Colonization Of Patches Research Articles

Seed dispersal of Zoysia japonica by sika deer: An example of the “foliage is the fruit” hypothesis

AbstractZoysia japonica, a low growing grass, is tolerant to grazing and trampling. Kinkazan Island in northern Japan is inhabited by sika deer (Cervus nippon). The deer population increased in the 1970s at a shrine garden in the western part of the island, leading to expansion of Zoysia swards around the shrine garden and their colonization of remote open patches. The expansion around the garden is due to elongation of the rhizome, but expansion to remote places may be due to endozoochory by deer. This appears to be a good example of the “foliage is the fruit” hypothesis (the FF hypothesis) proposed by Janzen (1984; American Naturalist 123:338–353). To demonstrate this, we confirmed the expansion of the Zoysia swards and tested the traits of Zoysia by field surveys and indoor experiments. The Zoysia peduncles stood among the leaves, and sika deer fed on both the seeds and leaves. One deer fecal pellet contained about 20 seeds at its peak in June. In the feeding experiment, the survival rate through digestion was 38%. In the greenhouse experiment, the germination rate was 72%. An outdoor experiment showed that germination rates of the ingested seeds were 5% in a dark habitat and 58% in a bright habitat. Zoysia exhibited many of the traits presented by the FF hypothesis, and sika deer functioned as seed dispersal agents. Therefore, the Zoysia—sika deer relationship seems to support the FF hypothesis.

Patchiness caused by aphid herbivory and ozone events affects aphid's spread

AbstractAphids exploit different patches that offer a favourable habitat during their life cycle. Continuous colonization of new patches is critical for the survival of these insect pests. We developed a mesocosm experimental system to study the effects of stress regimes on the colonization of plants by aphids. In the first experiment, we treated Eruca sativa Mill (arugula) plants with either low ozone (O3) (ambient air with no O3 added), elevated O3 (ambient air with O3 addition) or low O3 + Myzus persicae aphid feeding, with subsequent observation of natural aphid infestation over time. The second experiment consisted of aphid sources and differently treated aphid sinks. The aphid sources were also exposed to either low or high O3 levels. The colonization of the sinks was then monitored over time and distance from source. The infestation rate was increased if the patches had been recently exposed to aphid herbivory. On the contrary, aphids did not colonize patches that experienced a recent O3 episode. The patches of E. sativa plants without prior biotic or abiotic stress were colonized by aphids at the beginning of the experiment, but infestation was poor and most of the plants remained aphid‐free throughout the experiment. Aphids from control patches had a better chance of successfully disseminate on hosts with previous herbivory, and aphid spread from O3‐stressed plants was generally poor. Hence, the colonization risk for a generalist aphid plague will depend on the space–time arrangement between crop patches with different stress levels. Ozone contamination could have a negative effect on the spread infestation of aphids in annual crops, because of habitat fragmentation. Here, we present important information to understand how physiological traits of individuals can be scaled up to predict changes within populations in a scenario of climate change.

Movements of a Specialist Butterfly in Relation to Mowing Management of Its Habitat Patches

Over the centuries, mowing and grazing have been crucial for sustaining populations of grassland insects and their overall diversity in Europe. While long-term positive effects of mowing have been studied in more detail, little is known about the direct impacts of mowing on adult butterflies. Here, we explore how different habitat management (mown, recovered after mowing and unmown) affects movements and population estimates of the endangered specialist butterfly Phengaris teleius. The results showed higher dispersal probability from mown (22%) and recovered meadows (16%) than from the unmown ones (9%). However, mowing shortened the average dispersal distances (mown = 102 m, recovered = 198 m, unmown = 246 m) and reduced butterfly population size. In contrast, a larger area of the habitat patches promoted long-distance dispersal and sustained larger populations. We hypothesise that mowing caused depletion of resources and triggered dispersal of poorly adapted individuals. This behaviour is maladaptive and could lead to higher dispersal-related mortality; thus, mowing should be avoided before and during the butterfly flight period. This study suggests that the species' persistence in a fragmented landscape depends on large, unmown and interconnected habitats that support more viable populations, promote long-distance dispersal, and enable (re)colonisation of vacant patches.

