Dispersal Movements Research Articles

Habitat preference, movements and growth of giant mottled eels, Anguilla marmorata, in a small subtropical Amami-Oshima Island river.

Although anguillid eel populations have decreased remarkably in recent decades, few detailed ecological studies have been conducted on tropical eels such as the giant mottled eel whose range extends across the whole Indo-Pacific. This species was studied throughout the entire 0.5 km mainstem reaches of Oganeku River on the subtropical Amami-Oshima Island of Japan over a two-year period using four sampling periods to understand its habitat preference, early life-stage dispersal process, movements, and annual growth using a mark-recapture experiment conducted with quantitative electrofishing. A total of 396 juvenile growth-phase A. marmorata eels were caught and tagged, with 48 individuals being recaptured at least once. Their density irrespective of size of eels was most strongly determined by distance from the river mouth, followed by riverbank type according to random forest models. Eel density decreased with increasing distance from the freshwater tidal limit located about 100–150 m from the river mouth. Eels preferred vegetated riverbanks, while they avoided those of concrete and sand. The density of small eels (total length: TL < 240 mm) was also associated with depth and velocity, with small eels tending to prefer riffle or run habitats. In contrast, large eels (TL ≥ 240 mm) were found in habitats of any depth and velocity. The TL of eels had a minimum peak at around the tidal limit, and it increased with increasing distance from the tidal limit. The observed density and size gradients of eels in relation to the distance from the river mouth suggested that A. marmorata initially recruited to freshwater tidal limit areas and then dispersed in both downstream and upstream directions. The growth rate of eels varied greatly among individuals that were at large for various periods of time and ranged from 0 to 163.2 mm/year (mean ± SD of 31.8 ± 31.0 mm/year). Of the recaptured eels, 52.1% were recaptured in a section that was different from the original capture section, and their mean ± SD distance travelled was 46.5 ± 72.5 m (median = 20 m). 47.9% of the eels were recaptured from the original section of capture (i.e., <10 m distances travelled), suggesting that they had strong fidelity to specific habitats with limited movements. The distance travelled of eels that had moved was greater for small eels (range = 10–380 m; mean ± SD = 84.4 ± 121.9 m) than large individuals (range = 10–120 m; mean ± SD = 30.9 ± 31.0 m), which indicates that the mobility of the eels declines as they grow. This is the first clear detailed documentation of the spatial distribution, growth, and movements of tropical eels in a small river system in relation to environmental conditions that provides an example of how future studies can be conducted in other areas to understand how conservation efforts can be most efficiently targeted for maximum success.

Grapevine phenolic compounds influence cell surface adhesion of Xylella fastidiosa and bind to lipopolysaccharide.

Bacterial phytopathogen Xylella fastidiosa specifically colonizes the plant vascular tissue through a complex process of cell adhesion, biofilm formation, and dispersive movement. Adaptation to the chemical environment of the xylem is essential for bacterial growth and progression of infection. Grapevine xylem sap contains a range of plant secondary metabolites such as phenolics, which fluctuate in response to pathogen infection and plant physiological state. Phenolic compounds are often involved in host-pathogen interactions and influence infection dynamics through signaling activity, antimicrobial properties, and alteration of bacterial phenotypes. The effect of biologically relevant concentrations of phenolic compounds coumaric acid, gallic acid, epicatechin, and resveratrol on growth of X. fastidiosa was assessed in vitro. None of these compounds inhibited bacterial growth, but epicatechin and gallic acid reduced cell-surface adhesion. Cell-cell aggregation decreased with resveratrol treatment, but the other phenolic compounds tested had minimal effect on aggregation. Expression of attachment (xadA) and aggregation (fimA) related genes were altered by presence of the phenolic compounds, consistent with observed phenotypes. All four of the phenolic compounds bound to purified X. fastidiosa lipopolysaccharide (LPS), a major cell-surface component. Information regarding the impact of chemical environment on pathogen colonization in plants is important for understanding the infection process and factors associated with host susceptibility.

