Neutral processes forming large clones during colonization of new areas
Artikel i vetenskaplig tidskrift, 2017

In species reproducing both sexually and asexually clones are often more common in recently established populations. Earlier studies have suggested that this pattern arises due to natural selection favouring generally or locally successful genotypes in new environments. Alternatively, as we show here, this pattern may result from neutral processes during species' range expansions. We model a dioecious species expanding into a new area in which all individuals are capable of both sexual and asexual reproduction, and all individuals have equal survival rates and dispersal distances. Even under conditions that favour sexual recruitment in the long run, colonization starts with an asexual wave. After colonization is completed, a sexual wave erodes clonal dominance. If individuals reproduce more than one season, and with only local dispersal, a few large clones typically dominate for thousands of reproductive seasons. Adding occasional long-distance dispersal, more dominant clones emerge, but they persist for a shorter period of time. The general mechanism involved is simple: edge effects at the expansion front favour asexual (uniparental) recruitment where potential mates are rare. Specifically, our model shows that neutral processes (with respect to genotype fitness) during the population expansion, such as random dispersal and demographic stochasticity, produce genotype patterns that differ from the patterns arising in a selection model. The comparison with empirical data from a post-glacially established seaweed species (Fucus radicans) shows that in this case, a neutral mechanism is strongly supported.

invasive species


aquatic plant


adaptive variation

Fucus radicans

gene surfing

range expansion


asexual wave

long-distance dispersal



baltic sea


long-range dispersal

sexual reproduction


Marina Rafajlovic

Göteborgs universitet

David Kleinhans

Göteborgs universitet

Universitat Oldenburg

Christian Gulliksson

Chalmers, Matematiska vetenskaper

Göteborgs universitet

J. Fries

Chalmers University of Technology

D. Johansson

Göteborgs universitet

A. Ardehed

Göteborgs universitet

L. Sundqvist

Göteborgs universitet

R. T. Pereyra

Göteborgs universitet

B. Mehlig

Göteborgs universitet

P. R. Jonsson

Göteborgs universitet

K. Johannesson

Göteborgs universitet

Journal of Evolutionary Biology

1010-061X (ISSN) 1420-9101 (eISSN)

Vol. 30 1544-1560