Dispersal Distance Research Articles

Correlated evolution of dispersal traits and habitat preference in the melicgrasses.

Seed dispersal is a critical process impacting individual plants and their communities. Plants have evolved numerous strategies and structures to disperse their seeds, but the evolutionary drivers of this diversity remain poorly understood in most lineages. We tested the hypothesis that the evolution of wind dispersal traits within the melicgrasses (Poaceae: Meliceae Link ex Endl.) was correlated with occupation of open and disturbed habitats. To evaluate wind dispersal potential, we collected seed dispersal structures (diaspores) from 24 melicgrass species and measured falling velocity and estimated dispersal distances. Species' affinity for open and disturbed habitats were recorded using georeferenced occurrence records and land cover maps. To test whether habitat preference and dispersal traits were correlated, we used phylogenetically informed multilevel models. Melicgrasses display several distinct morphologies associated with wind dispersal, suggesting likely convergence. Open habitat taxa had slower-falling diaspores, consistent with increased wind dispersal potential. However, their shorter stature meant that dispersal distances, at a given wind speed, were not higher than those of their forest-occupying relatives. Species with affinities for disturbed sites had slower-falling diaspores and greater wind dispersal distances, largely explained by lighter diaspores. Our results are consistent with the hypothesized evolutionary relationship between habitat preference and dispersal strategy. However, phylogenetic inertia and other plant functions (e.g., water conservation) likely shaped dispersal trait evolution in melicgrasses. It remains unclear if dispersal trait changes were precipitated by or predated changing habitat preferences. Nevertheless, our study provides promising results and a framework for disentangling dispersal strategy evolution.

Dispersal of the Golden-mantled Ground Squirrel (Callospermophilus lateralis)

Abstract Dispersal is common in mammals and can have an important role in shaping demography, genetics, distribution, and social structure. Dispersal entails potential costs but also potential benefits, and the dispersal decision is thought to be conditional; the potential disperser assesses prospects for success at its current location and disperses to improve its fitness. However, the costs and benefits of dispersal, as well as factors influencing the dispersal decision, are not well known. We used trapping and observation to study dispersal in the Golden-mantled Ground Squirrel (Callospermophilus lateralis), a species for which dispersal is largely unknown. We characterized the dispersal process by evaluating dispersal timing and distance, assessed factors that might influence the dispersal decision, and analyzed the fitness cost of dispersal after settlement. We found that most dispersal occurred during the summer of birth, as is expected for a small-bodied sciurid. However, some squirrels delayed dispersal until early in their yearling summer. Dispersal was male-biased in dispersal tendency, and it was also male-biased in dispersal distance, but only over shorter dispersal distances. The dispersal decision for juvenile females appeared to originate as soon as 10 days after they emerged from the natal burrow, and the decision was not associated with body mass or several measures of competition. Instead, dispersal of juvenile females was associated with the number of littermate sisters, with each sister present increasing the likelihood of dispersal by 26%. Littermate sisters might be a cue foretelling the effects of kin competition the following year. We did not find a significant difference in lifetime reproductive success between philopatric and dispersing females after settlement, suggesting that for golden-mantled ground squirrels, any cost of dispersal is experienced primarily during the transience phase.

Lignite reduces odour from broiler farms without reducing production performance

An unavoidable consequence of chicken meat production is the generation of substantial quantities of spent litter. This poses several environmental and social challenges, as broiler farms become hotspots for odour emissions. The main source of odour from broiler litter is the microbial decomposition of organic material. Thus, lignite's previously shown capacity to reduce microbial activity in broiler litter was expected to reduce odour emissions from broiler housing. The effect of lignite on odour emission rate (OER) (ou/s) was investigated using dynamic olfactometry over two consecutive summer broiler grow-out cycles in Victoria, Australia, with lignite applied at 3.5 kg/m2. The air quality dispersion model, AERMOD, was used to investigate how lignite's effect on OER influenced the predicted odour dispersion distances and concentrations in the context of various Australian regulatory requirements. Additionally, the effect of lignite on bird production performance was also determined. This study showed that lignite reduced the OER from commercial broiler housing by an average of 56% over both grow-outs. This effect was observed for the duration of the trial. The observed reduction in OER reduced the required separation distances by 44–53% according to the state odour criteria for Victoria, New South Wales, Queensland and South Australia. There were no observed differences in feed conversion ratio, bird live weight or mortality throughout either grow-out. This study demonstrated the capacity of lignite to reduce odour emissions from commercial broiler housing without reducing bird production performance.

