The Flight of the Condor: How the Andes shapes patterns of gene flow

Study shows how the topography of the Andes influences genetic patterns of Andean condor populations.

Where would you fly to if you were an Andean condor (Vultur gryphus)? These majestic birds can travel up to 350 kilometers per day. Given their dispersal capacity, you would expect that their genetic population structure is panmictic. This means that each individual can interbreed with any other individual in the population, without restrictions. But is this really the case? A recent study in the journal Diversity and Distributions put this expectation to the test.

subject-andean condor.jpg

A soaring Andean condor (from: http://www.nationalgeographic.com.au/andean-condor/)

 

South American Ecoregions

Julian Padró and his colleagues sequenced 278 individual birds from four different regions in Argentina: Puna, Chaco, Monte and Patagonia. For those of you unfamiliar with ecological regions in South America, here is a quick overview and map:

  • Puna: montane grasslands and shrublands biome in the central Andes
  • Chaco: hot and semi-arid lowland in Argentina, Bolivia and Paraguay
  • Monte: region of dry thorn scrub and grasslands in Argentina
  • Patagonia: southern section of the Andes in Argentina and Chile
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Sampling locations across the range of Andean condors in Argentina (from Padró et al. 2018)

 

Mountain Hopping

The genetic analyses – based on 13 microsatellites – indicated the existence of two subpopulations: one in the north (Puna and Chaco) and one in the south (Patagonia) with a contact zone in the middle (Monte). So, despite their impressive dispersal capacity, there is some population structure.

Interestingly, genetic divergence is higher between Patagonia and Chaco compared to Patagonia and Puna, although the former locations are geographically closer. What is going on here? Given that condors try to optimize their energy expenditure during flight, the researchers think that mountains might provide a clue:

The Puna and Patagonia are connected by the Andes mountain range, which create strong updrafts and a “high-lift” efficient environment for large soaring birds, like condors, to move. In contrast, thermal updrafts in areas with little topographic relief, as the plains surrounding the central mountains of Chaco, are weaker and prone to disruption by wind speed.

In a sense, the ‘archipelago’ of mountains provides a series of stepping stones between Puna and Patagonia. This observation nicely shows how topographic features can influence genetic patterns.

 

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An Andean condor in Patagonia (from: http://www.conservacionpatagonica.org/)

 

Endangered

From a conservation point of view, this mountainous corridor needs to protected. Along with 15 (out of 22) other vulture species, the Andean condor is threatened. These birds are listed as “Near Threatened” by the IUCN and numbers are still declining. Surprisingly, this endangered status is not reflected in their genes. The present study found no evidence for reduced genetic diversity or recent bottlenecks. However, the effects of population decline might take some time to become apparent. Hence, there is no reason to lay back and relax. We wouldn’t want to lose such an amazing bird.

 

References

Padró, J., Lamertucci, S.A., Perrig, P.L. & Pauli, J.N. (2018) Evidence of genetic structure in a wide-ranging and highly mobile soaring scavenger, the Andean condor. Diversity and Distributions.

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