Abstract
Biological invasions can induce rapid evolutionary change. As cane toads (Rhinella marina) have spread across tropical Australia over an 80-year period, their rate of invasion has increased from around 15 to 60 km per annum. Toads at the invasion front disperse much faster and further than conspecifics from range-core areas, and their offspring inherit that rapid dispersal rate. We investigated morphological changes that have accompanied this dramatic acceleration, by conducting three-dimensional morphometric analyses of toads from both range-core and invasion-front populations. Morphology of heads, limbs, pectoral girdles and pelvic girdles differed significantly between toads from the two areas, ranging from 0.5% to 16.5% difference in mean bone dimensions between populations, with invasion-front toads exhibiting wider forelimbs, narrower hindlimbs and more compact skulls. Those changes plausibly reflect an increased reliance on bounding (multiple short hops in quick succession) rather than separate large leaps. Within an 80-year period, invasive cane toads have converted the basic anuran body plan – which evolved for occasional large leaps to evade predators – into a morphotype better-suited to sustained long-distance travel.
Highlights
Biological invasions impose profound new evolutionary pressures both upon the invader, and upon the recipient ecosystem [1]
As cane toads have invaded across tropical Australia they have evolved substantial changes in doi:10.1371/journal.pone.0156950.g006
The rapid evolution of a high-dispersal phenotype of cane toads in Australia has been achieved via a remarkable divergence in skeletal morphology between individual toads from invasionfront versus range-core populations
Summary
Biological invasions impose profound new evolutionary pressures both upon the invader, and upon the recipient ecosystem [1]. In response to those pressures, organisms can exhibit phenotypic evolution at rates far higher than are usually observed in equilibrial systems [2,3]. Individuals at an expanding range edge often exhibit distinctive traits of behavior, physiology and morphology that enhance their rates of dispersal [4,5,6]. One of the most intensively studied invasions is that of the cane toad (Rhinella marina) through tropical Australia [13]. Laboratory-bred offspring raised in common-garden conditions inherit the distinctive dispersal rate [19], dispersal behavior (path straightness: [20]), and immunological functioning [21] of their parents
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