Paul M. Dolman

Reliable, verifiable and efficient monitoring of biodiversity via metabarcoding

To manage and conserve biodiversity, one must know what is being lost, where, and why, as well as which remedies are likely to be most effective. Metabarcoding technology can characterise the species compositions of mass samples of eukaryotes or of environmental DNA. Here, we validate metabarcoding by testing it against three high-quality standard data sets that were collected in Malaysia (tropical), China (subtropical) and the United Kingdom (temperate) and that comprised 55,813 arthropod and bird specimens identified to species level with the expenditure of 2,505 person-hours of taxonomic expertise. The metabarcode and standard data sets exhibit statistically correlated alpha- and beta-diversities, and the two data sets produce similar policy conclusions for two conservation applications: restoration ecology and systematic conservation planning. Compared with standard biodiversity data sets, metabarcoded samples are taxonomically more comprehensive, many times quicker to produce, less reliant on taxonomic expertise and auditable by third parties, which is essential for dispute resolution.

Density compensation in neotropical primate communities: evidence from 56 hunted and nonhunted Amazonian forests of varying productivity

Abstract Density compensation is a community-level phenomenon in which increases in the abundance of some species may offset the population decline, extirpation, or absence of other potentially interacting competitors. In this paper we examine the evidence for density compensation in neotropical primate assemblages using data from 56 hunted and nonhunted, but otherwise undisturbed, forest sites of Amazonia and the Guianan shields from which population density estimates are available for all diurnal primate species. We found good evidence of density compensation of the residual assemblage of nonhunted mid-sized species where the large-bodied (ateline) species had been severely reduced in numbers or driven to local extinction by subsistence hunters. Only weak evidence for density compensation, however, was detected in small-bodied species. These conclusions are based on the effects of ordinal measures of hunting pressure on the aggregate primate biomass across different size classes after controlling for the effects of forest type and productivity. These results are interpreted primarily in relation to patterns of niche partitioning between different primate functional groups or ecospecies. This study suggests that while overhunting drastically reduces the average body size in multi-species assemblages of forest vertebrates, depletion of large-bodied species is only partially offset (i.e. undercompensated) by smaller taxa.

The intensity of interference varies with resource density: evidence from a field study with snow buntings, Plectrophenax nivalis

Intake rates of snow buntings feeding on artificial seed patches were measured at different bird densities, for each of two different seed densities. Interference occurred in the low seed-density treatment, with intake rates declining at high bird densities. However, interference was not found in the high seeddensity treatment. The finding that the strength of interference may depend on resource density contradicts the hypothesis that the functional response is ratio-dependent (Arditi and Akçakaya 1990). The formulation for interference from Hassell and Varley (1969), and the models of Beddington (1975), Ruxton et al. (1992) and Holmgren (1995), also assume that the strength of interference is independent of resource density. The development of behaviour-based models that consider the relation between the intensity of interference, resource density and individual state may provide a more accurate description of the process of interference.

Combining Behaviour and Population Dynamics with Applications for Predicting Consequences of Habitat Loss

A population model for migratory vertebrates is developed by combining game theory models of foraging behaviour with population biology. Models of foraging behaviour which incorporate interference and resource depletion are developed to determine the density-dependent mortality occurring within sites. Population size can then be related to the strength of interference, the variance in competitive ability and the rate at which resources are depleted. The model is extended to predict evolutionarily stable migration strategies. This novel framework is then used to predict the population decline resulting from habitat loss.