Interpopulation variation in dispersal behavior of fat minnow Rhynchocypris oxycephalus jouyi juveniles inhabiting fragmented habitats.

In many organisms, including fishes, downstream dispersal is often phenotype-dependent. Phenotype-dependent downstream dispersal can generate evolutionary pressure via spatial sorting, which non-randomly removes phenotypes enhancing downstream dispersal from upstream populations. Spatial sorting due to downstream dispersal could accumulate in fish populations in above-barrier habitats to which dispersed individuals cannot return, resulting in functional traits that reduce downstream dispersal. This evolutionary mechanism may be more important in smaller above-barrier habitats where downstream emigration occurs over shorter dispersal distances. This study observed the dispersal behavior of fat minnow Rhynchocypris oxycephalus jouyi juveniles in an experimental tank to examine whether juveniles from small above-barrier habitats show more behaviors favorable for reducing downstream dispersal than those from large above-barrier habitats. Juveniles from small above-barrier habitats avoided downstream dispersal for longer durations than those from large above-barrier habitats, but there was no difference in the frequency of ascending attempts. These results support the notion that behavioral traits of juveniles in small above-barrier populations have been refined by spatial sorting to reduce downstream dispersal. The finding that interpopulation variation in dispersal behavior occurred only for certain dispersal directions implies that the behavioral consequences of habitat fragmentation are more complex than previously assumed.

The integration of diel vertical migration and hydrodynamic process influences the transport of swimming crab zoea (Portunus trituberculatus)

AbstractVertical migration and dispersal processes during the marine crab larval stage markedly affect transport, habitat selection, population connectivity, and resource replenishment success rates. However, not much is known of the reproductive ecology of swimming crabs in the nearshore waters of the northwest Pacific shelf. Here, we investigated the diel vertical migration (DVM) characteristics and transport patterns of the swimming crab zoea (Portunus trituberculatus) in this area. A Lagrangian particle‐tracking algorithm coupled with a hydrodynamic model, incorporating a DVM pattern of zoeae based on observations from a field survey of the diurnal distribution of swimming crab zoea, was used to simulate the transport of zoeae, and the impact of zoeal transport on population connectivity was explored. The results revealed that particles were predominantly transported in a nearshore direction from the particle release point, with short dispersal distances during the zoeal stages. In nearshore waters on the continental shelf, the swimming crab zoeae are exposed to shoreward‐moving currents with the aid of prolonged daytime locations in the lower water column, whereas larvae migrate upward to the middle and upper layers of the water column at night rather than the most superficial layer, potentially avoiding surface offshore‐moving currents that may be responsible for the retention and shoreward transport of larvae. Most zoeae are transported to shallow waters, and the contribution of transport to population connectivity during the zoeal stages is relatively limited. The findings here have considerable implications for understanding the mechanisms governing the early recruitment dynamics of this species, as well as for fisheries management and conservation of marine biodiversity.

Arthropod community composition in urban landscapes is shaped by both environmental filtering and dispersal limitation.

We assessed the relative importance of environmental filtering and dispersal limitation in structuring foliage- and ground-dwelling arthropod communities in central North Carolina. We hypothesized that differences in both local environment and dispersal distance between sites would predict differences in community composition, but that dispersal distance would be more important for ground arthropods than for foliage arthropods. We used variance partitioning to quantify the relative explanatory power of differences in the local environment and dispersal distance between sampling plots. For foliage arthropods, the full set of predictors explained 37-39% of the variance in community dissimilarity, while the full set of predictors explained 42-56% of the variance for ground arthropods. Environmental predictors alone consistently explained more variance in community dissimilarity than geographic predictors alone for ground arthropods, but the variance explained by each predictor set alone varied for foliage arthropods depending on the metric of community dissimilarity. Examining communities of multiple arthropod groups across the same spatial gradient highlights the scale-dependence of these processes and illustrates how variation in the environment can alter the relative abundance of specialist and generalist taxa.

