The biodiversity of species and their rates of extinction, distribution, and protection

Recent studies clarify where the most vulnerable species live, where and how humanity changes the planet, and how this drives extinctions. We assess key statistics about species, their distribution, and their status. Most are undescribed. Those we know best have large geographical ranges and are often common within them. Most known species have small ranges. The numbers of small-ranged species are increasing quickly, even in well-known taxa. They are geographically concentrated and are disproportionately likely to be threatened or already extinct. Current rates of extinction are about 1000 times the likely background rate of extinction. Future rates depend on many factors and are poised to increase. Although there has been rapid progress in developing protected areas, such efforts are not ecologically representative, nor do they optimally protect biodiversity.

Species number and endemism: the galapagos archipelago revisited

Regression analyses to determine plant species number are repeated for the Galápagos Islands with new data. The multiple curvilinear regression gives the best prediction of species number, with island area making the only significant contribution. The proportion of species endemic to the Galápagos is highest in the arid, transition zone and on small islands, and lowest in the littoral and mesic zones. This is explained in terms of zone-specific immigration and extinction rates and the very recent appearance of moist upland climates in the archipelago.

The origins of taxonomy

There are approximately 10 million kinds of olganisms in the world, of which we have described some 15 percent. The rapid growth of the human population will cause most of the remainder to disappear from the earth before they are seen by a taxonomist. These facts suggest a more rigorous application of priorities in systematic biology as well as a careful review of the principles upon which our taxonomic system is based. Folk taxonomies all over the world are shallow hierarchically and comprise a strictly limited number of generic taxa ranging from about 250 to 800 forms applied to plants and a similar number applied to animals. These numbers are consistent, regardless of the richness of the environment in which the particular people live. Very few specific and varietal taxa are recognized in folk taxonomic systems. Until the invention of movable type in the mid-l5th century, written taxonomies were simply records of the folk taxonomies of particular regions. Subsequently, with the possibility for the wide distribution of books, it began to seem worth while to attempt to describe and name all species of plants and animals in the world. By the year 1700, 698 genera of plants were recognized; and by the year 1778, some 1350 genera, including tens of thousands of species. In 1789 de Jussieu interpolated the family as a higher level taxonomic category in an attempt to reduce the number of important units in the system to a memorable number. The family is still the focal point in systems of angiosperm classification at present, several hundred families being recognized. Problems with the taxonomic system stem largely from the fact that it is not designed as an information retrieval device. In folk taxonomies, names are given to organisms and these are used to communicate about the organisms with others who already know the culturally significant properties of the organisms being discussed. In dealing with the vast numbers of organisms that exist, we tend to overemphasize the process of classification and the decisions it involves at the expense of the information about the organisms that we are supposedly accumulating. Frequent changes in names exacerbate the difficulties of the system and render it still less useful for information retrieval. With modern electronic data processing equipment, it has become possible to record information about organisms, to retain this information in a data bank, and to utilize it for various purposes, including the construction of various taxonomic systems. The invention of high-speed electronic data processing equipment is seen as analogous to but more important than the invention of movable type in the history of systematic biology. By using such equipment to its full potentialities, we should be able to achieve a qualitative improvement in our perception of the living world.

Ecological and evolutionary significance of mycorrhizal symbioses in vascular plants (A Review)

MYCORRHIZAE, THE SYMBIOSES BETWEEN FUNGI AND PLANT ROOTS, ARE NEARLY UNIVERSAL IN TERRESTRIAL PLANTS AND CAN BE CLASSIFIED INTO TWO MAJOR TYPES: endomycorrhizae and ectomycorrhizae. About four-fifths of all land plants form endomycorrhizae, whereas several groups of trees and shrubs, notably Pinaceae, some Cupressaceae, Fagaceae, Betulaceae, Salicaceae, Dipterocarpaceae, and most Myrtaceae form ectomycorrhizae. Among legumes, Papilionoideae and Mimosoideae have endomycorrhizae and usually form bacterial nodules. The members of the third subfamily, Caesalpinioideae, rarely form nodules, and one of the included groups, the two large, pantropical, closely related tribes Amherstieae and Detarieae, regularly form ectomycorrhizae. Nodules and ectomycorrhizae may well be alternative means of supplying organic nitrogen to the plants that form them.Those plants having endomycorrhizae usually occur in forests of high species richness, whereas those with ectomycorrhizae usually occur in forests of low species richness. The roots of ectomycorrhizal trees, however, support a large species richness of fungal symbionts, probably amounting to more than 5000 species worldwide, whereas those of endomycorrhizal trees have low fungal species richness, with only about 30 species of fungi known to be involved worldwide. Ectomycorrhizal forests are generally temperate or occur on infertile soils in the tropics. They apparently have expanded in a series of ecologically important events through the course of time from the Middle Cretaceous onward at the expense of endomycorrhizal forests.

Long-term biological consequences of nuclear war

Subfreezing temperatures, low light levels, and high doses of ionizing and ultraviolet radiation extending for many months after a large-scale nuclear war could destroy the biological support systems of civilization, at least in the Northern Hemisphere. Productivity in natural and agricultural ecosystems could be severely restricted for a year or more. Postwar survivors would face starvation as well as freezing conditions in the dark and be exposed to near-lethal doses of radiation. If, as now seems possible, the Southern Hemisphere were affected also, global disruption of the biosphere could ensue. In any event, there would be severe consequences, even in the areas not affected directly, because of the interdependence of the world economy. In either case the extinction of a large fraction of the Earth's animals, plants, and microorganisms seems possible. The population size of Homo sapiens conceivably could be reduced to prehistoric levels or below, and extinction of the human species itself cannot be excluded.

The migration and evolution of floras in the southern hemisphere

As modern groups of angiosperms have appeared over a period of more than 80 million years, the relative position of the southern continents has changed. For the First 20 m.y. of this period, opportunities for migration were good between Africa and Europe, and this constituted the main pathway for migration between the northern and southern hemispheres. South America progressively moved away from Africa and towards North America over the past 90 m.y. Southern South America and Australasia shared a rich, warm temperate rainforest flora until about 40 m.y. ago. The development of modern climates during the past 10 m.y. has set up modern patterns of vegetation.

Genetic Self-Incompatibility in Oenothera subsect Euoenothera

Although it has been postulated that genetic self-incompatibility was involved in the origin of complex heterozygotes in Oenothera subsect Euoenothera, it has not been detected in any species of this well-studied group. It is now reported for populations of Oenothera grandiflora from west central Alabama, and should be sought in other populations of this species, which has been in cultivation for nearly two centuries.

Pollination by Lemurs and Marsupials: An Archaic Coevolutionary System

Existing geographical and ecological relationships between bats, non-flying mammals, and birds that visit flowers for food suggest novel interpretations of their evolutionary history.

A multiple origin for plastids and mitochondria

The impressive homologies between mitochondria and plastids, on the one hand, and procaryotic organisms, on the other, make it almost certain that these important cellular organelles had their origin as independent organisms. The vast number of symbiotic relationships of all degrees of evolutionary antiquity which have been found in contemporary organisms point to the ease with which such relationships can be established.

Folk Taxonomies and Biological Classification

A sample of 200 native plant names from the Tzeltal-speaking municipio of Tenejapa, Chiapas, Mexico, was found to consist of 41 percent that comprised more than one botanical species, 34 percent with a one-to-one correspondence, and 25 percent that referred to only a part of a botanical species. Cultural significance was least for the plants in the first group, greatest for those in the last group. Over half (60 percent) of the names for which there was one-to-one correspondence were plants associated with Hispanic culture, introduced as named entities following the Spanish conquest.