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

The number of prokaryotes and the total amount of their cellular carbon on earth are estimated to be 4-6 3 10 30 cells and 350-550 Pg of C (1 Pg 5 10 15 g), respectively. Thus, the total amount of prokaryotic carbon is 60-100% of the estimated total carbon in plants, and inclusion of prokaryotic carbon in global models will almost double estimates of the amount of carbon stored in living organisms. In addition, the earth's prokaryotes contain 85-130 Pg of N and 9-14 Pg of P, or about 10-fold more of these nutrients than do plants, and represent the largest pool of these nutrients in living organisms. Most of the earth's prokaryotes occur in the open ocean, in soil, and in oceanic and terrestrial subsurfaces, where the numbers of cells are 1.2 3 10 29 , 2.6 3 10 29 , 3.5 3 10 30 , and 0.25-2.5 3 10 30 , respectively. The numbers of het- erotrophic prokaryotes in the upper 200 m of the open ocean, the ocean below 200 m, and soil are consistent with average turnover times of 6-25 days, 0.8 yr, and 2.5 yr, respectively. Although subject to a great deal of uncertainty, the estimate for the average turnover time of prokaryotes in the subsurface is on the order of 1-2 3 10 3 yr. The cellular production rate for all prokaryotes on earth is estimated at 1.7 3 10 30 cellsyyr and is highest in the open ocean. The large population size and rapid growth of prokaryotes provides an enormous capacity for genetic diversity. Although invisible to the naked eye, prokaryotes are an essential component of the earth's biota. They catalyze unique and indispensable transformations in the biogeochemical cy- cles of the biosphere, produce important components of the earth's atmosphere, and represent a large portion of life's genetic diversity. Although the abundance of prokaryotes has been estimated indirectly (1, 2), the actual number of pro- karyotes and the total amount of their cellular carbon on earth have never been directly assessed. Presumably, prokaryotes' very ubiquity has discouraged investigators, because an esti- mation of the number of prokaryotes would seem to require endless cataloging of numerous habitats. To estimate the number and total carbon of prokaryotes on earth, several representative habitats were first examined. This analysis indicated that most of the prokaryotes reside in three large habitats: seawater, soil, and the sedimentysoil subsur- face. Although many other habitats contain dense populations, their numerical contribution to the total number of pro- karyotes is small. Thus, evaluating the total number and total carbon of prokaryotes on earth becomes a solvable problem. Aquatic Environments. Numerous estimates of cell density, volume, and carbon indicate that prokaryotes are ubiquitous in marine and fresh water (e.g., 3-5). Although a large range of cellular densities has been reported (10 4 -10 7 cellsyml), the

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Prokaryotes: The unseen majority

Birds are difficult to sex. Nestlings rarely show sex-linked morphology and we estimate that adult females appear identical to males in over 50% of the world's bird species. This problem can hinder both evolutionary studies and human-assisted breeding of birds. DNA-based sex identification provides a solution. We describe a test based on two conserved CHD (chromo-helicase-DNA-binding) genes that are located on the avian sex chromosomes of all birds, with the possible exception of the ratites (ostriches, etc.; Struthioniformes). The CHD-W gene is located on the W chromosome; therefore it is unique to females. The other gene, CHD-Z, is found on the Z chromosome and therefore occurs in both sexes (female, ZW; male, ZZ). The test employs PCR with a single set of primers. It amplifies homologous sections of both genes and incorporates introns whose lengths usually differ. When examined on a gel there is a single CHD-Z band in males but females have a second, distinctive CHD-W band.

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A DNA test to sex most birds

A DNA test to sex most birds.

