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Flowers are relatively recent innovations. The first land plants arose around 470 million years ago, but fossil evidence indicates that only after another 340 million years did the angiosperms (flowering plants) appear. However, following their appearance in the fossil record of the early Cretaceous period, the angiosperms spread geographically from their point of origin in the tropics and diversified dramatically to become the ecologically dominant plant group in the great majority of terrestrial habitats. This extraordinary radiation into an enormous range of morphological diversity took a mere 40 million years. This chapter examines the origin of the flowering plants, and then looks in detail at those first flowers, considering their morphology, their development, and their diversification.

This chapter focuses on the developmental evolution of flowers and flower organ identity. It reviews some of the most important insights that have been gained from research on the developmental evolution of flowers regarding the nature of organ identity, organ integration, and the origin of evolutionary novelties. The chapter begins with a discussion of the uniqueness of flowers and the evolution of phylogeny and flower characters in angiosperms. It then examines the genetics of canonical flower development, along with the developmental genetic architecture of the flower Bauplan. It also considers flower variation and the identities of novel flower organs, the origin of the bisexual flower developmental type, perianth evolution and the origin of petals, and the realization that additional organ identities can evolve after gene duplications.

This chapter examines abiotic pollination via wind or water. It begins with a discussion of wind pollination or anemophily, which is a common occurrence in modern plants, especially in most gymnosperms, in the catkin-bearing angiosperm trees, and in cereals (Poaceae and Cyperaceae). Anemophily is predominantly a derived condition in angiosperms, associated with ecological conditions where zoophily is difficult. Transition from zoophily to anemophily has occurred at least sixty-five times in such circumstances. The chapter looks at wind-pollinated angiosperm and conifer flowers and goes on to consider critical factors affecting pollen movement in anemophilous plants. It concludes with an overview of hydrophily, or water pollination.

This chapter introduces some of the book’s central themes on animal pollination, beginning with a discussion of animals that visit flowers. At least 130,000 species of animals, and probably up to 300,000, are regular flower visitors and potential pollinators. At least 25,000 species of bees are included in this total, all of them obligate flower visitors and often the most important pollinators in a given habitat. There are currently about 260,000 species of angiosperms and it has been traditional to link particular kinds of flowers to particular groups of pollinators. The chapter proceeds by explaining why animals visit flowers, how flowers encourage animal visitors, and what makes a visitor a good pollinator. It also considers the costs, benefits, and conflicts in animal pollination before concluding with an enumeration of reasons why pollination is worth studying.

This chapter examines the evolution of flowers, pollination, and plant diversity. There is good evidence for pollinator-mediated selection and appropriate trait heritability in flowers, and there are well-established mechanisms by which this could bring about floral change, reproductive isolation, and evolutionary divergence or specialization. The chapter first considers the origin and early evolution of flowers before discussing the diversification of angiosperms. It then explores the advantages of animal pollination and goes on to discuss the extent to which pollination may have contributed to floral variation, plant speciation, and plant diversification. In particular, it explains whether pollinators select for floral divergence and describes five ways in which floral divergence could arise by selection: adaptation to distinct niches, character displacement, adaptive “wandering,” character correlations, and genetic drift.

This chapter describes the intimate ties between the early history of animal life and plant life. More broadly, it examines the changing diversity of plant groups through geologic time, and how the changing vegetation has left a profound impact on animal life, and vice versa. The chapter first describes the gymnosperms, “naked seeds” in which the fertilized embryos are protected and nourished but not enclosed in an ovary. Angiosperms—the earliest flowering plants—began to flourish by mid-Cretaceous times, and unlike the naked seeds of their gymnosperm predecessors, the seeds of angiosperms are covered and protected within a carpel or ovary, providing protection against pests and desiccation, as well as providing a vehicle for seed dissemination, as carpels evolved into edible fruits in certain groups of flowering plants. Finally, the chapter describes Cenozoic flora—their increasing modernization, their changing distribution, and the spread of grasses.

Flowers evolved around 130–180 million years ago. This chapter discusses the origins and radiations of the angiosperms and the flowers they produce, analysing both fossil and molecular phylogenetic data. The morphological context within which flowers arose is discussed, with an analysis of seed plant reproductive structures and the key morphological transitions necessary to generate the angiosperm flower – development of a bisexual reproductive shoot and production of perianth organs. The diversity of current floral morphology and the explanations for floral diversification are discussed. The chapter concludes with an introduction to current hypotheses on the relationships of the different orders of angiosperms.

This chapter discusses the relationships among lepidopteran evolutionary lineages based on changes in their morphological adaptation. It begins by discussing fossil records of Lepidoptera, followed by the morphological adaptations of ancient and subsequent lineages. The chapter then illustrates a theoretical scenario for the origins of angiosperm-feeding in basal lepidopteran lineages that led to radiations of Lepidoptera. It also describes the evolutionary origin of the present-day flora of western North America.

