Local and Regional Forces
In ecology, the change in species diversity across space and time is one of the oldest studied subjects, however the underlying causes of many diversity patterns is under much debate (Field et al. 2001; MacArthur, 1972; Rosenzweig, 1995). How does diversity arise (Erwin 1991)? How is diversity distributed in space (Dean et al. 1997, Fonseca et al. 2000)? And how is diversity maintained (Lande, 1988)? Are three fundamental questions that ecologist look to answer. Early studies focused around the role of competition in determining diversity at local scales, today however it is emphasized that many factors on top of competition, such …show more content…
Majority of studies have shown the first model to be most frequent in findings (Cornell & Lawton, 1992; Caley & Schluter, 1997; Lawton, 1999) with regional richness explaining a large proportion (> 75%) of variance in local richness, and local richness constituting a marked proportion (> 50%) of regional richness (Gaston, 2000) as document in fig wasps and parasitoids in Africa (Compton & Hawkins 1992) Lacustrine fish in North America (Griffiths, 1997) and primates in Africa and South America (Eeley & Lawes 1999),
These methods however assume that both local and regional areas are as environmentally similar as possible, species can disperse to each locality and niche space is the same across regions. This leads to the uncertainty of the relative importance of local and regional factors due to the fact they act on different spatial and temporal scales (Cornell 1999; Cornell & Karlson, 1996, 1997; Cornell & Lawton L1992; Ricklefs & Schluter 1993; Shurin 2001; Srivastava 1999). Therefor care must be taken so that the pool in study is not disproportionally overestimated in larger regions relative to smaller regions. This may lead to spurious saturation LSR-RSR relationships (Srivastava