in and around paddy fields but also in fluvial habitats, which are abundant in Japan.     

Wind and Water Dispersal of Wetland Plants Across Fragmented Landscapes

Biodiversity in wetlands is threatened by habitat loss and fragmentation, of which agricultural activities often are a cause. Dispersal of plant seeds via wind and ditches (water) may contribute to connecting remnant wetland plant populations in modern agricultural landscapes, and help to maintain and restore biodiversity. We developed a spatially explicit model to assess the relative importance of dispersal by wind and dispersal by water through drainage ditches for two wetland plant species in agricultural landscapes: a typical wind disperser and a typical water-disperser. Simulation results show that the typical wind disperser had a much higher capability to disperse by wind (90th percentile <30 m) than the typical water-disperser (90th percentile <2 m). Surprisingly, the capability to disperse via water was similar for the two species: 90th percentile dispersal distances following a combination of wind and water dispersal were between approximately 100 and 1000 m. Dispersal by water transported more seeds over long distances for both species. The main determinants for dispersal distance by water were roughness of the ditch (determined by, for example, bank vegetation) and the presence of obstructions (for example, culverts). Density or direction of the ditch network did not seem to affect water dispersal distances substantially. From a biodiversity conservation perspective, it would be most useful if areas with suitable riparian wetland habitat were intersected with a network of shallow ditches with a high roughness promoting seed deposition. These areas should then be connected to other suitable areas by a few regularly cleaned ditches with no obstructions and low seed trapping probability.     

Sexual difference of lifetime movement in adults of the Japanese skimmer,Orthetrum japonicum (Odonata: Libellulidae), in a forest-paddy field complex

The mark-and-recapture method was used to study the lifetime movement of the Japanese skimmer,Orthetrum japonicum, in a forest-paddy field complex in the warmtemperate zone of Japan. The flight season was from mid April to late June. The age structure showed that the maiden flight occurred towards the forest from the emergence sites (paddy fields) for both sexes. The insects returned to the paddy fields after maturation. The total number of skimmers estimated in the whole survey area was about 1000–2000, of which about 200 males were found in the paddy fields. The average lengths of the immature and reproductive periods were about 10 and 20 days in both sexes, respectively. Most mature males tended to stay in the paddy fields and showed territorial behavior, while most mature females moved frequently between the forest and the paddy fields. The average extent of each territory was about 19 m², being established mainly in the shady paddy fields. Few males were sneakers. The available habitat throughout the life span for the skimmers was both the paddy fields and the forest.     

Patterns of pollen dispersal in a small population of the Canarian endemic palm (Phoenix canariensis)

The genetic diversity of small populations is greatly influenced by local dispersal patterns and genetic connectivity among populations, with pollen dispersal being the major component of gene flow in many plants species. Patterns of pollen dispersal, mating system parameters and spatial genetic structure were investigated in a small isolated population of the emblematic palm Phoenix canariensis in Gran Canaria island (Canary Islands). All adult palms present in the study population (n=182), as well as 616 seeds collected from 22 female palms, were mapped and genotyped at 8 microsatellite loci. Mating system analysis revealed an average of 5.8 effective pollen donors (N_ep) per female. There was strong variation in correlated paternity rates across maternal progenies (ranging from null to 0.9) that could not be explained by the location and density of local males around focal females. Paternity analysis revealed a mean effective pollen dispersal distance of ∼71 m, with ∼70% of effective pollen originating from a distance of <75 m, and 90% from <200 m. A spatially explicit mating model indicated a leptokurtic pollen dispersal kernel, significant pollen immigration (12%) from external palm groves and a directional pollen dispersal pattern that seems consistent with local altitudinal air movement. No evidence of inbreeding or genetic diversity erosion was found, but spatial genetic structure was detected in the small palm population. Overall, the results suggest substantial pollen dispersal over the studied population, genetic connectivity among different palm groves and some resilience to neutral genetic erosion and subsequently to fragmentation.     

