ibclogo XVI International Botanical Congess


Abstract Number: 3280
Poster No. = 1259


LATITUDINAL GRADIENTS IN SPECIES DIVERSITY CAUSED BY ORBITAL FORCING OF CLIMATES


Mats Dynesius & Roland Jansson, Umeå University, Sweden


We present a new mechanistic theory proposing a latitudinal gradient in orbitally forced climatic fluctuations as the ultimate cause for the similar gradient in taxonomic diversity. Extinction rates may be higher at higher latitudes as species fail to disperse or experience population bottlenecks as the greater climatic changes force them to larger changes in their distributional ranges. This is counteracted by selection for high vagility and generalism. Speciation rates should be lower at high latitudes because large range-shifts cause differentiated populations to go extinct or interbreed, before speciation is completed. The high vagility and generalism of high latitude species further lowers the speciation rate. We conclude that the resulting strong gradient in speciation rate explains the gradient in species diversity.


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