PHYSIOLOGICAL-RESPONSES TO INCREASING AMBIENT-TEMPERATURE IN 3 ECOLOGICALLY DIFFERENT, CONGENERIC LIZARDS (GEKKONINAE, PTYODACTYLUS)

Interspecific differences in the responses to increasing ambient tempe rature (up to 40 degrees C) were studied in three species of Ptyodacty lus that differ in their distribution in Israel, in their daily activi ty pattern and in their preferred body temperatures: the northern, diu rnal P, puiseuxi, the southern, nocturnal P, hasselquistii and the diu rno-nocturnal P. guttatus, The diurnal P, puiseuxi was a more precise thermoregulator and was less sensitive to heat, and P, hasselquistii w as the most sensitive to heat exposure, P, guttatus was intermediate, P, puiseuxi maintained relatively stable oxygen consumption and heart frequency in the range of 25-40 degrees C and maintained a lower body temperature at 35 and 40 degrees C, compared with both other species, The nocturnal P, hasselquistii doubled its oxygen consumption between 35 and 40 degrees C and significantly increased its heart and respirat ion frequencies as a function of ambient temperature, The diurno-noctu rnal P, guttatus was intermediate in its responses with both its oxyge n consumption and its heart frequency increasing moderately as a funct ion of ambient temperature, The heating/cooling rate ratio is related to the degree of diurnality, I conclude that the physiological respons es of the three congeners to increasing ambient temperature are closel y related to their distribution and ecology.