Dispersal Distance Of Species Research Articles

Impact of different grade roads on ecological networks: A case study of Fuzhou City, China.

The expansion of roads exacerbates the fragmentation of ecological networks and obstructs landscape connectivity. Scientific analysis of the impacts of different grades of roads on landscape connectivity and ecological networks is crucial for guiding road planning and ecological conservation. Based on the data of 2020 road network, land cover types, and digital elevation models, we used morphological spatial pattern analysis and circuit theory to construct ecological networks within different species dispersal distances (1, 3, 5, 10 km) in Fuzhou. We analyzed the impacts of roads of different grades (motorway, urban expressway, primary and secondary highway) on landscape connectivity at the landscape-patch-corridor scale. The results showed that at the landscape scale, overall landscape connectivity was significantly positively correlated with species dispersal distance. The motorway, urban expressway, primary and secondary highway had the lowest decline rate of overall landscape connectivity within a 10 km species dispersal range, being reduced by 15.6%, 5.3%, 1.5% and 5.2%, respectively. At the patch scale, in the comparison of roads of different grades, motorway led to the highest decline rate of patch connectivity within 1 and 5 km species dispersal range, while primary highway led to the highest decline rate of patch connectivity within 3 and 10 km species dispersal range. At the corridor scale, urban expressway led the highest increase rate of indices. The cost-weighted distance of the overall least-cost path, the ratio of cost-weighted distance to length, ove-rall effective resistance, and total corridor length within 5 km species dispersal range were increased by 43.4%, 33.2%, 57.3%, and 7.3%, respectively. As the distance of species dispersal increased, the patches with high importance were reduced from the northern, central, and northwestern regions to the northern regions, leading to a decrease in the living space of species, and the key corridors were gradually extending from the northwestern and southern regions to the central regions. Our results can guide the construction and optimization of Fuzhou's ecological network from an overall perspective, and provide a scientific basis for biodiversity conservation, ecological restoration, and road network planning under the context of limited land resource utilization.

The role of maternal environment and dispersal ability in plants' transgenerational plasticity

Transgenerational effects enable the transmission of environmental cues from parents to offspring. Adaptive maternal effects are expected to evolve if the maternal (or parental) environment contains information about the environment experienced by offspring. This correlation between maternal and offspring environments should be strongest in plant species with reduced dispersal ability. However, studies relating dispersal ability to the strength of maternal effects are rare. This study aimed to explore whether and how the dispersal distance of species and individuals affects offspring plant performance. Using seven common European plant species, we conducted a multi‐year common garden experiment exposing maternal plants to three different water conditions (mesic, drought and waterlogging). At the end of the season in the first year, seed heads were collected from the lower and upper parts of each mother plant and used for dispersal distance calculation. Offspring coming from the maternal lower and upper parts were exposed to the same water treatments as mothers. Contrasting our hypothesis, we found that maternal water experience and species' dispersal abilities did not influence offspring performance (plant aboveground, belowground, reproductive and dead biomass). We did not detect maternal effects, meaning that offspring plants with the same water conditions as their mothers had the same fitness as offspring with different water conditions. However, opposite to our expectations, the longer dispersal distance of individual seeds ensured a stronger maternal effect when exposed to the same water stress as their mothers. Consequently, a stressful environment would select for long‐distance dispersal.

Dynamic simulation of functional connectivity and identification of conservation priorities for grassland in China’s Poyang Lake considering ecological processes

Analysing dynamics of landscape functional connectivity and evaluating conservation priority of habitat patches are of great significance for biodiversity conservation. Taking the grassland of Poyang Lake as a case, and comprehensively considering the ecological processes of water level change and species dispersal, this study firstly identified the range and patch composition of grassland under different water levels. Then, the graph theoretical approach was applied to analyse the dynamics of functional connectivity of grassland with different water levels and dispersal distances. Finally, the delta value for probability of connectivity (dPC) and betweenness connectivity (BC) were respectively used to identify the most important grassland patches and key grassland nodes. The results showed as follows: (1) The grassland presented the characteristics of “expanding when water falls while shrinking when water rises”. The grassland patches faced both the segmentation effect and the inundation effect of water. With the increase of water level, the distribution of grassland was gradually shrinking, the distribution of grassland decreased from 1813.61 km2 at the water level of 7.54 m to 182.36 km2 at the water level of 17.17 m, and the fragmentation of large patches and the disappearance of small patches coexisted. (2) From the perspective of water level change, the functional connectivity of grassland has progressively decreased with the increase of water level. From the perspective of species dispersal, the species dispersal distance had an absolutely positive impact on landscape functional connectivity. With the increase of dispersal distance, the functional connectivity of grassland increased dramatically. (3) The 124 important grassland patches were identified and mapped. They were all larger ones in area and primarily distributed in the center of Poyang Lake, especially concentrated in the two national nature reserves. The 16 key grassland nodes were determined and mapped. They were very small in size and mainly scattered in the central and southern margin of Poyang Lake. Giant patches and large patches play an extremely vital role in maintaining the grassland connectivity. However, small patches in pivotal locations can not be ignored as stepping stones or connecting elements. Our study provides a scientific reference for the protection and management of natural habitats in lake areas.

