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

So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Identifying and quantifying planetary boundaries that must not be transgressed could help prevent human activities from causing unacceptable environmental change, argue Johan Rockstrom and colleagues.

/pdf/a-safe-operating-space-for-humanity-tynyc6i2kf.pdf

A safe operating space for humanity

The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

/pdf/planetary-boundaries-guiding-human-development-on-a-changing-5gmf909etg.pdf

Planetary boundaries: Guiding human development on a changing planet

Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the re- lationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are struc- tured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.

/pdf/effects-of-biodiversity-on-ecosystem-functioning-a-consensus-13j8vabcus.pdf

Effects of biodiversity on ecosystem functioning: a consensus of current knowledge

1 Hemiparasitic plants, such as Rhinanthus species, have substantial effects on community composition and biomass For example, the presence of parasites often increases diversity but reduces the combined biomass of hosts and parasites by c 25% compared with unparasitized controls We present and test a simple model of the host-parasite interaction in which parasite growth rate is a function of host growth rate that offers a new explanation for why hemiparasitic plants reduce ecosystem productivity 2 The model predicts that the combined mass of the host-parasite system is always less than the mass of the host grown alone, because the combined biomass is dependent only on host growth rate, which is reduced by the parasite The model also predicts that the parasite should adopt an intermediate virulence to maximize its own performance, but that the optimum virulence depends on host growth characteristics 3 The key assumption of the model is that parasite growth rate and hence parasite biomass is tightly coupled to host growth rate We tested this assumption by measuring the performance of Rhinanthus alectorolophus, a widespread hemiparasitic annual plant, on nine common European grass species First, we determined size-corrected growth rates for the grasses by fitting power-law growth curves to multiple-harvest data on host individuals grown without Rhinanthus Second, we grew Rhinanthus on each of the grass species and related Rhinanthus final biomass to the grass species' growth rates 4 Rhinanthus performance was strongly correlated with the growth rate of the host grass species, thus validating a key assumption of our model However, Rhinanthus biomass on three of the nine grass species differed significantly from the value predicted based on host growth rate alone, suggesting that grass species differ in their resistance to parasitism 5 Synthesis Parameterizing such models of the host-parasite relationship could help to explain variation in Rhinanthus performance on different hosts, variation in the effects of hemiparasites in grasslands of different productivity and differences in virulence among parasite populations

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2745.2010.01657.x

Modelling the growth of parasitic plants

The relationship between biodiversity and ecosystem functioning (BEF) has been one of the most vibrant research fields in ecology and environmental sciences over the past two decades Hundreds of experiments have now manipulated species diversity to test its effects on a wide range of ecosystem properties Methods that partition the effect of functional complementarity between species from that of selection for species with particular traits have been instrumental in clarifying the results of these experiments and in resolving debates about potential underlying mechanisms (Loreau and Hector 2001, Cardinale et al 2007) Relatively few studies, however, have sought to disentangle the actual biological mechanisms at work in the effects of biodiversity on ecosystem functioning Yet theory shows that different coexistence mechanisms can lead to different BEF relationships (Mouquet et al 2002) Understanding the mechanisms that drive the functional consequences of biodiversity and their connections with those that determine the maintenance of biodiversity is key to making BEF research more predictive and more relevant to natural, non-experimentally manipulated ecosystems (Loreau 2010) The recent theoretical study by Carroll, Cardinale, and Nisbet (2011; hereafter CCN) makes a valuable contribution toward the goal of linking the maintenance of diversity and its functional consequences CCN use MacArthur’s (1972) classical consumer

/pdf/niche-and-fitness-differences-relate-the-maintenance-of-16lnmdc4jx.pdf

Niche and fitness differences relate the maintenance of diversity to ecosystem function: comment

Summary
Most experimental evidence on the relationship between biodiversity and ecosystem functioning comes from ecosystems with fast-growing plants, such as grasslands. Although forests provide essential ecological services, they have been less well investigated.
We used dendrochronology to compare the tree radial growth rates of four important timber species in replicated, spatially mapped stands that differed in tree composition and diversity within a central European managed forest.
Growth rates differed among species but were largely unaffected by the density of neighbouring trees.
Increasing stand diversity enhanced individual growth rates, after accounting for the effects of tree density and size. These increases were statistically indistinguishable among the four species. In contrast, the effects of stand and neighbourhood species composition on growth rates were non-significant.
Policy implications. Our study of long-established central European forest stands revealed levels of tree diversity can be increased in managed forests, with the potential for modest increases in tree growth rates. These results suggest that in addition to the biodiversity and risk mitigation benefits associated with shifting practices away from monoculture management, increased carbon sequestration and yields in mature forests are likely to be realized. Our results suggest that it is possible to increase forest diversity with little or no costs to production and even with the potential for modest increases in tree growth rates.

/pdf/forest-diversity-promotes-individual-tree-growth-in-central-49pmivcx7q.pdf

Forest diversity promotes individual tree growth in central European forest stands

Through complementary use of canopy space in mixtures, aboveground niche separation has the potential to promote species coexistence and increase productivity of mixtures as compared to monocultures. We set up an experiment with five perennial grass species which differed in height and their ability to compete for light to test whether plants partition light under conditions where it is a limiting resource, and if this resource partitioning leads to increased biomass production in mixtures (using relative yield-based methods). Further, we present the first application of a new model of light competition in plant communities. We show that under conditions where biomass production was high and light a limiting resource, only a minority of mixtures outperformed monocultures and overyielding was slight. The observed overyielding could not be explained by species differences in canopy structure and height in monoculture and was also not related to changes in the canopy traits of species when grown in mixture rather than monoculture. However, where overyielding occurred, it was associated with higher biomass density and light interception. In the new model of competition for light, greater light use complementarity was related to increased total energy absorption. Future work should address whether greater canopy space-filling is a cause or consequence of overyielding.

Andy Hector

Papers

Modelling the growth of parasitic plants

Niche and fitness differences relate the maintenance of diversity to ecosystem function: comment

Forest diversity promotes individual tree growth in central European forest stands

Light partitioning in experimental grass communities

The £15 billion cost of ash dieback in Britain.