Short-distance Dispersal Research Articles

Phenotypic variation of wild radishes Raphanus pugioniformis and R. raphanistrum associated with local conditions in the southeast Mediterranean

The geographical distribution of Raphanus pugioniformis (Brassicaceae), endemic to the southeast Mediterranean, covers distinct and heterogeneous habitats over a slight rainfall and elevation gradients. In contrast, the closely related R. raphanistrum is widely distributed only in well-drained sandy soils along the Mediterranean coastal plain. Here we hypothesize that the allopatric distribution of the two species, assisted by short- and long-seed dispersal of R. pugioniformis and R. raphanistrum, respectively, is also associated with inter- and intra-species phenotypic variation. In a common garden experiment, we assessed various phenological, morphological and fitness-related traits in five populations of each species. The results showed significant differences between the two species, generally in phenological and fitness-related traits. The results point to the role of early flowering and large reproductive output in the wide distribution of R. raphanistrum. In contrast, phenotypic variation in most of the measured traits among populations of R. pugioniformis suggests that short dispersal distance contributed to increased phenotypic differentiation among populations. Moreover, significant correlations between several of the measured traits with rainfall and elevation (e.g., bolting date and duration of flowering) suggest adaptive phenotypic differentiation. In R. raphanistrum, differences in most phenotypic traits were not found between populations, supporting the hypothesis that long distance dispersal of single seeded units contributes to relatively low genetic variation. Finally, we suggest that it is also possible that R. raphanistrum exhibits strong plastic responses, explaining its worldwide distribution, although this remained to be investigated.

Efficient spatial multi-state capture-recapture model to study natal dispersal: An application to the Alpine marmot.

Studying natal dispersal in natural populations using capture-recapture data is challenging as an unknown proportion of individuals leaves the study area when dispersing and are never recaptured. Most dispersal (and survival) estimates from capture-recapture studies are thus biased and only reflect what happens within the study area, not the population. Here, we elaborate on recent methodological advances to build a spatially explicit multi-state capture-recapture model to study natal dispersal in a territorial mammal while accounting for imperfect detection and movement in and out of the study area. We validate our model using a simulation study where we compare it to a non-spatial multi-state capture-recapture model. We then apply it to a long-term individual-based dataset on Alpine marmot Marmota marmota. Our model was able to accurately estimate natal dispersal and survival probabilities, as well as mean dispersal distance for a large range of dispersal patterns. By contrast, the non-spatial multi-state estimates underestimated both survival and natal dispersal even for short dispersal distances relative to the study area size. We discuss the application of our approach to other species and monitoring setups. We estimated higher inheritance probabilities of female Alpine marmots, which suggests higher levels of philopatry, although the probability to become dominant after dispersal did not differ between sexes. Nonetheless, the lower survival of young adult males suggests higher costs of dispersal for males. We further discuss the implications of our findings in light of the life history of the species.

Population assignment tests uncover rare long-distance marine larval dispersal events.

Long-distance dispersal (LDD) is consequential to metapopulation ecology and evolution. In systems where dispersal is undertaken by small propagules, such as larvae in the ocean, documenting LDD is especially challenging. Genetic parentage analysis has gained traction as a method for measuring larval dispersal, but such studies are generally spatially limited, leaving LDD understudied in marine species. We addressed this knowledge gap by uncovering LDD with population assignment tests in the coral reef fish Elacatinus lori, a species whose short-distance dispersal has been well-characterized by parentage analysis. When adults (n = 931) collected throughout the species' range were categorized into three source populations, assignment accuracy exceeded 99%, demonstrating low rates of gene flow between populations in the adult generation. After establishing high assignment confidence, we assigned settlers (n = 3,828) to source populations. Within the settler cohort, <0.1% of individuals were identified as long-distance dispersers from other populations. These results demonstrate an exceptionally low level of connectivity between E. lori populations, despite the potential for ocean currents to facilitate LDD. More broadly, these findings illustrate the value of combining genetic parentage analysis and population assignment tests to uncover short- and long-distance dispersal, respectively.

