Mechanistic modelling of animal dispersal offers new insights into range expansion dynamics across fragmented landscapes

Understanding and predicting the dynamics of range expansion is a major topic in ecology both for invasive species extending their ranges into non‐native regions and for species shifting their natural distributions as a consequence of climate change. In an increasingly modified landscape, a key question is ‘how do populations spread across patchy landscapes?‘ Dispersal is a central process in range expansion and while there is a considerable theory on how the shape of a dispersal kernel influences the rate of spread, we know much less about the relationships between emigration, movement and settlement rules, and invasion rates. Here, we use a simple, single species individual‐based model that explicitly simulates animal dispersal to establish how density‐dependent emigration and settlement rules interact with landscape characteristics to determine spread rates. We show that depending on the dispersal behaviour and on the risk of mortality in the matrix, increasing the number of patches does not necessarily maximise the spread rate. This is due to two effects: first, individuals dispersing at the expanding front are likely to exhibit lower net‐displacement as they typically do not travel far before finding a patch; secondly, with increasing availability of high quality habitat, density‐dependence in emigration and settlement can decrease the number of emigrants and their net‐displacement. The rate of spread is ultimately determined by the balance between net travelled distance, the dispersal mortality and the number of dispersing individuals, which in turn depend on the interaction between the landscape and the species’ dispersal behaviour. These results highlight that predicting spread rates in heterogeneous landscapes is a complex task and requires better understanding of the rules that individuals use in emigration, transfer and settlement decisions.     

Spatial dynamics of Microtus vole populations in continuous and fragmented agricultural landscapes

Small mammal populations often exhibit large-scale spatial synchrony, which is purportedly caused by stochastic weather-related environmental perturbations, predation or dispersal. To elucidate the relative synchronizing effects of environmental perturbations from those of dispersal movements of small mammalian prey or their predators, we investigated the spatial dynamics of Microtus vole populations in two differently structured landscapes which experience similar patterns of weather and climatic conditions. Vole and predator abundances were monitored for three years on 28 agricultural field sites arranged into two 120-km-long transect lines in western Finland. Sites on one transect were interconnected by continuous agricultural farmland (continuous landscape), while sites on the other were isolated from one another to a varying degree by mainly forests (fragmented landscape). Vole populations exhibited large-scale (>120 km) spatial synchrony in fluctuations, which did not differ in degree between the landscapes or decline with increasing distance between trapping sites. However, spatial variation in vole population growth rates was higher in the fragmented than in the continuous landscape. Although vole-eating predators were more numerous in the continuous agricultural landscape than in the fragmented, our results suggest that predators do not exert a great influence on the degree of spatial synchrony of vole population fluctuations, but they may contribute to bringing out-of-phase prey patches towards a regional density level. The spatial dynamics of vole populations were similar in both fragmented and continuous landscapes despite inter-landscape differences in both predator abundance and possibilities of vole dispersal. This implies that the primary source of synchronization lies in a common weather-related environment.     

Targeting habitat management in fragmented landscapes: a case study with forest vertebrates

Although improving the quality of habitat patches in fragmented landscapes is a main conservation target few studies have examined patch management in relation to the surrounding landscape. Tackling such an issue needs a cross-scale approach that takes the hierarchical nature of landscapes into account. Here I show the results of a cross-scale study focusing on the distribution patterns of ten forest vertebrate species (birds and mammals). The overarching goal of this study was to understand the strength of patch scale determinants of distribution, following the appropriate control for relevant landscape properties (e.g. habitat loss vs. habitat subdivision). I show how, after controlling for uncertainty in the detection of the species and for the role of landscape properties, patch scale variables still played an important role in determining occupancy patterns of forest vertebrates. For some species variation in the values of patch structure variables increased occurrence probability with only moderate levels of habitat loss, highlighting the fact that habitat management should be targeted towards precise landscape conditions. In other cases the effect of patch variables was strong therefore variation in their values always brought substantial increase/decrease of presence probability. Overall these results strongly suggest that habitat management should never be carried out irrespective of the properties of the surrounding landscape, rather, it should be carefully targeted towards specific landscape contexts (e.g. above a certain amount of habitat) where it is more likely to be effective.     