Landscape genetics of spruce grouse at the trailing edge of the boreal forest

Populations on the periphery of a species range generally occupy marginal or less continuous habitat and can have greater extinction risk than populations in the range‐center. For climate‐sensitive populations on the trailing edge of a species' distribution (i.e. low latitude or low elevation), the effects of climate change are expected to compound these threats, increasing the vulnerability of these populations. The spruce grouse Canachites canadensis is a boreal forest specialist that is expected to experience range contraction at the trailing edge of its range due to climate change. In this study, we investigated the genetic structure, genetic diversity, and connectivity of spruce grouse in Minnesota, along the southeastern range limit in the United States. Clustering algorithms and genetic diversity indices suggested a single continuous population occurred throughout northern Minnesota. We detected no signatures of recent inbreeding or population bottlenecks. We used maximum likelihood population effects modeling and identified coniferous forest land cover and lower average spring temperatures as predictors of gene flow. We used two approaches based on circuit theory to map the potential for gene flow and identified regions of consistently high gene flow in the northwest and northeast of the study area. Omniscape, which incorporated additional parameters representing the likely origins of dispersers and the maximum dispersal distance, suggested a more continuous gene flow landscape than did Circuitscape. Our work highlights the current genetic integrity of one of the largest populations of the eastern subspecies of spruce grouse C. c. canadensis in the United States, identifies key landscape attributes for functional connectivity, and demonstrates complementary approaches of Circuitscape and Omniscape for gene flow mapping.

Agitation dredging of silt and fine sand with Water Injection Dredging, Tiamat and Underwater Plough: a case study in the Port of Rotterdam

Abstract Purpose Agitation dredging has gained popularity as an environmentally friendly and cost-effective method for port maintenance. One of the advantages of agitation dredging is the ability to transport sediments out of the port area using natural currents. The effect of the different agitation methods on sediment and water properties has rarely been investigated in a single pilot project. This research aims to study the effects of agitation methods in silt and sand-dominated areas that are frequently maintained. Methods The effects of water injection dredging, (WID) underwater ploughing (UWP) and Tiamat on sediment properties are investigated in the Port of Rotterdam. In-situ measurements and laboratory measurements are carried out to determine changes in the bed level, the particle size distribution of the bed, the turbidity in the water column and the dispersion distance of the sediment plume due to agitation dredging. Results The results of the in-situ monitoring of the agitation pilots allow a comparison of the changes in sediment and water properties before, during and after agitation dredging. The production, advantages and limitations of the tested agitation dredging methods are discussed. Conclusion The in-situ measurements show that WID, Tiamat and UWP can be successfully used for the agitation of sediments and their removal from the silt and sand-dominated areas. The production of the tested agitation methods is higher for silty than sandy sediments. In general, the selection of the agitation equipment can be made based on environmental regulations, sediment properties and hydrodynamic conditions.

Local versus regional patterns in zoospore dispersal of the kelp Eisenia bicyclis (Laminariales, Phaeophyceae)

SummaryIt is generally accepted that kelp populations have a metapopulation structure. Most zoospores settle near to their parent individual, and infrequent but long‐distance dispersal of zoospores contributes to gene flow between local populations. Population genetic analysis of single nucleotide polymorphism genotyping by MIG‐seq (i.e. multiplexed inter‐simple sequence repeats genotyping by sequencing) was performed on the dominant kelp, Eisenia bicyclis, in two areas: Kitsunezaki (a sheltered area) and Shimoda (an exposed site). Regional scale analysis of genetic structure was conducted at six sites in Kitsunezaki and three sites in Shimoda. When viewed on a regional scale based on the inbreeding coefficient within the local population, the inbreeding ratio was higher in Shimoda than in Kitsunezaki, probably as a result of the limited vertical zonal distribution in the exposed environment. Vertically wide distribution in the sheltered environment apparently enabled frequent crossing among individuals in Kitsunezaki. By contrast, when viewed on a local scale based on the pairwise kinship coefficient (FST) between populations, gene flow among local populations in Shimoda occurred over a wide area, but was limited in Kitsunezaki. In Shimoda, genetic exchange between local populations, even if inbreeding is locally active, is likely to support metapopulation maintenance and rapid recovery of local populations. In Kitsunezaki, however, genetic exchange among local populations is limited within few 100 m, and the metapopulation structure will decline in the long term because of inbreeding depression. Local dispersal distance of zoospores was investigated based on parent–offspring analysis in the Kitsunezaki population, which revealed that zoospores mainly settled within 5 m of their parent. However, some zoospores traveled over 27 m within the 4 × 30 m study area. The present study shows the importance of examination at different spatial scales when investigating zoospore dispersal of laminarialean kelps.