Resource relocations in relation to dispersal in Tetranychus ludeni Zacher

Life history strategies of a species may affect its invasion success. Here, we used a haplodiploid pest, Tetranychus ludeni Zacher (Acari: Tetranychidae), which is native to Europe but now cosmopolitan, to investigate its life history strategies in relation to its dispersal tendency and distance. We tested whether and how dispersal influenced survival, lifetime fecundity, age-specific reproduction, and life table parameters of mated females. We show that mated females did not trade off their survival and lifetime reproductive output with dispersal but adjusted their resource allocations during different reproductive stages depending on whether and how far they dispersed. Long-distance dispersers invested more in dispersal in their early life while resident mites and short-distance dispersers invested more in reproduction during their early life. These resource allocation strategies may allow long-distance dispersers to explore the novel environment more effectively without compromising lifetime reproductive fitness, contributing to the invasion success of T. ludeni.

Increased sediment deposition triggered by climate change impacts freshwater pearl mussel habitats and metapopulations

Abstract The freshwater pearl mussel Margaritifera margaritifera is a benthic organism sensitive to hydrological regime alterations and habitat degradation driven by excessive fine bed material deposit (FBMD). Both issues are potentially exacerbated by climate change. Understanding how climate change affects future mussel habitats and the dispersal among them (dependent on the brown trout as fish host) can support the planning of effective conservation actions. To project the impacts of climate change on the mussel, a semi‐mechanistic modelling cascade was implemented for the Aist catchment in Austria (630 km2), including a hydrological model, a hydraulic model, Random Forest Models for FBMD accumulation risk and Species Distribution Models. Two climate change models (RCPs 4.5 and 8.5) for two future horizons (2060 and 2090) were considered. A graph‐based assessment of the structural connectivity was used to measure the probability of successful dispersal. Results show a reduction of peak discharge that cascades into a widespread reduction in shear stresses during high flow. The mussel's habitats, defined by hydraulics (i.e. patches with low shear stresses during high flow), are predicted to be stable over the simulated scenarios. The pressure of FBMDs over the delineated habitat patches is predicted to increase in the future due to the reduced stream transport capacity, reducing up to 25% of the available patches in 2090 for RCP 8.5. Consequently, the mussel's dispersal probability decreases to 44.3%–75.6% of the maximum theoretical value, with the highest drops for short dispersal distances, impacting metapopulation dynamics. Synthesis and applications. The widespread issue of fine sediment deposition in the streambed will be exacerbated for those catchments where climate change reduces the stream transport capacity. The impacts on the freshwater pearl mussel include habitat loss due to the formation of a new unsuitable substrate, and a decrease in the potential dispersal among the residual habitats. Thus, conservation plans that aim to protect the mussel in the future should focus on the mitigation of fine bed material deposits, prioritizing those subreaches that offer the highest potential for preserving connectivity among suitable habitats.

Chasing Northern Pike under Ice: Long‐Distance Movements Following Catch‐and‐Release Ice Angling

AbstractCatch‐and‐release ice angling is a popular recreational activity, but little is known about the postrelease behavior of fish in the winter. Cold water temperatures and an ambush hunting strategy may constrain Northern Pike Esox lucius, limiting their postrelease movements to a small area near the capture location. We used manual acoustic telemetry to track 15 Northern Pike ranging from 56 to 98.5 cm total length for up to 7 d after catch‐and‐release ice angling in Buffalo Pound Lake, Saskatchewan, Canada. All of the fish but one moved unexpectedly long distances of several km over the tracking period. For the fish that were tracked over all 7 d, path lengths traveled ranged from 1.4 to 18.4 km. The minimum daily distance traveled ranged from 0 to 4.6 km and varied significantly by tracking day; the fish moved shorter distances on day 4 postrelease. There was a significant interaction between fish size and day postrelease; larger fish moved shorter minimum daily distances and dispersed shorter distances from the release site over the first 2 d of tracking. In contrast, by 5 d after release, both the largest and smallest fish had dispersed the longest distances from the release site and intermediate‐sized fish dispersed the least. The cumulative path length traveled by day 5 of tracking did not reveal any significant size‐based patterns. Our study raises the possibility that relatively large movements may be common for Northern Pike in the winter despite cold water temperatures and their expected foraging behavior. In addition, postrelease behavior varies with fish size. Habitat and space requirements for Northern Pike in the winter can encompass much larger areas and more habitat features than has been previously envisioned.

