Find research datasets worth reusing

opencc-zeroDec 2016View details →

Data from: Pioneer cells established by the [SWI+] prion can promote dispersal and out-crossing in yeast

To thrive in an ever-changing environment, microbes must widely distribute their progeny to colonize new territory. Simultaneously, they must evolve and adapt to the stresses of unpredictable surroundings. In both of these regards, diversity is key—if an entire population moved together or responded to the environment in the same way, it could easily go extinct. Here, we show that the epigenetic prion switch [SWI+] establishes a specialized subpopulation with a "pioneer" phenotypic program in Saccharomyces cerevisiae. Cells in the pioneer state readily disperse in water, enabling them to migrate and colonize new territory. Pioneers are also more likely to find and mate with genetically diverse partners, as inhibited mating-type switching causes mother cells to shun their own daughters. In the nonprion [swi−] state, cells instead have a "settler" phenotype, forming protective flocs and tending to remain in their current position. Settler cells are better able to withstand harsh conditions like drought and alkaline pH. We propose that these laboratory observations reveal a strategy employed in the wild to rapidly diversify and grant distinct, useful roles to cellular subpopulations that benefit the population as a whole.

Data from: Spatial patterning of prey at reproduction to reduce predation risk: what drives dispersion from groups?

Group-living is a widespread behaviour thought to be an evolutionary adaptation for reducing predation risk. Many group-living species, however, spend a portion of their life cycle as dispersed individuals, suggesting that the costs and benefits of these opposing behaviours vary temporally. Here, we evaluated mechanistic hypotheses for explaining individual dispersion as a tactic for reducing predation risk at reproduction (i.e. birthing) in an otherwise group-living animal. Using simulation analyses parameterized by empirical data, we assessed whether dispersion increases reproductive success by: (i) increasing predator search time, (ii) reducing predator encounter rates because individuals are inconspicuous relative to groups, or (iii) eliminating the risk of multiple kills per encounter. Simulations indicate that dispersion only becomes favourable when detectability increases with group size and there is risk of multiple kills per encounter. This latter effect, however, is likely the primary mechanism driving females to disperse at reproduction because group detectability effects are presumably constant year round. We suggest that the risk of multiple kills imposed by highly vulnerable offspring may be an important factor influencing dispersive behaviour in many species and conservation strategies for such species will require protecting sufficient space to allow dispersion to effectively reduce predation risk.

opencc-zeroDec 2013View details →

Data from: The founding of Mauritian endemic coffee trees by a synchronous long-distance dispersal event

The stochastic process of long-distance dispersal is the exclusive means by which plants colonize oceanic islands. Baker's rule posits that self-incompatible plant lineages are unlikely to successfully colonize oceanic islands because they must achieve a coordinated long-distance dispersal of sufficiently numerous individuals to establish an outcrossing founder population. Here, we show for the first time that Mauritian Coffea species are self-incompatible and thus represent an exception to Baker's rule. The genus Coffea (Rubiaceae) is composed of approximately 124 species with a paleotropical distribution. Phylogenetic evidence strongly supports a single colonization of the oceanic island of Mauritius from either Madagascar or Africa. We employ Bayesian divergence time analyses to show that the colonization of Mauritius was not a recent event. We genotype S-RNase alleles from Mauritian endemic Coffea, and using S-allele gene genealogies, we show that the Mauritian allelic diversity is confined to just seven deeply divergent Coffea S-RNase allelic lineages. Based on these data, we developed an individual-based model and performed a simulation study to estimate the most likely number of founding individuals involved in the colonization of Mauritius. Our simulations show that to explain the observed S-RNase allelic diversity, the founding population was likely composed of fewer than 31 seeds that were likely synchronously dispersed from an ancestral mainland species.

opencc-zeroSep 2019View details →

Bandicoots return to Booderee: initial survival, dispersal, home range and habitat preferences of reintroduced southern brown bandicoots (eastern sub species; Isoodon obesulus obesulus)

