EE 13- Global Biodiversity Patterns Lecture Notes

Flashcards covering global biodiversity patterns, including key hypotheses for tropical diversity and specific taxonomic examples and research citations provided in the lecture notes.

Latitudinal biodiversity gradient

The general pattern describing how species are distributed across the earth, typically showing higher richness at the equator and decreasing toward the poles.

Area hypothesis

A hypothesis for tropical diversity suggesting that the larger land surface area in the tropics supports more species.

Energy hypothesis

The proposal that higher productivity and energy availability in the tropics lead to higher biomass, more individuals, and thus more species.

Cradle hypothesis

A hypothesis stating that the tropics are more diverse because they experience faster rates of speciation.

Time hypothesis

The idea that tropical regions have had more time for speciation to occur, resulting in higher biodiversity.

Museum hypothesis

A hypothesis suggesting the tropics are diverse because they have slower rates of extinction, effectively 'preserving' species.

Carrying capacity hypothesis

The suggestion that the tropics contain more niches, allowing them to support a higher number of species.

Niche conservatism

The hypothesis that it is easier for species to adapt within tropical environments and harder to evolve the traits needed to migrate to temperate or polar zones.

Geometric constraints

A hypothesis (often associated with Willig and Lyons 1998) suggesting that biodiversity patterns can emerge from the physical boundaries of a domain, also known as the mid-domain effect.

Potential evapotranspiration (PET)

An environmental variable measured in $mm\,yr^{-1}$ used by researchers like Currie (1991) and Gaston (2000) to correlate energy availability with species richness.

Mammalian Quadrupeds

A group studied by Rozensweig (1995) showing a clear latitudinal gradient in North America, with average species numbers peaking at lower latitudes.

North and Central American bats

A taxon that exhibits a sharp increase in species richness (up to 75 species) as latitude decreases toward $10^{\circ}$, according to Rozensweig (1995).

Herpetofauna

A collective term for snakes, frogs, and lizards which show a latitudinal species gradient in both the New World and Old World.

Termites

An insect group whose species richness is shown to be highest between $0^{\circ}$ and $20^{\circ}$ latitude, dropping significantly by $40^{\circ}$.

Coastal fishes

A group whose log number of species decreases from approx $3.5$ to $1.5$ as latitude increases from $0^{\circ}$ to $70^{\circ}$.

Foraminifera

Marine organisms whose fossil records are used by Rozensweig (1995) to demonstrate that the latitudinal biodiversity gradient has existed over geological time.

Geographic area hypothesis land distribution

Data indicating that land area in millions of square kilometers per $5^{\circ}$ latitude zone is significantly larger in the Northern Hemisphere's subtropics compared to other zones.

Epicauta beetles

A genus of beetles used to show the relationship between the square root of species richness and PET ($mm\,yr^{-1}$), following Gaston (2000).

Fox Glacier

A specific location in New Zealand referenced in the lecture to illustrate the impact of glaciations on physical landscapes.

LGM (Last Glacial Maximum)

A historical period where the distribution of vegetation (e.g., tropical moist forests, tundra, ice sheets) was significantly different than modern day.

Environmental stability

A factor visualized through the comparison of past and present day species numbers, showing higher stability and species retention in the tropics.

Evolutionary time

A concept relating species richness to the duration a region has remained stable, allowing for the accumulation of biodiversity.

Sea surface temperature (SST)

A climatic variable measured in $^{\circ}C$ that stays high and stable in the tropics but fluctuates seasonally in temperate zones.

Tropical Evergreen Forest

A biome whose area in $10^3\,km^2$ has fluctuated over the last $120\,ka\,BP$, as documented by Allen et al. (2020).

Temperate Mixed Forest

A biome whose area fluctuations over the last $120\,ka\,BP$ are compared to tropical forests to understand historical habitat availability.

Willig and Lyons (1998)

Authors of the study 'Oikos' which explored geometric constraints and predicted bat species richness in the Americas based on latitude.

Mannion et al. 2014

The citation for research published in Trends Ecol. Evol. regarding the latitudinal biodiversity gradient.

Rozensweig (1995)

Author of 'Species Diversity in Space and Time', a primary source for much of the species distribution data in the lecture.

Currie (1991)

Researcher who studied species richness in Aves, Mammalia, Amphibia, and Reptilia in North America relative to Potential Evapotranspiration.

Energy flux path

The causal chain: $\uparrow \text{Energy} \rightarrow \uparrow \text{Biomass} \rightarrow \uparrow \text{Individuals} \rightarrow \uparrow \text{Species}$.