Dynamic simulation of the grassland connectivity and the effects of landscape pattern in China's Poyang Lake from the integrated perspective of habitat and biology

AbstractAnalysing the dynamics of landscape connectivity is of great significance for biodiversity conservation, but the scientific expression of ecological processes and the depth of coupling landscape pattern and ecological process requires to be strengthened. Taking the grassland of Poyang Lake as a case, based on the integrated perspective of habitat and biology, and comprehensively considering the ecological process of water level change and species dispersal, this study firstly analysed the changes of functional connectivity of grassland with different water levels and dispersal distances by using the graph‐based connectivity indices. Then, landscape pattern indices were applied to analyse the dynamics of landscape pattern of grassland and further study the effects of landscape pattern on landscape functional connectivity. The results showed as follows: (1) From the perspective of habitat, the functional connectivity of grassland has progressively decreased with the increase of water level. From the perspective of ecology, the species dispersal distance had an absolutely positive impact on landscape functional connectivity. With the increase of dispersal distance, the functional connectivity of grassland increased significantly. (2) The dynamics of landscape pattern of grassland showed that with the increase of water level, the patch area shrank, the patch shape tended to be simple, the patch density decreased and the patch fragmentation aggravated. (3) The correlation results between landscape pattern and functional connectivity indicated that flux index (F) had a significant positive relationship with patch density (PD), edge density (ED), probability of connectivity (PC) had a strong significant positive relationship with largest patch index (LPI), COHESION and number of components (NC) had a negative relationship with LPI, ED, COHESION. This study provides theoretical guidance for the protection and management of grassland in Poyang Lake.

Relative importance of landscape and species characteristics on extinction debt, immigration credit and relaxation time after habitat turnover

AbstractHabitat turnover concomitantly causes destruction and creation of habitat patches. Following such a perturbation, metapopulations harbor either an extinction debt or an immigration credit, that is the future decrease or increase in population numbers due to this disturbance. Extinction debt and immigration credit are rarely considered simultaneously and disentangled from the relaxation time (time to new equilibrium). In this contribution, we test the relative importance of two potential drivers of time‐delayed metapopulation dynamics: the spatial configuration of the habitat turnover and species dispersal ability. We provide a simulation‐based investigation projecting metapopulation dynamics following habitat turnover in virtual landscapes. We consider two virtual species (a short‐distance and a long‐distance disperser) and five scenarios of habitat turnover depending on net habitat loss or gain and habitat aggregation. Our analyses reveal that (a) the main determinant of the magnitude of the extinction debt or immigration credit is the net change in total habitat area, followed by species dispersal distance and finally by the post‐turnover habitat aggregation; (b) relaxation time weakly depends on the magnitude of the immigration credit or of the extinction debt; (c) the main determinant of relaxation time is dispersal distance followed by the net change in total habitat area and finally by the post‐turnover habitat aggregation. These results shed light on the relative importance of dispersal ability and habitat turnover spatial structure on the components of time‐delayed metapopulation dynamics.

The spatial scale of time‐lagged population synchrony increases with species dispersal distance