Genetic diversity and differentiation of isolated rear‐edge populations of a cold adapted butterfly, Erebia aethiops, in Britain

Abstract Rear‐edge populations of cold‐adapted species are highly vulnerable to climate change, their adaptations maybe critical for the persistence of the species as a whole. Using AFLP, we investigated population genetic diversity and differentiation of Scotch argus (Erebia aethiops), a cold‐adapted butterfly, comparing isolated rear‐edge and core populations in Britain, a relict part of the species range. We also examined genetic differences among sub‐populations and dispersal distances conducting a mark‐release‐recapture (MRR) study at the rear‐edge. Genetic diversity was higher in the isolated rear‐edge populations than populations at the core of the range and declined with latitude, supporting the idea that current differences in genetic diversity levels across Britain are likely the result of historical range changes after the last glaciation. Populations were genetically differentiated among regions, meaning that losing the isolated rear‐edge populations may prove detrimental for the survival of the species in Britain, as these populations are likely to be better adapted to warmer climates. We found that the largest population at the rear‐edge is genetically robust, with gene flow among patches, likely maintained by males as indicated by the higher dispersal distances recorded for males in the MRR, but colonisation of empty patches is constrained by females' low mobility. Our results highlight that isolated populations at the rear‐edge of cold‐adapted species should be considered of high conservation priority, as they hold higher levels of genetic diversity and differentiation which may prove to be key for the survival of these species under global warming.

Electrospun fibers coated with nanostructured biomimetic hydroxyapatite: A new platform for regeneration at the bone interfaces

Reconstruction of gradient organic/inorganic tissues is a challenging task in orthopaedics. Indeed, to mimic tissue characteristics and stimulate bone regeneration at the interface, it is necessary to reproduce both the mineral and organic components of the tissue ECM, as well as the micro/nano-fibrous morphology. To address this goal, we propose here novel biomimetic patches obtained by the combination of electrospinning and nanostructured bone apatite. In particular, we deposited apatite on the electrospun fibers by Ionized Jet Deposition, a plasma-assisted technique that allows conformal deposition and the preservation in the coating of the target's stoichiometry. The damage to the substrate and fibrous morphology is a polymer-dependent aspect, that can be avoided by properly selecting the substrate composition and deposition parameters. In fact, all the tested polymers (poly(l-lactide), poly(D,l-lactide-co-glycolide, poly(ε-caprolactone), collagen) were effectively coated, and the morphological and thermal characterization revealed that poly(ε-caprolactone) suffered the least damage. The coating of collagen fibers, on the other hand, destroyed the fiber morphology and it could only be performed when collagen is blended with a more resistant synthetic polymer in the nanofibers. Due to the biomimetic composition and multiscale morphology from micro to nano, the poly(ε-caprolactone)-collagen biomimetic patches coated with bone apatite supported MSCs adhesion, patch colonization and early differentiation, while allowing optimal viability. The biomimetic coating allowed better scaffold colonization, promoting cell spreading on the fibers.

Moss establishment success is determined by the interaction between propagule size and species identity

Colonization of new habitat patches is a key aspect of metacommunity dynamics, particularly for sessile organisms. Mosses can establish in new patches through fragmentation, with different vegetative structures acting as propagules. Despite the importance of these propagules for successful colonization the specific aspects that favour moss colonization by vegetative propagules remain poorly understood, including the effect of propagule size. We examine the intra- and interspecific variation of establishment and colonization success in culture of propagules of different sizes in six widespread soil moss species of contrasting growth form (Dicranum scoparium, Homalothecium aureum, Hypnum cupressiforme, Ptychostomum capillare, Syntrichia ruralis and Tortella squarrosa). We obtained three different size classes of propagules from artificially fragmented vegetative material, and assessed their establishment under controlled light and temperature conditions. We characterize the size, shape, apparent viability, morphological type and size changes due to hydration states of the propagules, all of them traits with potentially significant influence in their dispersal pattern and establishment. Then we assess the effect of these traits on moss establishment, using indicators of surface establishment (number of established shoots and colonized surface) and biomass production (viable biomass) as proxies of colonization success. The establishment indicators related to colonization surface and biomass production differ among species and propagule sizes. The magnitude of the interspecific differences of all indicators of establishment success was larger at the smaller propagule size class. T. squarrosa was the most successful species, and D. scoparium showed the lowest performance. We also found interspecific differences in the hydration dynamics of the propagules. The process of establishment by vegetative fragments operates differently among moss species. Besides, differences between hydration states in propagules of some species could be part of syndromes for both dispersal and establishment. This study unveils several functional traits relevant for moss colonization, such as wet versus dry area and length of fragments, which may improve our understanding of their spatial dynamics.

