5. Adaptive Radiation
85
further increase the pool of short-statured species over evolutionary time.
Finally, the proportion of species with fleshy fruits dispersed by animals increases with rainfall in tropical forests (Gentry 1982, 1988). Many of these taxa are
understory plants, so their reliance on sedentary forest-interior birds for dispersal
should further accelerate speciation and increase the size of the pool of short-statured
tree species, even if it has no immediate effect on the number of such species that
coexist locally. It is remarkable that many of the most species-rich genera of angiosperms - such as Chamaedorea, Dipsi~~ and Geonoma (Arecaceae), Piper
(Piperaceae), and Psychotria (Rubiaceae) - are fleshy-fruited shrubs, treeiets, and
trees in tropical rain-forest understories (Givnish 1998, 1999). Further research is
needed to test whether the exceptional diversity of such groups is mainly a result of
limited dispersal ability, density-dependent mortality, and/or adaptive radiation.
Acknowledgments
This research was supported by NSF grant DEB-9509550. Restriction-site and sequence analyses were conducted in collaboration with my colleagues Ken Sytsma,
Tom Patterson, Jeff Hapeman, Jim Smith, Bill Hahn, Heather Corliss, Chris Pires,
and Aaron Rodriguez; Eric Knox kindly provided access to DNAs of [sotoma, L.
co!umnaris, L. exceisa, L. nicotianijoiia, and L. petiolata. I would like to thank
Professor Masahiro Kato and the Ministry of Education, Science, Sports and Culture of Japan for inviting me to participate in this symposium, associated with the
awarding of the International Prize in Biology to Otto T. Solbrig. Solbrig's seminal
contributions to our understanding of biosystematics, plant adaptation, and the ecological factors constraining plant diversity have long been a personal inspiration.
References
Albertson RC, Markert lA, Danley PD, Kocher TD (1999) Phylogeny of a rapidly evolving
clade: the cichlid fishes of Lake Malawi, East Africa. Proc Natl Acad Sci USA 96:51015106
Aplet GH, Hughes RF, Vitousek PM (1998) Ecosystem development on Hawaiian lava flows:
biomass and species composition. J Veg Sci 9:17-26
Baldwin BG (1992) Phylogenetic utility of the internal transcribed spacers of nuclear ribosomal DNA in plants: an example from the Compositae. Mol Phyl EvoI1:3-16
Baldwin BG (1997) Adaptive radiation of the Hawaiian silversword alliance: congruence
and conflict of phylogenetic evidence from molecular and non-molecular investigations. In: Givnish TJ, Sytsma KJ (Eds) Molecular evolution and adaptive radiation.
Cambridge Univ Press, New York, pp 103-128
Baldwin BG, Robichaux RH (1995) Historical biogeography and ecology of the Hawaiian
silversword alliance (Asteraceae): new molecular phylogenetic perspectives. In: Wagner
WL, Funk VA (Eds) Hawaiian biogeography: evolution on a hot spot archipelago.
Smithsonian Institution Press, Washington, D. c., pp 259-287
85
further increase the pool of short-statured species over evolutionary time.
Finally, the proportion of species with fleshy fruits dispersed by animals increases with rainfall in tropical forests (Gentry 1982, 1988). Many of these taxa are
understory plants, so their reliance on sedentary forest-interior birds for dispersal
should further accelerate speciation and increase the size of the pool of short-statured
tree species, even if it has no immediate effect on the number of such species that
coexist locally. It is remarkable that many of the most species-rich genera of angiosperms - such as Chamaedorea, Dipsi~~ and Geonoma (Arecaceae), Piper
(Piperaceae), and Psychotria (Rubiaceae) - are fleshy-fruited shrubs, treeiets, and
trees in tropical rain-forest understories (Givnish 1998, 1999). Further research is
needed to test whether the exceptional diversity of such groups is mainly a result of
limited dispersal ability, density-dependent mortality, and/or adaptive radiation.
Acknowledgments
This research was supported by NSF grant DEB-9509550. Restriction-site and sequence analyses were conducted in collaboration with my colleagues Ken Sytsma,
Tom Patterson, Jeff Hapeman, Jim Smith, Bill Hahn, Heather Corliss, Chris Pires,
and Aaron Rodriguez; Eric Knox kindly provided access to DNAs of [sotoma, L.
co!umnaris, L. exceisa, L. nicotianijoiia, and L. petiolata. I would like to thank
Professor Masahiro Kato and the Ministry of Education, Science, Sports and Culture of Japan for inviting me to participate in this symposium, associated with the
awarding of the International Prize in Biology to Otto T. Solbrig. Solbrig's seminal
contributions to our understanding of biosystematics, plant adaptation, and the ecological factors constraining plant diversity have long been a personal inspiration.
References
Albertson RC, Markert lA, Danley PD, Kocher TD (1999) Phylogeny of a rapidly evolving
clade: the cichlid fishes of Lake Malawi, East Africa. Proc Natl Acad Sci USA 96:51015106
Aplet GH, Hughes RF, Vitousek PM (1998) Ecosystem development on Hawaiian lava flows:
biomass and species composition. J Veg Sci 9:17-26
Baldwin BG (1992) Phylogenetic utility of the internal transcribed spacers of nuclear ribosomal DNA in plants: an example from the Compositae. Mol Phyl EvoI1:3-16
Baldwin BG (1997) Adaptive radiation of the Hawaiian silversword alliance: congruence
and conflict of phylogenetic evidence from molecular and non-molecular investigations. In: Givnish TJ, Sytsma KJ (Eds) Molecular evolution and adaptive radiation.
Cambridge Univ Press, New York, pp 103-128
Baldwin BG, Robichaux RH (1995) Historical biogeography and ecology of the Hawaiian
silversword alliance (Asteraceae): new molecular phylogenetic perspectives. In: Wagner
WL, Funk VA (Eds) Hawaiian biogeography: evolution on a hot spot archipelago.
Smithsonian Institution Press, Washington, D. c., pp 259-287