Movement of sturgeons (Acipenser oxyrinchus oxyrinchusandA. fulvescens) in the St. Lawrence Estuary: A 35‐year tagging study

Movement of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) and lake sturgeon (A. fulvescens) in the St. Lawrence Estuary (Québec, Canada) are not fully understood. To assess the movement extent of both species, a mark–recapture study was conducted in collaboration with commercial fishermen operating in the St. Lawrence Estuary. Between 1981 and 2015, 3,367 Atlantic sturgeon (fork length 21.8–199.5 cm) and 3,180 lake sturgeon (fork length 17.8–190.8 cm) were tagged and released. Of these, 673 Atlantic sturgeon and 42 lake sturgeon were recaptured. The maximum distances traveled between capture and recapture locations were 1,307 km for Atlantic sturgeon (8 years after initial capture) and 252 km for lake sturgeon (less than 1 year after initial capture). Statistical analyses identified differences in the dispersal distance of both species as revealed by a first component characterized by individuals with short dispersal distances (98% and <35 km for Atlantic sturgeon; 58% and <1 km for lake sturgeon) and a second component characterized by individuals with longer dispersal distances (2% and >600 km for Atlantic sturgeon; 42% and >190 km for lake sturgeon). We suggest that the short dispersal distances detected in the vast majority of Atlantic sturgeon recaptures likely reflect strong site fidelity, highlighting the importance of the St. Lawrence Estuary as a preferred habitat for juveniles and subadults. Although recaptures were low for lake sturgeon because this species is only marginally targeted by commercial fishermen in the St. Lawrence Estuary, our results also showed that this species uses estuarine habitats and that half of the population seems to exhibit strong site fidelity (67% of individuals were recaptured within 2 km).

Road preference of ants in a Japanese warm temperate forest and its implications for the regeneration of myrmecochorous sedges

AbstractIn warm temperate forests where light availability is generally low, roadsides often provide a refuge for myrmecochores. Therefore, whether or not ants disperse seeds along the roadsides should critically affect the regeneration of myrmecochores. Nonetheless, the dispersal behaviors of ants along roadsides have rarely been investigated in warm temperate forests. This study examined the road preference of two seed dispersing ants in warm temperate Japan, Formica japonica and Pheidole nodus. We located ant nests using baits placed at the vicinity of myrmecochorous sedges and examined the road preferences of ants and their consequences for seed dispersal by comparing the observed road proximity of ant nests with the simulated value assuming a random dispersal direction. Nests of both ant species were significantly closer to the road than in those simulated assuming random dispersal, which confirmed their road preferences. The road preference of F. japonica reduced the risk of seed loss into the forest interior to one‐ninth of the random dispersal. This trend was not observed in P. nodus due to its short dispersal distance relative to roadside width. Although light availability was higher around nests of P. nodus due to their closer proximity to the road than nests of F. japonica, adult sedges were located farther from the road than the nests of P. nodus. This implies that nests of P. nodus are unsuitable microhabitats for sedges. These results suggest that ants can disperse seeds along forest roadsides in warm temperate forests, but the efficiency vary among ant species.

Biphasic range expansions with short- and long-distance dispersal

Long-distance dispersal (LDD) has long been recognized as a key factor in determining rates of spread in biological invasions. Two approaches for incorporating LDD in mathematical models of spread are mixed dispersal and heavy-tailed dispersal. In this paper, I analyze integrodifference equation (IDE) models with mixed-dispersal kernels and fat-tailed (a subset of the heavy-tailed class) dispersal kernels to study how short- and long-distance dispersal contribute to the spread of invasive species. I show that both approaches can lead to biphasic range expansions, where an invasion has two distinct phases of spread. In the initial phase of spread, the invasion is controlled by short-distance dispersal. Long-distance dispersal boosts the speed of spread during the ultimate phase, and can have significant effects even when the probability of LDD is vanishingly small. For fat-tailed kernels, I introduce a method of characterizing the “shoulder” of a dispersal kernel, which separates the peak and tail.

