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).

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The Natural Flow Regime

The flow regime is regarded by many aquatic ecologists to be the key driver of river and floodplain wet- land ecosystems. We have focused this literature review around four key principles to highlight the important mech- anisms that link hydrology and aquatic biodiversity and to illustrate the consequent impacts of altered flow regimes: Firstly, flow is a major determinant of physical habitat in streams, which in turn is a major determinant of biotic com- position; Secondly, aquatic species have evolved life history strategies primarily in direct response to the natural flow regimes; Thirdly, maintenance of natural patterns of longitu- dinal and lateral connectivity is essential to the viability of populations of many riverine species; Finally, the invasion and success of exotic and introduced species in rivers is facilitated by the alteration of flow regimes. The impacts of flow change are manifest across broad taxonomic groups including riverine plants, invertebrates, and fish. Despite growing recognition of these relationships, ecologists still struggle to predict and quantify biotic responses to altered flow regimes. One obvious difficulty is the ability to distin- guish the direct effects of modified flow regimes from im- pacts associated with land-use change that often accom- panies water resource development. Currently, evidence about how rivers function in relation to flow regime and the flows that aquatic organisms need exists largely as a series of untested hypotheses. To overcome these problems, aquatic science needs to move quickly into a manipulative or experimental phase, preferably with the aims of restora- tion and measuring ecosystem response.

/pdf/basic-principles-and-ecological-consequences-of-altered-flow-4u5bupofua.pdf

Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity.

Classification of streams and stream habitats is useful for research involving establishment of monitoring stations, determination of local impacts of land-use practices, generalization from site-specific data, and assessment of basin-wide, cumulative impacts of human activities on streams and their biota. This article presents a frame-work for a hierarchical classification system, entailing an organized view of spatial and temporal variation among and within stream systems. Stream habitat systems, defined and classified on several spatiotemporal scales, are associated with watershed geomorphic features and events. Variables selected for classification define relative long-term capacities of systems, not simply short-term states. Streams and their watershed environments are classified within the context of a regional biogeoclimatic landscape classification. The framework is a perspective that should allow more systematic interpretation and description of watershed-stream relationships.

https://faculty.washington.edu/cet6/pub/Temp/CFR521e/Frissell_etal_1986.pdf

A hierarchical framework for stream habitat classification: Viewing streams in a watershed context

Food webs in nature have multiple, reticulate connections between a diversity of consumers and resources. Such complexity affects web dynamics: it first spreads the direct effects of consumption and productivity throughout the web rather than focusing them at particular "trophic levels." Second, consumer densities are often donor controlled with food from across the trophic spectrum, the herbivore and detrital channels, other habitats, life-history omnivory, and even trophic mutualism. Although consumers usually do not affect these resources, increased numbers often allow consumers to depress other resources to levels lower than if donor-controlled resources were absent. We propose that such donor-controlled and "multichannel" omnivory is a general feature of consumer control and central to food web dynamics. This observation is contrary to the normal practice of inferring dynamics by simplifying webs into a few linear "trophic levels," as per "green world" theories. Such theories do not accommodate commo...

Food Web Complexity and Community Dynamics

The role of salinity in decomposition of leaves of Phragmites australis in desert streams.

Spartina alterniflora leaf litter bundles were placed in a North Carolina salt marsh to study the effects of environmental heterogeneity on decomposition and animal colonization. Sediment type (mud vs. sand), tidal inundation zone (near bay, mid-marsh and upper marsh) and Spartina growth form (tall vs. short) were studied. Tidal zone had the greatest effect on decomposition rate. The main effects of sediment type and growth form were not significant. All treatments affected animal distribution patterns in the leaf bundles. Nearly all common taxa were more common on mud than sand. Most taxa showed a strong association with one tidal zone. Half of the taxa were associated with one of the Spartina growth forms. Many interactions among the treatments were also significant. This study demonstrates the significance of environmental heterogeneity in a Spartina marsh both for litter decomposition and animal distributions.

Environmental patchiness, litter decomposition and associated faunal patterns in a Spartina alterniflora marsh

The use of BACI (before–after, control–impact), comparisons to assess environmental impacts on communities requires strict adherence to the principles of good experimental design in order to derive unambiguous conclusions. Unplanned natural ecological experiments seldom meet these requirements. What unplanned experiments lack in rigor, they often make up for in an abundance of data that has the potential to make even weak signals detectable. To realize this potential the following conditions should be satisfied. (1) High taxonomic resolution is achieved in identification (species level if possible). (2) Species-specific tolerance values are available for most of the collected taxa. (3) An individual measure of impact is obtained for each taxon at a site. (4) All taxa are used in impact assessment. As a practical illustration we examine the effect of sedimentation from construction runoff on the population levels of stream benthic macroinvertebrates. Our purpose is to assess the efficacy of erosion- and sedimentation-control regulations and their enforcement in three North Carolina (USA) jurisdictions. Due to the asynchronous onset and duration of construction events, samples from different sites varied both in their timing and frequency. As a result, the benthos (both the kinds and numbers of taxa collected) overlapped so little between sites that the standard multimetric approaches to impact assessment were of little use. The typical multivariate methods of impact assessment examine changes at the community level. Our approach focuses on changes at the individual species level for all collected taxa. By correlating species-level population changes with known species-level tolerance values we are able to construct an impact score for each site along with a measure of its reliability. Impact scores are then used to test for jurisdiction differences using a weighted regression approach to analysis of variance. If the immediate goal of a study is not to assess the impact at a single site but to compare the degree of impact across a number of impacted sites and to relate this to one or more classification variables, then we believe this approach can be broadly applicable.

Seth R. Reice

Papers

The role of salinity in decomposition of leaves of Phragmites australis in desert streams.

Environmental patchiness, litter decomposition and associated faunal patterns in a Spartina alterniflora marsh

The aggregation of impacts: using species‐specific effects to infer community‐level disturbances

How to Save a River: A Handbook for Citizen Action. River Network, David M. Bolling