Get access

The effects of thermal biology and refuge availability on the restricted distribution of an alpine lizard

Authors

  • Camila Monasterio,

    1. Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC,
    2. Departamento de Zoología y Antropología Física (Vertebrados), Facultad de Biología, Universidad Complutense, Madrid, Spain
    Search for more papers by this author
  • Alfredo Salvador,

    1. Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC,
    Search for more papers by this author
  • Pablo Iraeta,

    1. Departamento de Zoología y Antropología Física (Vertebrados), Facultad de Biología, Universidad Complutense, Madrid, Spain
    Search for more papers by this author
  • José A. Díaz

    1. Departamento de Zoología y Antropología Física (Vertebrados), Facultad de Biología, Universidad Complutense, Madrid, Spain
    Search for more papers by this author

Camila Monasterio, Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, E-28006 Madrid, Spain.
E-mail: camila@mncn.csic.es

Abstract

Aim  In an effort to disentangle the ecological processes that confine ectotherms to alpine environments, we studied the thermoregulatory and microhabitat selection behaviours of the rock lizard Iberolacerta cyreni, which is endemic to some mountains of central Spain, and of the wall lizard Podarcis muralis, which is a potential competitor of rock lizards.

Location  We chose three areas in the Sierra de Guadarrama (central Spain) that differed in their thermal quality [mean deviation of environmental operative temperatures from the lizards’ preferred thermal range (PTR)] and refuge availability: a pine forest (1770 m a.s.l.) in which P. muralis was the only species found, and two mixed shrub and rock sites (1770 and 1900 m a.s.l.) where both species were present.

Methods  In the field we collected data on refuge availability, sun exposure, body temperature (Tb) and operative temperature (Te). Thus, we estimated the thermal habitat quality of the areas sampled and the thermoregulation accuracy and effectiveness of both species.

Results  The pine forest had the lowest thermal quality and refuge availability. The lower-elevation shrub site offered the best thermal quality, but refuges were much scarcer than at the higher-elevation site. Both species thermoregulated accurately, because mean deviations of body temperature (Tb) from PTR were considerably smaller than those of Te. Podarcis muralis had higher Tb values than did I. cyreni, which had similar Tb values at both shrub sites, whereas P. muralis had lower Tb values at higher elevation. Overall, the thermoregulatory effectiveness (extent to which Tb values are closer to the PTR than are Te values) of both species was similar, but whereas I. cyreni thermoregulated more efficiently at higher elevation, the opposite was true for P. muralis. At the lower-elevation shrub site, I. cyreni remained closer to refuges than did P. muralis.

Main conclusions  Our results suggest that the pine forest belt might prevent the expansion of rock lizards towards lower elevations as a result of its low thermal quality and scarcity of refuges, that the thermoregulatory effectiveness of rock lizards in alpine environments depends more on refuge availability than on thermal habitat quality, and that competition with wall lizards is unlikely to explain either the distribution or the thermoregulatory effectiveness of rock lizards.

Ancillary