Context Reintroductions can be an effective means of re-establishing locally extinct or declining faunal populations. However, incomplete knowledge of variables influencing survival and establishment can limit successful outcomes. Aim We aimed to examine the factors (e.g. sex, body mass, release order) influencing the survival, dispersal, home range and habitat selection of reintroduced southern brown bandicoots (eastern subspecies; Isoodon obesulus obesulus) into an unfenced, predator-managed environment in south-eastern Australia (Booderee National Park). Methods Over 2 weeks in May 2016, six female and five male bandicoots were wild-caught in state forest and hard released into the park. Release locations were approximately evenly distributed between three primary vegetation types assessed as suitable habitat: heath, woodland and forest. Bandicoots were radio-tracked day and night for 4 weeks from the initial release date. Key results No mortality was detected. Males dispersed more than twice as far as females (male 704 m, female 332 m), but there was no significant sex bias in home range size. At the landscape scale, bandicoots preferentially selected home ranges that contained heath and avoided forest. Within home ranges, heath and woodland were both favoured over forest. Conclusions Post-release dispersal is sex-biased, but more data are required to determine the influence of other predictors such as body mass and release order. Within the release area, bandicoots favoured non-forest vegetation types. Implications Our study outlines factors influencing the establishment of reintroduced bandicoots. We recommend that future bandicoot reintroductions to Booderee National Park occur within areas of heath and woodland, and that subsequent releases consider the potentially larger spatial requirements and conspecific avoidance among male bandicoots. Our findings contribute new knowledge for improving translocation methods of a nationally endangered medium-sized mammal.

Data from: The highs and lows of dispersal: how connectivity and initial population size jointly shape establishment dynamics in discrete landscapes

Identifying the main factors driving introduced populations to establishment is a major challenge of invasion biology. Due to their small initial size, introduced populations are most vulnerable to extinction because of demographic stochasticity or Allee effects. While an increase in initial population size is known to increase establishment success, much remains to be understood regarding its interplay with connectivity in spatially structured environments. In order to better understand how demographic mechanisms interact at such spatial scale, we developed a stochastic model of population dynamics in discrete space to investigate the effect of connectivity and initial population size on establishment. The predictions derived from the model were then tested using experimental introductions of an insect parasitoid (Trichogramma chilonis) in spatially structured laboratory microcosms. Both theoretical and experimental results demonstrated that the connectivity of the introduction site had 1) a deleterious effect in the first generation when the introduced population was small and 2) a beneficial impact brought about by metapopulation effects in the subsequent generations. Interestingly, populations displayed a weakly pushed invasion pattern promoting early establishment, which was mainly underpinned by dispersal stochasticity and the discrete nature of the landscape. These results shed light on the critical influence of landscape connectivity on establishment dynamics.

Data from: Bird-mediated seed dispersal: reduced digestive efficiency in active birds modulates the dispersal capacity of plant seeds

Plant populations in fragmented ecosystems rely largely on internal dispersal by animals. To unravel the mechanisms underlying this mode of dispersal, an increasing number of experimental feeding studies is carried out. However, while physical activity is known to affect vertebrate digestive processes, almost all current knowledge on mechanisms of internal seed dispersal has been obtained from experiments with resting animals. We investigated how physical activity of the mallard Anas platyrhynchos, probably the quantitatively most important biotic dispersal agent in aquatic habitats in the entire Northern Hemisphere, affects gut passage survival and retention time of ingested plant seeds. We fed seeds of nine common wetland plants to mallards trained to subsequently swim for six hours in a flume tank at different swimming speeds (activity levels). We compared gut passage survival and retention times of seeds against a control treatment with mallards resting in a conventional dry cage. Intact gut passage of seeds increased significantly with mallard activity (up to 80% in the fastest swimming treatment compared to the control), identifying reduced digestive efficiency due to increased metabolic rates as a mechanism enhancing the dispersal potential of ingested seeds. Gut passage speed was modestly accelerated (13% on average) by increased mallard activity, an effect partly obscured by the interaction between seed retention time and probability of digestion. Gut passage acceleration will be more pronounced in digestion-resilient seed species, thereby modulating their dispersal distances. Our findings imply that seed dispersal potential by mallards calculated from previous experiments with resting birds is highly underestimated, while dispersal distances may be overestimated for some plant species. Similar effects of physical activity on digestive efficiency of mammals suggests that endozoochorous dispersal of plant seeds by vertebrates is more effective and plays a quantitatively more important ecological role in both terrestrial and aquatic ecosystems than previously thought.