Tracking a voyager: mitochondrial DNA analyses reveal mainland-to-island dispersal of an American crocodile (Crocodylus acutus) across the Caribbean

Abstract Conservation efforts have allowed American crocodile (Crocodylus acutus) populations to recover to the point that dispersal movements are beginning to be documented. The environmental authority of San Andres Island in Colombia reported, for the first time, the arrival of two C. acutus from unknown localities in 2012 and 2018. The former was sacrificed, and the latter was captured and kept in captivity to determining its potential origin. We used wildlife forensics to establish the origin of the animal that arrived in 2018 based on two mitochondrial genes (COI and Cytb). Additionally, five other samples from Tayrona National Natural Park (TNNP), and Salamanca Island Road Park (SIRP) were sequenced for molecular attribution of these populations to the currently described lineages. Phylogenetic and phylogeographic analyses showed that the American crocodile found in San Andrés belongs to a continental evolutionary lineage endemic to Colombia, showing also a strong genetic similarity with animals from SIRP. Thus, the most likely origin for this individual was not the nearest continental area but somewhere around the central Colombian Caribbean, located ~700 km from the island. We discuss the implication of our findings in the systematics and conservation of the species and the potential of mitochondrial DNA analysis to identify such migrants.

Assessing the current state of ecological connectivity in a large marine protected area system.

The establishment of marine protected areas (MPAs) is a critical step in ensuring the continued persistence of marine biodiversity. Although the area protected in MPAs is growing, the movement of individuals (or larvae) among MPAs, termed connectivity, has only recently been included as an objective of many MPAs. As such, assessing connectivity is often neglected or oversimplified in the planning process. For promoting population persistence, it is important to ensure that protected areas in a system are functionally connected through dispersal or adult movement. We devised a multi‐species model of larval dispersal for the Australian marine environment to evaluate how much local scale connectivity is protected in MPAs and determine whether the extensive system of MPAs truly functions as a network. We focused on non‐migratory species with simplified larval behaviors (i.e., passive larval dispersal) (e.g., no explicit vertical migration) as an illustration. Of all the MPAs analyzed (approximately 2.7 million km2), outside the Great Barrier Reef and Ningaloo Reef, <50% of MPAs (46‐80% of total MPA area depending on the species considered) were functionally connected. Our results suggest that Australia's MPA system cannot be referred to as a single network, but rather a collection of numerous smaller networks delineated by natural breaks in the connectivity of reef habitat. Depending on the dispersal capacity of the taxa of interest, there may be between 25 and 47 individual ecological networks distributed across the Australian marine environment. The need to first assess the underlying natural connectivity of a study system prior to implementing new MPAs represents a key research priority for strategically enlarging MPA networks. Our findings highlight the benefits of integrating multi‐species connectivity into conservation planning to identify opportunities to better incorporate connectivity into the design of MPA systems and thus to increase their capacity to support long‐term, sustainable biodiversity outcomes.

Leave or Die: Dispersal of Red-Bellied Mudsnakes (Farancia abacura) from their Home Ranges in an Isolated Wetland

We radiotracked eight, free-living, Red-Bellied Mudsnakes (Farancia abacura) from April to October 2019 in a bottomland hardwood forest wetland in Central Arkansas. Four snakes emerged in April from their overwintering sites in an earthen dam of a 1.2 ha pond and confined all of their movements to the pond basin. All four snakes were lost to predators during the course of the year. Four other snakes emerged from overwintering and dispersed up to 1580 m from the pond. One dispersing snake was lost to a predator when it returned to the pond. Dispersing snakes followed ephemeral streams upstream and downstream, ditches, and flooded bottomlands. The dispersal movements occurred in an extraordinarily wet period that began in August 2018 and continued through August 2019. These results contrasted sharply with the radiotracking results of eight, free-living, F. abacura at the same locality in 2018, each of which maintained a home range in the pond and experienced no predation. Included in the eight 2018 snakes were three of the dispersing snakes radiotracked in 2019. Possible year-to-year variation in movement patterns driven by environmental variability and predator pressure should be considered in designing management plans for at-risk wetland species.