Conserving small and fragmented populations of large mammals: Non-invasive genetic sampling in an isolated population of Asian elephants in Nepal

The Terai is one of the world's most spectacular landscapes, encompassing parts of Nepal and northern India. This area used to harbour large and continuous populations of charismatic species like elephants, tigers and rhinoceros. However, recent habitat fragmentation reduced these populations into small, partially or completely isolated remnants. The largest of these fragments in Nepal is the Bardia National Park. Here, the elephant population was functionally extinct in the early 1970s and -80s, but was rescued by a considerable number of immigrants in 1994. In order to assess population size, sex ratio, age structure, and levels of genetic variation, we carried out non-invasive genetic sampling, using elephant dung as the source of DNA. A capture-mark-recapture estimate of population size suggested that there were 57 individuals in the study area, which agrees well with field observations. Notably, a strongly male-biased sex ratio was evident among sub-adult individuals. This observation suggests the presence of sub-adult immigrants in the population, which was supported by formal migrant detection analysis. Genetic variation was quite high and the evidence for male immigrants suggests that there are good prospects for maintenance of genetic diversity. A decade ago a large-scale project was initiated in the Terai region to link remaining populations of large mammals through dispersal corridors. The program is basically founded on the assumption that habitat fragments are isolated with little or no migration between them. Our results indicate that this may not be the case, at least not for the Asian elephant in western Nepal, which therefore reduces the alleged extinction risk from genetic erosion and stochastic demographic events.     

Habitat selection and the change in distribution of asian elephants in Mengyang Protected Area, Yunnan, China

Elephants were confined to Mengyang Protected Area in China and their distribution range had reduced greatly compared to past records. A preliminary study of habitat selection by Asian elephantsElephas maximus Linnaeus, 1758 and their distribution was conducted in Mengyang Protected Area and its surrounds using site visits and transect surveys from July 2003 to December 2006. Although no variable significantly influenced their habitat selection, elephants still showed preference for altitudes between 900 and 1200 m, gradients <30°, and orientations to the south-east, south and south-west. Human activities, including habitat transformation and degradation, disturbance by large infrastructure and poaching were considered to be the main factors inducing elephant distribution changes.     

Plastic ingestion in Asian elephants in the forested landscapes of Uttarakhand,India

Ecological impacts of plastic contamination on marine environment have been documented extensively, however its spread and impacts on terrestrial and freshwater fauna are still poorly understood. In the present study, we investigated diet of Asian elephant (Elephas maximus indicus) for plastic ingestion around forested habitats of Uttarakhand state in India. We quantified plastic particles and other anthropogenic waste from elephant dung samples collected from edges and interiors of forest areas, confirming plastic ingestion by this endangered mammal species. Each human-derived item was identified, measured, and sub-categorized into plastic or other anthropogenic waste. About one-third (32%) of the elephant dung samples showed presence of anthropogenic waste. Plastic particles ranging from size 1–355 mm, comprised of 85% of the waste recovered from elephant dung samples (47.08 ± 12.85 particles per sample). We found twice as many plastic particles (85.27 ± 33.7/ 100 g) in samples collected from inside forest as compared to forest edge (35.34 ± 11.14 plastic particles/100 g). A higher count (34.79 ± 28.41 items/100 g sample) of non-biodegradable anthropogenic waste (glass, metal, rubber bands, clay pottery and tile pieces) was obtained from samples collected inside the forest area samples as compared to forest edge samples (9.44 ± 1.91items/100 g). There were higher proportion of macroplastic (>5 mm) retrieved than microplastic (1–5 mm) in the elephant dung. The present study is the first systematic documentation of non-biodegradable waste ingestion by Asian elephants. High plastic presence in elephant dung highlights its widespread use near protected habitats and lack of waste segregation practices underlining the vulnerability of wild animals to plastic ingestion risk. We provide recommendations for developing a comprehensive solid waste management strategy to mitigate the threat of plastic pollution around critical elephant habitats in India.     

Competing populations on fragmented landscapes with spatially structured heterogeneities: improved landscape generation and mixed dispersal strategies

Interactions between two species competing for space were studied using stochastic spatially explicit lattice-based simulations as well as pair approximations. The two species differed only in their dispersal strategies, which were characterized by the proportion of reproductive effort allocated to long-distance (far) dispersal versus short-distance (near) dispersal to adjacent sites. All population dynamics took place on landscapes with spatially clustered distributions of suitable habitat, described by two parameters specifying the amount and the local spatial autocorrelation of suitable habitat. Whereas previous results indicated that coexistence between pure near and far dispersers was very rare, taking place over only a very small region of the landscape parameter space, when mixed strategies are allowed, multiple strategies can coexist over a much wider variety of landscapes. On such spatially structured landscapes, the populations can partition the habitat according to local conditions, with one species using pure near dispersal to exploit large contiguous patches of suitable habitat, and another species using mixed dispersal to colonize isolated smaller patches (via far dispersal) and then rapidly exploit those patches (via near dispersal). An improved mean-field approximation which incorporates the spatially clustered habitat distribution is developed for modeling a single species on these landscapes, along with an improved Monte Carlo algorithm for generating spatially clustered habitat distributions.      