The order Sirenia is the only extant group of mammals adapted to feed exclusively on aquatic plants. In view of the worldwide abundance of aquatic macrophytes and the few other large herbivores competing for this resource, it is noteworthy that Recent sirenians comprise only three genera and five species. One of these, Steller's sea cow (Hydrodamalis gigas) of the North Pacific, was exterminated by humans in the eighteenth century. Uniquely among sirenians, the Steller's sea cow was adapted to cold-temperate climates and a diet of kelp and other algae. All the living sirenians are tropical forms that feed preferentially on angiosperms, and this appears to have been the primitive condition for the order. The Indian Ocean and West Pacific tropics are today inhabited by a single species, Dugong dugon, distributed in nearshore marine waters from East Africa and the Red Sea to Japan, Micronesia, and Australia. There are four families of sirenians: Prorastomidae, Protosirenidae, Trichechidae, and Dugongidae. This chapter describes the systematic paleontology of Sirenia.

There is much excellent phylogenetic work on California plant species, but the molecular tools used thus far are generally more useful at discerning evolutionary relationships that occurred prior to the Pleistocene. Some species were survivors of disjunctions among previously widely distributed taxa and some arrived via dispersal. There is good evidence that many California plant clades are the result of Miocene migrations across Beringia. Although likely originating from the Old World, several California genera have evolutionary divergence centered in western North America and illustrate the phylogeography of flowering plants of California. Diversification on complex substrates during fluctuating climates has resulted in high levels of endemism throughout the state, but particularly in the Klamath-Siskiyou and Coast Ranges. Evolutionary processes within California’s many endemic species undoubtedly included allopolyploidy, autopolyploidy, and apomixis. Secondary contact resulting in hybridization—as a result of colonization from multiple refugia—has led to interesting genetic patterns of reticulation in many taxa. Much phylogeographic work remains to be conducted on the flora of California, particularly those species that occur in the Klamath-Siskiyou region and those with distributions in the Transverse Ranges and southern Sierra Nevada. Endemics with the most restricted distributions are present in the central Coast Ranges, the Sierra Nevada, and the San Bernardino Range, with the youngest neoendemics identified from the Desert and Great Basin.

Among the greatest cooperative examples of biotic evolution that released a virtually unbounded world of complexity, particularly conspicuous among eukaryotic organisms, was the evolution of sex. In sex, each individual of a mating pair contributes part of its genetic makeup (genome) to offspring—always cells are the seminal agents of the genetic contribution from each self—that participate in an emergent new generation. Thus a self, upon engaging in sex, abandons a substantial portion of its integrity and weaves together a molecular-to-cellular-to-organismal fractal interface with a partner. Throughout the sexual world, self seeks a profound intimacy with non-self. The chapter first describes gene sharing by bacteria through conjugation, a prokaryotic version of sex. An allegory of dancing snakes metaphorically represents cellular reproduction by mitosis and the reduction divisions of chromosomes in meiosis, the basis of gene sharing in sex among eukaryotes. Genetic recombination via meiosis enormously accelerates the diverse expressions of myriad life forms. Among angiosperm plants, sex is manifest in immensely variable flowers and, with some exceptions, their colors and forms evolved in response to a profound cooperative imperative with animal partners that spread their pollen. Darwin’s major insight on sexual selection among animals has explained male-female dimorphisms from subtle to spectacular.

Archaeologically, the use of marine kelps and seaweeds is poorly understood, yet California's islands are surrounded by extensive and highly productive kelp forests with nearshore habitats containing more than 100 edible species. Historical accounts from around the Pacific Rim demonstrate considerable use of seaweeds and seagrasses by native people, but there has been little discussion of seaweeds as a potential food source on California's islands. This chapter summarizes the biology, diversity, ecology, and productivity of marine macroalgae and marine angiosperms in the California Bight, supporting the likely consumption of seaweeds in the past. The potential use of plentiful and nutritious seaweeds by California Island peoples has major implications for the perceived marginality of the islands.

In the case studies of taxa presented here, where times and directions of migrations and reintroductions have been suggested, 27 or ca. 60% appear to have used land bridges, based on the fossil record or on their limited means of long-distance dispersal. That means ca. 40% migrated by other means over, around, or through barriers by birds, ocean currents, or wind, or were residues of ancient land collision and fragmentation. In all cases climatic conditions and trends were an important if not overriding factor in determining movements and successful establishment in the arrival area. That places land bridges in a better perspective for understanding past and present radiation, diversification, and patterns of distribution among organisms. Certain taxa have a reasonably good fossil record and a sound taxonomy/phylogeny and can be used for establishing parameters in models proposed for those less well known. Pinus, Ilex, Nipa, Lythraceae, Rhizophoraceae, and many deciduous trees (Nothofagus) are examples.