Short DNA sequences from a standardized region of the genome provide a DNA barcode for identifying species. Compiling a public library of DNA barcodes linked to named specimens could provide a new master key for identifying species, one whose power will rise with increased taxon coverage and with faster, cheaper sequencing. Recent work suggests that sequence diversity in a 648-bp region of the mitochondrial gene, cytochrome c oxidase I (COI), might serve as a DNA barcode for the identification of animal species. This study tested the effectiveness of a COI barcode in discriminating bird species, one of the largest and best-studied vertebrate groups. We determined COI barcodes for 260 species of North American birds and found that distinguishing species was generally straightforward. All species had a different COI barcode(s), and the differences between closely related species were, on average, 18 times higher than the differences within species. Our results identified four probable new species of North American birds, suggesting that a global survey will lead to the recognition of many additional bird species. The finding of large COI sequence differences between, as compared to small differences within, species confirms the effectiveness of COI barcodes for the identification of bird species. This result plus those from other groups of animals imply that a standard screening threshold of sequence difference (10× average intraspecific difference) could speed the discovery of new animal species. The growing evidence for the effectiveness of DNA barcodes as a basis for species identification supports an international exercise that has recently begun to assemble a comprehensive library of COI sequences linked to named specimens.

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Identification of Birds through DNA Barcodes

The classification numbering system species accounts taxanomic approach species-group English names.

Distribution and taxonomy of birds of the world

A Classification of the Living Birds of the World Based on Dna-Dna Hybridization Studies

Many field ornithologists record where and when they identify species of birds, especially when they encounter a species out of its normal range or for the first time Until now, however, a checklist based on the Sibley-Ahlquist-Monroe classification has not been available In this book, Burt L Monroe, Jr, and Charles G Sibley provide a list of 9,702 living avian species based on their 1990 book Distribution and Taxonomy of Birds of the World and its 1993 Supplement Distribution and Taxonomy of Birds of the World was awarded the title of "Best Bird Book of the Year" for 1991 by the journal British Birds A World Checklist of Birds gives the Latin and English names for the species recognised in that work and in the Supplement, abbreviated geographic distributions, and spaces for checking species observed in the field and for brief notes As a complete, standardised bird name list and a summary of avian biogeography and biodiversity, this book should be useful to professional and amateur ornithologists, museum curators, wildlife biologists, and nature writers

A World Checklist of Birds

....................................................... xv INTRODUCTION ....................................................................................................... 1 GENERAL PHYSIOGRAPHY ................................................................................... 12 GEOLOGY .................................................................................................................... 19 SOILS .................................................................. 26 C LIM A TE.............................................. 29 HABITATS ............................ 38 T r o p i c a l lo w la n d r a i n f o r e s t .................... 43 T r o p i c a l d e c id u o u s (m o n so o n ) f o r e s t ....................................... 46 C lo u d (m o n ta n e r a i n ) f o r e s t ................................. 48 A r id (m ix e d ) s c r u b a n d t h o r n f o r e s t *........................ 31 H ig h la n d p i n e ( o c o t a l ) an d p i n e o a k a s s o c i a t i o n s ( e n c i n a l r o b l e d a l ) .................................................................. 52 L ow land p i n e s a v a n n a ............................................................................. 54 M a rsh a n d s w a m p .................. 56 M a n g r o v e ............... 57 HISTORY OF HONDURAN ORNITHOLOGY ...................................................... 59 v i i i

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A distributional survey of the birds of Honduras

"Distribution and Taxonomy of Birds of the World" was published in 1990, and was named best bird book of the year by "British Birds" magazine. Written by two eminent ornithologists, the book is a taxonomic listing of 9672 living species of birds of the world, with details of the geographic range of each species. The accounts of the species are arranged according to a new classification developed by the authors in collaboration with Jon Ahlquist. In this supplement, Sibley and Monroe update their original material, presenting changes in systematics that they have noted through May 1992, including a change in the total number of living species to 9702. The supplement is keyed to the original volume by page number.

Burt L. Monroe

Papers

Distribution and taxonomy of birds of the world

A Classification of the Living Birds of the World Based on Dna-Dna Hybridization Studies

A World Checklist of Birds

A distributional survey of the birds of Honduras

A Supplement to Distribution and taxonomy of birds of the world