Seed Size and Plant Growth Form as Factors in Dispersal Spectra

All vascular plant species were listed on eight sites near Sydney, Australia. Four sites were on infertile and four on fertile soil. Each of the 355 species was classified according to seed mass (measured as fresh mass of embryo plus endosperm), morphological adaptations for dispersal by different vectors, and growth form. The infertile—soil sites had more species and more cover adapted for dispersal by ants, and the fertile—soil sites had more species and more cover with fleshy fruits adapted for dispersal by vertebrates. We tested the hypothesis that this difference could be interpreted as a secondary correlate of seed size or of growth form. Species with smaller seed mass of growing to <2 m tall were significantly more likely to be adapted for dispersal by ants relative to vertebrates. An indirect association via growth form was capable of accounting for up to 84% of the relationship between soil type and dispersal mode, and indirect association via seed mass for up to 23% of the relationship; the two together could account for a maximum of 85%. The indirect association association via seed mass relatively weaker because seed masses proved not to be very different between these soil types. There remained a significant residual tendency for species in any given seed size class and growth form to be more likely to be dispersed by vertebrates relative to ants on fertile soils than on infertile soils.

[1]  John L. Harper,et al.  The Shapes and Sizes of Seeds , 1970 .

[2]  N. Beadle.  Soil Phosphate and Its Role in Molding Segments of the Australian Flora and Vegetation, with Special Reference to Xeromorphy and Sclerophylly , 1966 .

[3]  M. Willson,et al.  Plant reproductive ecology , 1983 .

[4]  A. Beattie,et al.  Effects of ant mounds on soil chemistry and vegetation patterns in a Colorado montane meadow , 1983 .

[5]  W. Bond,et al.  Convergence of myrmecochory in mediterranean Australia and South Africa , 1982 .

[6]  R. Y. Berg.  SEED DISPERSAL OF DENDROMECON: ITS ECOLOGIC, EVOLUTIONARY, AND TAXONOMIC SIGNIFICANCE , 1966 .

[7]  S. Handel,et al.  Ants Disperse a Majority of Herbs in a Mesic Forest Community in New York State , 1981 .

[8]  H. G. Baker.  Seed Weight in Relation to Environmental Conditions in California , 1972 .

[9]  A. Beattie,et al.  THE FATE OF VIOLA SEEDS DISPERSED BY ANTS , 1980 .

[10]  J. Majer.  Ant-plant interactions in the Darling Botanical District of Western Australia , 1982 .

[11]  E. J. Kraus.  The Reproductive Capacity of Plants , 1943, Ecology.

[12]  A. Gill,et al.  CHAPTER 3 – Seed Dispersal Syndromes in Australian Acacia , 1986 .

[13]  D. Janzen.  SEED‐EATERS VERSUS SEED SIZE, NUMBER, TOXICITY AND DISPERSAL , 1969, Evolution; international journal of organic evolution.

[14]  Dr. Leendert van der Pijl.  Principles of Dispersal in Higher Plants , 1970, Springer Berlin Heidelberg.

[15]  J. Harper.  Population Biology of Plants , 1979 .

[16]  D. Haig,et al.  Plants’ use of ants for dispersal at West Head, New South Wales , 1982 .

[17]  M. Willson.  Avian Frugivory and Seed Dispersal in Eastern North America , 1986 .

[18]  C. H. Gimingham,et al.  Mediterranean-Type Ecosystems: The Role of Nutrients , 1983 .

[19]  S. H. Bullock.  Seed Dispersal of Dendromecon by the Seed Predator Pogonomyrmex , 1974 .

[20]  M. Westoby,et al.  Myrmecochory in sclerophyll vegetation of the West Head, New South Wales , 1981 .

[21]  A. E. Sorensen.  Seed Dispersal by Adhesion , 1986 .

[22]  A. Milewski.  The Occurrence of Seeds and Fruits Taken by Ants Versus Birds in Mediterranean Australia and Southern Africa, in Relation to the Availability of Soil Potassium , 1982 .

[23]  W. Bond.  Seed dispersal by ants in shrublands of the Cape Province and its evolutionary implications , 1983 .

[24]  M. Westoby,et al.  Evidence Against the Hypothesis that Ant‐Dispersed Seeds Reach Nutrient‐Enriched Microsites , 1986 .

[25]  N. Beadle.  Soil Phosphate and the Delimitation of Plant Communities in Eastern Australia , 1954 .

[26]  E. Salisbury.  Seed size and mass in relation to environment , 1974, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[27]  A. Gentry,et al.  Patterns of neotropical plant species diversity. , 1982 .

[28]  M. Mossop.  Comparison of seed removal by ants in vegetation on fertile and infertile soils , 1989 .

[29]  Species diversity and reproductive mechanisms in Jamaican trees , 1982 .