Testing a mechanistic dispersal model against a dispersal experiment with a wind‐dispersed moss

Wind is the main dispersal agent for a wide array of species and for these species the environmental conditions under which diaspores are released can potentially modify the dispersal kernel substantially. Little is known about how bryophytes regulate spore release, but conditions affecting peristome movements and vibration of the seta may be important. We modelled airborne spore dispersal of the bryophyte species Discelium nudum (spore diameter 25 μm), in four different release scenarios, using a Lagrangian stochastic dispersion model and meteorological data. We tested the model predictions against experimental data on colonization success at five distances (5, 10, 30, 50 and 100 m) and eight directions from a translocated point source during seven two‐day periods. The model predictions were generally successful in describing the observed colonization patterns, especially beyond 10 m. In the laboratory we established spore release thresholds; horizontal wind speed sd > 0.25 m s^?1 induced the seta to vibrate and in relative humidity < 75% the peristome was open. Our dispersal model predicts that the proportion of spores dispersing beyond 100 m is almost twice as large if the spores are released under turbulent conditions than under more stable conditions. However, including release thresholds improved the fit of the model to the colonization data only minimally, with roughly the same amount of variation explained by the most constrained scenario (assuming both vibration of the seta and an open peristome) and the scenario assuming random release. Model predictions under realised experimental conditions suggest that we had a low statistical power to rank the release scenarios due to the lack of measurements of the absolute rate of spore release. Our results hint at the importance of release conditions, but also highlight the challenges in dispersal experiments intended for validating mechanistic dispersal models.     

Competition–colonization dynamics of spore‐feeding beetles on the long‐lived bracket fungi Ganoderma in New Zealand native forest

We investigated the competition–colonization dynamics of three species of spore‐feeding beetles on wood‐decaying bracket fungi, Ganoderma spp., in New Zealand. One beetle species (Holopsis sp. 1) was a pore‐tube specialist hypothesized to be superior in exploitative competition; the other two (Zearagytodes maculifer and Holopsis sp. 2) were surface grazers. We surveyed beetle abundance, daily spore release per square centimetre, pore surface area, and environmental variables over 30 patches (sporocarps) monthly for one year. We constructed a competitive‐interaction web by fitting models to the cross‐sectional resource–multiconsumer data. We compared flight behaviour and the associated physiological traits of beetles in wind tunnel experiments, and morphological characters. An examination of the competition–colonization dynamics found (1) the competitive equivalence of Holopsis sp. 1 to Z. maculifer and superiority to Holopsis sp. 2; (2) a reduced population persistence time of Z. maculifer that results from the dominance of Holopsis sp. 1; (3) the dominance of Z. maculifer and Holopsis sp. 1 in larger patches and that of Holopsis sp. 2 in smaller patches; (4) a greater spatial extent of population synchrony in Z. maculifer than in the Holopsis spp.; and (5) more frequent departures (takeoffs) of Z. maculifer than of Holopsis spp., concordant with its greater development of flight muscles and longer hindwing. These beetles may coexist through two types of spatial niche partitioning, each of which explains the pairwise coexistence of competitors but not the coexistence of the three species: Z. maculifer can evade competition with Holopsis sp. 1 by flying frequently or strongly to colonize distant patches, whereas Holopsis sp. 2 can dominate only in smaller and newly emergent patches until the arrival of Holopsis sp. 1.     

The spore‐associated protein BclA1 affects the susceptibility of animals to colonization and infection by Clostridium difficile

The BclA protein is a major component of the outermost layer of spores of a number of bacterial species and Clostridium difficile carries three bclA genes. Using insertional mutagenesis each gene was characterized and spores devoid of these proteins had surface aberrations, reduced hydrophobicity and germinated faster than wild‐type spores. Therefore the BclA proteins were likely major components of the spore surface and when absent impaired the protective shield effect of this outermost layer. Analysis of infection and colonization in mice and hamsters revealed that the 50% infectious dose (ID₅₀) of spores was significantly higher (2‐logs) in the bclA1^? mutant compared to the isogenic wild‐type control, but that levels of toxins (A and B) were indistinguishable from animals dosed with wild‐type spores. bclA1^? spores germinated faster than wild‐type spores yet mice were less susceptible to infection suggesting that BclA1 must play a key role in the initial (i.e. pre‐spore germination) stages of infection. We also show that the ID₅₀ was higher in mice infected with R20291, a ‘hypervirulent’ 027 strain, that carries a truncated BclA1 protein.     