Comparative study on mechanical properties and biomineralization of hooks in the diaspores of three epizoochorous plant species

Most of the plants using epizoochory show adaptations to this diaspore dispersal strategy by having the diaspores covered by barbs, hooks, spines or viscid outgrowths, which allow diaspores to easily attach to an animal surface. Many previous studies have been mainly focused on the dispersal distances and efficiency, or effectiveness of diverse attachment structures depending on their size, anatomy, and morphology. However, the knowledge about the mechanical properties of these structures remains rather poor. In this study, we use a combination of scanning electron microscopy, energy dispersive X-ray element analysis and nanoindentation, to examine the microstructure, biomineralization and mechanical properties of single hooks in Arctium minus, Cynoglossum officinale and Galium aparine. Both the biomineralization and mechanical properties of the hooks strongly differ in examined plant species; mechanical properties depend on the biomineralization pattern, such as the accumulation of silicon and calcium. Elastic modulus and hardness decrease in the series C. officinaleG. aparineA. minus. Anisotropic mechanical properties are found between the radial and longitudinal directions in each single hook. By characterizing the mechanical properties and biomineralization of plant hooks, this paper contributes to the understanding of attachment biomechanics related to seed dispersal. Statement of significanceThe dispersal of seeds is essential for plant survival. Many of the plants that use the outside surface of animals to transport the seeds show adaptations to this dispersal strategy by having the seeds covered with hooks. Although these hooks have various sizes, morphologies and anatomical structures, all of them provide mechanical interlocking to animal surfaces. To reduce the risk of interlocking failure, the hooks are usually reinforced by mineralization. However, the relationship between mineralization, mechanical properties and specialized function of plant hooks has been largely overlooked. Here we perform a characterization study on the hooks of three plant species. Our results deepen the current understanding of the mineralization-material-function relationship in specialized hooks of plant seeds.

Effects of stochastic intraspecific seed dispersal variation on dispersal distance predictions in a temperate forest in Japan

The incorporation of seed dispersal models into conservation practices plays a pivotal role in predicting future ecosystems. Seed dispersal significantly influences plant population dynamics; however, our understanding of its implications at a landscape scale remains limited. We investigated how different seed dispersal processes impact the distributions of individual species within a 20 km × 20 km plot centered around a temperate old-growth forest reserve in Japan. We hypothesized that random variation in seed dispersal (i.e., stochastic processes) and variation mediated by distance (i.e., deterministic processes) would explain landscape-scale species distributions more effectively than deterministic seed dispersal processes alone. We evaluated 16 tree species with different seed dispersal modes by simulating seed dispersal processes. Stochastic simulations predicted higher dispersal distances for the majority of species. The findings of this study suggest that stochastic simulations are a more reliable tool for identifying dispersal restrictions in the context of climate change and biodiversity loss, highlighting the significance of using stochastic simulations for analyzing seed dispersal patterns in temperate forests, rather than more conventional deterministic methods.

Genetic diversity and population structure of an insect-pollinated and bird-dispersed dioecious tree Magnolia kwangsiensis in a fragmented karst forest landscape.

This study combined population genetics and parentage analysis to obtain foundational data for the conservation of Magnolia kwangsiensis. M. kwangsiensis is a Class I tree species that occurs in two disjunct regions in a biodiversity hotspot in southwest China. We assessed the genetic diversity and structure of this species across its distribution range to support its conservation management. Genetic diversity and population structure of 529 individuals sampled from 14 populations were investigated using seven nuclear simple sequence repeat (nSSR) markers and three chloroplast DNA (cpDNA) fragments. Parentage analysis was used to evaluate the pollen and seed dispersal distances. The nSSR marker analysis revealed a high genetic diversity in M. kwangsiensis, with an average observed (Ho) and expected heterozygosities (He) of 0.726 and 0.687, respectively. The mean and maximum pollen and seed dispersal distances were 66.4 and 95.7 m and 535.4 and 553.8 m, respectively. Our data revealed two distinct genetic groups, consistent with the disjunct geographical distribution of the M. kwangsiensis populations. Both pollen and seed dispersal movements help maintain genetic connectivity among M. kwangsiensis populations, contributing to high levels of genetic diversity. Both genetically differentiated groups corresponding to the two disjunct regions should be recognized as separate conservation units.

