Thermal ecology and the structure of an assemblage of adult tiger beetle species ( Cicindelidae).

The thermal ecology of 13 Cicindela species was studied in Sulphur Springs Valley, SE Arizona. For each species, thoracic temperature (T_b) extremes for activity were determined in the laboratory and compared to T_b at which various behavioral activities occurred voluntarily in the field. T_b for coordinated walking showed few significant differences among species for lethal maximum (LT₅₀) values (47.2-48.9oC) but considerable differences for mean minimum values (14.4-21.2oC). Field measurements showed significant differences among species for mean T_b while foraging. These means were correlated with laboratory measurements of mean minimum T_b for coordinated walking but not with LT₅₀ maximum. The extreme difference in species mean minimum T_b for activity is best interpreted as a mechanism for temporal and spatial separation of species that minimizes predation and simultaneous use of limiting resources. The significance of the general similarity in species LT₅₀ maximum thoracic temperature for activity is likely a convergent adaptation to thermally extreme habitats. It may have facilitated the species' historical dispersal abilities through thermally similar habitats over broad geographical areas and enhanced such factors as egg and larval development times.-Authors