Ecosystem and competition impacts of introduced deer

Numerous deer species have been introduced beyond their native range into ecosystems around the world. Their economic value leads to further accidental and deliberate releases and lack of control is contributing to range expansion in Australia, South America and Europe. Despite localised or regional concern, the scale and generality of detrimental impacts have not been widely recognised. We review the direct and indirect impacts on ecosystems and evidence for interspecific effects on native deer. In New Zealand, where large herbivores were previously absent, severe and novel impacts have been found in susceptible forests. Even where ecosystems contain native deer, invasion by taxonomically exotic deer species carries the risk of cascade effects on spatial plant dynamics and forest composition. In Patagonia, introduced deer have disrupted forest composition, whereas in Europe, ecosystem impacts of introduced species can differ from those of over-abundant native deer. Introduced Chinese muntjac (Muntiacus reevesi) within a coniferous forestry landscape in eastern England differ from native European roe deer (Capreolus capreolus) in their distribution of herbivory among differing habitats, and provide much lower rates of endozoochorous seed dispersal. Frequent concern is expressed that introduced deer species may have detrimental effects on native deer and other ungulates, although potential epidemiological effects have not been investigated. Apparent competition, with introduced prey resulting in increased predation rates on native deer, may be occurring between South American huemul (Hippocamelus bisulcus) and southern pudu (Pudu puda). Habitat and dietary overlap is often substantial among native and introduced ungulates, including deer, and exploitation competition is likely. Evidence includes spatial responses of native to non-native deer and negatively correlated changes in population abundance, but demographic mechanisms have not been demonstrated previously. In a coniferous forestry landscape in eastern England, substantial habitat and dietary overlap occurs between native roe deer and high-density introduced Chinese muntjac. This roe deer population has shown a reduction in body weight and fertility following establishment and increasing abundance of non-native Chinese muntjac, compatible with interspecific competition. European roe deer also appear susceptible to competition from larger grazing deer, including native red deer (Cervus elaphus) and introduced fallow (Dama dama). The widely introduced fallow deer may be a particularly effective competitor in sympatry with intermediate or concentrate feeders. There is need for further investigation of potential interactions of introduced and native deer species, and a wider recognition of the ecological impacts of introduced deer.

The ecological changes of Breckland grass heaths and the consequences of management

1. Sites of previous vegetation quadrats were revisited and reanalysed. There was a trend from characteristic Breckland communities with an abundance of lichens, winter annuals and cushion-forming mosses towards rank grassland. 2. A survey of Breckland grass heaths showed that the characteristic plant communities were found on rabbit-grazed but not sheep-grazed sites. 3. Sites which had been rotovated had shorter grass, a higher abundance of lichens and annual plants, less organic matter and greater rabbit activity than control plots. 4. Encouraging rabbits and disturbing the soil are essential to maintain these heaths.

Interpretations of sustainable agriculture in the UK

With the advent of Agenda 21, the blueprint for the transition to sustainable development for every nation on the globe, the issue of what exactly is sustainable agriculture is now being addressed, certainly throughout Europe. The food chain as a whole is the ultimate framework for a scrutiny of sustainability. However, this review looks only at the changing policy setting for seeking to define and implement sustainable agricultural practice in the UK. It analyses the key documents, reviews the state of science and assesses policy developments in wildlife/habitat management and the enhancement of scenery, from individual farms to whole landscapes. It concludes that there is neither the scientific understanding nor the economic tools to define and justify self-reliant agriculture on a farm-by-farm basis. Rather, it is more advantageous to devise integrated agricultural management arrangements for whole landscapes, crossing the borders of individual holdings. To do this, it is necessary to involve key stakeholders in the determination of the final landscape design. Then there is the tricky issue of how this may be implemented. That will be a sign that a policy for sustainable agriculture has come of age.

Spatial patterns of depletion imposed by foraging vertebrates : theory, review and meta-analysis

