Long-distance Dispersal Research Articles

Genomic patterns of strain-specific genetic structure, linkage, and selection across fall armyworm populations

BackgroundMolecular genetic approaches have become vital to understanding the evolutionary processes that act on insect pest populations. From mapping the development of resistance to monitoring and predicting pest movement, genomic tools can inform and enhance pest management programs. Here, we used whole genome sequencing population genomics to unravel novel patterns of population structure, linkage, and selection across the genome of a notorious agricultural pest, the fall armyworm.ResultsOur data strongly support the existence of two genetically distinct strains of fall armyworm in North America, which have previously been referred to as the C-strain and the R-strain. Although these strains have diverged genetically, we find that differentiation is not uniform across the genome. The Z-chromosome appears to drive divergence between strains with high levels of linkage observed across this chromosome. We also show that a region of the Z-chromosome containing a circadian clock gene implicated in allochronic reproductive isolation is under strain-specific selection. Our data indicates that strains differ in their geographic distributions and exhibit distinct patterns of geographic sub-structuring indicative of unique dispersal patterns. We provide the first evidence for nuclear genomic differentiation between the two major overwintering populations of fall armyworm in the US. Finally, our data reveal population-specific patterns of selection on genomic regions containing putative insecticide resistance alleles, which could relate to their biogeography.ConclusionsOur results support the existence of the fall armyworm as a pest dyad in the US, with genetically-distinct strains differing in their population structure, dispersal patterns, and genomic signatures of selection on regions likely involved reproductive isolation and insecticide resistance. These differences should be considered when devising and implementing management strategies.

Tradeoffs in growth and fuel reduction when using prescribed fire in young mixed conifer stands

BackgroundFollowing high-severity wildfires in conifer forests that rely on wind dispersal for regeneration, reforestation practices are used to hasten the development of large, fire-resistant trees that are better able to persist through the next fire. Planted forests, however, are particularly prone to high-severity wildfire effects for the initial decades following their establishment. This vulnerability suggests the need for surface fuel reduction treatments in the early stages of stand development. Such treatments would be aligned with the disturbance regime of frequent-fire forests and could also hasten the development of multi-aged structures dominated by fire-resistant trees. Conventional treatments early in stand development include shrub competition reduction and precommercial thinning, but prescribed fire is typically avoided. To assess the potential for inclusion of prescribed fire in young stand management, we investigated how four different treatments—mastication, mastication plus herbicide, two prescribed burns, and mastication plus two burns—affected individual and stand-level growth versus fuel loads in young mixed-conifer plantations in the north-central Sierra Nevada, CA, USA.ResultsTotal surface fuel load more than doubled over 5 years in the mastication only and mastication plus herbicide treatments. Fuel accumulation was avoided in the two treatments that included prescribed fire. Stand growth was similar across the mastication only, mastication plus herbicide, and mastication plus burn treatments. Stand growth was lowest in the burn only treatment. The mastication plus herbicide treatment maximized individual tree growth, especially for white fir and incense-cedar. Individual tree growth was similar among the burn only, mastication only, and mastication plus burn treatments.ConclusionsMastication followed by repeated prescribed burning could be a viable management strategy to reduce wildfire hazard without sacrificing growth in young mixed-conifer stands that are entering a vulnerable stage of fire risk. Mastication in combination with herbicide may facilitate the growth of large, fire-resistant trees, but does not address surface fuel buildup. The use of fire alone can effectively reduce fuels, but stand growth may be somewhat low relative to mastication and herbicide. Incorporating prescribed fire is a promising approach for protecting planted stands from high-severity fire while transitioning them into multi-aged structures. Gap-based silvicultural systems that facilitate the development of multi-cohort stands can also use prescribed fire broadly in order to restore heterogeneity and low surface fuel loads.

Identification of Wheat Stripe Rust Inoculum Sources and Dispersal Routes Responsible for Initial Rust Establishment in Southern Henan of China.

