PALMS Chazdon: Palm Literature Volume 47(3) 2003

PALM LITERATURE that the topography of Henderson’s landscape will undergo some seismic shifts in the next decade. EVOLUTION AND ECOLOGY OF PALMS. By Andrew Henderson. The New York Botanical Following the introduction, Henderson begins with two chapters on palm stem morphology and Garden Press, Bronx, NY. 2002. SBN 0-89327- an analysis of size and shape of palm stems. 444-5. US$35.00. Paperback.259 pp., numerous Henderson distinguishes two types of stem halftone photos and diagrams. morphology within the family – palms with Palms, the princes of the kingdom, internodal elongation and palms lacking command respect from many loyal subjects. Their internodal elongation. The former group shows royal heritage gives palms the freedom to make more restricted variation of stem height and and follow their own sets of rules. Unraveling the diameter ratios, whereas the latter group exhibits complex linkages among palm morphology, more variation in these ratios. To the extent that ecology, and evolution is a major task that has these groupings represent clades, Henderson posits preoccupied many prominent botanists, including that phyletic changes in stem growth rate can be Holttum, Corner, Tomlinson, Moore, Uhl, and related to phyletic variation in morphology, Dransfield. Andrew Henderson follows this reproductive structures, and the duration and progression of big palm thinkers in this synthetic timing of reproduction. He makes a convincing volume. The central thesis he develops in the hypothesis that remains to be tested conclusively Introduction and revisits in virtually every across the entire family. chapter, is that stem morphology has pervasive The next chapter focuses on leaf morphology and consequences for morphology of and arrangement, again emphasizing relationships reproductive structures and therefore influences all between stem and leaf development. Henderson aspects of vegetative and reproduction function. points out that leaf size and stem diameter co- The evolutionary processes that have shaped the vary in some palm genera, but not in others, a diversification of palm forms are viewed within pattern that he later interprets within the context the concept of heterochrony, the change in timing of beetle vs. bee/fly/wasp pollination syndromes. of rates of development and developmental I found these trends to be intriguing, but a sequences, as widely discussed by Gould in his remarkably small number of palm genera are 1997 book Ontogeny and Phylogeny. Related to actually compared here. The discussion proceeds these changes are allometric constraints that vary to development and maturation in in their expression within and among Chapter 5, which is followed by a chapter on evolutionary lines. Neither of these major reproductive duration. Phylogenetic hypotheses concepts is new; heterochrony and allometry have based on molecular data suggest that a shift from been previously applied to particular aspects of semelparity to iteroparity took place early in palm palm morphology and evolution. But here they evolution in the Calamoid group, with a later receive new life in the ways in Henderson’s broad reversal back to semelparity in the Coryphoid application and synthesis. His new vision enables genera Nannorrhops and Corypha, associated with linkages between vegetative and reproductive a reduction in growth rate and an extension of functions, and among growth rate, plant size and lifespan. Similarly, a reversal to semelparity took life history evolution. place in Caryota and Wallichia and some species of Arenga of the Caryotoid group, although in Henderson returns to Moore’s landmark 1973 these cases the connection with slow growth rate publication on the Major Groups of Palms and and increased longevity is less universal. their Distribution, leaving aside Moore’s biogeographic focus in favor of a focus on In Chapter 7, Henderson extends the discussion morphology, life history, and ecology. He of reproductive biology to phenology and resurrects Moore’s 15 major groups, abandoning breeding systems, leading to a detailed treatment the tribal classification later developed by Moore of pollination in Chapter 8. These topics are and published in Genera Palmarum by Uhl and strongly linked functionally as well as structurally. Dransfield (1987). Henderson splits Moore’s Henderson characterizes a set of traits associated Cocosoid group into spiny and non-spiny groups with beetle pollinated species, including high for a total of 16 groups. Molecular-based synchrony and short duration of flowering, phylogenetic studies suggest that 13 of these major condensed with closely-spaced groups are monophyletic; Coryphoids, Arecoids, flowers, rapid maturation with short, nocturnal and Nonspiny cocosoids are considered to be anthesis, basipetal maturation, temperature polyphyletic. A complete phylogenetic assessment elevation, protogyny, and lack of nectar of palms is not yet possible, and it is quite likely production. In contract, species pollinated by bees,