The spatial distribution of nests of the harvester ant Messor barbarus in dryland cereals

The harvester ant Messor barbarus can be responsible for substantial losses of weed seeds in arable fields in NE Spain. The spatial distribution of nests can have consequences for biological weed control, because foraging intensities decline with distance from the nest. The probability that seeds will escape harvesting will be lower if nests occur regularly distributed. We here investigated ‘large’-scale variability (up to 150 m), caused by habitat heterogeneity, and ‘small’-scale spatial variability (up to 12 m), caused by interactions between colonies, in nest distribution in a 50 × 150 m area in a cereal field in NE Spain, in 2009 and 2010. Large-scale variability was present in the data, but could not be explained by elevation, distance to the nearest field edge, or interpreted as simple trends across the area. Small-scale interactions could successfully be described by a multi-type/hard core Strauss process model, indicating territoriality among nests. Exclusion and interaction zones were identified, with radii that were smaller for small than for large colonies, and smaller for 2009 than for 2010. There was close resemblance between the observed and fitted spatial structure up to a radius of 3–4 m. Large-scale spatial variability, but not small-scale interactions, may be responsible for the existence of areas with few or no nests, where weed seeds have a higher probability of escaping the ants and entering the seed bank. Identifying and understanding the factors that influence the large-scale trends is, therefore, essential for optimizing weed control.     

Immigration and gene flow in a northern willow tit (Parus montanus) population

To study quantitatively the relationship between immigration rate and gene flow we used 9-year data from a willow tit Parus montanus population in a continuous forest habitat. We compared components of lifetime reproductive success, and parental survival rate between immigrant and resident (‘status’) birds by taking individual age into consideration also. Of the fitness components, survival was independent of status and sex, averaging 0.60 annually. Of the male and female breeders, on average 63.1% and 75.6%, respectively, originated from unknown natal areas, implying extensive immigration. Pair formation was nonassortative with respect to the origin of partners. The effect of status on reproductive success was significant only for females: immigrants produced larger clutches and hatched more young in all age classes studied. However, the difference between the groups diminished until fledging and the offspring produced by the immigrant females showed lower local survival rate (4.6% of the young) than did those by the residents (5.9%). Therefore, the contribution of immigrant females to the local gene pool was lower than expected on the basis of immigration rate. However, we propose that the result implies differential propensities to long-distance dispersal rather than overall survival prospects, since we detected no quality differences suggesting reduced survival chances among descendants of immigrant females. Therefore, gene flow into the population was slightly lower than immigration rate. It is possible that immigrant females are more prone to invest in progeny that effectively disperse further to search for new vacancies. The conditions prevailing during nestling growth may be crucial in determining whether an individual will later become a resident or leave the natal area, but the genetic component of this trait should also be considered. We suggest that widespread propagules is a better strategy than philopatry for a short-lived species to minimize the risk of losing all descendants in temporally and spatially varying conditions.     

Demographic features, distribution, and habitat selection of the gray mouse opossum (Tlacuatzin canescens) in Colima, Mexico

In western Mexico, gray mouse opossums Tlacuatzin canescens typically are not only in tropical deciduous and semideciduous woodlands but also in croplands and orchards. We conducted mark-recapture studies in January 2003–2007 and 2010 in coastal, northern, and central Colima, Mexico. Each year, five grids, established in areas of thick vegetation within a mosaic of habitats, had 100 stations (10?×?10), each with two Sherman traps, one on the ground and another elevated 1–2 m. On 24 of 30 grids, 82 individuals were captured 126 times (85.7 % in elevated traps). Sex ratio did not deviate from 1:1; there was no sexual dimorphism in mass (average for males, 28.21 g; average for females, 25.64 g); 46.3 % of animals were adults, 27.3 % of adult females were reproductively active, and 77.5 % of males had scrotal testes. Distance from centroid of trap locations averaged 15.24 m, with mean minimum distance moved between captures being 33.19 m. Densities usually were low (0.67–8.03/ha), with the species widespread in habitats studied. We assessed 14 environmental characteristics for each station using ANOVA, logistic regression, and nonparametric multiplicative regression (NPMR) to characterize habitat selection. T. canescens was more likely found where percent grass was about 30 % and litter over 50 %, with height of canopy less than 10 m and about 40 % closed. NPMR, being able to recognize hump-shaped response curves where intermediate variable values are preferred, identified two variables (percent grass and percent canopy closed) not detected by other techniques as important in characterizing habitat selection of T. canescens.     