Estimating response distances of lesser prairie‐chickens to anthropogenic features during long‐distance movements

AbstractSpatially distributed populations often rely on large‐scale processes for long‐term population stability. These processes are driven by individuals moving across the landscape through long‐distance dispersal movements. However, as landscapes are continually altered by anthropogenic development, increased fragmentation and avoidance behavior can affect landscape permeability and limit dispersal. Lesser prairie‐chickens (Tympanuchus pallidicinctus) are a species of concern that have lost significant portions (&gt;90%) of their historic distribution in the Southern Great Plains of the United States and are currently being impacted by continued anthropogenic development. Using GPS telemetry locations of 346 lesser prairie‐chickens across their entire geographic distribution, we identified 184 different long‐distance movements that drive population connectivity. We used empirical cumulative distribution functions to create a selection–avoidance–neutral curve and estimated the spatial scale of response to anthropogenic features (i.e., towers and windmills, large transmission and smaller distribution powerlines, oil wells, roads, and fences) during these movements. In addition, we tested for behavioral differences between movement types (e.g., exploratory loops vs. long‐distance movements between home ranges) and for regional differences in response among study areas. We found that during long‐distance movements, lesser prairie‐chickens generally avoided all anthropogenic feature types we tested despite some variation in the reported response distance among study areas. However, they avoided the tallest features (i.e., towers and windmills and transmission powerlines) at much greater distances in comparison with the shorter features in our analysis. Our results show that long‐distance movements are likely affected by responses to functional landscape fragmentation through increased development of anthropogenic features in important connectivity zones. As our estimated response distances during long‐distance movements varied in comparison with previously reported response distances during other behavioral states (e.g., breeding or nesting), using long‐distance or dispersal specific movement data may be more appropriate when asking questions related to connectivity across the landscape.

Flight Burst Duration as an Indicator of Flight Ability and Physical Fitness in Two Species of Tephritid Fruit Flies.

We introduce a method to quantify flight ability and physical fitness of individual fruit flies which we term 'Flight Burst Duration' (FBD). This consisted of tethering individual insects by the dorsal thorax using a vacuum and measuring the length of time the insect beats its wings while suspended off a surface. Consecutive measurements with Bactrocera dorsalis Hendel (Dipera: Tephritidae) and Zeugodacus cucurbitae Coquillett (Diptera: Tephritidae) in the same day and across days indicated that a single measurement was sufficient, and that FBD was consistent and repeatable. Insects under stress from starvation displayed shorter FBD over time, and we suggest that the measure also relates to the physical condition or survival fitness of the individual. Though somewhat laborious and time-consuming, we propose that FBD can be useful for research studies requiring individual-level phenome data and for obtaining estimates quality and dispersive movement for insects.

Movement patterns of lesser flamingos Phoeniconaias minor: nomadism or partial migration?

Waterbirds in stochastic environments exhibit nomadism in order to cater for the unpredictable availability of water resources. Lesser flamingos Phoeniconaias minor have long been thought to be nomadic waterbirds. In southern Africa, conservation efforts for lesser flamingos are hampered by a lack of knowledge about their movement trajectories. To investigate their movement ecology in southern Africa, we fitted GPS–GSM transmitters to 12 adults and tracked their movements over four years, from March 2016 to February 2020. Net squared displacement (NSD) was used in nonlinear least squares models classifying trajectories as nomadic, migratory, mixed‐migratory, home range restricted or dispersal movement types. Data from eight of the 12 birds met the criteria for the NSD analysis. Model success was good; only 8 out of 120 (6.7%) movement type models failed to reach convergence. Goodness of fit statistics from the NSD models supported migratory and mixed migratory movement types (concordance criteria coefficient (CC) = 0.78) for more than half of the annual trajectories investigated (57.2%). Dispersal, home range‐restricted and nomadic movements best described 28.6, 9.5 and 4.8% of annual trajectories, respectively, but all resulted in a mean CC of &lt; 0.4 and thus did not fit observed NSD patterns as well as the migratory movement types. We then used nonlinear mixed effects models to account for annual and individual differences in migration parameters. Variation in the timing and duration of all migrations were more important than variation in migration distance, indicating well‐established summer and winter ‘ranges’ and routes between Kamfers Dam (South Africa) and Sua Pan (Botswana). We propose that lesser flamingos in central southern Africa may be partial migrants, not true nomads, as most of their movements followed a regular, repeated pattern between two primary locations.

