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

Understanding the negative and positive effects of agricultural land use for the conservation of biodiversity, and its relation to ecosystem services, needs a landscape perspective. Agriculture can contribute to the conservation of high-diversity systems, which may provide important ecosystem services such as pollination and biological control via complementarity and sampling effects. Land-use management is often focused on few species and local processes, but in dynamic, agricultural landscapes, only a diversity of insurance species may guarantee resilience (the capacity to reorganize after disturbance). Interacting species experience their surrounding landscape at different spatial scales, which influences trophic interactions. Structurally complex landscapes enhance local diversity in agroecosystems, which may compensate for local high-intensity management. Organisms with high-dispersal abilities appear to drive these biodiversity patterns and ecosystem services, because of their recolonization ability and larger resources experienced. Agri-environment schemes (incentives for farmers to benefit the environment) need to broaden their perspective and to take the different responses to schemes in simple (high impact) and complex (low impact) agricultural landscapes into account. In simple landscapes, local allocation of habitat is more important than in complex landscapes, which are in total at risk. However, little knowledge of the relative importance of local and landscape management for biodiversity and its relation to ecosystem services make reliable recommendations difficult.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1461-0248.2005.00782.x

Landscape perspectives on agricultural intensification and biodiversity – ecosystem service management

Understanding the negative and positive effects of agricultural land use for the conservation of biodiversity, and its relation to ecosystem services, needs a landscape perspective. Agriculture can contribute to the conservation of high-diversity systems, which may provide important ecosystem services such as pollination and biological control via complementarity and sampling effects. Land-use management is often focused on few species and local processes, but in dynamic, agricultural landscapes, only a diversity of insurance species may guarantee resilience (the capacity to reorganize after disturbance). Interacting species experience their surrounding landscape at different spatial scales, which influences trophic interactions. Structurally complex landscapes enhance local diversity in agroecosystems, which may compensate for local highintensity management. Organisms with high-dispersal abilities appear to drive these biodiversity patterns and ecosystem services, because of their recolonization ability and larger resources experienced. Agri-environment schemes (incentives for farmers to benefit the environment) need to broaden their perspective and to take the different responses to schemes in simple (high impact) and complex (low impact) agricultural landscapes into account. In simple landscapes, local allocation of habitat is more important than in complex landscapes, which are in total at risk. However, little knowledge of the relative importance of local and landscape management for biodiversity and its relation to ecosystem services make reliable recommendations difficult.

http://biologie.uni-bayreuth.de/toek1_pop/de/pub/pub/60936/EcolLetters2005%2C8_857-874.pdf

REVIEWS AND SYNTHESES Landscape perspectives on agricultural intensification and biodiversity - ecosystem service management

Agricultural intensification has led to a widespread decline in farmland biodiversity measured across many different taxa. The changes in agricultural practices affect many different aspects of the farmland habitat, but agricultural industry, policy and much previous research has tended to be concerned with specific sectors or practices (e.g. pesticide use or cereal husbandry). Here, we review the empirical literature to synthesize the research effort that has been directed to investigate specific practices or goals to make general statements regarding the causes and consequences of farmland biodiversity decline. We argue that the loss of ecological heterogeneity at multiple spatial and temporal scales is a universal consequence of multivariate agricultural intensification and, therefore, that future research should develop cross-cutting policy frameworks and management solutions that recreate that heterogeneity as the key to restoring and sustaining biodiversity in temperate agricultural systems.

https://www.cell.com/trends/ecology-evolution/pdf/S0169-5347(03)00011-9.pdf

Farmland biodiversity: is habitat heterogeneity the key?

Human activities, especially conversion and degradation of habitats, are causing global biodiversity declines. How local ecological assemblages are responding is less clear--a concern given their importance for many ecosystem functions and services. We analysed a terrestrial assemblage database of unprecedented geographic and taxonomic coverage to quantify local biodiversity responses to land use and related changes. Here we show that in the worst-affected habitats, these pressures reduce within-sample species richness by an average of 76.5%, total abundance by 39.5% and rarefaction-based richness by 40.3%. We estimate that, globally, these pressures have already slightly reduced average within-sample richness (by 13.6%), total abundance (10.7%) and rarefaction-based richness (8.1%), with changes showing marked spatial variation. Rapid further losses are predicted under a business-as-usual land-use scenario; within-sample richness is projected to fall by a further 3.4% globally by 2100, with losses concentrated in biodiverse but economically poor countries. Strong mitigation can deliver much more positive biodiversity changes (up to a 1.9% average increase) that are less strongly related to countries' socioeconomic status.