Evidence of stress imprinting with population‐level differences in two moss species

Plants are often repeatedly exposed to stresses during their lives and have a mechanism called stress imprinting that provides “memories” of stresses they experience and increases their ability to cope with later stresses. To test hypotheses that primed bryophytes can preserve their stress imprinting after 6 days of recovery and induce higher levels of osmolytes and ROS‐scavenging activities upon later stress exposure, and there exist population‐level differentiation in their desiccation defenses, we transplanted samples of two populations of each of two moss species, Hypnum plumaeforme and Pogonatum cirratum, in a nature reserve in southern China. After 16 months of acclimation, sets of each population were subjected to control, one‐time desiccation stress, duplicated desiccation stress and cross‐stress (low temperature stress followed by desiccation stress) treatments. Levels of oxidant enzymes, osmolytes, and phytohormones in the samples were then determined. The desiccation stress generally led to increases in activities or contents of superoxide dismutase, guaiacol peroxidase, catalase, proline, soluble sugars, soluble proteins, and stress hormones including abscisic acid (ABA), jasmonates (JA), and salicylic acid (SA), with differences between both species and populations. After a 6‐day recovery period, contents of phytohormones (including ABA, JA, SA, and cytokinins) in stressed H. plumaeforme had substantially fallen toward control levels. The duplicated and cross‐stress treatments generally led to further accumulation of proline, soluble sugars, and soluble proteins, with further increases in activities of antioxidant enzymes in some cases. Furthermore, significant differences between allochthonous and native populations were found in contents of malondialdehyde and osmolytes, as well as antioxidant enzyme activities. Our results confirm the hypotheses and highlight the importance of osmolytes in mosses' stress responses.     

Population genetic connectivity of an endemic New Zealand passerine after large‐scale local extirpations: a model of re‐colonization potential

Little is known about how a 70% loss of native forests has affected the genetic connectivity of remnant bird populations in New Zealand. We use the common and widely distributed New Zealand Bellbird Anthornis melanura as an indicator species of population connectivity for well‐flighted birds. Using eight microsatellite loci, we identified five main genetic populations in the North Island, South Island, sub‐Antarctic Auckland Islands and two small remnant island populations adjacent to a large region of avian extirpations in northern North Island. Only one remnant island population, on a 30‐year‐old conservation reserve at Tiritiri Matangi, displayed a clear signature of recent genetic bottleneck. The 7% migration rate at Tiritiri Matangi indicates that bottlenecks can be maintained despite habitat rehabilitation, possibly through behavioural barriers to gene flow. Adjacent to the same extirpation zone, Bellbirds on the Poor Knights Islands were found to have low genetic diversity and low re‐colonization potential. Two gaps concordant with deforestation patterns separated the Kapiti Coast of southern North Island from populations to both the north and the south. In summary, we identified linked avian habitats, as well as isolated and inbred populations and suggest that Bellbirds are good re‐colonizers. We emphasize the importance of genetic studies that assess animal dispersal among newly rehabilitated habitat patches.     

The genetic basis of color‐related local adaptation in a ring‐like colonization around the Mediterranean

Uncovering the genetic basis of phenotypic variation and the population history under which it established is key to understand the trajectories along which local adaptation evolves. Here, we investigated the genetic basis and evolutionary history of a clinal plumage color polymorphism in European barn owls (Tyto alba). Our results suggest that barn owls colonized the Western Palearctic in a ring‐like manner around the Mediterranean and meet in secondary contact in Greece. Rufous coloration appears to be linked to a recently evolved nonsynonymous‐derived variant of the melanocortin 1 receptor (MC1R) gene, which according to quantitative genetic analyses evolved under local adaptation during or following the colonization of Central Europe. Admixture patterns and linkage disequilibrium between the neutral genetic background and color found exclusively within the secondary contact zone suggest limited introgression at secondary contact. These results from a system reminiscent of ring species provide a striking example of how local adaptation can evolve from derived genetic variation.     

Crab herbivory regulates re‐colonization of disturbed patches in a southwestern Atlantic salt marsh

Recent work exploring the effects of physical stress and herbivory on secondary succession in estuarine plant communities agrees with basic stress models and reveal that herbivory is an important force in brackish and oligohaline marshes but negligible in physically stressful salt marshes. In these systems, herbivores are terrestrial, and thus negatively affected by the same stressful factors that affect marsh plants (i.e. frequent flooding or high salinities). We evaluated the effects of a marine herbivore (i.e. the crab Neohelice granulata) on plant secondary succession in a southwestern Atlantic salt marsh. Field surveys revealed that disturbance‐generated bare patches have harsh physical conditions and that their edges suffer higher herbivore pressure compared to the marsh matrix. A factorial experiment demonstrated that asexual expansion of the surrounding plants is the only possible mechanism to re‐colonize disturbed patches and that crab exclusion can increase this colonization rate by more than 30 times. Our results show that even in highly stressful environments, herbivores strongly impact marsh structure by regulating patch recovery. The synergism of physical stress and herbivory may make plant succession an extremely slow process and lead to the prevalence of bare areas.     