Dealing with overprediction in species distribution models: How adding distance constraints can improve model accuracy

Species distribution models can be affected by overprediction when dispersal movement is not incorporated into the modelling process. We compared the efficiency of seven methods that take into account spatial constraints to reduce overprediction when using four algorithms for species distribution models. By using a virtual ecologist approach, we were able to measure the accuracy of each model in predicting actual species distributions. We built 40 virtual species distributions within the Neotropical realm. Then, we randomly sampled 50 occurrences that were used in seven spatially restricted species distribution models (hereafter called M-SDMs) and a non-spatially restricted ecological niche model (ENM). We used four algorithms; Maximum Entropy, Generalized Linear Models, Random Forest, and Support Vector Machine. M-SDM methods were divided into a priori methods, in which spatial restrictions were inserted with environmental variables in the modelling process, and a posteriori methods, in which reachable and suitable areas were overlapped. M-SDM efficiency was obtained by calculating the difference in commission and omission errors between M-SDMs and ENMs. We used linear mixed-effects models to test if differences in commission and omission errors varied among the M-SDMs and algorithms. Our results indicate that overall M-SDMs reduce overprediction with no increase in underprediction compared to ENMs with few exceptions, such as a priori methods combined with the Support Vector Machine algorithm. There is a high variation in modelling performance among species, but there were only a few cases in which overprediction or underprediction increased. We only compared methods that do not require species dispersal data, guaranteeing that they can be applied to less-studied species. We advocate that species distribution modellers should not ignore spatial constraints, especially because they can be included in models at low costs but high benefits in terms of overprediction reduction.

Unexplained patterns of grey wolf Canis lupus natal dispersal

AbstractNatal dispersal (movement from the site of birth to the site of reproduction) is a pervasive but highly varied characteristic of life forms. Thus, understanding it in any species informs many aspects of biology, but studying it in most species is difficult. In the grey wolf Canis lupus, natal dispersal has been well studied. Maturing members of both sexes generally leave their natal packs, pair with opposite‐sex dispersers from other packs, near or far, select a territory, and produce their own offspring. However, three movement patterns of some natal‐dispersing wolves remain unexplained: 1) long‐distance dispersal when potential mates seem nearby, 2) round‐trip travels from their natal packs for varying periods and distances, also called extraterritorial movements, and often not resulting in pairing, and 3) coincidental dispersal by individual wolves from a given area in the same basic directions and over the same long distances. This perspective article documents and discusses these unexplained dispersal patterns, suggests possible explanations, and calls for additional research to understand them more clearly.

Cross-continental test of natal philopatry and habitat-imprinting hypotheses to explain host specificity in an obligate brood parasite.

Several hypotheses have been proposed to explain the mechanisms responsible for maintenance of host-specific gentes in the common cuckoo (Cuculus canorus). Some of them expect that when adult cuckoos return to lay their eggs to their natal site (natal philopatry hypothesis) or habitat in which they were reared (habitat-imprinting hypothesis), there is a higher probability of finding nests of the host species by which they were reared. Since published evidence is ambiguous, we here evaluate the natal philopatry and habitat-imprinting hypotheses using information on habitat homogeneity and cross-continental long-term ringing data. We found no evidence for the natal philopatry hypothesis-instead of returning to their natal site, juvenile cuckoos exhibited longer dispersal movements than adults, and the difference was even larger in comparison with a wide array of cuckoo host species. On the contrary, we found support for the habitat-imprinting hypothesis-juvenile cuckoos followed similar levels of natal habitat homogeneity at 5- and 25-km scale when returning to breed in the next years. Our results suggest that preference for the particular habitat structures may help cuckoos to find appropriate hosts.

Sex, personality and conspecific density influence natal dispersal with lifetime fitness consequences in urban and rural burrowing owls.