/pdf/global-effects-of-land-use-on-local-terrestrial-biodiversity-31yzxze5ly.pdf

Global effects of land use on local terrestrial biodiversity

A statistical model is developed for estimating species richness and accumulation by formulating these community-level attributes as functions of model-based estimators of species occurrence while accounting for imperfect detection of individual species. The model requires a sampling protocol wherein repeated observations are made at a collection of sample locations selected to be representative of the community. This temporal replication provides the data needed to resolve the ambiguity between species absence and nondetection when species are unobserved at sample locations. Estimates of species richness and accumulation are computed for two communities, an avian community and a butterfly community. Our model-based estimates suggest that detection failures in many bird species were attributed to low rates of occurrence, as opposed to simply low rates of detection. We estimate that the avian community contains a substantial number of uncommon species and that species richness greatly exceeds the number of species actually observed in the sample. In fact, predictions of species accumulation suggest that even doubling the number of sample locations would not have revealed all of the species in the community. In contrast, our analysis of the butterfly community suggests that many species are relatively common and that the estimated richness of species in the community is nearly equal to the number of species actually detected in the sample. Our predictions of species accumulation suggest that the number of sample locations actually used in the butterfly survey could have been cut in half and the asymptotic richness of species still would have been attained. Our approach of developing occurrence-based summaries of communities while allowing for imperfect detection of species is broadly applicable and should prove useful in the design and analysis of surveys of biodiversity.

Estimating species richness and accumulation by modeling species occurrence and detectability

The preservation of remaining semi-natural grasslands in Europe has a high conservation priority Previously, the effects of artificial fertilisation and grazing intensity on grassland animal and plant taxa have been extensively investigated In contrast, little is known of the effects of tree and shrub cover within semi-natural grasslands and composition of habitats in the surrounding landscape on grassland taxa We evaluated the effect that each of these factors has on species richness and community structure of vascular plants, butterflies, bumble bees, ground beetles, dung beetles and birds surveyed simultaneously in 31 semi-natural pastures in a farmland landscape in south-central Sweden Partial correlation analyses showed that increasing proportion of the pasture area covered by shrubs and trees had a positive effect on species richness on most taxa Furthermore, species richness of nectar seeking butterflies and bumble bees were negatively associated with grazing intensity as reflected by grass height At the landscape level, species richness of all taxa decreased (butterflies and birds significantly so) with increasing proportion of urban elements in a 1-km2 landscape area centred on each pasture, while the number of plant and bird species were lower in landscapes with large proportion of arable fields Our results differed markedly depending on whether the focus was on species richness or community structure Canonical correspondence analyses (CCA) showed that the abundance of most taxa was ordered along a gradient describing tree cover within pastures and proportion of arable fields in the landscape However, subsets of grassland birds and vascular plants, respectively, showed markedly different distribution patterns along axis one of the CCA In contrast to current conservation policy of semi-natural pastures in Sweden, our results strongly advise against using a single-taxon approach (ie, grassland vascular plants) to design management and conservation actions in semi-natural pastures Careful consideration of conservation values linked to the tree and shrub layers in grasslands should always precede decisions to remove trees and shrubs on the grounds of promoting richness of vascular plants confined to semi-natural grasslands Finally, the importance of landscape composition for mobile organisms such as birds entails that management activities should focus on the wider countryside and not exclusively on single pastures

Plants, insects and birds in semi-natural pastures in relation to local habitat and landscape factors

