Habitat fragmentation and connectivity : Spatial and temporal characteristics of the colonization process in plants

The connectivity between habitat patches or between populations indicates the potential for transfer of genetic material between habitat patches or populations. In plants, genetic material is usually transferred by dispersal of seeds or pollen. A sufficient level of connectivity is essential for regional species survival. Firstly, because it prevents inbreeding and loss of genetic material and adaptability. Secondly, because it is required for re-colonization of habitat patches in which populations have gone extinct, colonization of new habitat patches, migration, and range expansion. Connectivity is dependent on the dispersal ability of an organism and the spatial configuration of habitat patches or populations of that organism. Habitat fragmentation affects the spatial distribution of habitat patches or populations, and thus connectivity. The effect of habitat fragmentation on connectivity is relatively well-studied in animals, but not in plants; partly, because dispersal of plants is extremely difficult to assess. This study quantifies the effect of habitat fragmentation on connectivity for four plant species with different dispersal abilities (Centaurea jacea, Cirsium dissectum, Hypochaeris radicata and Succisa pratensis). The species main dispersal mechanism is seed dispersal by wind. Their habitat consists of nutrient-poor, wet to moist grasslands. The dispersal ability of the plant species was simulated with a mechanistic seed dispersal model. Simulation allows assessment of long-distance dispersal under different conditions, while measurement of long-distance dispersal is extremely difficult. Tests of simulation results against field data show that the model is accurate and gives more realistic results than previously developed models. Similarities and differences between the model and previous models are discussed. Simulations show that wind dispersal distances are not as long as commonly assumed; long-distance dispersal over >100 m is extremely rare in the current small populations, even for species with plumed seeds. The spatial habitat configuration in an 11x10 km study area in The Netherlands was mapped for a time series spanning the 20th century. The time series shows the rate and extent of habitat fragmentation. During the 20th century, more than 99.9 % of the grassland habitat was lost and minimum distances between the grassland patches increased from several meters to several hundreds of meters. The largest part of these effects occurred already during the first half of the 20th century. Habitat fragmentation greatly reduced the connectivity of the studied grassland habitat during the 20th century. This was mainly caused by the increasing distances between the habitat patches, but also by the decreasing sizes of the habitat patches and populations. Smaller populations produce fewer seeds and thus the probability that some of these seeds disperse over the long distances that separate habitat patches becomes even lower. Paradoxically, habitat fragmentation reduced the connectivity for plant species with plumed seeds with high long-distance dispersal ability more than for plant species with seeds with lower long-distance dispersal ability. This is because before fragmentation the connectivity was higher for the former plant species, but now populations of all species have become isolated regarding seed dispersal by wind. Suggestions for improvement of connectivity between habitat patches and between populations are give

Технологічне забезпечення виробничої потужності марганцевих кар’єрів при змінному попиті на рудну сировину

Запропонована технологічна схема, в якій розкривні уступи перерозподіляються по висоті у межах певної потужності розкриву при заданій продуктивності кар’єру, а верхній та нижче розташований уступи об’єднані та відробляються транспортно-відвальним способом, для чого у внутрішньому відвалі створюється додаткова приймальна ємність. Набула подальшого розвитку методика розрахунку виробничої потужності кар’єру. Удосконалено метод вибору комплексів технологічного устаткування для слабкостійких обводнених порід, де враховується коефіцієнт запасу стійкості укосів внутрішнього відвалу.The technological flow chart in which stripping bench are redistributed on a height within the limits of certain power of overburden at the set productivity of quarry is offered. It is proposed to merge overhead and below located benches and work out them by transport-dump method, for what an additional receiving capacity is created in an internal dump. The computational procedure of quarry production capacity is obtained the further development. The method of choice of complexes of technological equipment for weak-steady and watered rocks is improved. The coefficient of slope stability margin of internal dump is considered in this method

Critical transitions and evolutionary hysteresis in movement: Habitat fragmentation can cause abrupt shifts in dispersal that are difficult to revert