Green infrastructure can promote plant functional connectivity in a grassland species around fragmented semi‐natural grasslands in NW‐Europe

Species may benefit from green infrastructure, i.e. the network of natural and anthropogenic habitat remnants in human‐dominated landscapes, if it helps isolated populations in remaining habitat patches to be functionally connected. The importance of green infrastructure is therefore increasingly emphasized in conservation policy to counter biodiversity loss. However, there is limited evidence, particularly in plants, that green infrastructure promotes functional connectivity, i.e. supports the colonization of habitat patches across a landscape. We applied landscape genetics to test whether the green infrastructure supports structural and functional connectivity in the grassland perennial Galium verum, in 35 landscapes in Belgium, Germany and Sweden. We used multivariate genetic clustering techniques, nestedness analyses and conditional inference trees to examine landscape‐scale patterns in genetic diversity and structure of plant populations in the green infrastructure surrounding semi‐natural grasslands. Inferred functional connectivity explained genetic variation better than structural connectivity, yielding positive effects on genetic variation. The road verge network, a major structural component of the green infrastructure and its functional connectivity, most effectively explained genetic diversity and composition in G. verum. Galium verum ramets occupying the surrounding landscape proved to be genetic subsets of focal grassland populations, shaping a nested landscape population genetic structure with focal grasslands, particularly ancient ones, harbouring unique genetic diversity. This nested pattern weakened as road network density increased, suggesting road verge networks enable high landscape occupancy by increased habitat availability and facilitates gene flow into the surrounding landscape. Our study proposes that green infrastructure can promote functional connectivity, providing that a plant species can survive outside of core habitat patches. As this often excludes habitat specialist species, conservation practice and policy should primarily focus on ancient, managed semi‐natural grasslands. These grasslands both harbour unique genetic diversity and act as primary gene and propagule sources for the surrounding landscape, highlighting their conservation value.

Spatially-explicit population modeling to predict large carnivore recovery and expansion

Despite extensive range contractions, several large carnivore species have recently recolonized portions of their former range. Since the 1990s, American black bear reports have increased in Missouri, USA, corresponding with increasing abundance and distribution. As effective management benefits from sound information on wildlife demographics and spatial distribution, we used a spatially-explicit metapopulation model built from local data to inform a stage matrix, which was used in conjunction with a previously created habitat suitability model to quantify and predict the growth and expansion of the black bear population. We collected demographic data during 2011–2021 from 162 female bears with 159 young from 70 litters. Average litter size was 1.95, 42% of cubs were female, and cub survival to yearling was, on average, 95% for females and 70% for males. The habitat suitability model identified 53 core areas most suitable for bears in Missouri. Increasing from previous local estimates of bear population size (∼280 bears in 2012), the model estimated the total bear population inhabiting core habitat patches in year 10 as 732 individuals (598–873, 5th–95th percentiles), with an average annual growth rate of 1.11. The estimated carrying capacity of the core habitat patches (excluding cubs-of-the-year) was ∼2700 bears, but adding marginal and highly marginal habitat patches increased the carrying capacity to ∼5500 bears. Population estimates were most sensitive to variations in stage matrix parameters though overall patch colonization estimates were relatively stable. Our work is an important step toward understanding the recolonization potential of black bears in Missouri and can aid future studies projecting large carnivore density in other areas as well as values and attitudes toward these wide-ranging species. Developing holistic conservation frameworks will be critical if human acceptance toward large carnivores continues increasing and carnivore recolonization of historical range continues.

