Document: ROM-3-92-2

On the shape of species richness xurves: Area, latitude, disturbance, and productivity.

DIAL, R.*

Alaska Pacific University, Anchorage, AK 99508 USA ¹

Abstract:
Using a simple function relating species richness (S) to total abundance (A), minimum population (m), niche availability (0 = n = 1), and historical influences (h) as S=h(A/m)ⁿ, I explore some of the consequences of environmental variability in these community variables. In particular, analysis of the model shows: (1) If the predominant effect of increasing area is a linear increase of total abundance, then species-area curves are concave down. (2) If a greater effect of increasing area is a linear increase in niche availability, then a log-log plot of area and richness is concave up. (3) If the predominant effect of increasing latitude is a linear increase in minimum population, then latitudinal gradients of species richness are concave up. (4) If increasing disturbance linearly decreases abundance and linearly increases niche availability, then the relationship between richness and disturbance is humped and left skewed. (5) If increasing productivity linearly increases abundance, while linearly decreasing niche availability, then the relationship between richness and productivity is humped and right skewed. Together with other results (Rapoport's Rule, nestedness in species lists from island archipelagos, and the positive relation between abundance and distribution) shown last year, I suggest this to be the most robust general theory of species richness yet presented.

Keywords: general theory, diversity, productivity, disturbance, species-area, latitudinal gradient, niche

This abstract is being presented at: 11:15 AM in session:
Oral Session #39: Theoretical Ecology.