AbstractAimTime‐lagged population synchrony, where spatially separated populations show similar fluctuations in abundance lagged over time, is thought to be driven by dispersal among populations. When dispersal is proportional to population density or positively density dependent, and individuals move readily from population A to population B, then as population A increases, the increased number of dispersers from population A to B will cause a subsequent increase in population B. If true, then time‐lagged synchrony should be strongest at a species’ typical dispersal distance, because the rate of exchange between populations will be greatest at that distance.LocationUnited Kingdom (U. K.).Time period1994 – 2013.Major taxa studiedBirds (class Aves).MethodsWe estimated the spatial scale of 1‐year‐lagged population synchrony for 76 U.K. bird species, using 20 years of bird count data collected at 2,415 locations by the British Breeding Bird Survey. We then compared these spatial scales with published mean natal and breeding dispersal distance estimates (ranging from 0.1 to 25.8 km) for the same species based on an independent, large‐scale, mark–recapture dataset of 492,272 bird recaptures in Britain and Ireland.ResultsWe found strong, positive cross‐species relationships between the spatial scale of time‐lagged synchrony and mean natal and breeding dispersal distance estimates from the mark–recapture study. However, average spatial scales of time‐lagged synchrony were more than 60 km longer than those from mark–recapture data, with scales ranging from 5 to 185 km.Main conclusionsOurs is the first study to show that the spatial scale of time‐lagged synchrony increases with species dispersal distance. The scale of synchrony was larger than expected, probably because mark–recapture data underestimated the real dispersal distances, or because dispersal synchronizes populations at a larger spatial scale than that of dispersal (e.g., through formation of travelling waves), or both. Nevertheless, the strong relative concordance is consistent with the explanation that time‐lagged synchrony results from dispersal among populations.

Ecological correlates of dispersal distance in terrestrial mammals

Dispersal distance in mammals is a fundamental information for several ecological and conservation applications. Although dispersal can depend on many intrinsic and extrinsic factors, in recent years many studies have shown that it scales with body size and home range area. However, the role of further ecological correlates to distance travelled is still unclear and the predictive models proposed so far have suffered from small sample size and lack of error estimates. This reduces the practical relevance of the models for ecological and conservation applications. We conducted a comprehensive meta-analysis on 327 studies on the dispersal of 164 mammal species, and performed linear and non-linear regression analyses to explore the relationships of body size and home range area with dispersal distance. We tested the effect of various life history traits and ecological factors on the relationships and performed a sensitivity analysis to evaluate the robustness of the models to sample size. The linear relationships of both home range and body size with dispersal distance were influenced by various life history traits and ecological factors. We developed allometric functions to estimate species dispersal distance based on different predictors and life history traits. Linear models representing the relationship between dispersal distance and body size or home range area received good support; however logistic models better approximates both relationships. Despite receiving less support than a logistic curve, a linear model between dispersal and home range is a good approximation for applicative purposes. Sensitivity analysis showed that our results are robust to subsampling of the original dataset until a sample of 40 species. Our empirical models have the potential to improve theoretical and applied population biology studies by extending the applicability and improving the accuracy of dispersal distance estimation to a large number of mammals.

Dispersal strategies, few dominating or many coexisting: the effect of environmental spatial structure and multiple sources of mortality.

Interspecific competition, life history traits, environmental heterogeneity and spatial structure as well as disturbance are known to impact the successful dispersal strategies in metacommunities. However, studies on the direction of impact of those factors on dispersal have yielded contradictory results and often considered only few competing dispersal strategies at the same time. We used a unifying modeling approach to contrast the combined effects of species traits (adult survival, specialization), environmental heterogeneity and structure (spatial autocorrelation, habitat availability) and disturbance on the selected, maintained and coexisting dispersal strategies in heterogeneous metacommunities. Using a negative exponential dispersal kernel, we allowed for variation of both species dispersal distance and dispersal rate. We showed that strong disturbance promotes species with high dispersal abilities, while low local adult survival and habitat availability select against them. Spatial autocorrelation favors species with higher dispersal ability when adult survival and disturbance rate are low, and selects against them in the opposite situation. Interestingly, several dispersal strategies coexist when disturbance and adult survival act in opposition, as for example when strong disturbance regime favors species with high dispersal abilities while low adult survival selects species with low dispersal. Our results unify apparently contradictory previous results and demonstrate that spatial structure, disturbance and adult survival determine the success and diversity of coexisting dispersal strategies in competing metacommunities.

Broad-leaf species composition in Cryptomeria japonica plantations with respect to distance from natural forest

To address the pressing need to evaluate how conifer plantations can serve biodiversity functions in addition to other economic and social roles they play, we assessed the diversity of broad-leaf seedlings and saplings in Cryptomeria japonica plantations in Ogawa, Ibaraki Prefecture, Japan at increasing distances (0–1000 m) from old growth natural forest edge. For saplings, there was no overall significant trend in the frequency, species richness, and Shannon index with respect to distance. Seedlings on the other hand showed a decrease in frequency and species richness with increasing distance from the old growth forest, implying that should recruitment limitation occur in the plantations, it will be stronger at the seed-to-seedling transition than at the seedling-to-sapling transition. Assigning species into groups based on functional traits that are associated with recruitment and regeneration was more revealing. Relative frequency of species that are moderately shade-tolerant, are shrubs, have small seeds, and are frugivore-dispersed increased in the plantations. In comparison, species that are tall trees, have large seeds and are gravity-dispersed decreased in the plantations. Multi-trait analysis showed that propagule size was the trait that could best explain the difference in the distribution of broad-leaf species in the plantations. Based on our results, we suggest to policy-makers that plantation sizes be kept to within a few hundred meters wide, and should ideally be within dispersal distance of species from natural forests that could potentially be seed sources of broad-leaf species. Otherwise, steps must be taken to drive succession such that potentially recruitment-limited species may be able to overcome barriers to regeneration.