Plant life‐history traits rather than soil legacies determine colonisation of soil patches in a multi‐species grassland

Abstract Interactions between plants and soil biota are increasingly shown to play critical roles in plant species coexistence processes. Plant species coexistence is thought to be promoted via biotic legacies that plant species leave behind in the soil after a plant disappears. These soil legacies are hypothesised to supress colonisation success when the preceding plant is of the same species, that is, when a plant species encounters its own, species‐specific soil antagonists. However, colonisation of vacant spots in plant communities is in the first place determined by the ability of plants to reach such vacant locations. We currently lack an understanding of the explicit role of soil legacy effects and their relative contribution to colonisation processes in plant communities consisting of plant species inherently differing in colonisation ability. In experimental, outdoor plant communities consisting of eight grassland species, we tested the effect of five differently conditioned soil patches on plant species colonisation success over three consecutive growing seasons. We found that colonisation success was largely determined by the species' reproductive strategy, lateral spread and growth rate, and not by the plant species that conditioned the soil patch. Fast spreading, clonal plant species reached the soil patches first and initially attained the highest biomass inside the patch. One year later, slower spreading plant species colonised the patch via seedlings. Species with intrinsically high growth rates attained the highest biomass, decreasing biomass of the initial colonisers. While subtle differences between conditioned soil patches did occur, these were not strong enough to overcome the inherent differences in colonisation ability between the various plant species. Synthesis. Our results reject the hypothesis that colonisation of vacant soil patches in plant communities is strongly affected by the legacy that is left behind by the preceding plant species. Instead, plant species life‐history strategy plays a prominent role, driving sequential plant species replacements. Based on our results and recent accounts in literature we present a conceptual model for local cyclic dynamics in grassland communities, where soil legacy plays a role in affecting the performance of established plant species rather than colonisation of vacant patches.

The relationship between pathogen life-history traits and metapopulation dynamics.

Summary Plant pathogen traits, such as transmission mode and overwintering strategy, may have important effects on dispersal and persistence, and drive disease dynamics. Still, we lack insights into how life‐history traits influence spatiotemporal disease dynamics.We adopted a multifaceted approach, combining experimental assays, theory and field surveys, to investigate whether information about two pathogen life‐history traits – infectivity and overwintering strategy – can predict pathogen metapopulation dynamics in natural systems. For this, we focused on four fungal pathogens (two rust fungi, one chytrid fungus and one smut fungus) on the forest herb Anemone nemorosa.Pathogens infecting new plants mostly via spores (the chytrid and smut fungi) had higher patch occupancies and colonization rates than pathogens causing mainly systemic infections and overwintering in the rhizomes (the two rust fungi). Although the rust fungi more often occupied well‐connected plant patches, the chytrid and smut fungi were equally or more common in isolated patches. Host patch size was positively related to patch occupancy and colonization rates for all pathogens.Predicting disease dynamics is crucial for understanding the ecological and evolutionary dynamics of host–pathogen interactions, and to prevent disease outbreaks. Our study shows that combining experiments, theory and field observations is a useful way to predict disease dynamics.

Insect dispersal ability is crucial to overcome limitations in patch colonization of Eichhornia crassipes floating meadows

Insect dispersal ability is crucial to overcome limitations in patch colonization of Eichhornia crassipes floating meadows

The Temporal Dimension of Plant-Soil Microbe Interactions: Mechanisms Promoting Feedback between Generations.

AbstractSoil microbes can influence plant competitive outcomes by stabilizing plant community dynamics or mediating plant competitive hierarchies. Which effect dominates depends on whether microbial effects can extend beyond the focal conditioning individual. While it is well known that microbial effects can extend to other individuals through space, we lack an explicit theoretical understanding of the factors that regulate their spread to other individuals in subsequent generations. Here, we examine how the commonly assumed stabilizing effects of host-specific pathogens in fact depend on two factors that allow microbial effects to be cross-generational-which plant demographic vital rate is influenced by microbes and the conditioning and decay rates of soil microbial communities. With a novel patch occupancy model that incorporates the transition of soil states following plant colonization and mortality, we show that host-specific pathogens enable plant coexistence when they suppress conspecific plant colonization of empty patches but contribute to competitive hierarchies when they modify only the mortality and fecundity of the conditioning plant individual. In a series of model extensions, we further demonstrate that these latter microbial effects can still promote coexistence, but only when microbial communities decay slowly following plant death, thereby allowing microbial effects to be cross-generational. Our study calls for further empirical work quantifying the demographic rates most affected by soil microbes as well as the timescales of conditioning and decay.

