Effect of temperature on rearing of the first brood by the founder females of the ant Lasius niger (Hymenoptera, Formicidae):: Latitude-dependent variability of the response norm

It has been established that duration of brood development and success of rearing of the first worker individuals by founder females of the ant Lasius niger from the northern population (St. Petersburg) depend on temperature conditions to a larger extent than of individuals from the southern a real (Borisovka Village, Belgorod Region) The development rate of individuals from the northern population is lower as compared with individuals from the southern population in the low temperature range (17-20degreesC), but is higher at elevated temperatures (22-27degreesC). This leads to a greater slope of the temperature regression line of the development rate on the temperature, to lower values of the sum of effective temperatures, and to a higher temperature threshold of development in the northern population. Lower temperatures have a stronger effect on development of larvae from the northern population by inducing diapause in the greater number of individuals as compared with larvae from the southern population. The L. niger founder females require, on average, higher temperatures than the females from the southern populations of this species for rearing the first worker ants during the same summer season (i.e., without winter diapause). Thus, ants of the southern populations, when rearing the first brood, use a strategy of faster development at higher temperatures, while low temperatures restrict to the greater extent the development of their brood as compared with ants from the southern populations. It is concluded that one of the ways of physiological adaptation of ants for inhabitance on the North is such change of the norm of response to temperature, at which development becomes more temperature-dependent, the physiological response to higher temperatures increasing at the cost of its decrease at lower temperatures.