Under habitat fragmentation, plant species' survival hinges on the ability of individuals to disperse from one habitat patch to another. While there is evidence that severe habitat fragmentation leads to evolution of reduced dispersal ability and that such decreased mobility is generally detrimental for species' survival, it is unknown whether species adapt via a gradual loss in dispersal ability or via a sudden shift from frequent to infrequent dispersal between patches (i.e., a critical transition). Using both a spatially explicit deterministic and individual-based stochastic model of hydrochorous seed dispersal, we show that a small increase in inter-patch distance can generate an abrupt shift in plant seed dispersal strategy from long to short distances. Most importantly, we found that a substantial increase in connectivity between habitat fragments is required to reverse this loss of long-distance dispersal, due to an evolutionary hysteresis effect. Our theory prompts for re-consideration of the eco-evolutionary consequences of habitat fragmentation as restoring habitat connectivity may require restoration of much higher connectivity levels than currently assumed

Реакція української інтелігенції на Голокост: моделі ситуативної поведінки

The article regards the types of behawor attitude of the Ukranian intellegensy to the Holocaust, which was realigeb by nazi on the Kiev region

Dispersal of Plants by Waterbirds

The widespread distribution of fresh-water plants and of the lower animals, whether retaining the same identical form or in some degree modified, I believe mainly depends on the wide dispersal of their seeds and eggs by animals, more especially by fresh-water birds, which have large powers of flight, and naturally travel from one to another and often distant piece of water. — Charles Darwin (1859)Peer reviewe

Seed dispersal by dabbling ducks: an overlooked dispersal pathway for a broad spectrum of plant species

1. Dabbling ducks (Anatinae) are omnivorous birds that are widespread, numerous, highly mobile and often migratory, and therefore have great potential for (long distance) dispersal of other organisms, including plants. However, their ability to act as plant dispersal vectors has received little attention compared to frugivores and is often assumed to be relevant only for wetland species. 2. To evaluate the potential for plant dispersal by dabbling ducks, we collated and analysed existing data. We identified all plant species whose seeds have been recorded in the diets of the seven dabbling duck (Anas) species in the Western Palaearctic, as reported from gut content analyses. We then analysed the habitats and traits of these plant species to identify general patterns, and related these to data on gut passage survival and duck movements. 3. A large number of plant species (> 445 species of 189 genera and 57 families) have been recorded in the diet of dabbling ducks. These plant species represent a very wide range of habitats, including almost the full range of site fertility, moisture and light conditions, excluding only very dry and deeply shaded habitats. The ducks prefer seeds of intermediate sizes (1–10 mm3), which have good chances to survive gut passage, but also ingest smaller and larger seeds. Ingested seeds represent a wide range of dispersal syndromes, including fleshy fruits. Many species (62%) were not previously considered animal- dispersed in plant data bases, and 66% were not identified as bird-dispersed. Rarefaction analyses suggest that our analysis still greatly underestimates the total number of plant species ingested. 4. Synthesis. Dabbling ducks do not exclusively ingest seeds of wetland plants, which make up only 40% of the ingested species. Rather, they feed opportunistically on a wide cross-section of plant species available across the landscapes they inhabit. Given the millions of ducks, the hundreds to thousands of seeds ingested per individual on a daily basis, and known gut passage survival rates, this results in vast numbers of seeds dispersed by ducks per day. Internal seed dispersal by dabbling ducks appears to be a major dispersal pathway for a far broader spectrum of plant species than previously consideredPeer reviewe

Weak negative associations between avian influenza virus infection and movement behaviour in a key host species, the mallard Anas platyrhynchos