Data from: Special delivery: scavengers direct seed dispersal towards ungulate carcasses

Cadaver decomposition-islands around animal carcasses can facilitate establishment of various plant life. Facultative scavengers have great potential for endozoochory, and often aggregate around carcasses. Hence, they may disperse plant seeds that they ingest across the landscape towards cadaver decomposition-islands. Here, we demonstrate this novel mechanism along a gradient of wild tundra reindeer carcasses. First, we show that the spatial distribution of scavenger feces (birds and foxes) was concentrated around carcasses. Second, feces of the predominant scavengers (corvids) commonly contained viable seeds of crowberry, a keystone species of the alpine tundra with predominantly vegetative reproduction. We suggest that cadaver decomposition-islands function as endpoints for directed endozoochory by scavengers. Such a mechanism could be especially beneficial for species that rely on small scale disturbances in soil and vegetation, such as several Nordic berry-producing species with cryptic generative reproduction.

opencc-zeroDec 2015View details →

Data from: What is long-distance dispersal? and a taxonomy of dispersal events

Dispersal is a key individual-based process influencing many life-history attributes and scaling up to population-level properties (e.g. metapopulation connectivity). A persistent challenge in dispersal ecology has been the robust characterization of dispersal functions (kernels), a fundamental tool to predict how dispersal processes respond under global change scenarios. Particularly, the rightmost tail of these functions, that is the long-distance dispersal (LDD) events, are difficult to characterize empirically and to model in realistic ways. But, when is it a LDD event? In the specific case of plants, dispersal has three basic components: (i) a distinct (sessile) source, the maternal plant producing the fruits or the paternal tree acting as a source of pollen; (ii) a distance component between source and target locations; and (iii) a vector actually performing the movement entailing the dispersal event. Here, I discuss operative definitions of LDD based on their intrinsic properties: (i) events crossing geographic boundaries among stands; and (ii) events contributing to effective gene flow and propagule migration. Strict-sense long-distance dispersal involves movement both outside the stand geographic limits and outside the genetic neighbourhood area of individuals. Combinations of propagule movements within/outside these two spatial reference frames result in four distinct modes of LDD. Synthesis. I expect truncation of seed dispersal kernels to have multiple consequences on demography and genetics, following to the loss of key dispersal services in natural populations. Irrespective of neighbourhood sizes, loss of LDD events may result in more structured and less cohesive genetic pools, with increased isolation by distance extending over broader areas. Proper characterization of the LDD events helps to assess, for example, how the ongoing defaunation of large-bodied frugivores pervasively entails the loss of crucial LDD functions.

opencc-zeroAug 2019View details →

Data from: An experimental test of the effects of dispersal and the paradox of enrichment on metapopulation persistence

Many species exhibit high-amplitude, extinction-prone cycles, for instance due to resource enrichment (called the paradox of enrichment). How do such species manage to persist? One possibility is metapopulation dynamics, but it is unclear if these can mitigate the paradox of enrichment. The paradox of enrichment might increase local population extinction rates, and might also increase the spatial synchrony of population fluctuations because population cycles are easily synchronized by even low rates of dispersal. Spatially-synchronous population fluctuations would leave no scope for rescue effects, and spatially-synchronous local extinctions would leave no source for recolonization. We conducted a protist microcosm experiment to test how dispersal and enrichment affect the persistence of predator-prey metapopulations by altering spatial synchrony. We assembled 54, 4-patch metapopulations of the protist predator Euplotes patella and its protist prey Tetrahymena pyriformis. Each metapopulation experienced one of nine dispersal rates, crossed with one of 6 enrichment levels. We tested the effects of enrichment and dispersal on predator-prey cycle amplitude, predator population extinction risk, spatial synchrony of predator population fluctuations, and predator metapopulation persistence time. Enrichment increased predator-prey cycle amplitude but had no detectable effect on population extinction risk. Dispersal had no effect on predator-prey cycle amplitude. Spatial synchrony increased with enrichment and dispersal. Metapopulation persistence decreased with enrichment and spatial synchrony. We conclude that increasing enrichment reduced metapopulation persistence primarily by increasing spatial synchrony of local extinctions, rather than by increasing their frequency. These results highlight the importance of synchrony-preventing mechanisms for metapopulation persistence.

opencc-zeroDec 2018View details →

Data from: Effects of increasing aridity and chronic anthropogenic disturbance on seed dispersal by ants in Brazilian Caatinga

