Summary
Rhamnus alaternus L. is a dioecious, fleshy-fruited shrub, typical of Mediterranean vegetation, which has been recorded from the region since the tropical Tertiary. Reproductive biology of this species has been studied in Southern Italy over a period of 4 years with both field and laboratory experiments. In all the studied populations male plants predominate over the females, have a higher flower density and flower regularly every year while females are usually alternate-bearing. A strong negative association between fruit formation and vegetative growth has been found indicating that the presence of fruits on a branch reduces the growth of new shoots. This phenomenon, together with alternate-bearing, is evidence of a strong competition between vegetative growth and reproductive activity and indicates resource limitation. Flower morphology and quantity of pollen produced are typical of insect pollinated species, and flies of the Empididae and Muscidae were trapped bearing pollen at female plants but pollen is also dispersed by wind. Field experiments on pollination success showed that the exclusion of insects as pollen vectors produces a significant decrease in fruit development. Excess pollen provided by hand-pollination increases fruit set over open-pollination and reproductive success in the field is therefore pollen limited. The variability of sex expression, male fitness, fruit production, regrowth and pollination presented here suggests that these predispersal characteristics ofR. alaternus have been subject to evolutionary change since the tropical Tertiary climate was replaced by a Mediterranean one. This points to the possibility that reproductive, as well as morphological and physiological characteristics, may be equally selected for in extreme environments such as the Mediterranean.
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References
Aronne G, Wilcock CC (1992) Reproductive evolution and breeding system in relation to environmental stress in shrubs of the Mediterranean region. In: Thanos CA (ed) Plant-animal interactions in Mediterranean-type ecosystems. University of Athens Press, Athens, pp 223–227
— — (1994 a) First evidence of myrmecochory in fleshy fruited shrubs of the Mediterranean region. New Phytol 127: 781–788
— — (1994 b) Reproductive characteristics and breeding system of shrubs of the Mediterranean region. Funct Ecol 8: 69–76
— —, Pizzolongo P (1993) Pollination biology and sexual differentiation ofOsyris alba L. (Santalaceae) in the Mediterranean. Plant Syst Evol 88: 1–16
Axelrod DI (1975) Evolution and biogeography of Madro-Tethyan sclerophyll vegetation. Ann Missouri Bot Gard 62: 280–334
Baker HG, Baker I (1983 a) Floral nectar sugar constituents in relation to pollinator type. In: Jones CE, Little R (eds) Handbook of experimental pollination biology. Van Nostrand Reinhold, New York, pp 117–141
— — (1983 b) Some evolutionary and taxonomic implications of variation in the chemical reserves of pollen. In: Mulcahy DL (Ed) Pollen biology and implications for plant breeding. Elsevier, New York, pp 43–52
Chapin FS (1980) The mineral nutrition of wild plants. Annu Rev Ecol Syst 11: 233–260
Currier HB (1957) Callose substance in plant cells. Amer J Bot 44: 478–488
Dafni A (1984) Mimicry and deception in pollination. Annu Rev Ecol Syst 15: 259–278
— (1992) Pollination ecology: a practical approach. Oxford University Press, Oxford
Daget P (1977) Le bioclimat mediterraneen: caractères generaux, mode de caracterisation. Vegetatio 34: 1–20
Darwin C (1977) The different forms of flowers on plants of the same species. J Murray, London
Davis LD (1957) Flowering and alternate bearing. Proc Am Soc Hort Sci 70: 545–556
Frankel R, Galun E (1977) Pollination mechanisms, reproduction and plant breeding. Springer, Berlin Heidelberg New York
Franken AA (1970) Sex characteristics and inheritage of sex in asparagus (Asparagus officinalis L.). Euphytica 19: 277–287
Freeman DC, Klikoff LG, Harper KT (1976) Differential resource utilization by the sexes of dioecious plants. Science 193: 597–599
