Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.

Biodiversity hotspots for conservation priorities

Cooperation in organisms, whether bacteria or primates, has been a difficulty for evolutionary theory since Darwin. On the assumption that interactions between pairs of individuals occur on a probabilistic basis, a model is developed based on the concept of an evolutionarily stable strategy in the context of the Prisoner's Dilemma game. Deductions from the model, and the results of a computer tournament show how cooperation based on reciprocity can get started in an asocial world, can thrive while interacting with a wide range of other strategies, and can resist invasion once fully established. Potential applications include specific aspects of territoriality, mating, and disease.

/pdf/the-evolution-of-cooperation-pwc4krac7e.pdf

The Evolution of Cooperation

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

Definitions of diversity. Measuring species diversity. Choosing an index and interpreting diversity measures. Sampling problems. Structural diversity. Applications of diversity measures. Summary.

/pdf/ecological-diversity-and-its-measurement-4az8bcrmxt.pdf

Ecological Diversity and its Measurement

A high number of tree species, low density of adults of each species, and long distances between conspecific adults are characteristic of many low-land tropical forest habitats. I propose that these three traits, in large part, are the result of the action of predators on seeds and seedlings. A model is presented that allows detailed examination of the effect of different predators, dispersal agents, seed-crop sizes, etc. on these three traits. In short, any event that increases the efficiency of the predators at eating seeds and seedlings of a given tree species may lead to a reduction in population density of the adults of that species and/or to increased distance between new adults and their parents. Either event will lead to more space in the habitat for other species of trees, and therefore higher total number of tree species, provided seed sources are available over evolutionary time. As one moves from the wet lowland tropics to the dry tropics or temperate zones, the seed and seedling predators in ...

Herbivores and the Number of Tree Species in Tropical Forests

Astraptes fulgerator, first described in 1775, is a common and widely distributed neotropical skipper butterfly (Lepidoptera: Hesperiidae). We combine 25 years of natural history observations in northwestern Costa Rica with morphological study and DNA barcoding of museum specimens to show that A. fulgerator is a complex of at least 10 species in this region. Largely sympatric, these taxa have mostly different caterpillar food plants, mostly distinctive caterpillars, and somewhat different ecosystem preferences but only subtly differing adults with no genitalic divergence. Our results add to the evidence that cryptic species are prevalent in tropical regions, a critical issue in efforts to document global species richness. They also illustrate the value of DNA barcoding, especially when coupled with traditional taxonomic tools, in disclosing hidden diversity.

/pdf/ten-species-in-one-dna-barcoding-reveals-cryptic-species-in-26rdxjs9xw.pdf

Ten species in one: DNA barcoding reveals cryptic species in the neotropical skipper butterfly Astraptes fulgerator

Herbivores: Their Interaction With Secondary Plant Metabolites

Many plants suffer very heavy preand/or post-dispersal seed predation by animals. A few exemplary studies (2,18,38,52,74,87, 106, 110, 111, 124, 140, 161, 162, 171, 181, 187, 196, 197, 203, 205, 207, 217, 220, 227) and a variety of shorter reports scattered through the agricultural, botanical, and zoological literature suggest a large and important, yet unexploited, field of study. It is clear that the pattern of seed predation is highly structured and that it co evolved at, the chemical, spatial, and temporal level. It involves all levels of animal-plant interaction from the internal energy budget of indi­ viduals to the entire community (203 ) . Owing to parental and sibling com­ petition, successful development of a seedling may depend on the seed's dis­ persal (101). Equally important, thc seed must escape from the predators at the seed crop and in the parent plant's habitat before and after dispersal (111 ) . The game is played by mobile predators in search of sessile prey; escape is through a single dispersal move, seed chemistry, parental morphol­ ogy and behavior, and evolutionary change. The processes and patterns are:ideal candidates for ecological and evolu­ tionary analyses (83, 111 ) of the typcs traditionally conducted by zoologi­ cally oriented biologists (37, 51,73, 141, 155,156, 182) or applied to plants in general ( 40,116,208,209,241) . Seed predators and leaf eaters are often lumped together in ecological discussions, but they differ in ways especially important in the coevolution of seed predators and seeds: (a) Like leaves, seeds are highly subdivided and small, but unlike leaves and other vegetative parts, they have very high nutrient values per unit volume. ( b) While obvious in large quantities, they may be extremely inconspicuous once dispersed. ( c) Being comparatively dormant, seeds have low self-repair abilities but can contain high concentra­ tions of toxic compounds (secondary substances) with less sophisticated ad­ aptations against self-intoxication than can leaves and meristematic tissues. ( d ) Seed production is not continually required for direct survival of the parent plant; seed timing, quantity, and quality can therefore be manipu­ lated more freely by natural selection than can these traits of leaves and other vegetative parts. (e ) Seeds are not directly replaced· when killed or germinated; once removed, seeds may be absent far longer than edible vege­ tative parts and thus a common plant species may be rare in time,toa seed

Seed Predation by Animals

Methods for identifying species by using short orthologous DNA sequences, known as “DNA barcodes,” have been proposed and initiated to facilitate biodiversity studies, identify juveniles, associate sexes, and enhance forensic analyses. The cytochrome c oxidase 1 sequence, which has been found to be widely applicable in animal barcoding, is not appropriate for most species of plants because of a much slower rate of cytochrome c oxidase 1 gene evolution in higher plants than in animals. We therefore propose the nuclear internal transcribed spacer region and the plastid trnH-psbA intergenic spacer as potentially usable DNA regions for applying barcoding to flowering plants. The internal transcribed spacer is the most commonly sequenced locus used in plant phylogenetic investigations at the species level and shows high levels of interspecific divergence. The trnH-psbA spacer, although short (≈450-bp), is the most variable plastid region in angiosperms and is easily amplified across a broad range of land plants. Comparison of the total plastid genomes of tobacco and deadly nightshade enhanced with trials on widely divergent angiosperm taxa, including closely related species in seven plant families and a group of species sampled from a local flora encompassing 50 plant families (for a total of 99 species, 80 genera, and 53 families), suggest that the sequences in this pair of loci have the potential to discriminate among the largest number of plant species for barcoding purposes.

https://www.pnas.org/content/pnas/102/23/8369.full.pdf

Daniel H. Janzen

Papers

Herbivores and the Number of Tree Species in Tropical Forests

Ten species in one: DNA barcoding reveals cryptic species in the neotropical skipper butterfly Astraptes fulgerator

Herbivores: Their Interaction With Secondary Plant Metabolites

Seed Predation by Animals

Use of DNA barcodes to identify flowering plants