Long‐term colonization ecology of forest‐dwelling species in a fragmented rural landscape – dispersal versus establishment

Species colonization in a new habitat patch is an efficiency indicator of biodiversity conservation. Colonization is a two‐step process of dispersal and establishment, characterized by the compatibility of plant traits with landscape structure and habitat conditions. Therefore, ecological trait profiling of specialist species is initially required to estimate the relative importance of colonization filters. Old planted parks best satisfy the criteria of a newly created and structurally matured habitat for forest‐dwelling plant species. We sampled species in 230 ancient deciduous forests (source habitat), 74 closed‐canopy manor parks (target habitats), 151 linear wooded habitats (landscape corridors), and 97 open habitats (isolating matrix) in Estonia. We defined two species groups of interest: forest (107 species) and corridor specialists (53 species). An extra group of open habitat specialists was extracted for trait scaling. Differing from expectations, forest specialists have high plasticity in reproduction mechanisms: smaller seeds, larger dispersules, complementary selfing ability, and diversity of dispersal vectors. Forest specialists are shorter, less nutrient‐demanding and mycorrhizal‐dependent, stress‐tolerant disturbance‐sensitive competitors, while corridor specialists are large‐seeded disturbance‐tolerant competitors. About 40% of species from local species pools have immigrated into parks. The historic forest area, establishment‐related traits, and stand quality enhance the colonization of forest specialists. The openness of landscape and mowing in the park facilitate corridor specialists. Species traits in parks vary between a forest and corridor specialist, except for earlier flowering and larger propagules. Forest species are not dispersal limited, but they continue to be limited by habitat properties even in the long term. Therefore, the shady parts of historic parks should be appreciated as important forest biodiversity‐enhancing landscape structures. The habitat quality of secondary stands can be improved by nurturing a heterogeneous shrub and tree layer, and modest herb layer management.     

Importance of assemblage‐level thinning: A field experiment in an alpine meadow on the Tibet plateau

Question: Which fraction of the decrease in species richness under fertilization can be explained by assemblage‐level thinning? Location: An alpine meadow on the eastern Tibet plateau. Methods: 60‐m² plots were randomly assigned to a control or one of four levels of ammonium phosphate fertilizer. Treatments were repeated for three years. The effect of as semblage‐level thinning was decided based on similarity in quadrats within and between fertilizing levels, bootstrap simulation based on random thinning of the high density (low production, low fertility) quadrats and correlation of species’ biomass in low fertility and high fertility. Results: Fertilization increased production, reduced species richness and reduced density of individuals. Heavily fertilized quadrats are more similar in species composition in 2000 but less similar in 2001 and 2002. Rarefaction showed that a decrease in density can account for 32.3‐42.9% decrease of species richness, but the simulated species richness is always significantly higher than the observed one. When production and species richness are similar at two levels of fertilization, species biomass in the higher fertility treatment is positively correlated with biomass at lower fertility. When the two fertilizer levels differed in production and species richness, there was no evidence of correlation in species biomass, suggesting that assemblage level thinning cannot explain all the loss of species. Conclusion: Although a decrease in density could explain much of the decrease (up to 42.9%) in species richness when this alpine meadow was fertilized, other important mechanisms such as interspecific competition cannot be ignored. Future studies should investigate the effect of assemblage level thinning on species diversity, and search for mechanisms responsible for a decrease in diversity.     