Population dynamics of Hypothenemus hampei (Ferrari) according to the phenology of Coffea arabica L. in equatorial conditions of North Sumatra

In the Toba Highlands of North Sumatra (Indonesia), coffee production (Coffea arabica L. var. Sigarar Utang) is an important outcome for smallholders; however, the attack of the coffee berry borer (CBB) Hypothenemus hampei, is an obstacle for the development of coffee cultivation in this area. This pest causes great economic losses produced by the development of its offspring inside the coffee berries, making it difficult to control. This concerning situation has led us to consider the development of a CBB control strategy, but beforehand, it was necessary to acquire key information on the phenology of the coffee tree and its implication on the bioecology of the pest. Thus, two study designs were set up, one comprising six plots with two different age classes and the other corresponding to a single plot dedicated only to the study of short distance dispersal of CBB. Part of this study focused on the phenology of the coffee trees and showed that berry production mainly takes place in the upper parts of the trees and significantly decreases with tree age. Due to the equatorial climate, berries were practically always present. Berries were produced following two major flowering periods and some minor ones distributed over the year, and harvested at regular intervals. Berry distribution on the branches varied over time. Dynamics of infestations by CBB showed that ripe berries were more infested than unripe berries because they had been exposed longer to CBB attacks, that older trees were more exposed than younger trees and that infestation was evenly distributed along branches. In addition, internode pedestrian dispersal of CBBs was shown to occur, but considerably less frequently than airborne dispersal. In conclusion, it appears that in the agro-climatic context of the Toba region, the virtual year-round presence of berries - which fosters CBB infestations and CBB short-distance dispersal - is a constraint that must be taken into consideration for designing future pest management measures. To this end, it will be necessary in particular to evaluate the potential of trapping mainly used in tropical areas and to put into practice the sanitation harvesting applied in other countries.

Morphological Differences in the Island-Endemic Hawaiian Subspecies of the Common Gallinule Gallinula galeata

The study of island subspecies provides excellent “natural experiments” for examining the impacts of different selective regimes on animal taxa. We examined the morphological differences between the Hawaiian and continental North American subspecies of the Common Gallinule (Gallinula galeata sandvicensis and G. g. cachinnans, respectively), for which the existing literature is both scant and contradictory. More than 200 live gallinules and >100 museum specimens were measured, and a meta-analysis of literature values on North American Common Gallinules was conducted to quantitatively assess differences in wing chord, culmen and tarsus length, and body mass between these subspecies. Hawaiian Common Gallinules had smaller wing chords (–2.5 to –4.0%), larger culmen (+4.5 to +7.0%) and tarsi (+5.5 to +23.0%), and slightly larger body masses (∼+4.0%) than their mainland conspecifics. This is likely due to several factors including reduced predation pressure, shorter dispersal distances, nonmigratory behavior, and sedentary lifestyles associated with ecological differences between the Hawaiian Islands and the North American mainland. We also introduce the novel hypothesis that intra- and interspecific agonistic interactions due to habitat limitation are an additional selective force in driving these morphological changes.

How common and dispersal limited are ant-dispersed plants in eastern deciduous forests?