—, Harper KT, Charnov EL (1980) Sex change in plants: old and new observation and new hypotheses. Oecologia 47: 222–232
Herrera J (1985) Nectar secretion patterns in southern Spanish Mediterranean scrublands. Israel J Bot 34: 47–58
Heslop-Harrison J (1957) The experimental modification of sex expression in flowering plants. Biol Rev 32: 38–90
—, Heslop-Harrison Y (1970) Evaluation of pollen viability by induced fluorescence; intracellular hydrolysis of fluorescein diacetate. Stain Technol 45: 115–120
Lamont BB (1983) Strategies for maximizing nutrient uptake in two mediterranean ecosystems of low nutrient status. In: Kruger FJ, Mitchell DT, Jarvis JUM (eds) Mediterranean-type ecosystems: the role of nutrients. Springer, Berlin Heidelberg New York Tokyo, pp 246–273 [Billings WD et al (eds) Ecological studies, vol 43]
Lange AH (1961) Factors affecting sex changes in the flowers ofCarica papaya. Proc Am Soc Hort Sci 77: 252–264
Margaris NS, Vokou D (1982) Structural and physiological features of woody plants in phryganic ecosystems related to adaptive mechanisms. Ecol Medit 8: 449–459
Minina EG (1952) Sex shifts in plants induced by environmental factors. Moscow Academy of Sciences USSR Publishing House, Moscow
Monselise SP, Goldschmidt EE (1982) Alternate bearing in fruit trees. Hort Rev 4: 128–173
Morettini A (1977) Frutticoltura generale e speciale. Ramo Editoriale degli Agricoltori, Roma
Nahal I (1981) The mediterranean climate from a biological view point. In: di Castri F, Goodal DW, Specht RL (eds) Mediterranean-type shrublands. Elsevier, Amsterdam, pp63–93 [Ecosystems of the world, vol 11]
Pickett FL (1915) A contribution to our knowledge ofArisaema triphyllum. Torr Bot Cl Mem 16: 1–55
Pignatti S (1982) Flora d' Italia. Edagricole, Bologna
Raven PH (1973) The evolution of mediterranean floras. In: di Castri F, Mooney HA (eds) Mediterranean type ecosystems. Origin and structure. Springer, Berlin Heidelberg New York, pp 213–224
Regal PJ (1982) Pollination by wind and animals: ecology of geographic patterns. Annu Rev Ecol Syst 13: 497–524
Richards AJ (1986) Male predominant sex ratios in Holly (Ilex aquifolium L., Aquifoliaceae) and Roseroot (Rhodolia rosea L., Crassulaceae). Watsonia 17: 53–57
Robbins WW, Jones HA (1926) Sex as a factor in growing asparagus. Proc Amer Soc Hort Sci 23: 19–23
Ryugo K (1988) Fruitculture: its science and art. Wiley, New York
Scaramuzzi F (1949) Presenza di frutti nelle piante maschili diRhamnus alaternus. G Bot Ital 59: 284–285
— (1950) II comportamento del sesso inRhamnus alaternus L. G Bot Ital 60: 718–720
Specht RL (1979) Heathlands and related shrublands of the world. In: Specht RL (ed) Heathlands and related shrublands: analytical studies. Elsevier, Amsterdam, pp 1–18 [Ecosystems of the world, vol 9 B]
Suc JP (1984) Origin and evolution of Mediterranean vegetation and climate in Europe. Nature 307: 429–432
Tebar FJ, Llorens L (1993) Heterocarpy inThymelaea velutina Endl.: a case of phenotypic adaptation to Mediterranean selective pressures. Bot J Linn Soc 111: 295–300
Thompson AE (1955) Methods of producing first generation hybrid seed in spinach. Cornell Univ Agric Exp Stat Mem 336
Trabaud L (1983) The effects of different fire regimes on soil nutrient levels inQuercus coccifera garrigue. In: Kruger FJ, Mitchell DT, Jarvis JUM (eds) Mediterranean-type ecosystems: the role of nutrients. Springer, Berlin Heidelberg New York Tokyo, pp 233–243 [Billings WD et al (eds) Ecological studies, vol 43]
Westoby M, French K, Hughes L, Rice BL, Rodgerson L (1991) Why do more plant species use ants for dispersal on infertile compared with fertile soils? Aust J Ecol 16: 445–455
Willson MF (1983) Plant reproductive ecology. Wiley, Toronto
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Aronne, G., Wilcock, C.C. Reproductive lability in pre-dispersal biology ofRhamnus alaternus L. (Rhamnaceae). Protoplasma 187, 49–59 (1995). https://doi.org/10.1007/BF01280232
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DOI: https://doi.org/10.1007/BF01280232