Seed Dispersal and Demography of Pioneer Trees: The Case of Hortia arborea

Abstract

This study investigates the relationships among seed dispersal, patterns of seedling recruitment and the spatial distribution of a pioneer tree (Hortia arborea, Rutaceae) in the Brazilian Atlantic forest. The study was carried out at Dois Irmãos Reserve, a 387.4 ha reserve in northeastern Brazil. Fruit shadow concentrated beneath parental trees (74.6 % < 6 m distant) and fruit removal averaged 5.6 % (0 - 25.5 %). Agoutis (Dasyprocta prymnolopha, Rodentia) ate fruits in the forest and in captivity and were the only vertebrates recorded feeding on Hortia fruits. Agoutis, however, destroyed 86.7 % of the seeds they ingested. In addition, only one seed from an expected number of 1980 germinated in a treefall gap after it passed through the digestive tract of agoutis. Both seed germination and seedling recruitment were restricted to gaps, and occurred among seeds manually released from the pulp or among those from fruits that naturally rotted in gaps. Moreover, exposed seedlings were taller than those covered by plants in a gap. H. arborea appears to self-maintain populations in the same patches of forest, which are delimited by a pool of old and newly created gaps. More specifically, there is successful recruitment in patches occupied by parents, resulting in dense clumps of H. arborea.

Brazilian Atlantic forest - Hortia arborea - pioneer species - Rutaceae - seed dispersal - treefall gaps.

