The evolution of anisogamy

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"Darwin identified the existence of separate male and female gametes as one of the central mysteries of evolutionary biology. 150 years later, the question of why male gametes exist remains an intriguing puzzle. In this, the first book solely devoted to the evolution of anisogamy, top theorists in the field explore why gamete dimorphism characterizes nearly all plants and animals. Did separate male and female gametes evolve as a result of competition, or does anisogamy instead represent selection for cooperation? If disruptive selection drove the evolution of anisogamy, with male gametes focused on search and fusion, and female gametes provisioning the new zygote, why do some algal species continue to produce gametes of a single size? Does sperm limitation, or escape from infection, better explain the need for extremely small, highly mobile sperm? Written by leaders in the field, this volume offers an authoritative and cutting-edge overview of evolutionary theory"--Provided by publisher. "The mystery which Darwin struggled with, the existence of sex in the plant and animal kingdoms, continues to fascinate biologists today. While many plant and animal species reproduce sexually, others continue to succeed with asexual reproduction. Consider for example Prorodon utahensis, a small animal which flourishes in the hypersaline waters of the Great Salt Lake (Figure 0.1). There are few other forms of life that can tolerate these salinities which have been measured up to 27%. The quivering hair-like cilia of Prorodon provide its tiny body-scarcely the width of a human hair-with sufficient locomotion to zip about its otherwise lethal environmental, consuming organic detritius, cyanobacteria, and the salt tolerant green alga Dunaliella. In the shallow waters of the Great Salt Lake, which are too salty for fish, these tiny Prorodon are the major hunters, the equivalent of sharks at the microscopic level. Reproduction in Prorodon is a simple matter-it simply splits in half. Without resorting to sexual recombination, Prorodon is able to lock in the genetic combination for survival and success in this most hostile of environments. Asexual reproduction also grants Prorodon utahensis a significant numerical advantage in progeny. A single individual splits, producing two, then four, then eight, then sixteen, then thirty-two genetically identical offspring. This ceaseless process of binary division can rapidly fill a small saline pond or even the Great Salt Lake with hundreds of millions of ciliates from a single immigrant. Were Prorodon to reproduce sexually, the number of offspring it produces would be halved since in a population characterized by separate males and females, only half of the individuals can produce offspring"--Provided by publisher.

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