Animal movements may contribute to the spread of pathogens. In the case of avian influenza virus, [migratory] birds have been suggested to play a role in the spread of some highly pathogenic strains (e.g. H5N1, H5N8), as well as their low pathogenic precursors which circulate naturally in wild birds. For a better understanding of the emergence and spread of both highly pathogenic (HPAIV) and low pathogenic avian influenza virus (LPAIV), the potential effects of LPAIVs on bird movement need to be evaluated. In a key host species, the mallard Anas platyrhynchos, we tested whether LPAIV infection status affected daily local ( 100 m) movements by comparing movement behaviour 1) within individuals (captured and sampled at two time points) and 2) between individuals (captured and sampled at one time point). We fitted free-living adult males with GPS loggers throughout the autumn LPAIV infection peak, and sampled them for LPAIV infection at logger deployment and at logger removal on recapture. Within individuals, we found no association between LPAIV infection and daily local and regional movements. Among individuals, daily regional movements of LPAIV infected mallards in the last days of tracking were lower than those of non-infected birds. Moreover, these regional movements of LPAIV infected birds were additionally reduced by poor weather conditions (i.e. increased wind and/or precipitation and lower temperatures). Local movements of LPAIV infected birds in t

Seed dispersal by waterbirds: a mechanistic understanding by simulating avian digestion

Waterbirds disperse plant species via ingestion and egestion of seeds (endozoochory). However, our understanding about the regulating effects of seed traits, underlying mechanisms and possible (co)evolutionary processes is limited by our traditional reliance on data from feeding experiments with living waterbirds. Here, we overcome these limitations by developing and applying a new bioassay that realistically simulates digestive processes for Anseriformes waterbirds. We test three hypotheses: 1) seed survival and germination are most affected by mechanical digestion in the waterbird gizzard; 2) seed size, hardness, imbibition and shape regulate seed survival; and 3) plants growing in aquatic habitats benefit most from endozoochory by waterbirds. Experiments with 28 200 seeds of 48 plant species demonstrated species-specific seed survival that was entirely determined by digestion in the avian gizzard. Intestinal digestion did not affect seed survival but affected seed establishment (germinability and germination time) for 21% of the species. Large, hard seeds survived the simulations the best, in contrast to generally higher seed survival for smaller seeds during in vivo experiments. This mechanistically explains that small seeds escape digestive processes rather than being inherently more resistant (the ‘escape mechanism'), while large seeds are retained until fully digested or regurgitated (the ‘resistance and regurgitation mechanism'). Plants growing in wetter habitats had similar seed survival, but digestive processes stimulated their germinability and accelerated their germination more than for terrestrial plants. This indicates a relative advantage of endozoochory for plant species growing in wet habitats, possibly reflecting a co-evolutionary response related to dormancy breaking by gut passage. Simulating seed gut passage using a bioassay allowed establishing mechanisms and identifying relevant seed traits involved in seed dispersal by waterbirds. This information enhances our understanding of how animal species shape plant species distributions, which is extremely relevant now that current anthropogenic pressures already severely impact plant dispersal capacities

Environmental morphing enables informed dispersal of the dandelion diaspore

Animal migration is highly sensitised to environmental cues, but plant dispersal is considered largely passive. The common dandelion, Taraxacum officinale, bears an intricate haired pappus facilitating flight. The pappus enables the formation of a separated vortex ring during flight; however, the pappus structure is not static but reversibly changes shape by closing in response to moisture. We hypothesised that this leads to changed dispersal properties in response to environmental conditions. Using wind tunnel experiments for flow visualisation, particle image velocimetry, and flight tests we characterised the fluid mechanics effects of the pappus morphing. We also modelled dispersal to understand the impact of pappus morphing on diaspore distribution. Pappus morphing dramatically alters the fluid mechanics of diaspore flight. We found that when the pappus closes in moist conditions, the drag coefficient decreases and thus the falling velocity is greatly increased. Detachment of diaspores from the parent plant also substantially decreases. The change in detachment when the pappus closes increases dispersal distances by reducing diaspore release when wind speeds are low. We propose that moisture-dependent pappus-morphing is a form of informed dispersal allowing rapid responses to changing conditions