街区尺度城市内部动态度的量化——以深圳市为例

城市动态度反应城市土地利用/土地覆盖动态变化的剧烈程度,对其进行量化是理解城市景观变化和进行城市生态空间监管的基础。现有研究主要聚焦城市扩张引起的特定地类(如人工表面、植被等)的动态变化,缺乏对城市内部精细尺度上(如街区尺度)景观动态的研究。以深圳市为例,首先利用多等级道路数据划分街区,进而基于高分辨率卫星影像解译的土地覆盖数据,利用土地利用动态度和土地利用强度指数量化街区尺度城市内部动态度。研究结果表明:(1)深圳市城市内部动态度较高,2017—2018年期间,14.93%的街区发生了不同程度的变化,热点区域主要分布在南山区、宝安区、盐田区等。(2)街区的变化包括多种地类的转变,其中,林地转变为裸土最为常见,占比为12.59%。由城市更新引起的地类变化也较普遍,如其他不透水地表向裸土的转移和建筑到裸地的转变分别为6.20%、5.59%。此外,深圳市街区的土地利用强度也存在较大差异,表现为土地利用强度增加的街区多分布在城市外围,而土地利用强度降低的街区则多分布在城市内部。(3)街区动态度与街区大小之间呈现非线性关系,街区动态度随着街区面积的增大,先急剧下降,后趋于平缓。本研究揭示了深圳市城市内部街区尺度上土地覆盖的动态变化特征,可为城市规划和生态空间管理提供科学支撑。     

The influence of non‐climate predictors at local and landscape resolutions depends on the autecology of the species

Species distribution models have come under criticism for being too simplistic for making robust future forecasts, partly because they assume that climate is the main determinant of geographical range at large spatial extents and coarse resolutions, with non‐climate predictors being important only at finer scales. We suggest that this paradigm might be obscured by species movement patterns. To explore this we used contrasting kangaroo (family Macropodidae) case studies: two species with relatively small, stable home ranges (Macropus giganteus and M. robustus) and three species with more extensive, adaptive ranging behaviour (M. antilopinus, M. fuliginosus and M. rufus). We predicted that non‐climate predictors will be most influential to model fit and predictive performance at local spatial resolution for the former species and at landscape resolution for the latter species. We compared residuals autocovariate – boosted regression tree (RAC‐BRT) model statistics with and without species‐specific non‐climate predictors (habitat, soil, fire, water and topography), at local‐ and landscape‐level spatial resolutions (5 and 50 km). As predicted, the influence of non‐climate predictors on model fit and predictive performance (compared with climate‐only models) was greater at 50 compared with 5 km resolution for M. rufus and M. fuliginosus and the opposite trend was observed for M. giganteus. The results for M. robustus and M. antilopinus were inconclusive. Also notable was the difference in inter‐scale importance of climate predictors in the presence of non‐climate predictors. In conclusion, differences in autecology, particularly relating to space use, may contribute to the importance of non‐climate predictors at a given scale, not model scale per se. Further exploration of this concept across a range of species is encouraged and findings may contribute to more effective conservation and management of species at ecologically meaningful scales.     

Changes in life‐history traits in an expanding moss species: phenotypic plasticity or genetic differentiation? A reciprocal transplantation experiment with Pogonatum dentatum

A transplant experiment was performed to investigate whether differences in life-history traits of the bryophyte Pogonatum dentatum that recently expanded its distribution range, were genetically or environmentally determined, or a combination of both. Plants were transplanted reciprocally between the original mountain area and a recently colonised lowland area. Vegetative biomass of annual segments and branches tended to be higher in the mountain area than in the lowland area. Reproductive investment was higher for plants transplanted to the lowland area, and lowland shoots tended to produce larger sporophytes than mountain shoots when placed in the same environment. Age of reproducing shoots showed no consistent pattern.
Native shoots were often outperformed by non-native shoots transplanted into the same site. Non-native shoots grew larger and produced larger sporophytes than native shoots. Much of the observed variation was at the site level instead of between mountain and lowland areas, with both genetic origin and environmental effects contributing together. Range expansion of P. dentatum may have taken place by dispersal from populations with shoots whose growth is plastic. Such shoots grow larger and potentially produce more spores for dispersal.     

How landscape dynamics link individual‐ to population‐level movement patterns: a multispecies comparison of ungulate relocation data