There is a growing need to understand how species respond to habitat changes and the potential key role played by natal dispersal in population dynamics, structure and gene flow. However, few studies have explored differences in this process between conspecifics living in natural habitats and those inhabiting landscapes highly transformed by humans, such as cities. Here, we investigate how individual traits and social characteristics can influence the natal dispersal decisions of burrowing owls (Athene cunicularia) living in urban and rural areas, as well as the consequences in terms of reproductive success and apparent survival. We found short dispersal movements among individuals, with differences between urban and rural birds (i.e., the former covering shorter distances than the latter), maybe because of the higher conspecific density of urban compared to rural areas. Moreover, we found that urban and rural females as well as bold individuals (i.e., individuals with shorter flight initiation distance) exhibited longer dispersal distances than their counterparts. These dispersal decisions have effects on individual fitness. Individuals traveling longer distances increased their reproductive prospects (productivity during the first breeding attempt, and long term productivity). However, the apparent survival of females decreased when they dispersed farther from their natal territory. Although further research is needed to properly understand the ecological and evolutionary consequences of dispersal patterns in transformed habitats, our results provide information about the drivers and the consequences of the restricted natal movements of this species, which may explain its population structuring through restricted gene flow between and within urban and rural areas.

Fragmentation mediates thermal habitat choice in ciliate microcosms.

Habitat fragmentation is expected to reduce dispersal movements among patches as a result of increased inter-patch distances. Furthermore, since habitat fragmentation is expected to raise the costs of moving among patches in the landscape, it should hamper the ability or tendency of organisms to perform informed dispersal decisions. Here, we used microcosms of the ciliate Tetrahymena thermophila to test experimentally whether habitat fragmentation, manipulated through the length of corridors connecting patches differing in temperature, affects habitat choice. We showed that a twofold increase of inter-patch distance can as expected hamper the ability of organisms to choose their habitat at immigration. Interestingly, it also increased their habitat choice at emigration, suggesting that organisms become choosier in their decision to either stay or leave their patch when obtaining information about neighbouring patches gets harder. This study points out that habitat fragmentation might affect not only dispersal rate but also the level of non-randomness of dispersal, with emigration and immigration decisions differently affected. These consequences of fragmentation might considerably modify ecological and evolutionary dynamics of populations facing environmental changes.

Evaluation of new aspect of styrene-butadiene-styrene modified bitumens: Damping property and mechanism

Damping is essential to bearing dynamic loads of construction structures, such as bridges, pavements, and high-speed rails. This paper presents a novel and preliminary understanding of the damping property and mechanism of styrene-butadienestyrene modified (SBS-modified) bitumens. The damping property was evaluated based on the temperature spectra of the loss factor (LF) by a dynamic shear rheometer and the damping mechanism was interpreted from molecular structure, morphology, and thermal analysis, respectively. The results first demonstrated that the SBS-modified bitumens appeared to maintain good damping property with a wide effective damping temperature range, low damping temperature susceptibility, and relatively high LF in normal working temperature range of pavement. In addition, the damping property seemed to be further improved separately by the crosslinker and plasticizer and the synthetic role on improving damping capacity was also observed by the combination of these two additives. Furthermore, the damping property of the SBS-modified bitumens appeared to be considerably influenced by temperature and the integrity of the hybrid via polymers blending and the use of additives. It was noted that the plasticizer promoted the swelling process of SBS polymers, by which improved the dispersion and chain movement ability. Moreover, the crosslinker increased the internal friction by forming denser polymer network. The findings in this paper will facilitate the development and application of the SBS-modified bitumen based damping materials in noise and vibration reducing and controlling to some extent.

Social status, forest disturbance, and Barred Owls shape long-term trends in breeding dispersal distance of Northern Spotted Owls