Moving apart together: co-movement of a symbiont community and their ant host, and its importance for community assembly

BackgroundSpecies interactions may affect spatial dynamics when the movement of one species is determined by the presence of another one. The most direct species-dependence of dispersal is vectored, usually cross-kingdom, movement of immobile parasites, diseases or seeds by mobile animals. Joint movements of species should, however, not be vectored by definition, as even mobile species are predicted to move together when they are tightly connected in symbiont communities.MethodsWe studied concerted movements in a diverse and heterogeneous community of arthropods (myrmecophiles) associated with red wood ants. We questioned whether joint-movement strategies eventually determine and speed-up community succession.ResultsWe recorded an astonishingly high number of obligate myrmecophiles outside red wood ant nests. They preferentially co-moved with the host ants as the highest densities were found in locations with the highest density of foraging red wood ants, such as along the network of ant trails. These observations suggest that myrmecophiles resort to the host to move away from the nest, and this to a much higher extent than hitherto anticipated. Interestingly, functional groups of symbionts displayed different dispersal kernels, with predatory myrmecophiles moving more frequently and further from the nest than detritivorous myrmecophiles. We discovered that myrmecophile diversity was lower in newly founded nests than in mature red wood ant nests. Most myrmecophiles, however, were able to colonize new nests fast suggesting that the heterogeneity in mobility does not affect community assembly.ConclusionsWe show that co-movement is not restricted to tight parasitic, or cross-kingdom interactions. Movement in social insect symbiont communities may be heterogeneous and functional group-dependent, but clearly affected by host movement. Ultimately, this co-movement leads to directional movement and allows a fast colonisation of new patches, but not in a predictable way. This study highlights the importance of spatial dynamics of local and regional networks in symbiont metacommunities, of which those of symbionts of social insects are prime examples.

Moose Habitat Selection and Fitness Consequences During Two Critical Winter Tick Life Stages in Vermont, United States†

The moose (Alces alces) is a charismatic species in decline across much of their southern distribution in North America. In the northeastern United States, much of the reduction has been attributed to winter tick (Dermacentor albipictus) infestations. Winter ticks are fairly immobile throughout all life stages, and therefore their distribution patterns at any given time are shaped largely by the occurrence of moose across the landscape during the peak of two critical time periods: fall questing (when ticks latch onto moose) and spring drop-off (when engorged female ticks detach from moose). We used recent land cover and lidar data within a dynamic occupancy modeling framework to estimate first-order habitat selection (use vs. non-use) of female moose (n = 74) during the tick questing and drop-off periods. Patch extinction and colonization rates between the fall questing and spring drop-off periods were strongly influenced by habitat and elevation, but these effects were diminished during the fall questing period when moose were more active across the landscape. From the fall questing period to the spring drop-off period, patches where colonization was high and extinction was low had higher proportions of young (shrub/forage) mixed forest at higher elevations. Further, we evaluated the fitness consequences of habitat selection by adult females during the fall questing period, when females and their calves acquire ticks. We compared Resource Selection Functions (RSF) for five females that successfully reared a calf to age 1 with five females whose calves perished due to ticks. Adult female moose whose offspring perished selected habitats in the fall that spatially coincided with areas of high occupancy probability during the spring tick drop-off period. In contrast, adult female moose whose offspring survived selected areas where the probability of occupancy during the spring drop-off was low; at present, natural selection may favor female adults who do not select the same habitats in fall as in spring. Our model coefficients and mapped results define “hotspots” that are likely encouraging the deleterious effects of the tick-moose cycle. These findings fill knowledge gaps about moose habitat selection that may improve the effectiveness of management aimed at reversing declining population trends.

