The Evolution of Conditional Dispersal and Reproductive Isolation Along Environmental Gradients

Payne, J.L., Mazzucco, R., & Dieckmann, U. ORCID: (2011). The Evolution of Conditional Dispersal and Reproductive Isolation Along Environmental Gradients. IIASA Interim Report. IIASA, Laxenburg, Austria: IR-11-017

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Dispersal modulates gene flow throughout a population's spatial range. Gene flow affects adaptation at local spatial scales, and consequently impacts the evolution of reproductive isolation. A recent theoretical investigation has demonstrated that local adaptation along an environmental gradient, facilitated by the evolution of limited dispersal, can lead to parapatric speciation even in the absence of assortative mating. This and other studies assumed unconditional dispersal, so individuals start dispersing without regard to local environmental conditions. However, many species disperse conditionally their propensity to disperse is contingent upon environmental cues, such as the degree of local crowding or the availability of suitable mates. Here, we use an individual-based model in continuous space to investigate by numerical simulation the relationship between the evolution of threshold-based conditional dispersal and parapatric speciation driven by frequency-dependent competition along environmental gradients. We find that, as with unconditional dispersal, parapatric speciation occurs under a broad range of conditions when reproduction is asexual, and under a more restricted range of conditions when reproduction is sexual. In both the asexual and sexual cases, the evolution of conditional dispersal is strongly influenced by the slope of the environmental gradient: shallow environmental gradients result in low dispersal thresholds and high dispersal distances, while steep environmental gradients result in high dispersal thresholds and low dispersal distances. The later, however, remain higher than under unconditional dispersal, thus undermining isolation by distance, and hindering speciation in sexual populations. Consequently, the speciation of sexual population under conditional dispersal is triggered by a steeper gradient than under unconditional dispersal. Enhancing the disruptiveness of frequency-dependent selection, more box-shaped competition kernels dramatically lower the speciation-enabling slope of the environmental gradient.

Item Type: Monograph (IIASA Interim Report)
Uncontrolled Keywords: Frequency-dependent selection; Sexual reproduction; Speciation; Evolutionary branching; Competition kernels
Research Programs: Evolution and Ecology (EEP)
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:46
Last Modified: 27 Aug 2021 17:22

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