Q. What do you mean by Alpha diversity?

Alpha (a) richness refers to the number of species found in small, homogenous area. Alpha diversity refers to the diversity in a particular area or ecosystem and is usually expressed by the number of species (i.e. species richness) in that ecosystem.

Alpha diversity is characterised by several widespread patterns that are characteristic of most taxa and are strongly correlated with physical environmental gradients. For example,

· Marine and terrestrial environments in tropical regions have more species of higher taxonomic groups than those in higher latitude communities.

· Richness of species in terms of most taxa is positively correlated with habitat structural complexity.

· Structurally simple habitats like open oceans, grasslands, etc. generally support fewer species than structurally complex communities such as forests and coral reefs. In the open oceans maximum richness of most groups is found at depths between 2000-4000 m. In contrast coral species richness peaks at depths between 15-30 m because corals obtain their energy from photosynthetic organisms embedded in their tissues, and are thus confined to the photic zone.

· Island communities are poor in species than comparable mainland communities.