This study examined predator faunas of artificial ground and shrub nests and whether nest predation risk was influenced by nest site, proximity to forest edge, and habitat structure in 38 grassland plots in south-central Sweden. There was a clear separation of predator faunas between shrub and ground nests as identified from marks in plasticine eggs. Corvids accounted for almost all predation on shrub nests whereas mammals mainly depredated ground nests. Nest predation risk was significantly greater for shrub than for ground nests at all distances (i.e. 0, 15 and 30 m) from the forest edge. However, nest predation risk was not significantly related to distance to forest edge, but significantly increased with decreasing distance to the nearest tree. Different corvid species robbed nests at different distances from the forest edge, with jays robbing nests closest to edges. We conclude that the relationship between the predation risk of grassland bird nests and distance to the forest edge mainly depends on the relative importance of different nest predator species and on the structure of the forest edge zone. A review of published articles on artificial shrub and ground nest predation in the temperate zone corroborated the results of our own study, namely that shrub nests experienced higher rates of depredation in open habitats close to the forest edge and that avian predators predominantly robbed shrub nests. Furthermore, the review results showed that predation rates on nests in general are highest <50 m inside the forest and lower in open as well as forest interior habitats (≥50 m from the edge).

Different nest predator faunas and nest predation risk on ground and shrub nests at forest ecotones: an experiment and a review.

An important question in conservation biology is whether the biodiversity of different taxa is correlated. We studied the extent to which the number of species of six different taxa—plants, birds, butterflies, bumblebees, ground beetles, and dung beetles—in 31 Swedish seminatural grasslands covary, and whether species diversity can be related to habitat variables. During 1996 and 1997, we surveyed plants and animals with appropriate techniques for each taxa and mapped the grassland habitat. In general, correlations between taxa were few. Grassland plant diversity (currently used as an indicator for conservation value) was only significantly positively correlated to total bird diversity. Bumblebee diversity was significantly positively related to both total and grassland butterflies, whereas there was a significant negative relationship between grassland birds and dung beetles. Plants, birds, bumblebees, and butterflies showed significant similarities in patterns of species composition, as did birds, butterflies, grassland butterflies, and ground beetles. The total number of plants and both subsets of birds (total and grassland) were significantly positively related to area, whereas there was a significant negative association between area and dung-beetle diversity. The diversity of both butterflies and bumblebees was significantly negatively related to the proportion of short-grazed field layer. Bumblebees showed a positive relationship with junipers, whereas ground beetles and grassland birds were negatively associated with trees. The total number of bird species was positively influenced by the occurrence of shrubs. Our results suggest that neither the species richness of grassland plants nor that of any other of the surveyed taxa can be used as an indicator for total biodiversity in seminatural grasslands. The lack of similar patterns of species composition among taxa also makes it difficult to define functional groups with similar habitat demands. Until we have more detailed knowledge of the demands of species and taxa, it is important that we direct management efforts so that we provide a wide spectrum of grassland characteristics.




Resumen: Una pregunta importante para la biologia de la conservacion es si se correlaciona la biodiversidad de los distintos taxones. Estudiamos hasta donde varia y se relaciona el numero de especies de seis diferentes taxones (plantas, aves, mariposas, abejas, escarabajos terrestres y coprofagos) con variables del habitat en 31 pastizales seminaturales en Suecia. Durante 1996 y 1997 muestreamos plantas y animales mediante tecnicas adecuadas para cada taxa y mapeamos el habitat del pastizal. En general, las correlaciones entre taxones fueron pocas. La diversidad de plantas de pastizal (actualmente utilizada como un indicador de valor de conservacion) solo estuvo significativamente correlacionada positivamente con la diversidad total de aves. La diversidad de abejas se relaciono significativa y positivamente tanto con la diversidad total de mariposas y de pastizales, mientras que hubo una relacion significativa negativa entre las aves de pastizal y los escarabajos coprofagos. Las plantas, aves, abejas y mariposas mostraron semejanzas significativas en cuanto a composicion de especies, tales como las aves, mariposas, mariposas de pastizal y escarabajos terrestres. El total de plantas y ambos subconjuntos de aves (total y pastizal) se relacionaron significativa y positivamente con el area, mientras que hubo una asociacion significativa negativa entre area y diversidad de escarabajos coprofagos. La diversidad tanto de mariposas como de abejas se relaciono significativa y negativamente con la proporcion del estrato de campo poco pastoreada. Las abejas mostraron una relacion positiva con arboles, mientras que los escarabajos terrestres y las aves de pastizal se asociaron negativamente con los arboles. El total de especies de aves estuvo influenciado positivamente por la ocurrencia de arbustos. Nuestros resultados sugieren que ni la riqueza de especies de plantas de pastizal ni los otros taxones muestreados pueden ser utilizados como un indicador de la biodiversidad total de pastizales seminaturales. La falta de patrones similares en la composicion de especies entre taxones tambien dificulta la definicion de grupos funcionales con demandas similares de habitat. Mientras no haya conocimientos mas detallados sobre las demandas de especies y taxones, es importante que dirijamos nuestros esfuerzos de manejo a proporcionar un amplio espectro de caracteristicas de los pastizales.