1. Anthropogenic disturbance and climate change are the main drivers of biodiversity loss and ecological services around the globe. There is concern that climate change will exacerbate the impacts of disturbance and thereby promote biotic homogenization, but its consequences for ecological services are unknown. 2. We investigated the individual and interactive effects of increasing chronic anthropogenic disturbance (CAD) and aridity on seed dispersal services provided by ants in Caatinga vegetation of northeastern Brazil. 3. The study was conducted in Catimbau National Park, Pernambuco, Brazil. Within an area of 214 km2, we established nineteen 50 x 20 m plots that encompassed gradients of both CAD and aridity. We offered diaspores of six plant species, three myrmecochorous diaspores and three fleshy fruits that are secondarily dispersed by ants. We then quantified the number of interactions, seed removal rate and dispersal distances, and noted the identities of interacting ant species. Finally, we used pitfall trap data to quantify the abundances of ant disperser species in each plot. 4. Our results show that overall composition of ant disperser species varied along the gradients of CAD and aridity, but the composition of high-quality dispersers varied only with aridity. The total number of interactions, rates of removal and mean distance of removal all declined with increasing aridity, but they were not related to CAD. These same patterns were found when considering only high-quality disperser species, driven by the responses of the dominant disperser Dinoponera quadriceps. We found little evidence of interactive effects of CAD and aridity on seed dispersal services by ants. 5. Our study indicates that CAD and aridity act independently on ant-mediated seed dispersal services in Caatinga, such that the impacts of anthropogenic disturbance are unlikely to change under the forecast climate of increased aridity. However, our findings highlight the vulnerability of seed dispersal services provided by ants in Caatinga under an increasingly arid climate due to low functional redundancy in high-quality disperser species. Given the large number of plant species dependent on ants for seed dispersal, this has important implications for future plant recruitment and, consequently, for the composition of Caatinga plant communities.

opencc-zeroDec 2018View details →

Data from: Competition, seed dispersal, and hunting: what drives germination and seedling survival in an Afrotropical forest?

Disentangling the contributions of different processes that influence plant recruitment, such as competition and seed dispersal, is important given the increased human-mediated changes in tropical forest ecosystems. Previous studies have shown that seedling communities in an Afro-tropical rainforest in Southeastern Nigeria are strongly affected by the loss of important seed dispersing primates, including Cross River gorillas (Gorilla gorilla diehli), chimpanzee (Pan troglodytes elioti), and drill (Mandrillus leucophaeus). Here we study how germination and survival of tree seedlings are affected by competition and reduced seed-dispersal in three contiguous forest reserves, in Southeastern Nigeria, with similar mature tree species composition and structure. We use an experimental design aimed at manipulating the effect of competition among seedlings in three protected and three hunted sites within the reserves. We use a total of sixty 5×5 m plots of three types: plots cleared of all seedlings, plots selectively cleared of all primate-dispersed seedlings and control plots. All seedlings were identified, measured, assigned to dispersal mode, and tagged, and after one year we evaluated survival, mortality and new recruits. We found that in hunted sites germination of abiotically dispersed species was over four times higher in cleared plots compared to control plots, whereas germination of primate dispersed species was the same, which indicated that dispersal limitation was the dominant force in seedling recruitment in hunted sites. This was supported by the fact that the germination of all dispersal modes in the selectively cleared plots in protected sites was similar to the control plots in the same sites, but germination of abiotically dispersed species was significantly lower than in cleared plots in hunted sites. Competition among seedlings was mostly evident from the fact that 75% more seedlings of primate dispersed species germinated in cleared compared to control plots in protected sites. We conclude that inter-seedling competition may be irrelevant to seedling recruitment in hunted sites, where dispersal limitation appears to be a much stronger force shaping the seedling plant community, and thus hunting indirectly reverses the importance of competition and dispersal limitation in structuring seedling communities.

opencc-zeroDec 2019View details →

Fruit syndromes in Viburnum: correlated evolution of color, nutritional content, and morphology in bird-dispersed fleshy fruits

