Local and Regional Forces

2472 Words May 8th, 2013 10 Pages
Section B. Is local diversity a product of regional forces, local forces, or both, and how might we know?

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,
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The second type of manipulation varies the isolation of regional areas from a species source region and thus the species pools for their embedded communities which is represented in a marine study where reef environments are associated with coral species assemblages (Cornell et al. 2004; 2008). Five regions with different diversities at three local scales along a longitudinal gradient from Indonesian archipelago, where species richness peaks at 600+ sp., to the French Polynesia, with only a peak of 130 (Cornell et al. 2004). The eastward decline in richness is explained by declining area of shallow water habitat within each region (Bellwood et al. 2005) partnered with isolation from the Indonesian diversity hotspot due to distance (Cornell & Karlson, 1998) and westward-flowing currents (Connolly et al. 2003) suggesting regional influence on species diversity. Slopes of regressions of log-LSR on log-RSR were linear suggesting local assemblages are again open to enrichment from regional species pool (Cornell et al. 2008).
Following on from this, substantial literature has sought to document what has come to be termed the local–regional richness relationship (Caley & Schluter, 1997; Cornell, 1999; Cornell & Lawton, 1992; Gaston, 2000; Gaston & Koleff, 2002; Lawton,
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