Unravelling arthropod movement in natural landscapes: Small-scale effects of body size and weather conditions.

Arthropod movement has been noticeably understudied compared to vertebrates. A crucial knowledge gap pertains to the factors influencing arthropod movement at habitat boundaries, which has direct implications for population dynamics and gene flow. While larger arthropod species generally achieve greater dispersal distances and large-scale movements are affected by weather conditions, the applicability of these relationships at a local scale remains uncertain. Existing studies on this subject are not only scarce but often limited to a few species or laboratory conditions. To address this knowledge gap, we conducted a field study in two nature reserves in Belgium, focusing on both flying and cursorial (non-flying) arthropods. Over 200 different arthropod species were captured and released within a circular setup placed in a resource-poor environment, allowing quantification of movement speed and direction. By analysing the relationship between these movement variables and morphological (body size) as well as environmental factors (temperature and wind), we aimed to gain insights into the mechanisms driving arthropod movement at natural habitat boundaries. For flying species, movement speed was positively correlated with both body size and tailwind speed. In contrast, movement speed of cursorial individuals was solely positively related with temperature. Notably, movement direction was biased towards the vegetated areas where the arthropods were originally caught, suggesting an internal drive to move towards suitable habitat. This tendency was particularly strong in larger flying individuals and under tailwind conditions. Furthermore, both flying and cursorial taxa were hindered from moving towards the habitat by strong upwind. In conclusion, movement speed and direction at patch boundaries are dependent on body size and prevailing weather conditions, and reflect an active decision-making process.

Seed dispersal effectiveness by greater one-horned rhinos and domestic bovids of a megafaunal fruit

The extinction of megafauna, such as rhinos, from tropical Asian forests may have detrimental effects on the regeneration of plant species that rely heavily on their dispersal services. Understanding the potential of other animals to substitute the ecological function of megafauna is important for predicting ecosystem change following declines or extirpation of megafauna. Anthropogenic activities have led to the presence of domestic bovids in many tropical habitats, and these animals could be capable of substituting seed dispersal roles of megafauna. Here, we conducted feeding trials, germination tests, and collected movement data on greater one-horned rhino (Rhinoceros unicornis) and domestic bovids (Bos primigenius; Bubalus bubalis) in the national parks of Chitwan and Shuklaphanta, Nepal. Our aim was to investigate whether domestic bovids can serve as effective substitutes for rhinos in dispersing the megafaunal-fruited Mallotus nudiflorus, which are specialized for rhino dispersal. Specifically, we assessed the long-distance seed dispersal capabilities of rhinos and bovids by combining gut passage times and movement patterns. Additionally, we compared the seed germination success rates among rhinos, bovids and other dispersal modes (e.g., deer and water dispersal). We found that rhinos dispersed 80 percent of seeds over distances greater than 1 km, with potential dispersal distances of up to approximately 5.4 km within their maximum gut passage time. In contrast, cattle dispersed 20 percent of seeds over 1 km, with a maximum distance of around 2.2 km, while buffaloes dispersed 15 percent of seeds over 1 km, with a maximum distance of around 1.4 km. Seeds consumed by rhinos exhibited similar or better germination rates compared to seeds retrieved from cattle and buffalo dung, as well as other dispersal modes. These findings indicate that rhinos provide a functionally unique dispersal service for this megafaunal fruit, especially in long-distance dispersal. While domestic bovids can partially substitute the seed dispersal functions of rhinos, they cannot fully compensate for the loss of seed dispersal that occurs with the disappearance of rhinos.

Signatures of selective sweeps in continuous-space populations.