Wheat stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is an important airborne disease worldwide. Pst inoculum strength in southern Henan in winter or early spring is important for spring epidemics in the main autumn-sown wheat-growing regions of China. However, there is limited knowledge about the source and time of initial infection on winter wheat in southern Henan. The first occurrence of wheat stripe rust in southern Henan was recorded annually from 2011 to 2022, from which we used the backward trajectory approach to infer the likely source of Pst inoculum responsible for the initial disease occurrence. The results suggested that the Pst inoculum responsible for initial rust established in the winter in southern Henan originated from the Gansu Pst oversummering area in China, whereas it originated from the adjacent winter Pst sporulation regions in southern Shaanxi and northwestern Hubei if Pst symptoms were first observed in early spring in southern Henan. Another possible Pst source is southern Hubei where Pst can also sporulate in the winter. Thus, early Pst development in winter in the main wheat production region in China (Henan) is likely to be caused by Pst inoculum spread from the oversummering inocula or Pst epidemics in autumn seedlings in Gansu.

Differential Primary Seed and Fruit Dispersal Mechanisms and Dispersal Biomechanics in Invasive Dehiscent and Indehiscent-Fruited Lepidium Species

This study explores primary dispersal, which involves diaspores’ detachment directly from mature plants, and secondary dispersal, which encompasses any further dispersal occurring after the primary dispersal. A comparison of the primary dispersal vectors of the invasive dehiscent fruit producing Lepidium campestre and the indehiscent fruit producing Lepidium draba was conducted. These vectors were examined in relation to the native and introduced distribution ranges of the species, and regarding biomechanical forces required detaching the fruits from mature plants. Our findings reveal that rainfall and animal contact serve as primary dispersal vectors for Lepidium campestre, while animal contact is rarely involved in primary dispersal of Lepidium draba. Primary dispersal is more important for Lepidium campestre than Lepidium draba, which requires significantly greater force for fruit detachment. While previous studies indicate wind and rainfall as major secondary dispersal vectors for Lepidium draba, our results suggest secondary dispersal via mucilage on seeds is more crucial for this species. The strong reliance of Lepidium draba on secondary dispersal, enabling long-distance dispersal, could contribute to its invasion success, linking it to the species’ geographic distribution. Understanding these different dispersal strategies is essential for effective management of invasive species.

Chasing the Rainbow: Decoupled phenotypic and genotypic evolution in New Guinea’s rainbow skinks (Squamata: Scincidae)

With the advent of molecular data, the discovery of cryptic species has become commonplace. New Guinea, a region of high vertebrate biodiversity and complex geological history, has been found to contain immense numbers of cryptic skink species. We present the first molecular phylogenetic analysis of Carlia Gray, 1845, and its sister genus Lygisaurus de Vis, 1884, across mainland New Guinea and the Solomon Islands. We find rainbow skinks exhibit significant genetic divergence with minimal morphological variation and our data suggest the existence of many undescribed species. Due to the morphologically cryptic nature of rainbow skinks, we demonstrate the efficacy of the COI gene as a “barcode” for difficult species determinations. Divergence time and biogeographic analyses support four separate dispersal events from Australia to New Guinea for rainbow skinks from ~10–5 mya, with most groups arriving first in the East Papua Composite Terrane (EPCT) and dispersing from there to other terranes and islands. Exceptions to this pattern were observed in Lygisaurus, which dispersed first to the West Papuan portion of the Craton ~8.4mya, and the island clade of the Carlia fusca group, which dispersed to the Vogelkop peninsula ~4.7mya and from there to many islands.

Phylogenetic origin of dioecious Callicarpa (Lamiaceae) species endemic to the Ogasawara Islands revealed by chloroplast and nuclear whole genome analyses.

