Ecology and Evolution of Flowers
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The reproductive organs and mating biology of angiosperms exhibit greater variety than those of any other group of organisms. Flowers and inflorescences are also the most diverse structures produced by angiosperms, and floral traits provide some of the most compelling examples of evolution by natural selection. Given that flowering plants include roughly 250,000 species, their reproductive diversity will not be explained easily by continued accumulation of case studies of individual species. Instead a more strategic approach is now required, which seeks to identify general principles concerning the role of ecological function in the evolution of reproductive diversity.
The Ecology and Evolution of Flowers uses this approach to expose new insights into the functional basis of floral diversity, and presents the very latest theoretical and empirical research on floral evolution. Floral biology is a dynamic and growing area and this book, written by the leading internationally recognized researchers in this field, reviews current progress in understanding the evolution and function of flowers. Chapters contain both new research findings and synthesis. Major sections in turn examine functional aspects of floral traits and sexual systems, the ecological influences on reproductive adaptation, and the role of floral biology in angiosperm diversification. Overall, this integrated treatment illustrates the role of floral function and evolution in the generation of angiosperm biodiversity.
This advanced textbook is suitable for graduate level students taking courses in plant ecology, evolution, systematics, biodiversity and conservation. It will also be of interest and use to a broader audience of plant scientists seeking an authoritative overview of recent advances in floral biology.
systems, which recognizes that plants can self-pollinate in several ways. Initially, Lloyd (1975a, 1979b) recognized three ‘‘modes’’ of self-pollination for plants with chasmogamous (open) ﬂowers, based on when self-pollination occurs relative to crosspollination: prior, competing, and delayed. Later, DAVID G. LLOYD AND THE EVOLUTION OF FLORAL BIOLOGY he sub-divided self-pollination that occurs simultaneously with cross-pollination to include: (1) selfpollination within a ﬂower that occurs
composed of several, relatively specialized native plants. However, changes in habitat structure, light and temperature, resource availability, and plant community composition should be, and usually are, FLOWER PERFORMANCE IN HUMAN-ALTERED HABITATS 165 (a) 1.5 Axis 2 0.5 0.0 –0.5 10 10 1.0 1000 0 500 100 1000 1000 100 1000 0 10 100 100 0 500 500 0 500 –1.0 10 –1.5 –1.5 –1.0 –0.5 0.0 1.0 0.5 Axis 1 1.5 2.0 2.5 (b) 1.0 Similarity 0.9 0.8 0.7 0.6 0.5 Edge 10 100 500 1000
disturbance. A survey of 45 species (Aizen et al. 2002) found no evidence that either plant sexual system or degree of specialization inﬂuences the probability of negative responses to habitat fragmentation in terms of either pollination or reproductive success. Also, this probability was independent of whether species occupied tropical or temperate areas, or their growth form. In contrast, Aguilar’s (2005) more detailed and complete meta-analysis supported one of our predictions (Fig. 9.6a).
must decrease investment in others. In this situation, natural selection favours the allocation pattern that maximizes overall ﬁtness, rather than performance of any individual function. As Lloyd demonstrated in a series of papers, this optimal allocation pattern satisﬁes a speciﬁc set of characteristics. As a simple example, consider two functions, A and B (such as the production of ovules versus pollen), which are ﬁnanced by the same resource pool. Suppose that proportion a of these resources
of the beneﬁciary on the benefactor (Johnson 1994), and the beneﬁt to the ‘‘mimic’’ is expected to diminish as its abundance relative to the ‘‘model’’ increases. 6.4.3 Pollinator-community composition If pollinator assemblages differ between plant communities and single-species populations, a plant species may encounter a new ﬂower visitor in the presence of other plant hosts (Ginsberg 1983). For example, in agricultural landscapes, pollinators attracted to native plants are likely to spread