Fine-scale social and spatial genetic structure in Sitka black-tailed deer

The spatial extent of Sitka black-tailed deer (Odocoileus hemionus sitkensis) populations below the regional scale is relatively unknown, as is dispersal between populations. Here, we use noninvasive samples to genotype 221 Sitka black-tailed deer in three watersheds on Prince of Wales Island, Alaska, separated by a maximum of 44 km, using traditional and spatial genetic approaches. We find that despite geographic proximity, multiple lines of evidence suggest fine-scale genetic structure among the three study sites. The 2 most geographically distant watersheds differed significantly in genetic composition, suggesting an isolation-by-distance pattern. Within study sites, deer exhibited spatial genetic structure within a radius of 1,000 m. Based on a reduced sample of known-sex individuals, females exhibited positive spatial genetic structure within a radius of 500 m but males showed no structure. Moreover, females were more likely to be related to their 5 nearest female neighbors, regardless of distance, than were males. Evidence indicates dispersal by both sexes although it may be more common, or dispersal distances are greater, in males. Nonetheless, analysis of assignment indices and comparison of sex-specific correlograms found no evidence of sex-biased dispersal between watersheds. Patterns of spatial relatedness and connectivity suggest limited dispersal among Sitka black-tailed deer, creating genetic structure on a fine spatial scale, perhaps as small as the watershed.     

Fine-scale genetic structure in populations of the Chagas’ disease vector Triatoma infestans (Hemiptera, Reduvidae)

Fine scale patterns of genetic structure and dispersal in Triatoma infestans populations from Argentina was analysed. A total of 314 insects from 22 domestic and peridomestic sites from the locality of San Martín (Capayán department, Catamarca province) were typed for 10 polymorphic microsatellite loci. The results confirm subdivision of T. infestans populations with restricted dispersal among sampling sites and suggest inbreeding and/or stratification within the different domestic and peridomestic structures. Spatial correlation analysis showed that the scale of structuring is approximately of 400 m, indicating that active dispersal would occur within this distance range. It was detected difference in scale of structuring among sexes, with females dispersing over greater distances than males. This study suggests that insecticide treatment and surveillance should be extended within a radius of 400 m around the infested area, which would help to reduce the probability of reinfestation by covering an area of active dispersal. The inferences made from fine-scale spatial genetic structure analyses of T. infestans populations has demonstrated to be important for community-wide control programs, providing a complementary approach to help improve vector control strategies.     

Salamander Dispersal Across a Forested Landscape Fragmented by a Golf Course

Abstract: We assessed dispersal behavior of 78 radiotagged adult spotted salamanders (Ambystoma maculatum) at a 36-hole golf course in southeastern Connecticut, USA. Lake of Isles Golf Course is atypical of most golf courses in North America because it is much larger (461 ha) than average 18-hole golf courses (54 ha) and deciduous forests accounted for 70% landscape composition on the course. We tracked individuals an average of 164 days as they emigrated from 3 seasonal pools surrounded by golf course fairways and one pool located in contiguous forest (control pool) from March through December 2004. Males and females dispersed similar distances at the control pool, averaging 71 ± 10 m. However, females migrating across the golf course dispersed twice as far (214 ± 25 m) as males on the golf course (102 ± 15 m) and both genders at the control pool. Over 40% the salamanders at the golf course crossed fairways; thus, fairways were not a dispersal barrier to adult spotted salamanders. Previous researchers have suggested establishing a 164-m life zone around breeding ponds to protect pond-breeding amphibian populations. Our results suggest that strategies that protect core upland habitat within 164 m of wetland boundaries would include 82% of adult males and only 50% of adult females. Empirical estimates based on our telemetry study suggest that core terrestrial habitat would have to extend 370 m to protect 95% of adult females, which is much farther than previous estimates.     

Immigration of olfactory searching insects into host plant patches: testing scaling rules for olfactory information

Herbivorous insects are commonly faced with host plants being distributed in scattered patches across a landscape. Immigration rates into habitat patches may strongly depend on the sensory cues used in the patch location process, and immigration rates of insects can be predicted based on the scaling of sensory cues. Here, we tested recent estimates of the scaling of olfactory information to patch size, which predicts a scaling coefficient ζ ≈ ?0.5 (A ^ζ , where A = patch size, ζ = scaling coefficient). We predicted that immigration rates of olfactory searching insects into patches of different sizes should scale according to the estimated slope. We investigated attraction of the weevils Cionus tuberculosus and Cionus scrophulariae to odors from figwort Scrophularia nodosa and quantified immigration rates of weevils into differently sized patches. We also investigated oviposition rates of the sawfly Tenthredo scrophulariae. The slope in the regression between density and patch size for herbivores was then compared with the predicted scaling coefficient. Using olfactometers, we found that weevils were attracted to figwort odors. Weevil densities were significantly affected by patch size, and the slope in the relationship between density and patch size was ζ = ?0.53. The slope in the relationship between larval densities of sawflies and patch size was less negative with a slope of ζ = ?0.15, indicating differences in search behavior compared with the weevils. The density–patch size relationship for the weevils closely matched the predicted slope and supported the previous estimations of the scaling of olfactory information to patch size.     