Premise A key question in plant dispersal via animal vectors is where and why fruit colors vary between species and how color relates to other fruit traits. To better understand the factors shaping the evolution of fruit color diversity, we tested for the existence of syndromes of traits (color, morphology, and nutrition) in the fruits of Viburnum. We placed these results in a larger phylogenetic context and reconstructed ancestral states to assess how Viburnum fruit traits have evolved across the clade. Results We find that blue Viburnum fruits are not very juicy, have high lipid content, and large, round endocarps surrounded by a small quantity of pulp. Red fruits display the opposite suite of traits: they are very juicy with low lipid content and smaller, flatter endocarps. The ancestral Viburnum fruit may have gone through a sequence of color changes before maturation (green to yellow to red to black), though our reconstructions are equivocal. In one major clade of Viburnum (Nectarotinus), fruits mature synchronously with reduced intermediate color stages. Most transitions between fruit colors occurred in this synchronously fruiting clade. Conclusions It is widely accepted that fruit trait diversity has primarily been driven by the differing perceptual abilities of bird versus mammal frugivores. Yet within a clade of largely bird-dispersed fruits, we find clear correlations between color, morphology, and nutrition. These correlations are likely driven by a shift from sequential to synchronous development, followed by diversification in color, nutrition, and morphology. A deeper understanding of fruit evolution within clades will elucidate the degree to which such syndromes structure extant fruit diversity.

Data from: Social information from immigrants: multiple immigrant based sources of information for dispersal decisions in a ciliate

1. Dispersal is increasingly recognized as being an informed process, based on information organisms obtain about the landscape. While local conditions are often found to drive dispersal decisions, local context is not always a reliable predictor of conditions in neighbouring patches, making the use of local information potentially useless or even maladaptive. In this case, using social information gathered by immigrants might allow adjusting dispersal decisions without paying the costs of prospecting. However, this hypothesis has been largely neglected despite its major importance for ecological and evolutionary processes. 2. We investigated three fundamental questions about immigrant-informed dispersal: Do immigrants convey information that influences dispersal, do organisms use multiple cues from immigrants, and is immigrant-informed dispersal genotype dependent? 3. Using Tetrahymena thermophila ciliates in microcosms, we manipulated the number of immigrants arriving, the density of congeners, the resource quality in neighbouring patches, matrix characteristics and the level of cooperation of individuals in the neighbouring populations. 4. We provide the first experimental evidence that immigrants convey a number of different cues about neighbouring patches and matrix (patch quality, matrix characteristics and cooperation in neighbouring populations) in this relatively simple organism. Furthermore, we demonstrate genotype-dependent immigrant-informed dispersal decisions about patch quality and matrix characteristics. 5. Multiple cues from immigrants and genotype-dependent use of cues have major implications for theoretical metapopulation dynamics and the potential for local adaptation.

Data from: Interactions between seed traits and digestive processes determine the germinability of bird-dispersed seeds

Waterbirds disperse a wide range of plant seeds via their guts, promoting biotic connectivity between isolated habitat patches. However, the intensity of digestive forces encountered by seeds, and therefore their potential to survive digestive tract passage, varies within and between waterbird species. Here, we investigate under controlled conditions how the interaction between seed traits and digestive strategies affect the germinability of seeds following waterbird-mediated dispersal. We exposed seeds of 30 wetland plant species to the main digestive processes in the dabbling duck digestive system: mechanical, chemical and intestinal digestion. These were simulated by 1) a pressure test and scarification treatment, 2) incubation in simulated gastric juice, and 3) incubation in intestinal contents of culled mallards (Anas platyrhynchos). We evaluated their separate and combined effects on seed germination, and identified the role of seed size and seed coat traits in resisting the digestive forces. Seeds were generally resistant to separate digestive processes, but highly sensitive to a combination. Resistance to mechanical break-down was reduced by up to 80% by chemical pre-treatment, especially for seeds with permeable coats. Scarified seeds were 12–17% more vulnerable to chemical and intestinal digestive processes than undamaged seeds. Large seeds and seeds with thin, permeable coats were particularly sensitive to chemical and intestinal digestion. These results indicate that efficient digestion of seeds requires multiple digestive processes. The gizzard, responsible for mechanical digestion, plays a key role in seed survival. Omnivorous birds, which have relatively light gizzards compared to pure herbivores or granivores, are thus most likely to disperse seeds successfully. Regardless of digestive strategy, small seeds with tough seed coats are most resistant to digestion and may be adapted to endozoochorous dispersal by waterbirds.