1. A simulation model is used to examine the spatial pattern of resource depletion imposed by vertebrates foraging in a heterogeneous environment; this may have important consequences for the dynamics of resource populations. It is assumed that consumers distribute themselves to maximize intake rates, that mutual interference occurs between competing consumers, and that the coefficient of interference, m, is less than one. 2. Where individuals are equal in their susceptibility to interference, depletion is density-dependent and variation in resource density is reduced towards zero. However, individuals often differ in their susceptibility to interference and incorporating such individual variation modifies the expected pattern of depletion. Spatial variation in resource density is no longer reduced to zero. After consumption of a given proportion of the total resource, spatial variation in the density of that remaining is greater when there is stronger interference, greater individual variation in susceptibility to interference, or a larger consumer population. With large individual variation and a large consumer population, domed or inversely density-dependent patterns of depletion are predicted, even where the coefficient of interference, m, is less than 1. 3. Field studies that quantify depletion of resource patches within the sampling range of a vertebrate population are reviewed and related to patterns predicted by the simulation model. The correlation between depletion and intial resource density is positive in 22 of 24 cases and significantly density-dependent (P < 0.05) in 11 of these, while only one correlation is significantly inversely density-dependent. The mean correlation in meta-analysis of vertebrate predators of invertebrate prey (22 cases) is significantly positive, showing that these groups tend to impose spatially density-dependent depletion. In contrast, reviews of invertebrate parasitoids find that inverse and positive density dependence are equally common. This difference may result partly from greater mobility of vertebrates, allowing them to sample the environment and distribute themselves closer to a rate-maximizing optimum. It is also possible that studies of vertebrates measure depletion at scales appropriate to the aggregative response of the consumers more frequently than studies of invertebrates.

Importance of climatic and environmental change in the demography of a multi-brooded passerine, the woodlark Lullula arborea

1. We examined the influence of local weather conditions on reproductive success, timing of breeding and survival in a population of a multi-brooded ground nesting passerine (woodlark Lullula arborea) over 35 years. 2. Woodlarks laid larger clutches when rainfall was low and temperature high during the egg-laying and pre-laying period. Nest success increased with higher temperatures during the nesting period. In successful nests, the number of chicks fledged per egg laid was greater when weather was drier during the brood stage. 3. Although woodlarks bred earlier in years with warmer early spring temperatures, with the onset of breeding varying by 25 days, there was no significant advance in the onset of breeding over the 35 years of study, due to considerable inter-annual variability, and no overall trend, in weather. 4. Simulation modelling of annual reproductive output demonstrated that earlier breeding could increase productivity by 23.5% in the warmest compared to the coldest year, due to birds having more nesting attempts. Other effects of weather on productivity affected breeding output to a lesser extent. 5. Effects of weather on productivity were minor compared to an increased rate of nest predation through the period of study, which reduced productivity by 49.8% by 2004 compared to 1971. 6. Turning points analysis identified three distinct demographic periods: from 1971 to 1988 the population grew slowly, during 1988-1999 the population grew rapidly, but after 1999 the population declined. Increased population growth after 1988 was associated with higher first-year survival rates (estimated using a population model). Population decline after 1999 was caused by a combination of reduced productivity (resulting from increased nest failure rates attributed to predation) and lower first-year survival rates, that appear unrelated to winter temperature. 7. Climate change (long-term changes in weather) did not explain the marked changes observed in the population trajectory over 35 years. We suggest that understanding effects of both climate and habitat change on populations is essential in predictive population modelling.

Using a GIS to select priority areas for conservation

Species richness and species rarity have been identified as important criteria when selecting conservation areas. Traditional approaches that choose sites based solely on local species richness often fail to protect those species most at risk. By assessing the representation of species across a network of sites, the protection of all species is more likely to be assured. A GIS approach based on the Maximal Covering Location Problem (MCLP) is compared to existing complementarity algorithms using data collected by the British Trust for Ornithology on the distribution of birds in Wales, UK. Despite a range of solutions depending on the algorithm used, the results presented here suggest that the overall pattern of species and the habitats with which they are associated remain largely unchanged. Community ordination is used to examine the species composition of sample units and to relate this to habitat composition. This shows that key marine, coastal and moorland sites are selected by most solutions while there is a greater degree of substitutability for sites that are predominantly woodland and farmland. The GIS-based MCLP approach is then extended by incorporating various priority weightings, considered in terms of conservation criteria relevant to birds in Wales.