Keeping it in the family: strong fine-scale genetic structure and inbreeding in <Emphasis Type="Italic">Lodoicea maldivica</Emphasis>, the largest-seeded plant in the world

The fine-scale spatial genetic structure (FSGS) of plant populations is strongly influenced by patterns of seed dispersal. An extreme case of limited dispersal is found in the charismatic yet endangered palm Lodoicea maldivica, which produces large fruits (up to 20 kg) dispersed only by gravity. To investigate patterns of seed dispersal and FSGS in natural populations we sampled 1252 individual adults and regenerating offspring across the species’ natural range in the Seychelles archipelago, and characterised their genotypes at 12 microsatellite loci. The average dispersal distance was 8.7?±?0.7 m. Topography had a significant effect on seed dispersal, with plants on steep slopes exhibiting the longest distances. FSGS was intense, especially in younger cohorts. Contrary to what might be expected in a dioecious species, we found high levels of inbreeding, with most neighbouring pairs of male and female trees (≤10 m) being closely related. Nonetheless, levels of genetic diversity were relatively high and similar in the various sampling areas, although these differed in disturbance and habitat fragmentation. We discuss potential trade-offs associated with maternal resource provisioning of progeny, seed dispersal and inbreeding, and consider the implications of our findings for managing this globally significant flagship species.     

Natal Dispersal and Philopatry in the Carnivorous Marsupial Phascogale tapoatafa (Dasyuridae)

The proximate and ultimate causes of dispersal in semelparous carnivorous marsupials (Phascogalinae) have previously been hypothesized to be maternal aggression and inbreeding avoidance, respectively. This study tests these hypotheses by exposing 26 litters of Phascogale tapoatafa to a diverse range of social and environmental conditions that potentially affect dispersal (e.g. supplemental feeding, post-weaning desertion by the mother, orphaning, and release of subadults into unoccupied habitat). The mean dispersal age was 162 ± 5.6 d, which is about 3 wk after weaning is complete. Juvenile dispersal was strongly male biased under all conditions, suggesting that extrinsic proximate causes do not adequately account for male emigration. Home range establishment by males was contingent on the presence of females. Half of the monitored daughters were philopatric, and others typically settled adjacent to the natal site, thus possibly enhancing their reproductive potential by occupying an area of known resource quality. Because philopatry increases the risk of incest, females may be selected to preferentially mate with unrelated males (immigrants), when they are available, to avoid inbreeding. If so, the presence of immigrant males would reduce the probability of locally born, related males reproducing at their natal site. Thus inbreeding avoidance by females may create local mate competition among males and select for male dispersal. Emigration also ensured that males avoided inbreeding, but, if they dispersed into unoccupied habitat, male P. tapoatafa often returned to the natal area. This 'boomerang strategy' of returning to mate with related females suggests that, in the absence of conspecifics along the dispersal path of a male, mate competition will be weak at the natal site and female mate choice will not preclude related males. Thus while inbreeding avoidance by either or both sexes is perhaps the most parsimonious explanation of male-biased emigration, dispersal patterns were apparently strongly influenced by additional factors, so that the ultimate causation of the dispersal regime may be more complex.     

Steel slag amendment reduces methane emission and increases rice productivity in subtropical paddy fields in China

Paddy field, being a man-made wetland, is recognized as one of the major sources of global methane (CH₄) emission. Since China has the second-largest area of rice cultivation in the world, it is important to develop valid and reliable strategies to reduce CH₄ emission and sustain rice productivity in Chinese paddy fields. In this study, we applied steel slag fertilizer, a by-product of steel industry with a high concentration of active iron (Fe), at rates of 0, 2, 4, and 8 Mg ha^?1 in subtropical rice (Oryza sativa L.) paddy fields in China to assess the effect of steel slag amendment on CH₄ emissions as well as rice growth and yield characteristics. Results showed that the Fe concentrations in paddy soils significantly increased with the application levels of steel slag fertilizer. Steel slag amendment in paddy fields largely reduced the CH₄ production rate, resulting in a decrease in the overall CH₄ emission rate. In response to the applications of steel slag at a rate of 2, 4 and 8 Mg ha^?1, total CH₄ emission during rice cultivation decreased by 26.6, 43.3 and 49.3 %, respectively. Furthermore, steel slag amendment had a significant, positive effect on the rice grain yield and the percentage of ripened grain, most probably due to the increased availability of inorganic nutrients such as silicate and manganese. Our results suggest that steel slag can be an effective soil amendment for reducing CH₄ emissions as well as increasing rice productivity in subtropical paddy fields in China.     

