The International Long Term Ecological Research Network: a platform for collaboration

Many scientists around the world became interested in the U.S. Long Term Ecological Research (U.S. LTER) Network\u27s research model during the 1990s and began to develop LTER and Long Term Socio-ecological Research networks in their own countries. These local networks, including the U.S. LTER Network, were loosely federated in 1993 to form the International Long Term Ecological Research (ILTER) Network, a “network of networks.” Although the first 10 yr of ILTER Network activities were largely supported by funds from the U.S. National Science Foundation, the ILTER Network had transformed into a robust, self-sustaining entity by 2006 following a two-year strategic planning process. The goal of the ILTER Network is to improve understanding of how pressures such as climate change and land use affect global ecosystems in order to inform solutions to current and future environmental problems. To fulfill this mission, the ILTER Network fosters collaborations among member scientists to extend the scope of their research across disciplinary boundaries and across more of the ILTER\u27s 600+ research sites. The ILTER Network also has many long-term data sets that are freely available for use by students, scientists, and policymakers all over the world. In this collection of papers, we consider how the ILTER Network has been, and will be, leveraged by U.S. researchers to advance understanding of ecological and socio-ecological systems around the globe

Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species

<p>Abstract</p> <p>Background</p> <p>In the mid 20^thcentury, Ernst Mayr and Theodosius Dobzhansky championed the significance of circular overlaps or ring species as the perfect demonstration of speciation, yet in the over 50 years since, only a handful of such taxa are known. We developed a topographic model to evaluate whether the geographic barriers that favor processes leading to ring species are common or rare, and to predict where other candidate ring barriers might be found.</p> <p>Results</p> <p>Of the 952,147 geographic barriers identified on the planet, only about 1% are topographically similar to barriers associated with known ring taxa, with most of the likely candidates occurring in under-studied parts of the world (for example, marine environments, tropical latitudes). Predicted barriers separate into two distinct categories: (i) single cohesive barriers (< 50,000 km²), associated with taxa that differentiate at smaller spatial scales (salamander: <it>Ensatina eschscholtzii</it>; tree: <it>Acacia karroo</it>); and (ii) composite barriers - formed by groups of barriers (each 184,000 to 1.7 million km²) in close geographic proximity (totaling 1.9 to 2.3 million km²) - associated with taxa that differentiate at larger spatial scales (birds: <it>Phylloscopus trochiloide</it>s and <it>Larus </it>(sp. <it>argentatus </it>and <it>fuscus</it>)). When evaluated globally, we find a large number of cohesive barriers that are topographically similar to those associated with known ring taxa. Yet, compared to cohesive barriers, an order of magnitude fewer composite barriers are similar to those that favor ring divergence in species with higher dispersal.</p> <p>Conclusions</p> <p>While these findings confirm that the topographic conditions that favor evolutionary processes leading to ring speciation are, in fact, rare, they also suggest that many understudied natural systems could provide valuable demonstrations of continuous divergence towards the formation of new species. Distinct advantages of the model are that it (i) requires no <it>a priori </it>information on the relative importance of features that define barriers, (ii) can be replicated using any kind of continuously distributed environmental variable, and (iii) generates spatially explicit hypotheses of geographic species formation. The methods developed here - combined with study of the geographical ecology and genetics of taxa in their environments - should enable recognition of ring species phenomena throughout the world.</p

Landscape Ecology vol. 3 nos. 229-243 (1989) SPB Academic Publishing bv, The Hague

this paper are to (1) identify concepts related to pattern and process in transition zones where steep gradients are likely to occur, (2) develop sample hypotheses of ecosystem dynamics associated with change in transition zones, and (3) provide examples of techniques and tools that allow measurement and extrapolation to scales appropriate for broad-scale transition zone studies. 2. Transition zones as sensitive indicators There is a growing literature on the role of ecotones in influencing ecological flows (i.e., energy, resources, information) and biodiversity and in detecting change in the global environment (Hansen et al. 1988). Ecotones can be defined as transition zones or tension zones and can be sensitive indicators of change. Although ecotones often are as- sociated with relatively fine-scale phenomena (e.g., forest edge, lake edge, patch edge), the concepts can be applied to broader-scale characteristics such as a biome boundary where ecological change may be distributed over many kilometers. The structural features of fine-scale ecotones (hundreds of meters) are likely determined by site-specific characteristics such as soil discontinuities, lake edge, and even fire. Climate appears as a constant across such small dis- tances. Broad-scale transition zones between mes (i.e., many kilometers) are more likely to be a result of large-scale climatic features working on a 231 Biomass Nutrient One-Dimensional Environmental Gradient (distance) STRUCTURAL CHARACTERISTICS Biomass Two-Dimensional Environmental Gradient (distance) Fig. I. Structural features that define the transition zone as an association of life-forms from adjoining biomes. A: Structural characteristics expected where biome transition is controlled by a single environmental factor, such ..