The evolution of interactions between plants and their pollinators provides some of the clearest examples of change in the outcome of interactions from antagonistic to mutualistic. Early insect pollinators of angiosperms fed on pollen, ovules, seeds, and flower parts. The vast majority of these interactions were detrimental to the plants, and the closed carpels of angiosperms were probably a defense against these flower visitors. However, these antagonistic interactions provided a basis on which selection could act, because some flower visitors were less detrimental to flower parts than others, while some plants possessed floral traits that caused the interaction to be less detrimental to the plant and, at some point in time, beneficial. This chapter explores antagonism and mutualism between ants and flowers, focusing on pollination by ants and how ants discourage floral visits.

Ants are probably the most dominant insect family on earth, and flowering plants have been the dominant plant group on land for more than 100 million years. The evolutionary success of angiosperms cannot be ascribed solely to benefits conferred by possessing flowers; it is also the result of benefits conferred by an array of interspecific interactions (for example, pollination, herbivory, and seed dispersal) that have helped shape their great diversity. On those bases alone, the results of studies on the ecology and evolution of ant–plant interactions are crucial to an understanding of the ecology of terrestrial biological communities. This chapter discusses the importance of studies on ant–plant interactions for evolutionary ecology and presents an overview of what has been learned by studying such interactions. It examines spatial and temporal variation in ant–plant interactions, the role of induced responses to herbivory, the phylogeny of ant–plant interactions, and plant defense by ants. The chapter concludes by suggesting perspectives on what needs to be studied and how these studies should be approached, and by reporting on research that is currently in development.

South America’s shape, size, and geographic position, now and in the past, have acted to influence the development of diverse coverings of land surfaces with plants of different sizes, adaptations, and origins. Underlying geologic structures have been exposed to weathering regimes, thereby resulting in a multiplicity of landforms, soil types, and ecological zones. The most notable large-scale features are the Andes, which curl along the western margin of the continent, and the broad swath of the Amazon lowlands in the equatorial zone. However, there are also extensive, more ancient mountain systems in the Brazilian Shield of east-central Brazil and the Guiana Shield in northern South America. The interplay of environmental factors has given rise to a panoply of vegetation types, from coastal mangroves to interior swamplands, savannas, and other grasslands, deserts, shrublands, and a wide array of dry to moist and lowland to highland forest types. The narrower southern half of South America is also complex vegetationally because of the compression of more vegetation types into a smaller area and the diverse climatic regimes associated with subtropical and temperate middle latitudes. Alexander von Humboldt began to outline the major features of the physical geography of South America in his extensive writings that followed his travels in the early nineteenth century (von Humboldt, 1815–1832). For example, he first documented the profound influences of contemporary and historical geologic processes such as earthquakes and volcanoes, how vegetation in mountainous areas changes as elevation influences the distributions of plant species, and the effect of sea surface temperatures on atmospheric circulation and uplift and their impacts on precipitation and air temperatures (Botting, 1973; Faak and Biermann, 1986). His initial insights, in combination with modern observations (Hueck and Seibert, 1972; Cabrera and Willink, 1973; Davis et al., 1997; Lentz, 2000), still serve to frame our synthesis of the major vegetation formations of South America. In this chapter, we relate vegetation formations to spatial gradients of soil moisture and elevation in the context of broad climatic and topographic patterns.

When the subject of extinctions in the geological past comes up, nearly everyone’s thoughts turn to dinosaurs. It may well be true that these long-extinct beasts mean more to most children than the vast majority of living creatures. One could even go so far as to paraphrase Voltaire and maintain that if dinosaurs had never existed it would have been necessary to invent them, if only as a metaphor for obsolescence. To refer to a particular machine as a dinosaur would certainly do nothing for its market value. The irony is that the metaphor is now itself obsolete. The modern scientific view of dinosaurs differs immensely from the old one of lumbering, inefficient creatures tottering to their final decline. Their success as dominant land vertebrates through 165 million years of the Earth’s history is, indeed, now mainly regarded with wonder and even admiration. If, as is generally thought, the dinosaurs were killed off by an asteroid at the end of the Cretaceous, that is something for which no organism could possibly have been prepared by normal Darwinian natural selection. The final demise of the dinosaurs would then have been the result, not of bad genes, but of bad luck, to use the laconic words of Dave Raup. In contemplating the history of the dinosaurs it is necessary to rectify one widespread misconception. Outside scientific circles the view is widely held that the dinosaurs lived for a huge slice of geological time little disturbed by their environment until the final apocalypse. This is a serious misconception. The dinosaurs suffered quite a high evolutionary turnover rate, and this implies a high rate of extinction throughout their history. Jurassic dinosaurs, dominated by giant sauropods, stegosaurs, and the top carnivore Allosaurus, are quite different from those of the Cretaceous period, which are characterized by diverse hadrosaurs, ceratopsians, and Tyrannosaurus. Michael Crichton’s science-fiction novel Jurassic Park, made famous by the Steven Spielberg movies, features dinosaurs that are mainly from the Cretaceous, probably because velociraptors and Tyrannosaurus could provide more drama.