Trends in Species Richness
The observed species richness is affected not only by the number of individuals but also by the heterogeneity of the sample. If individuals are drawn from different environmental conditions (or different habitats), the species richness of the resulting set can be expected to be higher than if all individuals are drawn from similar environments. The accumulation of new species with increasing sampling effort can be visualised with a species accumulation curve. Such curves can be constructed in different ways. Increasing the area sampled increases observed species richness both because more individuals get included in the sample and because large areas are environmentally more heterogeneous than small areas.
Many organism groups have most species in the tropics, which leads to latitudinal gradients in species richness. There has been much discussion about the relationship between productivity and species richness. Results have varied among studies, such that no global consensus on either the pattern or its possible causes has emerged.
Read more about this topic: Species Richness
Famous quotes containing the words trends in, trends, species and/or richness:
“Thanks to recent trends in the theory of knowledge, history is now better aware of its own worth and unassailability than it formerly was. It is precisely in its inexact character, in the fact that it can never be normative and does not have to be, that its security lies.”
—Johan Huizinga (18721945)
“A point has been reached where the peoples of the Americas must take cognizance of growing ill-will, of marked trends toward aggression, of increasing armaments, of shortening tempersa situation which has in it many of the elements that lead to the tragedy of general war.... Peace is threatened by those who seek selfish power.”
—Franklin D. Roosevelt (18821945)
“There are acacias, a graceful species amusingly devitalized by sentimentality, this kind drooping its leaves with the grace of a young widow bowed in controllable grief, this one obscuring them with a smooth silver as of placid tears. They please, like the minor French novelists of the eighteenth century, by suggesting a universe in which nothing cuts deep.”
—Rebecca West (18921983)
“Down to the Puritan marrow of my bones
Theres something in this richness that I hate.
I love the look, austere, immaculate,
Of landscapes drawn in pearly monotones.”
—Elinor Wylie (18851928)