Oceanic islands offer excellent opportunities to study the ecology, evolutionary biology, and biogeography of plants. To uncover the genetic basis of various evolutionary trends commonly observed on these islands, the origins and phylogenetic relationships of the species being studied should be understood. Callicarpa glabra, Callicarpa parvifolia, and Callicarpa subpubescens are evergreen woody plants endemic to the Ogasawara Islands, which are remote oceanic islands located off of the Japanese Archipelago. These species are ideal for studying evolutionary changes on oceanic islands because of their adaptive radiation and shift toward dioecious sex expression. We used a phylogenomic perspective to determine the evolutionary relationship of the three species within the genus and infer their colonization time. Based on the analysis of both chloroplast genomes and 86 nuclear single-copy genes, we found that these three species were monophyletic and embedded in a backbone clade that included multiple East Asian species. The phylogenetic tree based on over 10,000 nuclear genes placed the insular species in the East Asian clade, although the topology did not entirely correspond to the chloroplast tree, probably because of incomplete lineage sorting and interspecific hybridization. The three endemic species were estimated to have diverged from continental species approximately three million years ago (Mya). The results of this study suggested that the ancestor of the Ogasawara endemic species originated from long-distance dispersal from East Asia mainland in the late Pliocene, and then progressively speciated within the islands.

Phytolith evidence of agricultural emergence and its dispersal routes in the southeastern mountain area of China

Phytolith evidence of agricultural emergence and its dispersal routes in the southeastern mountain area of China

Comparative phylogeography of four lizard taxa within an oceanic island.

Comparative phylogeography aims to detect common patterns of differentiation among taxa attributed to the same geological or environmental barriers and, thus, find shared drivers of genomic splits and landscape features that explain patterns of occurrence and genetic diversity. Following this approach, this work focuses on four endemic lizard taxa, namely Acanthodactylus schreiberi schreiberi, Ophisops elegans schlueteri, Phoenicolacerta troodica, and Laudakia cypriaca, that co-occur in Cyprus, an isolated island of the Mediterranean. In an attempt to discern possible effects of the geological and ecological history of the region on diversity patterns along the lineages under study, samples were collected from all parts of Cyprus and phylogenetic reconstructions, species delimitation analyses, and biogeographic comparisons were conducted at both genetic and genomic levels (Sanger and ddRAD sequencing data, respectively) for all four taxa. The derived phylogenomic relationships provide evidence of a strong genetic structure within the island that agrees with the geographical origins of each population. A rare case of an island-to-mainland dispersal event is confirmed for one of the focal taxa, making it one of the few documented cases of this type. Estimated diversification times during the Miocene reflect the timing of the first arrival on the island, while further diversification seems to have been strongly affected by the Pleistocene oscillations.

Functional Traits and Phylogenetic Effects Drive Germination of Lemur-Passed Seeds.

Frugivore-mediated seed dispersal drives ecological functioning across tropical forests. The biological mechanisms affecting seed dispersal outcomes, as well as the role of specific functional traits in plants and their dispersers, is still not well understood. To address this gap, we conducted germination experiments in eight species of captive and two species of wild lemurs, which disperse different plant species. We (1) quantified the effects of pulp removal, seed priming, and feces effects (nutrient/microbial fertilization) through gut passage as mechanisms, (2) determined the effect of frugivore species on germination, and (3) assessed how individual plant and animal traits affected two seed germination outcomes: success rates and time-to-germination. Accounting for phylogenetic non-independence of plants and estimating phylogenetic signal, we evaluated the effects of lemur gut passage and functional traits in a Bayesian framework. Seed priming during gut passage was the primary mechanism through which lemurs improved germination rates and decreased time-to-germination. Gut passage influenced the effect of seed length on germination probability but not time-to germination. Germination outcomes varied by disperser species and seed size. Furthermore, seeds passed by male lemurs were 40% more likely to germinate than those passed by female lemurs. Germination probability was more similar for closely related plant species compared to those that were more distantly related, while the plant phylogenetic effects on time-to-germination were weaker. Moreover, germination depended on experimental setting; for example, lemur gut passage decreased time-to-germination in captive, but not wild settings. Our results highlight the complexity of biological mechanisms determining seed dispersal outcomes; ecological and evolutionary factors were important drivers of germination. Considering a diversity of potential effects is critical for advancing a mechanistic understanding of species interactions and their outcomes.