Species‐Richness Correlations of Six Different Taxa in Swedish Seminatural Grasslands

Little attention has been paid to fragmentation effects on organisms living in open habitats in which species may have high mobility and generalized habitat use. We investigated landscape effects on 23 farmland bird species breeding in 72 semi-natural dry pastures distributed equally among three landscape types (agricultural-dominated, mosaic, and forest-dominated) in southcentral Sweden. There were generally higher local abundances of farmland birds in pastures located in agricultural-dominated and mosaic landscapes than in forest-dominated landscapes. Species feeding on a mixed diet as well as resident species and temperate migrants were most numerous in pastures located in agricultural-dominated landscapes and least numerous in forest-dominated landscapes. While controlling for the effects of local pasture area and vegetation structure, we found that the local abundance of 18 ( 78%) farmland bird species was significantly associated with the composition and structure of the surrounding landscape. The landscape distance that explained the largest part of local variation in abundance varied among species according to the size of their breeding territories or foraging home ranges. Our results suggest that habitat use of farmland birds breeding in pastures is affected both by suitable foraging habitats in the surrounding landscape and by nest sites within local pastures. Despite the generally higher abundances of farmland birds in pastures located in agricultural-dominated landscapes, most species of European and Swedish conservation concern had higher abundance in pastures located in more forested landscapes. Thus, the rapid loss of semi-natural dry pastures in forest-dominated landscapes is a serious threat to the future of these species in Sweden.




Resumen: Se ha prestado poca atencion a los efectos de la fragmentacion sobre organismos que viven en habitats abiertos, en los que las especies tienen alta movilidad y uso generalizado del habitat. Investigamos el efecto del paisaje sobre 23 especies de aves que anidan en 73 pastizales secos semi-naturales distribuidos en tres tipos de paisaje (agricola, mosaico y bosque) en el sur de Suecia central. Generalmente hubo mayores abundancias locales de aves en pastizales localizados en paisajes agricolas y mosaico que en los bosques. Las especies de dieta mixta, asi como especies residentes y migratorias, fueron mas numerosas en pastizales localizados en paisaje agricola y menos numerosas en el bosque. Al controlar los efectos del area del pastizal local y la estructura de la vegetacion, encontramos que la abundancia local de 18 ( 78 %) de las especies de aves estaba asociada significativamente con la composicion y estructura del paisaje circundante. La distancia que explico la mayor parte de la variacion local de la abundancia vario entre especies en funcion del tamano de sus territorios reproductivos o de los rangos de hogar para forrajeo. Nuestros resultados sugieren que el uso de habitat por aves que anidan en pastizales es afectado tanto por los habitats de forrajeo adecuados en el paisaje circundante como por sitios para anidar dentro de los pastizales locales. A pesar de la generalmente mayor abundancia de aves en pastizales localizados en paisajes agricolas, la mayoria de las especies europeas y suecas de valor en conservacion fueron mas abundantes en pastizales ubicados en paisajes mas boscosos. Asi, la rapida perdida de pastizales secos, semi-naturales en paisajes boscosos es una seria amenaza para la ocurrencia de esas especies en Suecia en el futuro.

Bo Söderström

Papers

Estimating species richness and accumulation by modeling species occurrence and detectability

Plants, insects and birds in semi-natural pastures in relation to local habitat and landscape factors

Different nest predator faunas and nest predation risk on ground and shrub nests at forest ecotones: an experiment and a review.

Species‐Richness Correlations of Six Different Taxa in Swedish Seminatural Grasslands

Influence of Landscape Scale on Farmland Birds Breeding in Semi‐Natural Pastures