Selective sweeps describe the process by which an adaptive mutation arises and rapidly fixes in the population, thereby removing genetic variation in its genomic vicinity. The expected signatures of selective sweeps are relatively well understood in panmictic population models, yet natural populations often extend across larger geographic ranges where individuals are more likely to mate with those born nearby. To investigate how such spatial population structure can affect sweep dynamics and signatures, we simulated selective sweeps in populations inhabiting a two-dimensional continuous landscape. The maximum dispersal distance of offspring from their parents can be varied in our simulations from an essentially panmictic population to scenarios with increasingly limited dispersal. We find that in low-dispersal populations, adaptive mutations spread more slowly than in panmictic ones, while recombination becomes less effective at breaking up genetic linkage around the sweep locus. Together, these factors result in a trough of reduced genetic diversity around the sweep locus that looks very similar across dispersal rates. We also find that the site frequency spectrum around hard sweeps in low-dispersal populations becomes enriched for intermediate-frequency variants, making these sweeps appear softer than they are. Furthermore, haplotype heterozygosity at the sweep locus tends to be elevated in low-dispersal scenarios as compared to panmixia, contrary to what we observe in neutral scenarios without sweeps. The haplotype patterns generated by these hard sweeps in low-dispersal populations can resemble soft sweeps from standing genetic variation that arose from substantially older alleles. Our results highlight the need for better accounting for spatial population structure when making inferences about selective sweeps.

Long‐proboscid horseflies (Philoliche: Tabanidae) as pollinators of co‐adapted plants in Africa and Asia

AbstractElongated nectar‐feeding mouthparts have evolved in several fly families, most notably Nemestrinidae, Bombylidae and Tabanidae. Plants pollinated by these “long‐proboscid flies” tend to have relatively specialized pollination systems. In this review, I focus on the blood‐ and nectar‐feeding horsefly genus Philoliche (Tabanidae: Pangoniinae) which includes species that are important pollinators of plants in Africa and, to a lesser extent, in Asia. The nectar‐feeding mouthparts of flower‐visiting Philoliche species range from 5 to 65 mm in length, with considerable intraspecific variation evident in some taxa. Plants pollinated by Philoliche species tend to have corolla tubes (or highly exerted reproductive structures) that match the proboscis dimensions of their pollinators. Some Philoliche species and their nectar host plants show population‐level covariation in proboscis lengths and flower depths that is indicative of co‐adaptation. I summarize existing information on the distribution and morphology of Philoliche species known to pollinate flowers as well as the identity, morphology and nectar properties of plants pollinated by these insects. This survey identifies some Philoliche species as keystone pollinators. Distinct guilds of plants are adapted to different horsefly species in different geographical regions and are generally ecologically reliant on these insects, although some plant species share tabanid and nemestrinid pollinators that are functionally similar on account of convergent evolution of their proboscis dimensions. Lack of information about the larval biology, nectar host plants, fire ecology and dispersal distances of Philoliche species is the biggest challenge for the conservation of these specialized pollinators and the plants that depend on them.

The role of changing landscape in the dispersal of a soil‐feeding termite in Suriname and French Guiana

Abstract Neotropical forest ecosystems harbour significant biodiversity. To develop effective insect conservation practices, it is important to understand the factors that influence the diversity and population structure of the species. Dispersal, a key determinant of population structure, is well studied in termites nesting in wood, for which it can be influenced by wood transport, or in termites living in urban environments. However, understanding the dispersal of termites whose mobility remains unaffected by wood transport remains understudied. We investigated the dispersal of Embiratermes neotenicus, a soil‐feeding species with short dispersal distance, in the Neotropical region, where both intact and degraded forests exist. Using mitochondrial and nuclear data, we analysed genetic diversity, structure and factors contributing to population differentiation in Suriname and French Guiana at multiple scales for 70 colonies. The population in French Guiana is the ancestral population in the region that subsequently expanded. Significant genetic differentiation between populations was observed, with distinct patterns identified in Suriname and French Guiana. The Suriname population showed higher genetic diversity and no subpopulation differentiation, whereas the French Guiana population showed substructure into distinct genetic clusters. Analyses at the scale of all colonies suggest the influence of landscape features, such as the Maroni River, on genetic differentiation. At the local scale, genetic differentiation between colonies increases with forest alteration, even when this does not include major changes in forest cover. Our results highlight the sensitivity of soil‐feeding termite populations to habitat change. We argue that multi‐scale studies are needed for a comprehensive understanding of genetic patterns, especially for species with short dispersal distances.