PALMS 47(3): $$–$$ 149 PALMS Chazdon: Palm Literature Volume 47(3) 2003 flies, and wasps tend to have low synchrony and throughout the book’s ten dense chapters that my long duration of flowering, elongate inflorescences head was reeling. I felt a need for a less- with loosely spaced flowers, slow maturation, long concentrated conclusion, so I had to go back and diurnal anthesis, acropetal maturation, through the book at my own pace, revisiting the protandry, and production of sweet nectar. conclusions at the end of each chapter. In this Henderson also proposes a generalized trade-off book, Henderson boldly went where no palm between growth and reproduction, such that biologist has gone before. He chose to take a wide internodal growth is often reduced following view and, as a result, has produced a major sexual maturity. He further points out that beetle- contribution that may well extend beyond the pollinated genera, such as Bactris, are strongly borders of the palm kingdom. It is laudable that, selected for conservatism in inflorescence size, despite Henderson’s extensive New World whereas taxa pollinated by a greater variety of experience, the book includes many examples of insects, such as Sabal, Prestoea, and lack Old World palms. The topics are covered in these constraints on inflorescence size and also substantial detail, and are highly integrated lack integration among inflorescence size, stem throughout. The book illustrates the quantum leap diameter, and leaf size. in our understanding of palm evolution and diversification that has been enabled by molecular- Henderson describes fecundity and fruit based phylogenetic studies. maturation in Chapter 9, highlighting a general trend – species with larger stems produce more Henderson’s orientation in this book is clearly numerous, smaller fruits. The associations between more focused on evolution than ecology. palms and their fruit/seed dispersers and seed Including a section on the geographic distribution predators are detailed in Chapter 10. Henderson of major taxa would have made the treatment distinguishes two syndromes of seed dispersal in more complete. Population and community palms, the mammal/bruchid system and the ecology of palm species are not discussed. Palm bird/scolytid system. The former is exemplified by ecology involves much more than interactions non-spiny Cocosoid palms, which have with animals and distributions across major simultaneous fruit ripening and large, scented biomes. Palms often reach high abundance in fruits, that tend to fall beneath the parent tree areas frequently disturbed by hurricanes or fires. and are scatter-hoarded by various rodents. Seeds Furthermore, canopy palm species can play an that are left behind are highly susceptible to important role in plant and animal community predation by bruchid beetles. The bird/scolytid structure, as keystone resources for frugivores and system, in contrast, applies to palms with as agents of small-scale disturbance through leaf sequential ripening and small fruits. Fruits are fall. Finally, palms also show complex meso-scale generally red or purplish black and have no distribution patterns within tropical forests, noticeable scent. They attract a large number of suggesting affinities to particular soil and slope birds, including toucans, parrots, and oil birds. characteristics. It is important to understand the Scolytid beetles are common seed predators of ecology of palms in their complex ecological Oenocarpus, Prestoea, and Euterpe. matrix, rather than in manicured botanical gardens, where much of the research on their Henderson completes his work with a discussion growth, morphology, and reproductive biology of germination, contrasting characteristics of has been conducted. species with remote vs. adjacent modes. Palms with adjacent germination mode tend to have Palm aficionados and scholars alike will appreciate shorter, thinner stems with elongate internodes, the rich detail and broad synthesis achieved here higher growth rates, and smaller inflorescences (and, by the way, the Appendix is awesome). My and fruits. These species generally occur in moist copy will proudly take its place on the shelf forest habitats. This comparison is one of the few between Corner’s Natural History of Palms and Uhl in the book that are based on species-level traits and Dransfield’s Genera Palmarum. Congratu- rather than traits at the generic or major group lations to the author and publisher on a job well level. done! I must admit, by the time I got to the end of the Robin L. Chazdon book, I was anticipating more than the one-page Department of Ecology and Evolutionary Biology Epilogue. So much synthesis had been presented University of Connecticut, USA.

150