opencc-zeroDec 2012View details →

Data from: Dispersal, niche breadth, and population extinction/colonization ratios predict range size in North American dragonflies

1. Species' range sizes are shaped by fundamental differences in species' ecological and evolutionary characteristics, and understanding the mechanisms determining range size can shed light on the factors responsible for generating and structuring biological diversity. Moreover, because geographic range size is associated with a species' risk of extinction and their ability to respond to global changes in climate and land use, understanding these mechanisms has important conservation implications. 2. Despite hypotheses that dispersal behaviour is a strong determinant of species range areas, few data are available to directly compare the relationship between dispersal behaviour and range size. Here, we overcome this limitation by combining data from a multi-species dispersal experiment with additional species-level trait data that are commonly hypothesized to affect range size (e.g. niche-breadth, local abundance, and body size, etc.). This enables us to examine the relationship between these species-level traits and range size across North America for fifteen dragonfly species. 3. Ten models based on a priori predictions about the relationship between species traits and range size were evaluated and two models were identified as good predictors of species range size. These models indicated that only two species' level traits, dispersal behaviour and niche breadth were strongly related to range size. The evidence from these two models indicated that dragonfly species that disperse more often and further had larger North American ranges. 4. Extinction and colonization dynamics are expected to be a key linkage between dispersal behaviour and range size in dragonflies. To evaluate how extinction and colonization dynamics among dragonflies were related to range size we used an independent data set of extinction and colonization rates for eleven dragonfly species and assessed the relationship between these populations rates and North American range areas for these species. 5. We found a negative relationship between North American range size and species' extinction to colonization ratios. Our results indicate that metapopulation dynamics act to shape the extent of species' continental distributions. These population dynamics are likely to interact with dispersal behaviour, particularly at species range margins, to determine range limits and ultimately species range sizes.

Data from: Individual dispersal decisions in a cooperative breeder: ecological constraints, the benefits of philopatry, and the social queue for dominance

1. Delayed dispersal is a key step in the evolution of familial animal societies and cooperative breeding. However, no consensus has been reached on the ecological and social circumstances driving delayed dispersal. 2. Here we test predictions from the ecological constraints and benefits of philopatry hypotheses as well as the recently-proposed dual benefits hypothesis to better understand the evolution of group-living and cooperative breeding. Furthermore, we consider how individual social circumstances within groups affect dispersal decisions. 3. We examine 11 years of life-history information on a wild population of cooperatively breeding southern pied babblers (Turdoides bicolor). We investigate the effects of ecological conditions, natal-group membership and individual social context on male and female dispersal delays, disperser survival and acquisition of dominance. 4. Female dispersal decisions are generally unconstrained by ecological or social circumstances. In contrast, males disperse in response to relaxed ecological constraints, decreases in nepotistic tolerance, or when low social rank in the queue for dominance decreases their likelihood of gaining a dominant breeding position. Early dispersal by end-of-queue males often leads to a head-of-queue subordinate position in a non-natal group, thereby increasing access to dominant breeding positions. However, males and females remaining in natal groups gain benefits of philopatry via increased survival and, for head-of-queue males, very high likelihood of acquisition of a breeding position. 5. Overall, predictions from the dual benefits hypothesis best describe these results, while some predictions from each of the ecological constraints and benefits of philopatry hypotheses were supported. The benefits of living and working together (collective action benefits) in large stable groups are of central importance in shaping dispersal delays in southern pied babbler societies. In addition, position in the subordinate social queue for dominance is key in determining access to reproduction, particularly for males. This research highlights the importance of considering the costs and benefits of individual social circumstances in dispersal decisions and illustrates how the dual benefits hypothesis offers new perspectives in understanding delayed dispersal.

opencc-zeroDec 2013View details →

Data from: Hydrology, shore morphology and species traits affect seed dispersal, germination and community assembly in shoreline plant communities