Aim To demonstrate how the interrelations of individual movements form large‐scale population‐level movement patterns and how these patterns are associated with the underlying landscape dynamics by comparing ungulate movements across species. Locations Arctic tundra in Alaska and Canada, temperate forests in Massachusetts, Patagonian Steppes in Argentina, Eastern Steppes in Mongolia. Methods We used relocation data from four ungulate species (barren‐ground caribou, Mongolian gazelle, guanaco and moose) to examine individual movements and the interrelation of movements among individuals. We applied and developed a suite of spatial metrics that measure variation in movement among individuals as population dispersion, movement coordination and realized mobility. Taken together, these metrics allowed us to quantify and distinguish among different large‐scale population‐level movement patterns such as migration, range residency and nomadism. We then related the population‐level movement patterns to the underlying landscape vegetation dynamics via long‐term remote sensing measurements of the temporal variability, spatial variability and unpredictability of vegetation productivity. Results Moose, which remained in sedentary home ranges, and guanacos, which were partially migratory, exhibited relatively short annual movements associated with landscapes having very little broad‐scale variability in vegetation. Caribou and gazelle performed extreme long‐distance movements that were associated with broad‐scale variability in vegetation productivity during the peak of the growing season. Caribou exhibited regular seasonal migration in which individuals were clustered for most of the year and exhibited coordinated movements. In contrast, gazelle were nomadic, as individuals were independently distributed and moved in an uncoordinated manner that relates to the comparatively unpredictable (yet broad‐scale) vegetation dynamics of their landscape. Main conclusions We show how broad‐scale landscape unpredictability may lead to nomadism, an understudied type of long‐distance movement. In contrast to classical migration where landscapes may vary at broad scales but in a predictable manner, long‐distance movements of nomadic individuals are uncoordinated and independent from other such individuals. Landscapes with little broad‐scale variability in vegetation productivity feature smaller‐scale movements and allow for range residency. Nomadism requires distinct integrative conservation strategies that facilitate long‐distance movements across the entire landscape and are not limited to certain migration corridors.     

Land-use diversity index: a new means of detecting diversity at landscape level

Preservation of ecological diversity is a guiding principle of landscape management and planning. Although diversity is often quantified with measurable indices, common approaches used to measure diversity, for example the Shannon–Weaver index, are not adequate for many landscape studies, because they are affected by scale and sampling efforts. A robust index for measurement of landscape diversity should be able to quantify distinctive components of a landscape mosaic. This paper provides a new diversity index for landscape studies that improves the measurement of diversity at landscape level. The key features of the method are inclusion of an implication of physical moment and quantification of diversity by placing greater weight on the structure and composition of a patch. We have named the new index the land-use diversity index, or LUDI, and have concluded that the LUDI is the preferred measure of diversity at landscape level.     

Life history variation across a riverine landscape: intermediate levels of disturbance favor sexual reproduction in the ant‐dispersed herb Ranunculus ficaria

Global climate change can fundamentally alter disturbance regimes across landscapes, but little is known about how species adjust their life histories to shifts in disturbance regimes. In plants, dispersal by seeds may permit rapid re‐colonization under frequent disturbances, but often seed‐dispersing animals may be absent and local dispersal by vegetative diaspores may be a more efficient means of occupying open space in the vicinity of the plant. We tested the effect of disturbances due to inundation on the investment in seed production by the ant‐dispersed plant, Ranunculus ficaria ssp. bulbifer. During seed ripening we collected 392 plants within a landscape mosaic of 39 sites with different levels of inundation. We measured the mass of fruits and other tissues (leafs, roots, bulbils, stalks) and described plant growth form. We found that fruit numbers and masses were more variable among plants than numbers and masses of other tissues. We then standardized fruit mass against the mass of other tissues and other growth‐form parameters. Standardized fruit mass showed a highly significantly hump‐shaped relationship with the level of inundation disturbances. This pattern was consistent across 12 small‐scale transects and thus not confounded by spatial autocorrelation within landscapes. The pattern was also confirmed by analyses that simultaneously accounted for disturbance and morphological co‐variables. We thus conclude that plants invested most heavily into reproduction by seeds under intermediate levels of disturbance. Under intermediate disturbance, seeds are beneficial for rapidly re‐colonizing open space after disturbance while the seed‐dispersers are still available. The life history of mutualists such as ant‐dispersed plants and ants may thus change across a landscape, reflecting small‐scale variation in the disturbance regime.     

A study to assess the cross‐reactivity of cellulose membrane‐bound peptides with detection systems: an analysis at the amino acid level

The growing demand for binding assays to study protein–protein interaction can be addressed by peptide array‐based methods. The SPOT technique is a widespread peptide‐array technology, which is able to distinguish semi‐quantitatively the binding affinities of peptides to defined protein targets within one array. The quality of an assay system used for probing peptide arrays depends on the well‐balanced combination of screening and read‐out methods. The former address the steady‐state of analyte capture, whereas the latter provide the means to detect captured analyte. In all cases, however, false‐positive results can occur when challenging a peptide array with analyte or detecting captured analyte with label conjugates. Little is known about the cross‐reactivity of peptides with the detection agents. Here, we describe at the amino acid level the potential of (i) 5‐(and 6)‐carboxytetramethylrhodamine (5(6)‐TAMRA), (ii) fluoresceinisothiocyanate in form of the peptide‐bound fluorescein‐substituted thiourea derivative (FITC), and (iii) biotin/streptavidin‐POD to cross‐react with individual amino acids in a peptide sequence. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.