68 LUGO 



whole ecosystems, as shown, e.g., by Stearns (1975) in his discussion 

 of the effects of reservoir fluctuations on the evolution of popula- 

 tions of mosquitofish. Analyses of this type are becoming very 

 common in the hterature (Colwell, 1974; Sneyers, 1976; Dyer and 

 Tyson, 1977). Findings indicate that such potential stressors as 

 drought (Dyer and Tyson, 1977), fire (Houston, 1973), hurricanes 

 (Thomas, 1974; Gentry, 1974), flash floods (John, 1964), storms 

 that cause catastrophic drifts (Anderson and Lehmkuhl, 1968), or 

 rainfall (Beatley, 1974; Colwell, 1974) have recurrent, predictable 

 patterns to which ecosystems can adapt and which they depend on 

 for their survival and maintenance. 



Living systems "track" the environment through a number of 

 adaptations that have bearing on environmental anticipation, e.g., 

 storages of energy, life forms, strategies of life cycles, phenological 

 patterns, migrations, successional recovery, alterations in rates of 

 physiological processes, and lowering of productivity-to-biomass 

 ratios. At the population level, e.g., Bott (1975) showed that bacteria 

 in a stream with a fluctuating thermal event (up to 23°C/year) had 

 adapted to a temperature 5 to 20° C higher than the mean 

 temperature of the stream. An optimum growth temperature near 

 the lethal temperature becomes a predictive mechanism for random 

 temperature fluctuations; temperature increases have less likelihood 

 of exceeding the higher tolerance limit. 



Environmental fluctuations are stressful to ecosystems (Dunbar, 

 1960), and, as the environment becomes more variable, the cost of 

 anticipation should increase. Anticipating a changing environment 

 remains an essential prerequisite of life, however, if the organism or 

 the ecosystem is to survive. 



I agree with Margalef's idea (1969; 1975) that, as they develop 

 toward the steady state, ecosystems gain information that, in part, 

 allows them to anticipate fluctuations in their environments. At the 

 ecosystem level an event may cause mortality in certain sectors of 

 the system, but the system as a whole may be able to adapt to it. For 

 example, hurricanes kill mangrove trees, but they are essential for the 

 survival of the mangrove forest (Cintron et al., 1978). The annual 

 migration of the thermocline in a temperate dimictic lake creates 

 severe problems for certain populations of bacteria, zooplankton, 

 and phytoplankton, but, for the lake as a whole, this event is 

 predictable and essential for the distribution of heat, nutrients, and 

 organic fuels. Thus, if we select the whole ecosystem as a point of 

 reference, there cannot be naturally unpredictable environments that 

 are colonized by steady-state ecosystems. Harshness of the environ- 

 ment should not be confused with unpredictability. 