Abstract Dispersal among breeding sites in territorial animals (i.e. breeding dispersal) is driven by numerous selection pressures, including competition and spatiotemporal variation in habitat quality. The scale and trend of dispersal movements over time may signal changing conditions within the population or on the landscape. We examined 2,158 breeding dispersal events from 694 male and 608 female individually marked Northern Spotted Owls (Strix occidentalis caurina) monitored over 28 yr on 7 study areas to assess the relative importance of individual (sex, experience), reproductive (annual productivity, mate availability), and environmental (forest alteration, presence of competitor) sources of variation in breeding dispersal distance. Median breeding dispersal distance was 3.17 km, with 99% of all breeding dispersal events &amp;lt;37 km. Mean annual dispersal distances increased by 2.43 km in Oregon and 9.40 km in Washington between 1990 and 2017, which coincided with increases in annual detections of nonnative Barred Owl (S. varia). Frequency of breeding dispersal events, both among and within individuals, also increased over time. Female owls moved farther than males (median of 3.26 and 3.10 km, respectively), and birds with less experience (territory tenure) moved farther than those with more experience. Owls that were single in the year prior to dispersal moved 13–31% farther than those paired prior to dispersal. The greatest environmental change occurring over the course of our study was the expansion of Barred Owl populations. Breeding dispersal distance was positively related to Barred Owls in the study area and disturbance within the originating territory. While it appears that social factors continue to be important drivers of breeding dispersal distance in Spotted Owls, increased competition from Barred Owls and habitat alteration have a contributing effect. Increased breeding dispersal distances should be of concern for conservation efforts and considered in population monitoring because changing dispersal behavior may lead to higher rates of mortality and/or emigration from historical study areas.

Extensive larval dispersal and restricted movement of juveniles on the nursery grounds of sole in the Southern North Sea

Connectivity between spawning and nursery grounds influences the colonization, replenishment and resilience of populations of marine organisms. Connectivity rate, measured as the exchange of individuals between spawning and nursery grounds, is therefore a crucial determinant of stock size. However, connectivity of early-life stages is hard to explore due to sampling limitations and insufficient knowledge on potential larval sources. Here we present new insights into pre- and post-settlement dispersal of the common sole (Solea solea L.) at a spatial scale of 5–500 km in the Southern North Sea. Patterns at a scale of <100 km were considered local, whereas patterns further than 100 km were considered regional. Multi-elemental signatures of the otolith edge of 213 juvenile sole were used to discriminate at 79% of overall accuracy three main nursery grounds in the Southern North Sea, namely UK coast, Belgian coast and Dutch Wadden Sea. Interregional differences in otolith composition (especially for Mg, Mn and Ba) suggest that sole migration following settlement is limited in the Southern North Sea. Elemental signatures of the same fish indicated mixing during larval dispersal. Each nursery ground recruited an important mix of juveniles from three of the four chemically distinct natal sources identified from the larval otolith signatures. However the percentage of correct regional re-assignment varied from 67 to 80% with a maximum in the Wadden Sea. The results contributed to the validation of biophysical models of larval drift. Our findings support decision making for both fisheries management and marine spatial planning at the national and European level.

Spatial covariation of competing species in a fluctuating environment.

Understanding how stochastic fluctuations in the environment influence population dynamics is crucial for sustainable management of biological diversity. However, because species do not live in isolation, this requires knowledge of how species interactions influence population dynamics. In addition, spatial processes play an important role in shaping population dynamics. It is therefore important to improve our understanding of how these different factors act together to shape patterns of abundance across space within and among species. Here, we present a new analytical model for understanding patterns of covariation in space between interacting species in a stochastic environment. We show that the correlation between two species in how they experience the same environmental conditions determines how correlated fluctuations in their densities would be in the absence of competition. In other words, without competition, synchrony between the species is driven by the environment, similar to the Moran effect within a species. Competition between the two species causes their abundances to become less positively or more negatively correlated. The same strength of competition has a greater negative effect on the correlation between species when one of them has a more variable growth rate than the other. In addition, dispersal or other movement weakens the effect of competition on the interspecific correlation. Finally, we show that movement increases the distance over which the species are (positively or negatively) correlated, an effect that is stronger when the species are competitors, and that there is a close connection between the spatial scaling of population synchrony within a species and between species. Our results show that the relationships between the different factors influencing interspecific correlations in abundance are not simple linear ones, but this model allows us to disentangle them and predict how they will affect population fluctuations in different situations.