Biotic and abiotic dispersal of a large-seeded keystone genus in Madagascar

In tropical forests, most plant species rely on frugivorous animals for seed dispersal services. Such mutualisms are imperiled by defaunation, which disproportionately affects large-bodied vertebrates and may impact the interactions of the large-seeded plants they disperse. However, frugivore-mediated seed dispersal (zoochory) may not be the only mechanism ensuring the dispersal of a given plant species. With a focus on large-seeded canopy trees in the genus Canarium in the rainforests of Madagascar, thought to be dispersed by large-bodied lemur species, we investigated the contribution of multiple dispersal mechanisms to the movement of large seeds. Specifically, we (1) examined the potential for dispersal by abiotic factors, such as winds and runoff associated with frequent cyclones, (2) documented the animal species that could effectively contribute to their primary and secondary seed dispersal, and (3) determined how non-lemur and abiotic dispersal compare to the imperiled function of extant, though threatened, lemur primary dispersers. Using field observations and experiments, we found that wind, water, and secondary dispersal can move seeds considerable distances away from the parent plants, though they were less effective at long-distance dispersal than primary dispersers (i.e., large-bodied lemurs). For secondary dispersal, we found that dispersal distance is positively correlated with predation, potentially reducing dispersal effectiveness. Future comparisons with predation of primary or abiotically dispersed seeds will be necessary. Our research highlights the role of understudied mechanisms in the dispersal of large-seeded plants in Madagascar. Understanding the existence and impact of non-lemur dispersers in these imperiled forests can help complete our understanding of the mechanisms that shaped their astounding biodiversity and may mediate their response to ongoing environmental change.

Some reef-building corals only disperse metres per generation.

Understanding the dispersal potential of different species is essential for predicting recovery trajectories following local disturbances and the potential for adaptive loci to spread to populations facing extreme environmental changes. However, dispersal distances have been notoriously difficult to estimate for scleractinian corals, where sexually (as gametes or larvae) or asexually (as fragments or larvae) derived propagules disperse through vast oceans. Here, we demonstrate that generational dispersal distances for sexually produced propagules can be indirectly inferred for corals using individual-based isolation-by-distance (IbD) analyses by combining reduced-representation genomic sequencing with photogrammetric spatial mapping. Colonies from the genus Agaricia were densely sampled across plots at four locations and three depths in Curaçao. Seven cryptic taxa were found among the three nominal species (Agaricia agaricites, Agaricia humilis and Agaricia lamarcki), with four taxa showing generational dispersal distances within metres (two taxa within A. agaricites and two within A. humilis). However, no signals of IbD were found in A. lamarcki taxa and thus these taxa probably disperse relatively longer distances. The short distances estimated here imply that A. agaricites and A. humilis populations are reliant on highly localized replenishment and demonstrate the need to estimate dispersal distances quantitatively for more coral species.

Oviposition patterns of primary lepidopteran defoliators in soybean and the impact on structured refuge recommendations.

Transgenic Bt technology in soybean, with plants expressing Cry1Ac, has been adopted as an insect pest management tool. It was first adopted in large areas of South America and Asia in 2013. The risk of resistance in target pests to this technology demands insect resistance management (IRM) programs. In Brazil, a structured refuge (area of non-Bt soybean) planted adjacent to the Bt soybean crop has been an important IRM recommendation, particularly for the primary lepidopteran defoliators Anticarsia gemmatalis (Lepidoptera: Erebidae) and Chrysodeixis includens (Lepidoptera: Noctuidae). The overall goal of this study was to validate IRM recommendations to Bt soybean. The objectives were to document the impact of soybean phenology, cultivar choice and non-Bt soybean defoliation on moth oviposition. In addition, a mark-release-recapture study estimated the dispersal capacity of these species. Five field experiments per species were performed for 3 years. Our results revealed an increase in A. gemmatalis and C. includens oviposition, respectively, on Bt plants as a consequence of the difference in plant growth stage at the time of oviposition. Defoliation of non-Bt plants significantly increased the oviposition preference of both moth species for Bt plants. The mark-release-recapture experiment indicated an average dispersal distance of ~300 m from the release point for A. gemmatalis, with maximum recapture at 1000 m. Overall, our findings emphasize the importance of planting synchronization of Bt soybean and the structured refuge. In addition, when operational aspects in large soybean areas challenge this recommendation, the priority should be for planting the refuge area first. This approach will minimize the impact of selective oviposition of A. gemmatalis and C. includens. © 2024 Society of Chemical Industry.