{'fraction_non_alphanumeric': 0.020848573518653987, 'fraction_numerical': 0.005120702267739576, 'mean_word_length': 4.757894736842105, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Darwinian Fitness and Reproductive Power: Reply to Kozlowski

We are glad that our article (Brown et al. 1993, hereafter referred to as BMT) has engendered enough interest to elicit so rapid a critique from Kozlowski (1996). We are grateful for this opportunity tomake a few points that should clarify the energetic oncept of fitness developed in our article and address the issues raised by Kozlowski. Kozlowski's first and most important criticism of BMT concerns the energetic definition of fitness that we use. Darwinian fitness is a very slippery concept, which has almost as many definitions a authors who have written about it. Kozlowski suggests that number of offspring produced in a lifetime (N.) be used as a measure of fitness. This cannot be correct. Consider two genotypes that produce identical offspring. A female of genotype A produces two female offspring over a 2-yr lifetime, while a female of genotype B produces two female offspring over a 4-yr lifetime. Clearly, in a Darwinian sense, genotype A has greater fitness, because it produces otherwise identical offspring ata greater ate than genotype B. Kozlowski further suggests that number of offspring produced per lifetime can be converted to an energetic measure of fitness by assuming that energy content per unit mass of offspring is constant, so that lifetime energy allocation to reproduction can be calculated as N.M., where M. is the average mass of an offspring. If such lifetime nergy allocation to offspring could be equated to fitness, elephants would have much higher fitness than rats. Fitness clearly is a rate. Elephants do not have much higher fitness than rats largely because it takes elephants so much longer to produce their much larger babies. But if fitness is a rate, what is it the rate of? We suggest in BMT (see also Brown 1995) that it can be thought of as the rate at which organisms acquire energy and other scarce resources from the environment and convert hem into offspring. We call this rate reproductive power, and our model gives the maximal reproductive power as a function of body size. J. Damuth (personal communication) has suggested that this maximal reproductive power be called "potential energetic fitness," and we agree that this is a useful term. We recognize in BMT that energy is allocated to the survival of the parent as well as to the production of offspring, but we did not incorporate such features of life history explicitly into our model. We suggest, "Future elaborations of our model could incorporate these details of ecology, specifying how energy is allocated to survival and production of offspring over the lifetime. This would reconcile our treatment with theories of life history that are based on