Most plant diversity in eastern deciduous forests occurs in the understory herbaceous layer. Ant-dispersed plants (myrmecochores) reside within that layer, and they often are reported to be a substantial part of understory plant abundance and diversity that is particularly threatened by global change because of their relatively short dispersal distances. Indeed, they are often, but not always, reported to be lacking or absent from young forests where they may fail to re-colonize after extirpation due to their dispersal limitations. Our objective was to characterize the woodland myrmecochorous plant communities across the northern- and southernmost reaches of eastern deciduous forests using vegetation from 2687 plots in 44 U.S. National Parks. We asked whether (a) myrmecochorous plants are a substantial portion of understory herbaceous communities in eastern North American deciduous forests, and (b) if they are particularly dispersal limited relative to other understory herbaceous dispersal guilds. If myrmecochores are notable in abundance and extent in understory herbaceous communities, we expected that they would comprise ~ 30% of the species and ~ 55–60% of the abundance, as reported in the literature. If myrmecochores, as a guild, are more dispersal limited than other dispersal modes (anemochory, autochory, zoochory), we also expected that myrmecochore species richness would be more limited by park age and area than other dispersal guilds because they would take longer to re-colonize. In contrast with the published literature on myrmecochores, our data suggest that myrmecochorous plants are much less common as reported in eastern deciduous understory herbaceous communities (~ 9% of herbaceous species; ~ 12% of herbaceous abundance), but twice as common as the global percentage of myrmecochorous plants (~ 4.5%). We also found that they are not particularly impacted by forest size and fragmentation. Ants appear to disperse myrmecochorous seeds at 1/20th the distance of wind-dispersed plants, but the dispersal distances for myrmecochores are about the same as other animal-dispersed plants and slightly less than gravity-dispersed plants in these same forests. Moreover, our data also suggest that myrmecochores, particularly large-seeded myrmecochores, may not occur in enough abundance to contribute meaningful biomass toward ant diets. Of course, species abundance does not equal species importance, and many keystone species impact ecosystems more than their abundance might suggest. Ant-mediated seed dispersal is a model system for understanding ecological and evolutionary dynamics, and certainly contributes toward understanding the threats of fragmentation and climate change in eastern deciduous forest systems, but they may not be as abundance or threatened as previously reported.

Spatial propagation and patterns of abundance of Dryocosmus kuriphilus throughout an invaded region

AbstractDryocosmus kuriphilus (Hymenoptera: Cynipidae) was first detected in Galicia (NW Spain) in 2014. The wasp then began to spread by stratified dispersal, with the local abundance increasing thereafter. In this study, we analysed location data on wasp‐attacked trees, with the following aims: (i) to determine the relative importance of short distance dispersal (SDD) and long‐distance dispersal (LDD) on the geographical expansion of the wasp; and (ii) to assess whether the spatial clusters of areas with high and low numbers of attacked trees correspond to areas with different infestation levels and thus whether these areas can be considered suitable proxies for pest abundance. A Random Forest algorithm was used to identify the factors that best discriminate hotspot and coldspot areas. Distance matrix analysis was used considering a conservative expansion rate of the population front of 14 km/year as the threshold for distinguishing SDD and LDD events. Gradients of attacked tree abundance were delineated using the Getis‐Ord Gi* statistic. Although LDD events represented a small proportion of the locally dispersing offspring, they determined the rate of spread across the landscape. The infestation level differed significantly between hotspot and coldspot areas, which were therefore used as proxies for D. kuriphilus population abundance. Factors that were favourable or unfavourable in relation to population abundance were mainly associated with maximum temperatures in the summer months. Metrics of composition and configuration of host plant habitat proved less important than the time since invasion and the effect was partly masked by tree diversity at community scale.

What do tropical cryptogams reveal? Strong genetic structure in Amazonian bryophytes.

Lowland tropical bryophytes have been perceived as excellent dispersers. In such groups, the inverse isolation hypothesis proposes that spatial genetic structure is erased beyond the limits of short-distance dispersal. Here, we determine the influence of environmental variation and geographic barriers on the spatial genetic structure of a widely dispersed and phylogenetically independent sample of Amazonian bryophytes. Single nucleotide polymorphism data were produced from a restriction site-associated DNA sequencing protocol for 10 species and analyzed through F-statistics and Mantel tests. Neither isolation-by-environment nor the impact of geographic barriers were recovered from the analyses. However, significant isolation-by-distance patterns were observed for 8 out of the 10 investigated species beyond the scale of short-distance dispersal (>1km), offering evidence contrary to the inverse isolation hypothesis. Despite a cadre of life-history traits and distributional patterns suggesting that tropical bryophytes are highly vagile, our analyses reveal spatial genetic structures comparable to those documented for angiosperms, whose diaspores are orders of magnitude larger. Dispersal limitation for tropical bryophytes flies in the face of traditional assumptions regarding their dispersal potential, and suggests that the plight of this component of cryptic biodiversity is more dire than previously considered in light of accelerated forest fragmentation in the Amazon.