Recovery process of genetic diversity through seed and pollen immigration at the northernmost leading‐edge population of Fagus crenata

AbstractThe range expansion of a plant species begins with colonization of ecological empty patches from posterior source populations. This process involves stochastic loss of genetic diversity. However, the founder population could restore genetic diversity by gene flow from posterior populations via seeds and pollen and its recovery affects evolutionary potential for species expansion. To clarify the recovery process of genetic diversity during species range expansion, gene flow via seeds and pollen was investigated at the expansion front of Fagus crenata. Based on eight nuclear microsatellite genotypes of a total of 150 individuals and 225 seeds at the northernmost leading‐edge population, genetic diversity, fine‐scale spatial genetic structure (FSGS), and genetic differentiation from other five northern populations were investigated. Moreover, both seed and pollen immigration and their effects on genetic diversity at different successional stages were analyzed. The leading‐edge population showed lower genetic diversity and substantial genetic differentiation, reflecting its strong genetic drift. Non‐significant FSGS and a negative inbreeding coefficient for mature trees may indicate that the earliest generation consisted of founders from foreign seed sources. The significant proportion of seed and pollen immigration increased the number of different alleles for later successional stages. The effective number of pollen parents from foreign sources (20.8) was markedly higher than that from the local source (2.1). These results indicated that pollen immigration incorporated new and rare alleles and increased the genetic diversity of the population. However, the proportion of foreign gene flow decreased during succession, probably due to the increased reproductive success of local individuals as they reached maturity and grew in size.

Pollinator interaction flexibility across scales affects patch colonization and occupancy.

Global change alters ecological communities and may disrupt ecological interactions and the provision of ecosystem functions. As ecological communities respond to global change, species may either go locally extinct or form novel interactions. To date, few studies have assessed how flexible species are in their interaction patterns, mainly due to the scarcity of data spanning long time series. Using a ten-year species-level dataset on the assembly of mutualistic networks from the Central Valley in California, we test whether interaction flexibility affects pollinators' colonization and persistence and their resulting habitat occupancy in a highly modified landscape. We propose three metrics of interaction flexibility associated with different scales of organization within ecological communities and explore which species' traits affect them. Our results provide empirical evidence linking species' ability to colonize habitat patches across a landscape to the role they play in networks. Phenological breadth and body size had contrasting effects on interaction flexibility. We demonstrate the relationship between mutualistic networks and species' ability to colonize and persist in the landscape, suggesting interaction flexibility as a potential mechanism for communities to maintain ecosystem function despite changes in community composition.

Dependence of the dwarf sundew (Drosera brevifolia) on burrowing crayfish disturbance

Disturbance is necessary for the survival of most species of carnivorous plants to reduce competition and expose bare soil for germination. Historically, fire was the most widespread form of disturbance. Today, prescribed burns and mowing are the primary anthropogenic forms of disturbance maintaining populations of carnivorous plants. Other natural forms of disturbance have received little consideration such as grazing and small-scale disturbance by burrowing crayfish. In Mississippi, burrowing crayfish are beneficial to both sundews (Drosera capillaris) and bladderworts (Utricularia juncea). Because burrowing crayfish are found throughout much of southeastern North America, they may provide a vital form of disturbance for smaller species of carnivorous plants to the point of being ecosystem engineers. In this study, we investigated if the Kentucky state-endangered dwarf sundew (D. brevifolia) benefits from bare patches of soil created experimentally by us and naturally by the endemic Bluegrass crayfish (Cambarus batchi). We observed colonization of sundews on crayfish mounds, chimneys, and eroded chimneys (= flat mounds) over 16 months. We also observed colonization of patches of soil we scraped clear of plants. We found that dwarf sundews quickly colonized bare soil, and that bare patches created by burrowing crayfish may be an essential small-scale form of disturbance for these sundews. Dwarf sundews have a life history predicted by the colonization hypothesis that being, they grow in a restricted niche space within the meadow and appear to have a disturbance-mediated coexistence with crayfish. They are small, fast growing, and short lived, and produce a seed bank. Dwarf sundews are a “fugitive species” that quickly colonize intense, small-scale disturbed sites to temporarily escape competition. We briefly discuss other potentially important, yet over-looked, disturbance that historically has been beneficial to carnivorous plants in southeastern North America.

Dynamic spatio-temporal patterns of metapopulation occupancy in patchy habitats.