Connectivity, sustainability, and yield: bridging the gap between conventional fisheries management and marine protected areas

A substantial shift toward use of marine protected areas (MPAs) for conservation and fisheries management is currently underway. This shift to explicit spatial management presents new challenges and uncertainties for ecologists and resource managers. In particular, the potential for MPAs to change population sustainability, fishery yield, and ecosystem properties depends on the poorly understood consequences of three critical forms of connectivity over space: larval dispersal, juvenile and adult swimming, and movement of fishermen. Conventional fishery management describes the dynamics and current status of fish populations, with increasing recent emphasis on sustainability, often through reference points that reflect individual replacement. These compare lifetime egg production (LEP) to a critical replacement threshold (CRT) whose value is uncertain. Sustainability of spatially distributed populations also depends on individual replacement, but through all possible paths created by larval dispersal and LEP at each location. Model calculations of spatial replacement considering larval connectivity alone indicate sustainability and yield depend on species dispersal distance and the distribution of LEP created by species habitat distribution and fishing mortality. Adding MPAs creates areas with high LEP, increasing sustainability, but not necessarily yield. Generally, short distance dispersers will persist in almost all MPAs, while sustainability of long distance dispersers requires a specific density of MPAs along the coast. The value of that density also depends on the uncertain CRT, as well as fishing rate. MPAs can increase yield in areas with previously low LEP but for short distance dispersers, high yields will require many small MPAs. The paucity of information on larval dispersal distances, especially in cases with strong advection, renders these projections uncertain. Adding juvenile and adult movement to these calculations reduces LEP near the edges in MPAs, if movement is within a home-range, but more broadly over space if movement is diffusive. Adding movement of fishermen shifts effort on the basis of anticipated revenues and fishing costs, leading to lower LEP near ports, for example. Our evolving understanding of connectivity in spatial management could form the basis for a new, spatially oriented replacement reference point for sustainability, with associated new uncertainties.

Relative importance of spatial and temporal scales in a patchy environment

The purpose of this study was to examine the relative importance of temporal and spatial scales of habitat heterogeneity on regional abundance of populations in patchy environments. Temporal scale is habitat lifespan relative to the generation time of the organism, and spatial scale is the distance between habitat patches relative to the dispersal distance of the organism. A spatially explicit simulation model of population growth and dispersal was constructed for a population that is distributed on a grid. The grid contains two sorts of habitat, useable and nonuseable habitat; useable habitat occurs in habitat patches. Habitat patches are transient; they are “born” at random with a specified probability, and they exist for a specified length of time, the patch “lifespan.” Distance between patches is directly related to habitat patch size when the fraction of the grid in useable habitat is held constant. A factorial simulation experiment was conducted in which the fraction of the grid in useable habitat was held constant and patch lifespan, patch size, and species dispersal distance were varied. The relative importance of temporal scale (patch lifespan) and spatial scale (patch size, a surrogate for inter-patch distance per species dispersal distance) on regional population size was tested by analysis of variance. Population size increased with increasing temporal scale and decreased with increasing spatial scale. The effect of temporal scale far outweighed the effect of spatial scale. Implications for design of ecological research programmes are discussed.

Can the Variation in Samara Mass and Terminal Velocity on an Individual Plant Affect the Distribution of Dispersal Distances?

We examined the contribution of seed mass variation to (1) variation in terminal velocity and (2) variation in dispersal distances for species with winged seeds. Coefficients of variation of terminal velocity were usually on the order of 0.13. These values were too low to have a significant effect on distance variation because of the much larger magnitude of the turbulent intensities of the wind in the vertical and horizontal directions. This assertion was tested with a micrometeorological model of dispersal from an elevated point source within a forest canopy. The coefficient of variation of terminal velocity was necessarily low because of (1) the aerodynamic specification that terminal velocity be proportional to the square root of mass and (2) the design problems inherent in a negative correlation between mass and planform area. We conclude that there is unlikely to be selection for mass variation to reduce sibling densities and therefore intersib competition.