Staying close: short local dispersal distances on a managed forest of two Patagonian Nothofagus species

Abstract Understanding the impact of management on the dispersal potential of forest tree species is pivotal in the context of global change, given the implications of gene flow on species evolution. We aimed to determine the effect of logging on gene flow distances in two Nothofagus species from temperate Patagonian forests having high ecological relevance and wood quality. Therefore, a total of 778 individuals (mature trees and saplings) of Nothofagus alpina and N. obliqua, from a single plot managed 20 years ago (2.85 hectares), were mapped and genotyped at polymorphic nuclear microsatellite loci. Historical estimates of gene dispersal distance (based on fine-scale spatial genetic structure) and contemporary estimates of seed and pollen dispersal (based on spatially explicit mating models) were obtained. The results indicated restricted gene flow (gene distance ≤ 45 m, both pollen and seed), no selfing and significant seed and pollen immigration from trees located outside the studied plot but in the close surrounding area. The size of trees (diameter at breast height and height) was significantly associated with female and/or male fertility. The significant fine-scale spatial genetic structure was consistent with the restricted seed and pollen dispersal. Moreover, both estimates of gene dispersal (historical and contemporary) gave congruent results. This suggests that the recent history of logging within the study area has not significantly influenced on patterns of gene flow, which can be explained by the silviculture applied to the stand. The residual tree density maintained species composition, and the homogeneous spatial distribution of trees allowed the maintenance of gene dispersal. The short dispersal distance estimated for these two species has several implications both for understanding the evolution of the species and for defining management, conservation and restoration actions. Future replication of this study in other Nothofagus Patagonian forests would be helpful to validate our conclusions.

Dispersal patterns of large-seeded plants and the foraging behaviour of a frugivorous bat

AbstractMutualistic interactions are biologically important, diverse and poorly understood. Comprehending these interactions and the effectiveness of the mutualistic partners has been the central focus of ecological and evolutionary studies, as this task requires disentangling the pieces of mutualism under study. Here, we tested the hypothesis that feeding activity of Artibeus phaeotis influences density, diversity and distance effects of the seed rain of large-seeded plant species in a Neotropical dry forest of Costa Rica. We predicted that bats’ activity increases density and diversity metrics on dispersing sites and that bats behave as short-distance dispersers. Our data revealed that, by dispersing hundreds of seeds within their small foraging areas and mostly close to fruiting trees, the feeding activity of A. phaeotis increases the density and richness of seeds underneath night feeding roosts. The functional role of A. phaeotis as disperser may vary among plant species, as we also detected that some seeds are more dispersed than others. Further inquiries to elucidate mutualistic interactions between frugivorous bats and large-seeded plant species should focus on understanding demographic and fitness outcomes, as strong selective pressures may be shaping morphological and behavioural traits of both plants and animals, ultimately influencing the survival of each partner.

Movement of Rhagoletis mendax (Diptera: Tephritidae) in Fruit-Bearing Wild Blueberry Fields. Part II.

During dispersal into fruit-bearing wild blueberry fields, blueberry maggot flies were highly active during all daylight hours as revealed by trap captures, although in one trial afternoon activity was greater than morning activity. Flies were not captured in traps at night, although observations in growth chambers showed that their activity at night, measured as displacement of position, was equal to daylight conditions. Flies were shown to fly at low altitude, just above the crop canopy, and screen fencing was shown to be effective at reducing colonization of plots, presumably due to their low height during flight. Over a 4-yr mark-capture study, colonization rate was shown to be low at 9.7 m/d, although a separate 2010 study showed higher rates at 14.1 and 28.0 m/d. Movement was shown to be nondirectional or random in the field, but a constrained random walk exhibiting direction into the field. Weed cover and high fruit density were associated with higher fly relative abundance, suggesting these field characteristics served as attractors slowing colonization rate into a field. Transect trap studies showed the temporal and spatial pattern of fly colonization into commercial wild blueberry fields, one of a slow wave that penetrates into the field interior as the season progresses. There is also an increase in fly abundance within-field edges and adjacent forest. The 'stacking' of flies along a field edge and slow movement rate into a field was shown through simulation to be a result of nondirectional short-distance dispersal of flies.

