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DISPERSAL AS A MECHANISM LIMITING DIVERSITY OF HIGH LATITUDES
Citation:
Jorgensen*, E E. DISPERSAL AS A MECHANISM LIMITING DIVERSITY OF HIGH LATITUDES. BIOTA 1(2):11-20, (2000).
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Description:
The pervasiveness acress taxa, space, and time of the latitudinal gradient in species diversity is conventionally thought to suggest a common cause that is not yet identified. Conventionally, the cause of the gradient is thought to originate in the tropics where diversity is high, although recently causes originating at high latitdes or attributable to random patterns have been proposed. Most discussions of causes relative to the diversity gradient are elaborate and burdened with assumptions. A parsimonious causal mchanism that accounts for the accumulation of relatively high amounts of genetic homogeneity within populations at high latitudes could result in suppressed speciation rates. Suppressed speciation rates would, in turn, eventually lead to accumulation of fewer species at high latitudes and the appearance of a latitudinal diversity gradient. Dispersal ability could be a parsimonious cause for the diversity gradient, and species adapted to high latitudes should disperse widely. Therefore, adjacent local populations at high latitudes should be more genetically similar than adjacent local populations in the tropics - when the same longitudinal distance separates local populations. Ultimately, detailed genetic investigations and analyses of extant collections and data will be needed to test this proposed mechanism. Already, however, some genetic evidence supports this idea: low latitude populations of the Eastern Woodrat Neotoma floridana show more mtDNA variability that high latitude populations. Also, some behavioral data are suportive: Red Fox Vulpes vulpes displays a notable northward buas in their dispersal direction. The uncovering of a parsimonious mechanism that accounts for the latitudinal diversity gradient would resolve decades of discussion and provide valuable insights into the topic of biodiversity. It may be that a parsimonious mechanism for dispersal ability is supported by some data, and awaits more detailed investigations.
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