Biol305 Latitudinal gradient

Latitudinal Gradients of Biodiversity and Productivity

• Latitudinal gradients refer to the broad-scale patterns of geographic variation in biodiversity and productivity across different ecosystems.
• Productivity is defined as the rate of production, i.e., the amount of organic matter accumulated in any unit time, and it differs across different ecosystems.

Temperature in the Tropics

• The tropics have a broad belt of roughly homogeneous temperatures, with a linear decrease in mean annual temperature outside this belt.
• The absence of climatic catastrophes in the tropics allows populations to be closer to their carrying capacity, making them more K-selected than r-selected.
• In contrast, repeated climatic catastrophes in temperate regions keep populations well below their carrying capacity, making them more r-selected.

Gradients in Species Diversity

• The highest diversity of species is found in the tropics, which is attributed to the presence of more territory and habitats.
• The tropics occupy more area than other zones, and this is exaggerated by Mercator projection maps.
• The northern and southern tropics abut, resulting in an area about double that of other zones, leading to more species due to the presence of more habitats and niches.

Additional Factors Contributing to Latitudinal Diversity

• Mountain passes are more effective barriers in the tropics due to the narrower range of temperatures, leading to allopatric speciation.
• Organisms living in a more constant environment (like the tropics) are less able to handle change than those living in variable environments (like temperate regions).