Global biogeography of marine amphipod crustaceans: latitude, regionalization, and beta diversity

Studying the biogeography of amphipod crustaceans is of interest because they play an important role at lower trophic levels in ecosystems. Because they lack a planktonic larval stage, it has been hypothesized that marine benthic amphipod crustaceans may have short dispersal distances, high endemicity, and spatial turnover in species composition, and consequently high global species richness. In this study, we examined over 400000 distribution records of 4876 amphipod species, and identified 12 regions of endemicity. The number and percent of endemic species peaked at 30°-35°S and coincided with 3 of these regions of high endemicity: Australia, New Zealand, and southern Africa. Pelagic species of marine amphipod crustaceans were more cosmopolitan than benthic species. The latitudinal patterns of richness (alpha, gamma, and ES50) and species turnover were at least bimodal. Most occurrence records and greater alpha and gamma richness were in mid-latitudes, reflecting sampling bias. Both ES50 and beta diversity had similar richness in the tropics, mid-latitudes, and on the Antarctic shelf around 70°S. These 2 indices exhibited a sharp dip in the deep Southern Ocean at 55°S. ES50 peaked at 30°-35°S and a small dip was apparent near the equator at 5°-10°N. Beta diversity was driven mostly by turnover rather than nestedness. These findings support the need for conservation in each realm of species endemicity—and for amphipods, particularly in Antarctica and the coastal mid-latitudes (30°-35°S) of the Southern Hemisphere.

Anthropogenic Seed Dispersal: Rethinking the Origins of Plant Domestication.

It is well documented that ancient sickle harvesting led to tough rachises, but the other seed dispersal properties in crop progenitors are rarely discussed. The first steps toward domestication are evolutionary responses for the recruitment of humans as dispersers. Seed dispersal-based mutualism evolved from heavy human herbivory or seed predation. Plants that evolved traits to support human-mediated seed dispersal express greater fitness in increasingly anthropogenic ecosystems. The loss of dormancy, reduction in seed coat thickness, increased seed size, pericarp density, and sugar concentration all led to more-focused seed dispersal through seed saving and sowing. Some of the earliest plants to evolve domestication traits had weak seed dispersal processes in the wild, often due to the extinction of animal dispersers or short-distance mechanical dispersal.

Natal Dispersal Distance and Population Origins of Migrant Red-Tailed Hawks and Cooper's Hawks

We used a two-step process to determine region of geographic origin for migratory Red-tailed Hawks (Buteo jamaicensis) and Cooper's Hawks (Accipiter cooperii). First, we used encounter data from the USGS Bird Banding Laboratory to estimate natal dispersal distances of Red-tailed Hawks and Cooper's Hawks. Then we used this information to assess whether hawks banded at migration stations and later encountered as breeding birds could be assigned to an approximate region of origin. Across the USA, the average apparent natal dispersal distance of Red-tailed Hawks was 137 ± 287 km (n = 127, median = 23 km) and of Cooper's Hawks was 40 ± 90 km (n = 70, median = 13.5 km). There were no differences in apparent natal dispersal as a function of latitude or longitude across the continent. From data on birds banded at migration stations and then encountered later as likely breeders, we inferred that these encounter locations will, on average, reflect these birds' region of origin. Because individuals of these two species tend to have short natal dispersal distances, we can infer regions of origin from breeding-season encounters of banded individuals originally trapped at migration sites across North America. As an example, we used data from migrating Red-tailed and Cooper's Hawks trapped in the Marin Headlands, California, that were later encountered as likely breeders to assign the region of origin of these individuals. Using this information, we inferred that early-migration-season Red-tailed Hawks originated in central California and that later-migration-season Red-tailed Hawks were a mix of individuals originating from central California and eastern Oregon. Cooper's Hawks captured during migration at Marin originated west of the Cascade and Sierra Nevada Mountains, including areas in northern California, Oregon, and British Columbia. Encounter data for hawks banded during migration then captured later during the breeding season may help migration researchers better understand origins of birds captured at migration sites and better link population trends at migration stations with population trends of breeding birds.