What Do We Know About Non-Native, Invasive, and Transplanted Aquatic Mollusks in South America?

Global awareness of introduced species as one of the primary drivers of biodiversity change—causing environmental impacts, and economic and social effects—emphasizes the need to enhance our understanding of these species. Developing a comprehensive database will enable policymakers to identify global bioinvasion patterns and strengthen their capacity to manage them effectively. Aquatic mollusks play a crucial role in the ecosystems they inhabit, influencing food webs and nutrient cycling, and habitat formation and modification. They are also the dominant group in aquaculture, contributing significantly to the economy while also causing economic losses through macrofouling and posing health risks. Despite their importance, information on the introduction, establishment, and dispersal of mollusk species in South America remains scarce and is often confined to the grey literature. With the aim of organizing, increasing, and strengthening the knowledge of non-native and transplanted mollusks in general and aquatic mollusks in particular, 29 specialists in the introduced mollusks of South America, from seven countries, have been working collaboratively since 2016. Each member contributes expertise, data, and bibliographic resources to build the status of the introduced mollusks in South America and provide critical information to prevent future introductions and transplants. In aquatic environments, 41 non-native mollusk species and 18 transplanted species have been identified. Among them, the bivalve Limnoperna fortunei stands out with the greatest economic effect, while the gastropods Lymnaeidae and Thiaridae represent significant health concerns. Although this research represents a major step forward, it also highlights challenges such as the scarcity of taxonomic studies and the limited investigation of vast areas in South America. The information compiled in this review serves as a resource for researchers, policymakers, and the general public when addressing mollusk bioinvasions in South America.

Effects of laundry washing on germination of cloth-dispersed seeds depends on washing intensity not on detergent type.

Unintentional human-vectored seed dispersal (HVD) occurs when the seed dispersal vectors are humans, and the seeds are attached to clothing or footwear during various outdoor activities. Since most plant species spread by HVD are invasives or weeds, the process can have globally relevant adverse environmental effects due to the growing global tourism industry. Here we evaluated whether the germination capacity of seeds can be reduced by laundry washing treatments used in households, in order to decrease the chance of unintended dispersal of plant species by clothing. We experimentally tested the effects of seven types of detergents with different chemical composition and three washing intensities in a full factorial design on the germination capacity of 18 plant species. Washing at high intensity (60°C) significantly decreased the germination capacity in 15 species, probably due to high temperatures and longer exposure times. Washing at low (30°C) and medium intensities (40°C) had no effect. Detergent type affected the germination capacity of only three species. The findings underscore the importance of laundry washing in seed dispersal, since the low and medium washing intensities and detergent types that are commonly used in households do not decrease the germination capacity of the cloth-dispersed seeds. We urge addressing the spread of HVD-dispersed seeds through combined biosecurity measures. Self-regulation, such as removing of seeds from clothes and disposing them properly, is crucial. Informing outdoor workers, who play the largest role in HVD, can encourage small behavioural changes to decrease the adverse effects of this process.

Insights into the exceptional support phase effect on Ag/Sm2Ce2O7: Modulating Ag distribution and Ag-support interaction to construct reactive soot oxidation catalysts