Do Spatially-Implicit Estimates of Neutral Migration Comply with Seed Dispersal Data in Tropical Forests?

Neutral community models have shown that limited migration can have a pervasive influence on the taxonomic composition of local communities even when all individuals are assumed of equivalent ecological fitness. Notably, the spatially implicit neutral theory yields a single parameter I for the immigration-drift equilibrium in a local community. In the case of plants, seed dispersal is considered as a defining moment of the immigration process and has attracted empirical and theoretical work. In this paper, we consider a version of the immigration parameter I depending on dispersal limitation from the neighbourhood of a community. Seed dispersal distance is alternatively modelled using a distribution that decreases quickly in the tails (thin-tailed Gaussian kernel) and another that enhances the chance of dispersal events over very long distances (heavily fat-tailed Cauchy kernel). Our analysis highlights two contrasting situations, where I is either mainly sensitive to community size (related to ecological drift) under the heavily fat-tailed kernel or mainly sensitive to dispersal distance under the thin-tailed kernel. We review dispersal distances of rainforest trees from field studies and assess the consistency between published estimates of I based on spatially-implicit models and the predictions of the kernel-based model in tropical forest plots. Most estimates of I were derived from large plots (10–50 ha) and were too large to be accounted for by a Cauchy kernel. Conversely, a fraction of the estimates based on multiple smaller plots (1 ha) appeared too small to be consistent with reported ranges of dispersal distances in tropical forests. Very large estimates may reflect within-plot habitat heterogeneity or estimation problems, while the smallest estimates likely imply other factors inhibiting migration beyond dispersal limitation. Our study underscores the need for interpreting I as an integrative index of migration limitation which, besides the limited seed dispersal, possibly includes habitat filtering or fragmentation.     

Olfactory response of Stenotus rubrovittatus to rice and paddy weed,Scirpus juncoides

The olfactory response of the sorghum plant bug, Stenotus rubrovittatus (Matsumura) (Het., Miridae), to rice, Oryza sativa L., and paddy weed, Scirpus juncoides Roxb. var. ohwianus T. Koyama, was investigated with an olfactometer to clarify the mechanism of the invasion of the bugs in paddy fields. Both adult females and males were significantly attracted to panicles of rice in the flowering and full‐ripe stages. Whole plants (aboveground parts) of rice in the panicle‐formation stage, and stems and leaves of rice in the flowering stage significantly attracted only adult females. Other rice structures tested did not attract males or females. Both males and females were attracted to the flowering spikelets of S. juncoides. Although females showed no olfactory response to stems of S. juncoides in the flowering stage, males were repelled by them. Only females were attracted to whole plants of flowering S. juncoides. Whole plants of S. juncoides in the spikelet‐formation stage significantly attracted only females. The findings suggest that the invasions of S. rubrovittatus into paddy fields are caused by their olfactory responses to the volatiles emitted from rice and some paddy weeds such as S. juncoides.     

The interaction of dispersal and control methods for the riverine tsetse fly Glossina palpalis gambiensis (Diptera: Glossinidae): a modelling study

We used a spatial model of a riverine tsetse fly species Glossina palpalis gambiensis life cycle to investigate the interaction between their dispersal and three control methods and to document these interactions using sensitivity analyses. The model is currently limited to gallery forest habitat inhabited by Glossina palpalis gambiensis in the dry season in the sub-humid zone of West Africa. The control methods modelled were traps and targets (TT), insecticide-treated livestock (ITL), and the sterile insect technique (SIT). Both distance dispersed (up to 800 m) and percent of flies dispersing each day (up to 60 %) increased the efficiency of control by TT. Most of this increase occurred for low values of both distance dispersed and percent dispersing, but the increase continued up to the limits tried. The daily movement of cattle assisted the control program and when movement was considerable (up to 600 m daily) the effects were greater than the effects of tsetse dispersal. Random dispersal decreased aggregation and equilibrium population size, and thus also increased the efficiency of SIT. Dispersal that was mostly oriented towards clumps was of much less value for SIT but acted on TT and ITL similarly to random dispersal.