Diane M. Debinski

Bio: Diane M. Debinski is an academic researcher from Montana State University. The author has contributed to research in topics: Species richness & Grazing. The author has an hindex of 35, co-authored 125 publications receiving 5746 citations. Previous affiliations of Diane M. Debinski include University of Wyoming & Iowa State University.

A survey and overview of habitat fragmentation experiments.

Abstract: Habitat destruction and fragmentation are the root causes of many conservation problems. We conducted a literature survey and canvassed the ecological community to identify experimental studies of terrestrial habitat fragmentation and to determine whether consistent themes were emerging from these studies. Our survey revealed 20 fragmentation experiments worldwide. Most studies focused on effects of fragmentation on species richness or on the abundance(s) ofparticular species. Other important themes were the effect offragmentation in interspecific interactions, the role of corridors and landscape connectivity in in- dividual movements and species richness, and the influences of edge effects on ecosystem services. Our com- parisons showed a remarkable lack of consistency in results across studies, especially with regard to species richness and abundance relative to fragment size. Experiments with arthropods showed the best fit with the- oretical expectations of greater species richness on larger fragments. Highly mobile taxa such as birds and mammals, early-successional plant species, long-lived species, and generalist predators did not respond in the "expected" manner. Reasons for these discrepancies included edge effects, competitive release in the habitat fragments, and the spati.al scale of the experiments. One of the more consistently supported hypotheses was that movement and species richness are positively affected by corridors and connectivity, respectively. Tran- sient effects dominated many systems;,for example, crowding of individuals on fragments commonly was ob- served afterfragmentation, followed by a relaxation toward lower abundance in subsequentyears. The three long-term studies (?14 years) revealed strong patterns that would have been missed in short-term investiga- tions. Our results emphasize the wide range of species-specific responses to fragmentation, the need for eluci- dation of behavioral mechanisms affecting these responses, and the potentialfor changing responses to frag- mentation over time.

Connecting Soil Organic Carbon and Root Biomass with Land-Use and Vegetation in Temperate Grassland

Abstract: Soils contain much of Earth’s terrestrial organic carbon but are sensitive to land-use. Rangelands are important to carbon dynamics and are among ecosystems most widely impacted by land-use. While common practices like grazing, fire, and tillage affect soil properties directly related to soil carbon dynamics, their magnitude and direction of change vary among ecosystems and with intensity of disturbance. We describe variability in soil organic carbon (SOC) and root biomass—sampled from 0–170 cm and 0–100 cm, respectively—in terms of soil properties, land-use history, current management, and plant community composition using linear regression and multivariate ordination. Despite consistency in average values of SOC and root biomass between our data and data from rangelands worldwide, broad ranges in root biomass and SOC in our data suggest these variables are affected by other site-specific factors. Pastures with a recent history of severe grazing had reduced root biomass and greater bulk density. Ordination suggests greater exotic species richness is associated with lower root biomass but the relationship was not apparent when an invasive species of management concern was specifically tested. We discuss how unexplained variability in belowground properties can complicate measurement and prediction of ecosystem processes such as carbon sequestration.

Life-history traits predict species responses to habitat area and isolation: a cross-continental synthesis

Abstract: There is a lack of quantitative syntheses of fragmentation effects across species and biogeographic regions, especially with respect to species life-history traits. We used data from 24 independent studies of butterflies and moths from a wide range of habitats and landscapes in Europe and North America to test whether traits associated with dispersal capacity, niche breadth and reproductive rate modify the effect of habitat fragmentation on species richness. Overall, species richness increased with habitat patch area and connectivity. Life-history traits improved the explanatory power of the statistical models considerably and modified the butterfly species-area relationship. Species with low mobility, a narrow feeding niche and low reproduction were most strongly affected by habitat loss. This demonstrates the importance of considering life-history traits in fragmentation studies and implies that both species richness and composition change in a predictable manner with habitat loss and fragmentation.

Beyond Species Richness: Community Similarity as a Measure of Cross-Taxon Congruence for Coarse-Filter Conservation

Abstract: The use of a surrogate taxon in conservation planning has become questionable because recent evidence suggests that the correlation of species richness between pairs of taxa is highly variable both taxo- nomically and geographically. Species richness is only one measure of species diversity, however, and recent studies suggest that investigations of cross-taxon congruence should consider a broader range of assessment techniques. The cross-taxon congruence of community similarity between sites among taxa has rarely been examined and may be the most relevant measure of species diversity in the context of coarse-filter conservation strategies. We examined cross-taxon congruence patterns of species richness and community similarity (Bray- Curtis similarity) among birds, butterflies, and vascular plants in montane meadow habitats in the Greater Yellowstone Ecosystem. Although patterns of species richness (Spearman rank correlation) varied between taxa, we consistently found a positive correlation in community similarity (Mantel test) between all pair-wise comparisons of the three taxa (e.g., sites with similar bird communities also had similar butterfly communi- ties). We suggest that the success of a surrogate taxon depends on the technique used to assess surrogacy and the specific approach to conservation planning. In the context of coarse-filter conservation, measures of com- munity similarity may be more appropriate than measures of species richness. Furthermore, the cross-taxon congruency of community similarity in our study suggests that coarse-filter conservation may be tenable in montane meadow communities.