References

• 1 Ackerly D.. Canopy structure and dynamics: integration of growth processes in tropical pioneer trees. Mulkey, S. S., Chazdon, R. L., and Smith, A. P., eds. Tropical Forest Plant Ecophysiology. New York; Chapman & Hall (1996): 619-658
• 2 Alvarez-Buylla E. R., Chãos A., Pinero D., Garay A. A.. Demographic genetics of a pioneer tropical tree species: patch dynamics, seed dispersal, and seed banks.  Evolution. (1996);  50 1155-1166
• 3 Asquith N. M., Terborgh J., Arnold A. E., Riveros M.. The fruits the agouti ate: Hymenaea courbaril seed fate when its disperser is absent.  J. Trop. Ecol.. (1999);  15 229-235
• 4 Becker M., Dalponte J. C.. Rastros de Mamíferos Silvestres Brasileiros. Brasília; Editora Universidade de Brasília (1991)
• 5 Brokaw N. V. L.. The definition of treefall gap and its effects on measures of forest dynamics.  Biotropica. (1982);  11 158-160
• 6 Brokaw N. V. L.. Cecropia schreberiana in the Luquillo Mountains of Puerto Rico.  Bot. Rev.. (1998);  64 91-120
• 7 Coutinho R. Q., Lima-Filho M. F., Souza-Neto J. B., Silva E. P.. Características climáticas, geológicas, geomorfológicas e geotécnicas da Reserva Ecológica de Dois Irmãos.  Reserva Ecológica de Dois Irmãos: Estudos em um Remanescente de Mata Atlântica em Área Urbana (Recife - Pernambuco - Brasil) (Machado, I. C. S., Lopes, A. V., and Porto, K., Orgs.) Recife; Editora Universitária da UFPE (1998): 21-50
• 8 Dalling J. W., Lovelock C. E., Hubbell S. P.. Growth responses of seedlings of two neotropical pioneer species to simulated forest gap environments.  J. Trop. Ecol.. (1999);  15 827-839
• 9 Dalling J. W., Swaine M. D., Garwood N. C.. Dispersal patterns and seed bank dynamics of pioneer trees in moist tropical forest.  Ecology. (1998);  79 564-578
• 10 Davies S. J.. Tree mortality and growth in 11 sympatric Macaranga species in Borneo.  Ecology. (2001);  82 920-932
• 11 Denslow J. S., Hartshorn G. S.. Treefall gap environments and forest dynamics processes. McDade, L. A., Bawa, K., Hespenheide, H., and Hartshorn, G. S., eds. La Selva: Ecology and Natural History of a Neotropical Rain Forest. Chicago; Chicago University Press (1994): 120-127
• 12 Guedes M. L. S.. A vegetação fanerogâmica da Reserva Ecológica de Dois Irmãos.  Reserva Ecológica de Dois Irmãos: Estudos em um Remanescente de Mata Atlântica em Área Urbana (Recife - Pernambuco - Brasil) (Machado, I. C. S., Lopes, A. V., and Porto, K., Orgs.) Recife; Editora Universitária da UFPE (1998): 157-172
• 13 Hartshorn G. S.. Tree falls and tropical forest dynamics. Tomlinson, P. B. and Zimmermann, M. H., eds. Tropical Trees as Living Systems. Cambridge; Cambridge University Press (1978): 617-638
• 14 Hoch G. A., Adler G. H.. Removal of black palm (Astrocaryum standleyanum) seeds by spiny rats (Proechimys semispinosus). .  J. Trop. Ecol.. (1997);  13 51-58
• 15 Howe H. F.. Implications of seed dispersal by animals for tropical reserve management.  Biol. Conserv.. (1984);  30 261-281
• 16 Howe H. F., Smallwood J.. Ecology of seed dispersal.  Ann. Rev. Ecol. Syst.. (1982);  13 201-228
• 17 Hubbell S. P.. Tree dispersion, abundance, and diversity in a tropical dry forest.  Science. (1979);  203 1299-1309
• 18 IBGE .Atlas Nacional do Brasil: Região Nordeste. Rio de Janeiro; IBGE (1985)
• 19 Imbert D., Rousteau A., Labbe P.. Hurricanes and biological diversity in tropical forests - The case of Guadeloupe.  Acta Oecol.. (1998);  19 251-262
• 20 Janzen D. H.. Herbivores and the number of species in tropical forests.  Am. Nat.. (1970);  104 501-528
• 21 Krebs C. J.. Ecological methodology. New York; Library Congress (1989)
• 22 Lorenzi H.. Árvores brasileiras: manual de identificação e cultivo de plantas arbóreas nativas do Brasil, Vol. 2. Nova Odessa; Editora Plantarum (1998)
• 23 Machado I. C., Lopes A. V., Pôrto K. C.. Reserva Ecológica de Dois Irmãos: Estudos em um Remanescente de Mata Atlântica em Área Urbana (Recife - Pernambuco - Brasil). Recife; Editora Universitária da UFPE (1998)
• 24 Medellin R. A., Gaona O.. Seed dispersal by bats and birds in forest and disturbed habitats of Chiapas, Mexico.  Biotropica. (1999);  31 478-485
• 25 Peres C. A., Schiesari L. C., Dias-Leme C. L.. Vertebrate predation of Brazil-nut, an agouti-dispersed Amazonian seed crop (Bertholletia excelsa, Lecythidaceae): a test of the escape hypothesis.  J. Trop. Ecol.. (1997);  13 69-79
• 26 Richards P. W.. The Tropical Rain Forest. Second edition. Cambridge; Cambridge University Press (1996)
• 27 Van Roosmalen G. M.. Fruits of the Guianan Flora. Netherlands; Institute of Systematic Botany, Utrecht University (1985)
• 28 Silva J. M. C., Tabarelli M.. Tree species impoverishment and the future flora of the Atlantic forest of northeast Brazil.  Nature. (2000);  404 72-74
• 29 Smythe N.. Seed survival in the palm Astrocaryum standleianum: evidence for dependence upon its seed dispersers.  Biotropica. (1989);  21 50-56
• 30 Sokal R. R., Rohlf F. J.. Biometry. New York; W. H. Freeman and Company (1995)
• 31 Svenning J. C.. Environmental heterogeneity, recruitment limitation and the mesoscale distribution of palms in a tropical montane rain forest (Maquipucuna, Ecuador).  J. Trop. Ecol.. (2001);  17 97-113
• 32 Tabarelli M., Mantovani W.. Gap-phase regeneration in a tropical montane forest: the effects of gap structure and bamboo species.  Pl. Ecol.. (2000);  148 149-155
• 33 Veloso H. P., Rangel-Filho A. L. R., Lima J. C. A.. Classificação da Vegetação Brasileira Adaptada a um Sistema Universal. Rio de Janeiro; IBGE (1991)
• 34 Wenny D. G., Levey D. J.. Directed seed dispersal by bellbirds in a tropical cloud forest.  Proc. Natl. Acad. Sci.. (1998);  95 6204-6207
• 35 Whitmore T. C.. An Introduction to Tropical Rain Forests. Oxford; Clarendon Press (1990)
• 36 Wilkinson L.. SYSTAT, version 6.0. Chicago, Illinois, USA; SPSS (1996)

Section Editor: U. Lüttge