Diet of Andean leaf-eared mice (Phyllotis) living at extreme elevations
on Atacama volcanoes: insights from metagenomics, DNA metabarcoding, and
stable isotopes
Abstract
On the flanks of >6000 m Andean volcanoes that tower over the
Atacama Desert, leaf-eared mice (Phyllotis vaccarum) live at extreme
elevations that surpass known vegetation limits. What the mice eat in
these barren, hyperarid environments has been the subject of much
speculation. According to the arthropod fallout hypothesis, sustenance
is provided by windblown insects that accumulate in snowdrifts (‘aolian
deposits’). It is also possible that mice feed on saxicolous lichen or
forms of cryptic vegetation that have yet to be discovered at such high
elevations. We tested hypotheses about the diet of mice living at
extreme elevations on Atacama volcanoes by combining metagenomic and DNA
metabarcoding analyses of gut contents with stable-isotope analyses of
mouse tissues. Genomic analyses of contents of the gastrointestinal
tract of a live-captured mouse from the 6739 m summit of Volcán
Llullaillaco revealed evidence for an opportunistic but purely
herbivorous diet, including lichens. Although we found no evidence of
animal DNA in gut contents of the summit mouse, stable isotope data for
a larger sample of mice indicate that mice native to elevations at or
near vegetation limits (~5100 m) include a larger fraction
of animal prey in their diet than mice from lower elevations. Some
plants detected in the gut contents of the summit mouse are known to
exist at lower elevations at the base of the volcano and in the
surrounding Altiplano, suggesting that such species may occur at higher
elevations beneath the snowpack or in other cryptic microhabitats.