Spatio-temporal dynamics in habitat suitability and connectivity among mosaics of heterogeneous wetlands are critical for biological diversity and species persistence in aquatic patchy landscapes. Despite the recognized importance of stochastic hydroclimatic forcing in driving wetlandscape hydrological dynamics, linking such effects to emergent dynamics of metapopulation poses significant challenges. To fill this gap, we propose here a dynamic stochastic patch occupancy model (SPOM), which links parsimonious hydrological and ecological models to simulate spatio-temporal patterns in species occupancy in wetlandscapes. Our work aims to place ecological studies of patchy habitats into a proper hydrologic and climatic framework to improve the knowledge about metapopulation shifts in response to climate-driven changes in wetlandscapes. We applied the dynamic version of the SPOM (D-SPOM) framework in two wetlandscapes in the US with contrasting landscape and climate properties. Our results illustrate that explicit consideration of the temporal dimension proposed in the D-SPOM is important to interpret local- and landscape-scale patterns of habitat suitability and metapopulation occupancy. Our analyses show that spatio-temporal dynamics of patch suitability and accessibility, driven by the stochasticity in hydroclimatic forcing, influence metapopulation occupancy and the topological metrics of the emergent wetlandscape dispersal network. D-SPOM simulations also reveal that the extinction risk in dynamic wetlandscapes is exacerbated by extended dry periods when suitable habitat decreases, hence limiting successful patch colonization and exacerbating metapopulation extinction risks. The proposed framework is not restricted only to wetland studies but could also be applied to examine metapopulation dynamics in other types of patchy habitats subjected to stochastic external disturbances.

Multi-year occupancy of the hops blue butterfly (Celastrina humulus): habitat patch colonization and extinction

The hops azure (Celastrina humulus) is a locally-abundant, rare butterfly in Colorado and Montana, that uses wild hops (Humulus lupulus) as a host plant. Because of the patchy distribution of wild hops and current land use changes, the butterfly is a species of conservation concern. The hops azure is abundant along the riparian systems of the U.S. Air Force Academy (Academy) because wild hops is readily available and most land-use impacts have not reached much of the Academy. However, the riparian systems of the Academy are experiencing increased flooding from off-base, hard-surface development, making it harder for riparian vegetation, like wild hops, to thrive. To describe the prevalence and persistence of the hops azure, we conducted multi-year occupancy sampling to understand habitat-patch occupancy changes, such as patch extinction and colonization, and to identify factors that impact detectability. Wind speed, the area of wild hops, and the amount of cloud cover and solar exposure influenced probability of hops azure detection. Patch occupancy and extinction are influenced by the area of wild hops, suggesting that as host plant patch sizes get smaller, patch extinction increases and occupancy decreases. Detectability and occupancy were higher than expected, and the probability of patch extinction and colonization were extremely low. Management efforts to expand wild hops growth within the hops azure’s range, increase continuity of wild hops expanses, and retain the hydrology that supports wild hops should increase the stability of azure populations.

Local soil legacy effects in a multispecies grassland community are underlain by root foraging and soil nutrient availability

Abstract Plant‐soil legacies consisting of species‐specific microbial communities are hypothesized to play a critical, structuring role in plant species coexistence processes. Plant species are thought to perform worse on soil conditioned by the same species compared to soil of other species, which serves as a self‐limitation mechanism and averts monodominance of strong competitors. Here, we test in a multispecies community setting, whether root colonization and resource utilization of soil patches with distinct soil legacies are consistent with this hypothesis. We grew eight grassland species together in an outdoor mesocosm set‐up in unconditioned soil and created soil patches in these communities conditioned by one of four plant species, or a soil mixture of all four. During two subsequent growing seasons, we tested the effect of these conditioned soil patches on below‐ground root colonization into the patches of each surrounding plant species using a novel sequencing‐based approach. In addition, we tested the effect of soil conditioning on local root functioning by injecting tracers into the soil patches and measuring the recovery in above‐ground biomass. Against expectations, plant species did not place less roots in own soil patches compared to foreign soil patches, nor did species take up less tracer from own compared to foreign soil patches. Using structural equation modelling, we found that tracer uptake of the plant species was to a varying degree explained by root densities in the various soil patches and by differing soil nutrient availability of the soil patches. We conclude that soil legacy effects are inextricably connected to soil nutrient availability, which needs to be taken into account in plant‐soil feedback research to understand the processes that shape plant communities. Synthesis. We found that soil legacy effects in complex, multispecies semi‐field conditions did not match expectations based on theory and experiments in controlled conditions. Among the many complicating factors that may modify or even overrule soil legacy effects in semi‐field settings, we identified soil nutrient availability as a critical force that may, together with soil biota, shape plant species coexistence processes.