Butterfly responses to habitat edges in the highly fragmented prairies of Central Iowa

Abstract: Summary 1 The behaviour of two butterfly species, a habitat specialist (Speyeria idalia) and a habitat generalist (Danaus plexippus), was tracked at four prairie edges to determine the extent to which edges act as a barrier to emigration. The four edge types studied were crop, road, field and treeline. The edges differed in structure ranging from high-contrast (treeline) to low-contrast (field). 2 S. idalia, the habitat specialist, responded strongly to all edges, even those with low structural contrast. However, S. idalia’s response was strongly affected by conspecific density at crop and field edges; individuals were less likely to exit from high density plots. S. idalia responded to edges both by turning to avoid crossing them, and returning to the plot if they had crossed. 3 D. plexippus responded strongly only to treeline edges. Wind direction and time of year were important factors influencing behaviour at edges for this species. Conspecific density was not a significant factor affecting their behaviour. D. plexippus responded to edges by not crossing them, but rarely returned once they had crossed. 4 In highly fragmented landscapes, such as the one in which this study occurred, butterflies which show little or no response to edges may exhibit high emigration rates because of the high probability of encountering an edge in small habitat patches. Butterflies may respond strongly to even subtle habitat boundaries, but those responses may be modified by the edge structure, local environment or other conditions. Therefore, modifying edge structure may be a way to influence emigration rates, making it a useful tool for conservation.

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Effects of Habitat Fragmentation on Biodiversity

Abstract: ■ Abstract The literature on effects of habitat fragmentation on biodiversity is huge. It is also very diverse, with different authors measuring fragmentation in different ways and, as a consequence, drawing different conclusions regarding both the magnitude and direction of its effects. Habitat fragmentation is usually defined as a landscape-scale process involving both habitat loss and the breaking apart of habitat. Results of empirical studies of habitat fragmentation are often difficult to interpret because (a) many researchers measure fragmentation at the patch scale, not the landscape scale and (b) most researchers measure fragmentation in ways that do not distinguish between habitat loss and habitat fragmentation per se, i.e., the breaking apart of habitat after controlling for habitat loss. Empirical studies to date suggest that habitat loss has large, consistently negative effects on biodiversity. Habitat fragmentation per se has much weaker effects on biodiversity that are at least as likely to be positive as negative. Therefore, to correctly interpret the influence of habitat fragmentation on biodiversity, the effects of these two components of fragmentation must be measured independently. More studies of the independent effects of habitat loss and fragmentation per se are needed to determine the factors that lead to positive versus negative effects of fragmentation per se. I suggest that the term “fragmentation” should be reserved for the breaking apart of habitat, independent of habitat loss.

Defaunation in the Anthropocene

Abstract: We live amid a global wave of anthropogenically driven biodiversity loss: species and population extirpations and, critically, declines in local species abundance. Particularly, human impacts on animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire: 67% of monitored populations show 45% mean abundance decline. Such animal declines will cascade onto ecosystem functioning and human well-being. Much remains unknown about this “Anthropocene defaunation”; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet’s sixth mass extinction and also a major driver of global ecological change.

Animal species diversity driven by habitat heterogeneity/diversity: the importance of keystone structures

Abstract: Aim In a selected literature survey we reviewed studies on the habitat heterogeneity–animal species diversity relationship and evaluated whether there are uncertainties and biases in its empirical support. Location World-wide. Methods We reviewed 85 publications for the period 1960–2003. We screened each publication for terms that were used to define habitat heterogeneity, the animal species group and ecosystem studied, the definition of the structural variable, the measurement of vegetation structure and the temporal and spatial scale of the study. Main conclusions The majority of studies found a positive correlation between habitat heterogeneity/diversity and animal species diversity. However, empirical support for this relationship is drastically biased towards studies of vertebrates and habitats under anthropogenic influence. In this paper, we show that ecological effects of habitat heterogeneity may vary considerably between species groups depending on whether structural attributes are perceived as heterogeneity or fragmentation. Possible effects may also vary relative to the structural variable measured. Based upon this, we introduce a classification framework that may be used for across-studies comparisons. Moreover, the effect of habitat heterogeneity for one species group may differ in relation to the spatial scale. In several studies, however, different species groups are closely linked to ‘keystone structures’ that determine animal species diversity by their presence. Detecting crucial keystone structures of the vegetation has profound implications for nature conservation and biodiversity management.

Landscape modification and habitat fragmentation: a synthesis

Abstract: Landscape modification and habitat fragmentation are key drivers of global species loss. Their effects may be understood by focusing on: (1) individual species and the processes threatening them, and (2) human-perceived landscape patterns and their correlation with species and assemblages. Individual species may decline as a result of interacting exogenous and endogenous threats, including habitat loss, habitat degradation, habitat isolation, changes in the biology, behaviour, and interactions of species, as well as additional, stochastic threats. Human-perceived landscape patterns that are frequently correlated with species assemblages include the amount and structure of native vegetation, the prevalence of anthropogenic edges, the degree of landscape connectivity, and the structure and heterogeneity of modified areas. Extinction cascades are particularly likely to occur in landscapes with low native vegetation cover, low landscape connectivity, degraded native vegetation and intensive land use in modified areas, especially if keystone species or entire functional groups of species are lost. This review (1) demonstrates that species-oriented and pattern-oriented approaches to understanding the ecology of modified landscapes are highly complementary, (2) clarifies the links between a wide range of interconnected themes, and (3) provides clear and consistent terminology. Tangible research and management priorities are outlined that are likely to benefit the conservation of native species in modified landscapes around the world.