Interim Report IR - 09 - 063 Speciation and the evolution of dispersal along environmental gradients
نویسندگان
چکیده
9 We analyze the joint evolution of an ecological character and of dispersal distance in asex10 ual and sexual populations inhabiting an environmental gradient. Several interesting 11 phenomena resulting from the evolutionary interplay of these characters are revealed. First, 12 asexual and sexual populations exhibit two analogous evolutionary regimes, in which either 13 speciation in the ecological character occurs in conjunction with evolution of short-range 14 dispersal, or dispersal distance remains high and speciation does not occur. Second, transi15 tions between these two regimes qualitatively differ between asexual and sexual 16 populations, with the former showing speciation with long-range dispersal and the latter 17 showing no speciation with short-range dispersal. Third, a phenotypic gradient following 18 the environmental gradient occurs only in the last case, i.e., for non-speciating sexual popu19 lations evolving towards short-range dispersal. Fourth, the transition between the 20 evolutionary regimes of long-range dispersal with no speciation and short-range dispersal 21 with speciation is typically abrupt, mediated by a positive feedback between incipient 22 speciation and the evolution of short-range dispersal. Fifth, even though the model of sex23 ual evolution analyzed here does not permit assortative mating preferences, speciation 24 occurs for a surprisingly wide range of conditions. This illustrates that dispersal evolution 25 is a powerful alternative to preference evolution in enabling spatially distributed sexual 26 populations to respond to frequency-dependent disruptive selection. 27
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