How the zebra got its stripes: a problem with too many solutions.

Brenda Larison,Ryan J Harrigan,Daniel I Rubenstein,Alec M Chan-Golston,Elizabeth Li,Thomas B Smith,Henri A Thomassen

doi:10.1098/rsos.140452

Brenda Larison, Ryan J Harrigan + Show 5 more

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https://doi.org/10.1098/rsos.140452

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Abstract

The adaptive significance of zebra stripes has thus far eluded understanding. Many explanations have been suggested, including social cohesion, thermoregulation, predation evasion and avoidance of biting flies. Identifying the associations between phenotypic and environmental factors is essential for testing these hypotheses and substantiating existing experimental evidence. Plains zebra striping pattern varies regionally, from heavy black and white striping over the entire body in some areas to reduced stripe coverage with thinner and lighter stripes in others. We examined how well 29 environmental variables predict the variation in stripe characteristics of plains zebra across their range in Africa. In contrast to recent findings, we found no evidence that striping may have evolved to escape predators or avoid biting flies. Instead, we found that temperature successfully predicts a substantial amount of the stripe pattern variation observed in plains zebra. As this association between striping and temperature may be indicative of multiple biological processes, we suggest that the selective agents driving zebra striping are probably multifarious and complex.

Highlights

Coloration and patterning are important adaptive characteristics in many taxa [1,2,3] and species from fruit flies to humans exhibit2015 The Authors
Individuals run the gamut in terms of striping patterns: some have strong striping over their entire body, while others have few to no stripes on the legs, and faint shadow stripes interspersed with the primary stripes along the torso
Stripe characteristics were quantified for forelegs, hind legs, torso and belly, and included stripe number, thickness, length and colour saturation

Summary

Introduction

Coloration and patterning are important adaptive characteristics in many taxa [1,2,3] and species from fruit flies to humans exhibit2015 The Authors. The clinal modification in striping pattern that plains zebra (Equus quagga) exhibit (figure 2; electronic supplementary material, figure S4) suggests that environmental factors may create selective pressures that play a role in determining stripe patterns. Within this single species, individuals run the gamut in terms of striping patterns: some have strong striping over their entire body, while others have few to no stripes on the legs, and faint shadow stripes interspersed with the primary stripes along the torso. The quagga is thought to have diverged quite recently from other plains zebra and may have undergone stripe loss relatively rapidly, possibly associated with a more open, drier environment [7]. That the degree of striping has a genetic basis is clear from a recent heritability study conducted in captive plains zebra [12]

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