Developing efficient, cost-effective and robust catalysts for soot combustion is crucial yet challenging. In this study, we fabricated Ag-loaded Sm2Ce2O7 paramorphs catalysts (C-type and Cubic fluorite) via different methods, aiming to improve the distribution and interaction of Ag by modifying the crystalline structures of the supports to enhance oxygen activation. The oxygen vacancy concentration and redox performance of the rare earth C-type catalysts exceeded those of the cubic fluorite ones. In the case of the Ag-assisted catalysts, the Sm2Ce2O7–Ag interface with oxygen vacancies displayed an increased affinity for oxygen. The distribution state of Ag on the catalysts is closely related to the Ag–support interactions and the active sites on the support. Experimental analyses and density functional theory (DFT) calculations have revealed a more even dispersion of the Ag species on the C-type catalyst; differential charge density and Bader charge analysis have confirmed that the Ag loadings can alter the surface charge arrangement, resulting in stronger electronic interactions between Ag and the Sm2Ce2O7-C support. Uniformly dispersed Ag species can effectively promote the activation of gaseous O2 molecules, which is key in the oxidation of soot particles. This approach provides a promising strategy for developing more applicable catalysts for soot combustion.

Apparent survival and population turnover in a long-lived generalist raptor: a comparison of estimation methods

Adult survival and turnover rates are often estimated in long-lived species as the primary drivers of population dynamics. Various methods have been used, yet comparison of estimation methods is seldom undertaken. To address this gap, we used colour-ringing across different age groups, as well as GPS-tracking and genetic analysis of shed feathers, to estimate these critical parameters in a population of the medium-sized bird of prey, the Lesser Spotted Eagle. According to the colour-ringing data, the apparent survival during the first year of life (0.21) was more than four times lower than that of birds older than one year (0.88); the GPS-tracking (0.84) and genetic analysis (0.81) yielded similar survival estimates. All used techniques indicated a stable trend in apparent survival rates. However, population turnover rates derived from genetic feather analysis (0.17–0.43) exceeded expectations based on apparent survival estimates, as well as those derived from colour-rings (0.05–0.17) and GPS-tracking (0.05–0.08). Notably, all markers indicated high site fidelity among adult eagles, with breeding dispersal events being infrequent. Our findings underscore the utility of diverse methods for estimating apparent survival, though the ecological characteristics of the species may influence the efficacy of each method. However, estimates of population turnover rates were notably influenced by the choice of method and should be interpreted cautiously before recommending management actions.

Moving north under the eye of the public: the dispersal ecology of the Nosferatu spider, documented by citizen scientists

Moving north under the eye of the public: the dispersal ecology of the Nosferatu spider, documented by citizen scientists

Observation of Tropilaelaps mercedesae (Mesostigmata: Laelapidae) on Western honey bees (Apis mellifera) exiting colonies.

Tropilaelaps mercedesae (Delfinado and Baker) is an emerging parasitic mite that can severely impact the Western honey bee (Apis mellifera L.). While T. mercedesae has been reported to be expanding its geographical range, the routes of inter-colony dispersal between A. mellifera colonies are still largely unknown. In this study, we used funnel traps to collect foraging honey bees exiting their colonies before performing an alcohol wash to collect any phoretic T. mercedesae mites. We found T. mercedesae on exiting adult honey bees; however, they were only detected when a colony had an elevated T. mercedesae brood infestation. We show that T. mercedesae can exit colonies through phoresy on adult A. mellifera which demonstrates the potential of these mites to be spread through the natural movement of A. mellifera honey bees among colonies.

Tracing humanity’s path: the DISPERSALS project and the origins of global migration

Tracing humanity’s path: the DISPERSALS project and the origins of global migration DISPERSALS will compare human occupation and ecology between central Mozambique and eastern and southern Africa using a multi-scale approach based on the study of regional diachronic cultural traits. It will reconstruct regional population patterns, followed by comparative quantitative population genetics combined with GIS computational network analyses. The results will then be integrated through agent-based modelling, based on the incremental creation, elimination, or reorientation of network links to simulate a quantitative framework to study the evolution of population dispersal across southern-eastern Africa. The project will be crucial in providing ground-breaking high-resolution archaeological, chronological and paleoenvironmental data. DISPERSALS will deliver a fundamental perspective on the key processes that triggered migrations and dispersals within Africa and out-of-Africa, which ultimately resulted in the human diaspora over the entire planet.