Juvenile dispersal in an uninhabited continent: young Spanish Imperial Eagles in Africa

The Spanish Imperial Eagle (Aquila adalberti) disappeared from Africa as a breeding species in the 1960s coincident with a general decline of their populations in the Iberian Peninsula. Because of a combination of successful conservation actions and a general change in human attitudes, the Spanish Imperial Eagle population has been increasing in Iberia from 103 pairs in 1980 to more than 500 breeding pairs in 2018. As a consequence, the number of juveniles that cross the Strait of Gibraltar into Africa has increased recently. Abundance and distribution of potential prey should affect young eagles’ behaviour and could be a limiting factor for a potential re-colonization of previous North-African populations. Additionally, determination of temporary settlement areas is crucial from a conservation point of view. Conservation actions in these areas, particularly reduction of juvenile mortality, are a priority to facilitate future reestablishment of breeding populations of the species in North Africa. Here we report on the dispersal movements of juvenile Spanish Imperial Eagles marked with GPS-GSM transmitters in Andalusia (southern Spain), some of which crossed the Strait of Gibraltar into north-western Africa, an area that does not have populations of the eagle’s main prey, the European rabbit. We analysed the differences in dispersal patterns and temporary settlement behaviour in the two study areas. We found that dispersal movements were greater, temporary settlement areas were larger, and individuals stayed longer in areas and moved greater distances among them in Africa than in Iberia. We believe that our results are best explained by applying the Marginal Value Theorem, which predicts that individuals will leave a foraging area when the availability of prey drops to similar levels of those of the surrounding environment. We suggest that the increase in the records of the species in Africa could lead to a recolonization of the species in Africa based on birds coming from the “source” Iberian population, but only if the Iberian population continues to increase. We recommend that conservation measures must be established in these temporary settlement areas in Africa.

Phylogeography and Historical Demography of Two Sympatric Atlantic Snappers: Lutjanus analis and L. jocu

Lutjanus analis (mutton snapper) and L. jocu (dog snapper) are mesopredator species with extensive geographic distribution in the Atlantic Ocean. Although historically overfished, their genetic diversity, population structuring, and historical demography along the Brazilian coast are unknown. Here we present genetic data for the hypervariable region 1 (HVR1) of the mtDNA control region of both L. jocu and L. analis, and for cytB of L. analis from distinct geographic regions. Phylogeographic analyses based on HVR1 sequences revealed no geographic structuring of mtDNA lineages for either species. The bimodal mismatch distribution plots of mutton and dog snapper populations implied that they might have experienced secondary contact. Historical demographic parameters estimated that population expansions ranged from 13,631 to 61,171 years before present (ybp) for L. analis and 36,783-55,577 ybp for L. jocu, associated with events that occurred at the end of the last glaciation period. Estimates of the average effective population size for L. jocu were higher than those for L. analis, with the largest population occupying the Brazilian northeastern region coast. High migration rates are maintained among the three northernmost locations, with a substantial decrease to the further southern region. Our study suggests that a tripartite interaction of larval dispersion and interregional adult movement (aggregate spawning), allied to historical contingencies, contributed to contemporary population genetic patterns of these species, and adds relevant information for conservation management of such vulnerable - and valuable - marine resources.

Landscape connectivity and spatial prioritization in an urbanising world: A network analysis approach for a threatened amphibian

Habitat fragmentation affects amphibian populations worldwide. Urban expansion and associated infrastructure are a main cause of habitat degradation and loss of landscape-scale habitat connectivity. Mitigation measures such as underpasses and associated fences are implemented to reduce the impacts of development on protected species. However, such efforts focus largely on local outcomes rather than envisioning how mitigation may contribute to habitat connectivity and population persistence at the landscape scale. We used a graph-theoretic approach to model structural and functional connectivity for a widespread but declining pond-breeding amphibian, the great crested newt (Triturus cristatus). This involved assessing species movement among breeding ponds and associated landscapes with different levels of urban and rural development and linear barriers. We used recent regional pond survey data for great crested newts combined with published data on movement and habitat use to explore connectivity. Landscape connectivity was affected by factors such as habitat quality and quantity, scale of movement and different degrees of road permeability. Linear barriers to movement and differences in their permeability were critical for predicting their impact on both migratory and dispersal movements in Triturus cristatus. Incorporating landscape connectivity modelling which includes the impact of barriers such as roads would substantially improve population-level outcomes from mitigation schemes. An accurate understanding of the far-reaching consequences of road mitigation as well as immediate, local effects, combined with our methods of assessing road permeability could transform future mitigation efforts by directing action to places that not only improve individual survival but also maximise connectivity at the landscape-scale.