How many species are there, globally? Range of estimates: 2 – 100 million Best estimate: 10 million 1.4 – 2 million species have a name. An estimated 97% of all species are invertebrates, and within these, insects are by far the most numerous (an estimated 1-30 million species). In one study of just 19 trees in Panama, 1200 species of beetle were discovered, of which 80% were previously unknown to science. Within the vertebrates species: 23,500 ray-finned fish, ,000 birds, 7,984 reptiles, 5400 amphibians, mammals. 70% of the world's species occur in only 12 countries: Australia, Brazil, China, Columbia, Ecuador, India, Indonesia, Madagascar, Mexico, Peru, and Zaire. On average, 3 new species of birds are found each year An estimated 40 percent of freshwater fishes in South America have not yet been classified. The deep sea floor may contain as many as a million undescribed species. Hydrothermal vent communities, discovered less than two decades ago, >20 new families or subfamilies, 50 new genera, and 100 new species were found.

How to measure species diversity? Counting the number of species has several challenges: species recognition (especially the small ones) the influence of sampling effort and sample size 1 transect: 3 species 2 transects: 5 species 3 transects: 8 species 4 transects: 8 species 5 transects: 8 species

Number of individuals in sample Number of species in sample The sampling artifact: A bigger sample usually contains more species. Community 1 Community 2

The sampling artifact: Can be avoided by using diversity indices, rather than species numbers. Number of individuals in sample community 2 Fisher’s  does not change with sample size. community 1 Fisher’s 

How do you figure out how species numbers increase with area? Nested sampling design: Total species number in an area: 403 species. 403

Nested sampling design: Average species number of patches 288

How do you figure out of species numbers increase with area? Nested sampling design: Average species number of patches 256

How do you figure out of species numbers increase with area? Nested sampling design: Average species number of patches

How do you figure out of species numbers increase with area? Nested sampling design: Average species number of patches

Area size (ha) Species Number Log Area Log Species Number

The increase in the log of species number is proportional to the increase in log area. Log Area Log Species Number

Examples: From Rosenzweig 1995

z-values are quite similar between taxa, continents, ecosystems. z-values are often in the range: c-values vary, expressing systematic differences in biodiversity between taxa, ecosystems, etc. Generalized species-area curve for nested samples within continents: Log area Log species number

Productivity gradient: More productive ecosystems usually have more species per area. But, highly productive ecosystems often have reduced diversity. Spatial patterns of biodiversity: Latitudinal gradient: Biodiversity decreases between the species-rich equatorial tropics and the species-poor polar regions. Habitat heterogeneity gradient: More spatially variable environments have more species per area. Island patterns: Islands have fewer species per area than their associated mainlands. The further away the island, the fewer species.

Productivity gradient. Productivity From Rosenzweig 1995 Cold & dry Moist & warm

Habitat heterogeneity gradient. Number of plants per 300 m 2 plot beside the Hood River, Canada. From Rownsend, Begon and Harper 2003

Habitat heterogeneity gradient. Bird diversity in two continents From Rosenzweig 1995

Latitudinal gradient: From Rosenzweig 1995

Islands have fewer species than equal areas on the adjacent mainland. Species-area curves for islands are different:

mainlandislands Islands have fewer species than equal areas on the adjacent mainland. Species-area curves for islands are different:

From Rosenzweig 1995 Islands: Mainland:

New Guinea: New Guinea islands: From Rosenzweig 1995

mainlandislands Island further from the mainland have fewer species than islands of equal size closer to the mainland. Species-area curves for islands are different:

z-values for islands are usually greater than for mainlands. Generally, z = 0.2 – 0.6. z-values are greater with the farther they are from the mainland. Generalized species-area curve for islands and their associated mainlands: mainland Log area Log species number close far islands

Rosenzweig 1997 Interprovincial species-area curve: larger continents (provinces) also have more species and the z- value for interprovincial species-area curves is 1 or greater.

The three biological scales of species–area curves. Rosenzweig M L PNAS 2001;98:

Temporal patterns of biodiversity: In evolutionary time: Over millions of years diversity stays relatively constant. That means, relatively fast recovery from mass extinction events. In succession: Diversity increases in the course of succession. In the history of life on earth: Over hundreds of millions of years, diversity increased. With disturbance frequency: Intermediate disturbance frequencies have highest diversity.

Succession:

Disturbance frequency: Disturbance From Rosenzweig 1995

Algae and barnacles on rocks of different sizes From Rosenzweig 1995 Disturbance frequency:

Evolutionary time:

From Rosenzweig 1995

Uintatherium Hyracotherium From Rosenzweig 1995

In the history of life on earth: Pre-cambrian Cambrian Devonian Ordovician Triassic

Townsend, Begon and Harper 2003

Other patterns: Food web gradient: Higher trophic levels usually have lower diversity than lower trophic levels. Exception: there are more animal than plant species. There are more parasite than host species. Body size: Within a taxon, there are more intermediate-size species than either very large or very small species.

Food web gradients: From Rosenzweig 1995

Patterns with body size From Rosenzweig 1995 Dragonflies and Damselflies

Patterns with body size From Rosenzweig 1995

Patterns with body size From Rosenzweig 1995

Patterns in space Log area Log species number productivity # species Habitat variety # species Latitude # species mainland Log area Log species number close far islands

Time during succession Species number Disturbance frequency Species number Millions of years Species number Patterns in time Hundreds of Millions of years Species number

Trophic level # species Two more patterns Body size within taxon # species