Read the passage carefully and give the answers to the next five questions:

Does the number of species in a community really matter to the functioning of the ecosystem? This is a question for which ecologists have not been able to give a definitive answer. For many decades, ecologists believed that communities with more species generally tend to be more stable than those with less species. According to the International Union for Conservation of Nature and Natural Resources (IUCN) (2004), the total number of plant and animal species described so far is more than 1.5 million.

The scientist who proved that species richness directly correlates with the stability of a community was:

The correct option is David Tilman.

Explanation:

For several decades, ecologists debated whether the number of species (species richness) in a community affects the overall stability and functioning of that ecosystem. While many hypothesized a positive correlation, it was the pioneering research of ecologist David Tilman that provided experimental evidence to support this idea.

Tilman conducted long-term ecological experiments using outdoor plots to study community dynamics. His research demonstrated two key findings regarding ecosystem stability:
1. Plots with a higher number of species showed less year-to-year variation in total biomass, indicating greater community stability.
2. Increased species richness contributed to higher overall productivity of the ecosystem.

Let's briefly look at the contributions of the other scientists listed in the options to understand why they are not the correct choice for this specific question:
- Paul Ehrlich proposed the "Rivet Popper hypothesis" to explain the significance of species diversity using an analogy of rivets in an airplane.
- Robert May provided global estimates of species diversity, suggesting that global species diversity is about 7 million.
- Edward Wilson popularized the term "biodiversity" to describe the combined diversity at all levels of biological organization.

Therefore, David Tilman is the scientist who experimentally proved that species richness directly correlates with the stability of a community.