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

The Theory of Island Biogeography

H umans have long been fascinated by the dynamism of free-flowing waters. Yet we have expended great effort to tame rivers for transportation, water supply, flood control, agriculture, and power generation. It is now recognized that harnessing of streams and rivers comes at great cost: Many rivers no longer support socially valued native species or sustain healthy ecosystems that provide important goods and services (Naiman et al. 1995, NRC 1992).

/pdf/the-natural-flow-regime-3j2upj9j41.pdf

The Natural Flow Regime

http://www.geog.ucl.ac.uk/~mdisney/teaching/PPRS/papers/foody.pdf

Status of land cover classification accuracy assessment

▪ Abstract Local habitat and biological diversity of streams and rivers are strongly influenced by landform and land use within the surrounding valley at multiple scales. However, empirical associations between land use and stream response only varyingly succeed in implicating pathways of influence. This is the case for a number of reasons, including (a) covariation of anthropogenic and natural gradients in the landscape; (b) the existence of multiple, scale-dependent mechanisms; (c) nonlinear responses; and (d) the difficulties of separating present-day from historical influences. Further research is needed that examines responses to land use under different management strategies and that employs response variables that have greater diagnostic value than many of the aggregated measures in current use. In every respect, the valley rules the stream.      H.B.N. Hynes (1975)

http://deq.idaho.gov/media/525804-Landscapes_Riverscapes_Influence_landuse_stream_ecosystems_Allan_2004.pdf

Landscapes and Riverscapes: The Influence of Land Use on Stream Ecosystems

This report describes a number of substructural features which can help to identify compounds that appear as frequent hitters (promiscuous compounds) in many biochemical high throughput screens. The compounds identified by such substructural features are not recognized by filters commonly used to identify reactive compounds. Even though these substructural features were identified using only one assay detection technology, such compounds have been reported to be active from many different assays. In fact, these compounds are increasingly prevalent in the literature as potential starting points for further exploration, whereas they may not be.

/pdf/new-substructure-filters-for-removal-of-pan-assay-3e3dudtvn0.pdf

New Substructure Filters for Removal of Pan Assay Interference Compounds (PAINS) from Screening Libraries and for Their Exclusion in Bioassays

Measures of ecosystem structure and function derived from analysis of flows.

Many regulated streams are characterized by high variable and unpredictable flow regimes. Since changes in streamflow directly modify physical habitat, streams with such highly variable flows provide highly unstable aquatic habitats. We evaluated the effect of artificial streamflow fluctuations on stream fish communities by comparing fish densities, in species and habitat groups, between two rivers differing in daily flow regime: on with with a natural flow, and one with highly regulated flows. We developed a simple model describing the relationship between available streams habitat and its use by 15 species or size classes of fish in the natural river. Species and size classes that used a specific set of microhabitat conditions were identified by comparing habitat characteristics for samples with and without each type of fish; for fish that used a particular type of microhabitat, we grouped species and size classes according to similarity in microhabitat use. Next, we categorized stream habitat samples in both the natural and regulated rivers into groups on the basis of fish habitat use criteria. Fish densities for each fish and habitat group were ten individually compared between the two rivers. An abundant (>90% of all fish) and diverse (nine species) group of small—fish species and size classes were restricted to microhabitat that was characterized as shallow in depth, slow in current velocity, and concentrated along stream margins. This group of fish was reduced in abundance in the regulated river and absent at the study site with the greatest flow fluctuation. Another fish group included species and size classes that used either a broad range of habitat or a microhabitat that was deep, fast, or both, and was concentrated in midstream areas. The density of fish in this group was higher in the regulated river and peaked at the sites with the greatest fluctuations in flow. Highly variable and unpredictable flow regimes appear to be a high—frequency disturbance that effects fish differently depending on the way they use stream habitat and acts to reduce community complexity.

Streamflow regulation and fish community structure

Man's impact on his environment often involves a gradient of subsidy and stress effects, which vary along nutrient, climatic, developmental (successional), and other important ecological gradients. Since performance curves that simulate subsidy-stress responses are unimodal, the zone of optimality can be determined on the basis of relatively few experiments where specific input factors are of concern. We have emphasized the importance of assessing the response of the perturbed system at different levels of organization. In practice, at least two levels, the ecosystem and the population (species) level, are necessary for a complete impact evaluation. We have stressed the need for judicious use of terms and the desirability of sticking as closely as possible to basic dictionary definitions if one expects to communicate with large numbers of people. Most of all, we have tried to show how a systems approach, based on simple flow diagram models, can clarify the intended meaning of terms and the cause-and-effect relations, as well as identify the basic processes involved.

Perturbation Theory and the Subsidy-Stress Gradient

Several models of energy and nutrient flow on the Hubbard Brook Ecosystem, New Hampshire, USA, were analyzed for the pattern of flow through the models, cycling index CI, path length PL, and straight—though path length PLs. CI represents the proportion of flow that cycles through components of the system. PL is the average number of components that a unit of flow passes through on its way from inflow to outflow. PLs is that portion of PL attributable to flow passing straight through the system without cycling at all. The energy model had low values for PL, PLs, and CI, compared to nutrient models. Flow measures for nutrients varied greatly. The order of the elements in terms of CI and K > Na > N > Ca > P > Mg > S. This could be explained by the mobility and biological role of each element, although Na is somewhat anomalous. PL was very large for K (24.3) but small for S (5.2). PLs was near 4 for all elements but Na (2.6) and S (2.5). This was a reflection of different flow patterns for Na, which flows primarily between available nutrients and belowground biomass, and S, which flows primarily between available nutrients, and below— and aboveground biomass. Sulfur returns to available nutrients via stemflow and throughflow, bypassing the forest floor. The remaining elements cycle between above— and belowground biomass, forest floor, and available nutrients. Three different models of Ca flow were compared. When all three models were analyzed using the same nutrient flux data, flow measures become very close, despite structural differences in the models. For these models, flow values were more important than the architecture of the models in determining cycling and flow characteristics.

John T. Finn

Papers

Measures of ecosystem structure and function derived from analysis of flows.

Streamflow regulation and fish community structure

Perturbation Theory and the Subsidy-Stress Gradient

Flow analysis of models of the Hubbard Brook Ecosystem.

17 – Propagation of Cause in Ecosystems