Can spatial sorting associated with spawning migration explain evolution of body size and vertebral number in Anguilla eels?

• Spatial sorting is a process that can contribute to microevolutionary change by assemblingphenotypes through space, owing to nonrandom dispersal. Here we first buildupon and develop the “neutral” version of the spatial sorting hypothesis by arguingthat in systems that are not characterized by repeated range expansions, the evolutionaryeffects of variation in dispersal capacity and assortative mating might not beindependent of but interact with natural selection. In addition to generating assortativemating, variation in dispersal capacity together with spatial and temporal variationin quality of spawning area is likely to influence both reproductive success and survivalof spawning migrating individuals, and this will contribute to the evolution of dispersal-enhancingtraits. Next, we use a comparative approach to examine whether differencesin spawning migration distance among 18 species of freshwater Anguilla eelshave evolved in tandem with two dispersal-favoringtraits. In our analyses, we use informationon spawning migration distance, body length, and vertebral number thatwas obtained from the literature, and a published whole mitochondrial DNA-basedphylogeny. Results from comparative analysis of independent contrasts showed thatmacroevolutionary shifts in body length throughout the phylogeny have been associatedwith concomitant shifts in spawning migration. Shifts in migration distance werenot associated with shifts in number of vertebrae. These findings are consistent withthe hypothesis that spatial sorting has contributed to the evolution of more elongatedbodies in species with longer spawning migration distances, or resulted in evolution oflonger migration distances in species with larger body size. This novel demonstrationis important in that it expands the list of ecological settings and hierarchical levels ofbiological organization for which the spatial sorting hypothesis seems to have predictivepower.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

Evolutionary Biology

Evolutionsbiologi

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