Climate-driven range expansion via long-distance larval dispersal

Climate-driven warming and changes in major ocean currents enable poleward larval transport and range expansions of many marine species. Here, we report the population genetic structure of the gastropod Kelletia kelletii, a commercial fisheries species and subtidal predator with top-down food web effects, whose populations have recently undergone climate-driven northward range expansion. We used reduced representation genomic sequencing (RAD-seq) to genotype 598 adults from 13 locations spanning approximately 800 km across the historical and expanded range of this species. Analyses of 40747 single nucleotide polymorphisms (SNPs) showed evidence for long-distance dispersal of K. kelletii larvae from a central historical range site (Point Loma, CA, USA) hundreds of km into the expanded northern range (Big Creek, CA), which seems most likely to result from transport during an El Niño-Southern Oscillation (ENSO) event rather than consistent on-going gene flow. Furthermore, the high genetic differentiation among some sampled expanded-range populations and their close genetic proximity with distinct populations from the historical range suggested multiple origins of the expanded-range populations. Given that the frequency and magnitude of ENSO events are predicted to increase with climate change, understanding the factors driving changes in population connectivity is crucial for establishing effective management strategies to ensure the persistence of this and other economically and ecologically important species.

Crystal Phase-Dependent Dispersion and Catalysis of the Ag Species Supported on TiO2 for CO Oxidation with Excess Oxygen

Crystal Phase-Dependent Dispersion and Catalysis of the Ag Species Supported on TiO₂ for CO Oxidation with Excess Oxygen

Spontaneous adsorption of iridium chloride complex on oxychloride photocatalysts provides efficient and durable reaction site for water oxidation.

The visible-light-driven O2 evolution on oxychloride photocatalysts, such as Bi4NbO8Cl, was significantly enhanced by stirring in an aqueous solution containing IrCl63- in the dark. Various characterizations indicated that highly dispersed IrOxHyClz-like species spontaneously formed on the oxychloride surface, serving as effective and stable cocatalysts for enhancing O2 evolution.

Ecological and demographic drivers of kin-directed cooperation in a social bird: Insights from a long-term study.

The evolution of sociality is one of the major evolutionary transitions in the history of life and a key step in this transition is the occurrence of kin associations. Yet, the question of what demographic processes and environmental factors generate kin-structured populations and drive kin-directed cooperation remains open. In this review, we synthesise 30 years of studies of the long-tailed tit Aegithalos caudatus, which has a kin-selected cooperative breeding system with redirected help: failed breeders may help to raise offspring of conspecifics, typically relatives, breeding nearby. We describe the use of ecological, demographic, genetic and behavioural approaches to reveal: (a) how kin-structured populations (here 'kin neighbourhoods') arise; (b) why the prevalence of cooperation varies among populations and individuals; and (c) how variation in dispersal and opportunities for cooperation influence individual fitness. The kin neighbourhoods of long-tailed tits arise from three processes. First, natal dispersal is limited and sex-biased so many individuals, especially males, recruit as breeders close to their natal site. Second, neither dispersal nor migration necessarily disrupts kin associations because long-tailed tits often move with close relatives. Third, a small effective population size driven by high nest predation rates enhances within-population relatedness. Together, these processes set the scene for kin-directed helping behaviour by causing spatial clustering of relatives. The prevalence of cooperation within kin neighbourhoods depends on several factors, both at the population-level (annual nest predation rate and length of the breeding season) and individual-level (relatedness, familiarity, sex and condition). However, limited information on prior social association and the reliability of kin discrimination cues hampers our current understanding of individual helping decisions. Finally, variation in dispersal within and between sexes affects the probability of interacting with kin, the likelihood of cooperation, and accrual of the direct and indirect components of inclusive fitness. We use this comprehensive understanding of the factors driving cooperative behaviour in long-tailed tits to highlight gaps in knowledge and suggest future avenues for research in this system, and to make general inferences about the role of dispersal, demography and kinship in social evolution.