Simultaneous evolution of multiple dispersal components and kernel

Abstract

Global climate is changing rapidly and is accompanied by large-scale fragmentation and destruction of habitats. Since dispersal is the first line of defense for mobile organisms to cope with such adversities in their environment, it is important to understand the causes and consequences of evolution of dispersal. Although dispersal is a complex phenomenon involving multiple dispersal-traits like propensity (tendency to leave the natal patch) and ability (to travel long distances), the relationship between these traits is not always straight-forward, it is not clear whether these traits can evolve simultaneously or not, and how their interactions affect the overall dispersal profile. To investigate these issues, we subjected four large (N~2500) outbred populations of Drosophila melanogaster to artificial selection for increased dispersal, in a setup that mimicked increasing habitat fragmentation over 33 generations. The propensity and ability of the selected populations were significantly greater than the non-selected controls and the difference persisted even in the absence of proximate drivers for dispersal. The dispersal kernel evolved to have significantly greater standard deviation and reduced values of skew and kurtosis, which ultimately translated into the evolution of a greater frequency of long-distance dispersers (LDDs). We also found that although sex-biased dispersal exists in Drosophila melanogaster, its expression can vary depending on which dispersal component is being measured and the environmental condition under which dispersal takes place. Interestingly though, there was no difference between the two sexes in terms of dispersal evolution. We discuss possible reasons for why some of our results do not agree with previous laboratory and field studies. The rapid evolution of multiple components of dispersal and the kernel, expressed even in the absence of stress, indicates that dispersal evolution cannot be ignored while investigating eco-evolutionary phenomena like speed of range expansion, disease spread, evolution of invasive species and destabilization of metapopulation dynamics.peer-reviewed)

Evolution of dispersal syndrome and its corresponding metabolomic changes

“…1A and C), and spent lesser time in rest (Fig. This observation is consistent with previous results (Hanski et al 2006;Matsumura et al 2016) and also with the fact that the VBs were under intense selection to reach a new environment within the first 6 h of introduction to the source (Tung et al 2018). This observation is consistent with previous results (Hanski et al 2006;Matsumura et al 2016) and also with the fact that the VBs were under intense selection to reach a new environment within the first 6 h of introduction to the source (Tung et al 2018).…”

“…We used eight large (breeding size of ß2400) laboratory populations of Drosophila melanogaster, four of which (VB 1-4 , VB stands for "Vagabond") had been selected for greater dispersal ability and propensity for 67 generations (when the last set of assays reported here was performed) and the remaining four (VBC 1-4 , VBC stands for "VB-Control") were their corresponding ancestry-matched controls (Tung et al 2018). The VB 1-4 and VBC 1-4 flies were derived from the corresponding DB 1-4 populations (Sah et al 2013).…”

“…The apparatus used for dispersal selection had three components-a source, a path, and a destination (Tung et al 2018). To impose selection in a given VB population, the adults collected from 80 vials (ß4800 individuals) were divided equally in two sets and introduced into the sources (plastic containers of volume ß1.5 litre) of two independent dispersal set-ups.…”

“…To capture this initial hyperactivity in the selected and control flies in the presence and absence of food (Tung et al 2018), we recorded the activity for the first 6 h after introducing the flies into the glass tubes. This duration was the same as what was given to the flies to disperse during the selection process.…”

“…These populations have been subjected to artificial selection for the longest duration (69 generations, ongoing) documented in the dispersal literature, using a setup that mimics increasing habitat fragmentation over generations (Tung et al 2018). These populations have been subjected to artificial selection for the longest duration (69 generations, ongoing) documented in the dispersal literature, using a setup that mimics increasing habitat fragmentation over generations (Tung et al 2018).…”