1.Seed dispersal and germination are two primary processes influencing plant community assembly. On freshwater shores, water levels regulate both processes. However, it is still unclear how water levels, shore morphology and species traits interactively affect seed dispersal and germination, and how these interactions determine plant community assembly. We hypothesize that a drawdown water regime enhances seed establishment compared to a year-round stable water level, that this increases species richness and diversity, and that this is modulated by species traits and shore morphology. 2.Germination of 20 wetland plant species with different dispersal capacities (floating capacity expressed as seed floatation half-time) and soil moisture preferences for germination (Ellenberg F) was tested on artificial shores in 24 outdoor ponds in 2 complementary experiments over 8 weeks. The "dispersal experiment" tested the effect of water regime on recruitment of hydrochorously dispersing seeds. The "seed bank experiment" tested the effect of water regime on germination from a sown seed bank, on steep and gradual shores. 3.In the dispersal experiment, the drawdown regime increased recruitment and species richness. Longer floating species colonised a larger shoreline section. Soil moisture preference for germination did not determine colonisation patterns. 4.In the seed bank experiment, the drawdown regime increased the number of seedlings on gradual sloping shores, but not on steep shores. The number of germinating seedlings corresponded to the area subjected to the drawdown regime in both shore types. Species richness was not affected by water regime or shore morphology, and species traits did not determine shoreline colonisation. Most seeds germinated in moist soil conditions for all species. 5.Synthesis. A spring drawdown instead of stable water regime stimulates establishment of hydrochorously dispersing seeds in temperate wetlands, leading to higher species richness and diversity. Germination from the seed bank is more affected by water regime and shore surface than by the tested species traits. Species traits, water levels and shore morphology together determine wetland plant community assembly, with dispersal as the main driver of seedling community diversity. Water level regulations and shore morphology can be used to influence plant communities in wetland restoration.

Data from: Female mosquitoes disperse further when they develop under predation risk

Predation is one of the strongest selective forces in nature. Organisms characterized by a complex life cycle, undergoing an ontogenetic niche shift, can reduce predation risk on natal stages by metamorphosing earlier. Yet, this anti-predatory response may incur numerous life-history-related costs. Interestingly, the consequence of larval predation risk on adult dispersal, a key trait dictating the persistence of spatially-structured populations, is largely understudied. Here, we explored the effect of larval predation risk on the life-history and dispersal characteristics of female adults in the mosquito Culex pipiens. As predicted, mosquito larvae reared in the presence of a caged larvivorous-fish metamorphosed earlier, while also suffering from reduced survival. Despite this reduction in development time, the body size of emerging females was larger, implying that more resources were allocated to increase the growth rate, probably at the expense of reduced maintenance and storage. This shift in energy allocation translated into decreased pupa and adult survival. Remarkably, the respective dispersal distance of these larger bodied females was greater. We suggest that the increase in dispersal distance allows these females to cover larger areas, while searching for oviposition sites that are safer than their natal aquatic habitat. Exploring the effects of larval conditions on adult dispersal is central for understanding the distribution of organisms with a complex life cycle in spatially heterogeneous environments, and specifically for disease transmission by mosquitoes.

opencc-zeroAug 2019View details →

Data from: Interacting maternal and spatial cues influence natal dispersal out of social groups

Proximate cues for animal dispersal are complex and varied. Multiple cues may provide information about different aspects of habitat quality, and these aspects may interact with each other, as well as with population density in different ways. We examined how individuals incorporate multiple cues in their decisions to emigrate and immigrate in the colonial orb-weaving spider, Cyrtophora citricola. We manipulated maternal feeding as a cue for prey abundance and measured the size of the maternal web, which provides a limited space for philopatric offspring and a second potential dispersal cue. In addition, we recorded all immigration events to determine dispersal distances and the cues juveniles may use in settlement. Dispersal increased when mothers were poorly fed, web sizes were small, and clutch sizes were large. In addition to these overall effects, maternal feeding also interacted with web size, indicating that offspring from well-fed mothers were more tolerant of high sibling densities. We also detected a threshold for the effect of clutch size on dispersal for the first egg sac: below 20 offspring, there was no effect of clutch size, but dispersal increased with clutch size for larger clutches. Dispersal distances were often short, and immigrants preferred sheltered trees and those occupied by adult females. Dispersal not only depended on multiple cues, but these cues interacted, and the importance of web size suggested that saturation of the natal web might force dispersal, at least for spiders with poorly-fed mothers. How one aspect of habitat quality influences dispersal can therefore depend on the state of other aspects of habitat quality. In particular, some natal resources, such as a nest or territory, may become saturated and limit group size, but this limit will also depend on other factors, such as prey availability.