Community relaxation in fragmented landscapes: the relation between species richness, area and age

Estimates of species loss due to habitat destruction are normally based on calculations employing the species–area relation, S = cA ^z . The validity of this approach is based on the assumption that the value of the exponent ( z ) defining the slope of the species–area relation in nonfragmented communities is at a steady state and that z is thus a constant. However, departure from such an assumption renders this approach unreliable. Here I report the results from a natural field experiment using "model" bryophyte-based microlandscapes designed to follow the species richness dynamics of microarthropod communities postfragmentation. Community isolation due to fragmentation initiated a delayed community relaxation process and resulted in substantial local extinction. Over the period of the experiment z declined in the control communities and yet remained fairly stable in the fragmented communities. I conclude that predictions of species loss due to habitat fragmentation that do not take into account the fact that often z may not be a constant may lead to error-prone predictions of future species loss.     

Distribution and abundance of dung beetles in fragmented landscapes

Related species utilising similar resources are often assumed to show similar spatial population structures and dynamics. This paper reports substantial ecological variation within a set of Aphodius dung beetles occurring in the same patchily distributed resource, livestock dung in pastures. We show how variation in habitat and resource selectivity, in the rate of movements between pastures, and in the distribution of local population sizes all contribute to interspecific differences in spatial population structures. Local dung beetle assemblages are compared between two landscapes with different densities of pastures. In one of the landscapes, we contrast the abundances and regional distributions of Aphodius before and after 15 years of rapid habitat loss. Different species show very dissimilar responses to changes in the structure of the landscape. Our results suggest that generalist Aphodius species, and specialist species with high dispersal powers, occur as large "patchy" populations in the landscape. In contrast, a strict pasture specialist species with limited dispersal powers (A. pusillus) forms classical metapopulations. At the community level, interspecific differences in spatial population structures make the local community composition a function of the structure of the surrounding landscape.     

Biochemical and structural insights into mesotrypsin: an unusual human trypsin

Thirty five years ago mesotrypsin was first isolated from the human pancreas. It was described as a minor trypsin isoform with the remarkable property of near total resistance to biological trypsin inhibitors. Another unusual feature of mesotrypsin was discovered later, when it was found that mesotrypsin has defective affinity toward many protein substrates of other trypsins. As the younger sibling of the two major trypsins secreted by the pancreas, cationic and the anionic trypsin, it has been speculated to represent an evolutionary waste with no apparent function. We know now that mesotrypsin is functionally very different from the other trypsins, with novel substrate specificity that hints at distinct physiological functions. Recently, evidence has begun to emerge implicating mesotrypsin in direct involvement in cancer progression. This review will explore the biochemical characteristics of mesotrypsin and structural insights into its specificity, function, and inhibition.     

Fungi: individuals, populations, and speciation

Under considerations are specific features of the fungal individuals associated with their mycelial life mode and affecting their population structure and speciation. Special attention is paid to the sympatric speciation which can be caused by trophic niche segregation, by use of different host plants, by invasion to the plants at different stage of their ontogeny, and by differences in the weather requirements. Decrease of genetic interchanges in subdivided populations promoting speciation without spatial isolation is achieved by homotallism and pseudohomotallism, by a cassette mechanism of switching among various breeding systems, and by complete lost of sexual process. Recombination reduction in agamic fungi is achieved by means of vegetative incompatibility. As the latter is similar functionally to the immune system (recognition of an alien culture and death of conjugated cells), it is possible that the fungi were the first to have developed mechanisms of sympatric speciation on the basis of the simpliest immune system.     

Nestedness in fragmented landscapes: a case study on birds, arboreal marsupials and lizards

Aim The potential nestedness of assemblages of birds, arboreal marsupials and lizards was examined in a fragmented landscape in south‐eastern Australia. We assessed which ecological processes were related to the presence or absence of nestedness, particularly in relation to previous autoecological studies in the same study area. Location Data were collected at Buccleuch State Forest, c. 100 km to the west of the Australian Capital Territory in south‐eastern Australia. Methods Presence/absence matrices were compiled for birds (40 pine sites, 40 continuous forest sites, 43 fragments), arboreal marsupials (41 continuous forest sites, 39 fragments) and lizards (30 sites including all landscape elements) from a range of field surveys conducted since 1995. Nestedness was analysed using a standardized discrepancy measure, and statistical significance was assessed using the RANDNEST null model. For birds, species thought to be extinction‐prone were analysed separately to assess if assemblages comprising extinction‐prone species were more strongly nested than others. Also, sites with a substantial amount of Eucalyptus radiata were analysed separately to assess whether nestedness was stronger if environmental heterogeneity was minimized. Results The assemblages of lizards and arboreal marsupials were not nested, probably because of qualitative differences between species in response to environmental conditions. The assemblages of birds in fragments and pine sites were significantly nested, but nestedness was substantially stronger in fragments. For birds, nestedness appeared to be related to somewhat predictable extinction sequences, although there were many outliers in the analysis. Nestedness increased when extinction‐prone species were analysed by themselves. Nestedness decreased when environmental heterogeneity was minimized by including only sites dominated by E. radiata. Main conclusions In a given landscape, different vertebrate assemblages can respond in vastly different ways to fragmentation. Nestedness analyses can provide a useful overview of likely conservation issues in fragmented landscapes, for example by highlighting the possible roles of local extinction and immigration. However, nestedness analyses are a community‐level tool, and should be complemented by more detailed autoecological studies when applied in a conservation context.     

Habitat quality of source patches and connectivity in fragmented landscapes

Because spatial connectivity is critical to dispersal success and persistence of species in highly fragmented landscapes, the way that we envision and measure connectivity is consequential for biodiversity conservation. Connectivity metrics used for predictive modeling of spatial turnover and patch occupancy for metapopulations, such as with Incidence Function Models (IFM), incorporate distances to and sizes of possible source populations. Here, our focus is on whether habitat quality of source patches also is considered in these connectivity metrics. We propose that effective areas (weighted by habitat quality) of source patches should be better surrogates for population size and dispersal potential compared to unadjusted patch areas. Our review of a representative sample of the literature revealed that only 12.5% of studies incorporated habitat quality of source patches into IFM-type connectivity metrics. Quality of source patches generally was not taken into account in studies even if habitat quality of focal patches was included in analyses. We provide an empirical example for a metapopulation of a rare wetland species, the round-tailed muskrat (Neofiber alleni), demonstrating that a connectivity metric based on effective areas of source patches better predicts patch colonization and occupancy than a metric that used simple patch areas. The ongoing integration of landscape ecology and metapopulation dynamics could be hastened by incorporating habitat quality of source patches into spatial connectivity metrics applied to species conservation in fragmented landscapes.     

Distributions of occupied and vacant butterfly habitats in fragmented landscapes

Summary We found several rare UK butterflies to be restricted to relatively large and non-isolated habitat patches, while small patches and those that are isolated from population sources remain vacant. These patterns of occurrence are generated by the dynamic processes of local extinction and colonization. Habitat patches act as terrestrial archipelagos in which long-term population persistence, and hence effective long-term conservation, rely on networks of suitable habitats, sufficiently close to allow natural dispersal. Present address: School of Biological Sciences, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK     

Self-injurious behavior in rhesus monkeys: new insights into its etiology,physiology, and treatment

Self-injurious behavior (SIB) is a significant human health problem frequently associated with profound intellectual disabilities, genetic diseases, and psychiatric conditions. However, it also occurs in subclinical populations and appears to be on the rise in adolescents and young adults. SIB is also seen in a small percentage of nonhuman primates that injure themselves through biting. We have begun to characterize SIB in rhesus monkeys to identify some of the risk factors associated with this disorder, and to determine the parallels with the human condition. In our study population, 14% of individually housed monkeys (the vast majority of which are males) have a veterinary record for self-inflicted wounding. Wounding is rare, but self-directed biting is common. SIB can be elicited during aggressive altercations and may be associated with husbandry events. Some monkeys appear to be more vulnerable to acquiring SIB. This increased vulnerability is associated with certain social experiences in the first 2 years of life and with exposure to a larger number of moderately stressful events as compared to controls. Monkeys with SIB also have a dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, indicated by a blunted cortisol response to mild stressors. Our findings suggest that SIB may be a coping strategy to reduce arousal. Biting appears to rapidly lower an escalating heart rate. The potentially reinforcing effects of SIB may account for the failure of some treatment regimens. These findings are compared to studies of SIB in humans, and concordances are identified.