Sexual Dimorphism and Gynoecium Size Variation in the Andromonoecious Shrub Caesalpinia gilliesii

Abstract

The degree of sexual dimorphism in flowers and inflorescences can be evaluated early in flower development through the study of floral organ size co-variation. In the present work, the gynoecium-androecium size relationship was studied to assess the degree of sexual expression in flowers and inflorescences of the andromonoecious shrub Caesalpinia gilliesii. The co-variation pattern of floral organ sizes was compared between small and large inflorescences, under the hypothesis that inflorescence size reflected differential resource availability. Also, staminate and perfect flowers were collected from three populations and compared on the basis of gynoecium, ovule length, filament length, pollen size and number. The obtained results indicated that staminate and perfect flowers differed only in the gynoecium and ovule length, whereas filament length, pollen size, and number varied across populations. The gynoecium size was smaller and its variability was much higher in staminate than in perfect flowers, as explained by a recent hypothesis about pollinator-mediated gynoecium size selection acting upon perfect flowers. The analysis of the gynoecium-androecium size relationship during flower development, revealed a dissociation of gynoecium growth relative to other floral structures in some buds. Lower gynoecium-androecium regression slopes and smaller gynoecia length characterized smaller inflorescences, thus reflecting the fact that sexual expression was more male-biased. This trend is in agreement with a differential resource-related response at the inflorescence level, however, post-mating resource allocation and the inclusion of other modular levels may also help us to understand the variation in sexual dimorphism in this species.

Gynoecium-androecium size relationship - inflorescence size - sexual expression - floral dimorphism.

References

• 1 Anderson G. J., Symon D. E.. Functional dioecy and andromonoecy in Solanum. .  Evolution. (1989);  43 204-219
• 2 Baksh S., Iqbal M.. Floral features of Solanum macranthum Dun. with special reference to stylar heteromorphism and intercrossability.  Flora. (1978);  167 423-431
• 3 Bullock S. H.. Breeding systems in the flora of a tropical deciduous forest in Mexico.  Biotropica. (1985);  17 287-301
• 4 Caporali E., Spada A., Marziani G., Failla O., Scienza A.. The arrest of development of abortive reproductive organs in the unisexual flower of Vitis vinifera ssp. silvestris. .  Sexual Plant Reproduction. (2003);  15 291-300
• 5 Cocucci A. A., Galetto L., Sérsic A.. El síndrome floral de Caesalpinia gilliesii (Fabaceae - Caesalpinioideae).  Darwiniana. (1992);  31 111-135
• 6 Cox P. A.. Monomorphic and dimorphic sexual strategies: a modular approach. Lovett Doust, J. and Lovett Doust, L., eds. Plant Reproductive Ecology. Patterns and Strategies. New York; Oxford University Press (1988): 80-97
• 7 Diggle P. K.. Labile sex expression in andromonoecious Solanum hirtum: floral development and sex determination.  American Journal of Botany. (1991 a);  78 377-393
• 8 Diggle P. K.. Labile sex expression in andromonoecious Solanum hirtum: pattern variation in floral structure.  Canadian Journal of Botany. (1991 b);  69 2033-2043
• 9 Diggle P. K.. Development and the evolution of plant reproductive characters. Wyatt, R., ed. Ecology and Evolution of Plant Reproduction: New Aproaches. New York; Chapman and Hall (1992): 326-355
• 10 Diggle P. K.. Ontogenetic contingency and floral morphology: the effects of architecture and resource limitation.  International Journal of Plant Sciences. (1997);  158 99-107
• 11 Dulberger R., Levy A., Palevitch D.. Andromonoecy in Solanum marginatum. .  Botanical Gazette. (1981);  142 259-266
• 12 Eckhart V. M.. Sexual dimorphism in flowers and inflorescences. Geber, M. A., Dawson, T. E., and Delph, L. F., eds. Gender and Sexual Dimorphism in Flowering Plants. Berlin, Heidelberg; Springer Verlag (1999): 123-148
• 13 Emms S. K.. Andromonoecy in Zigadenus paniculatus (Liliaceae): spatial and temporal patterns of sex allocation.  American Journal of Botany. (1993);  80 914-923
• 14 Emms S. K.. Temporal pattern of seed set and decelerating fitness returns on female allocation in Zigadenus paniculatus (Liliaceae), an andromonoecious lily.  American Journal of Botany. (1996);  83 304-315
• 15 García M. B.. Sex allocation in a long-lived monocarpic plant.  Plant Biology. (2003);  5 203-209
• 16 Gibbs P. E., Lewis G. P., Lughadha E. N.. Fruit-set induced changes in the sex of flowers in Caesalpinia calycina (Leguminosae).  Plant Biology. (1999);  1 665-669
• 17 Gibson J. P., Diggle P. K.. Flower development and male sterility in Ocotea tenera (Lauraceae): A gynodioecious tropical tree.  International Journal of Plant Sciences. (1998);  159 405-417
• 18 Han S. S., Liu Q.. Developmental events associated with the critical stage for sex determination in wild-rice florets.  International Journal of Plant Sciences. (1999);  160 1127-1133
• 19 Harder L. D.. Pollen-size comparisons among animal-pollinated angiosperms with different pollination characteristics.  Biological Journal of the Linnean Society. (1998);  64 513-525
• 20 Huang S. Q.. Flower dimorphism and the maintenance of andromonoecy in Sagittaria guyanensis ssp. lappula (Alismataceae).  New Phytologist. (2003);  157 357-364
• 21 Ito E., Kikuzawa K.. Differentiation of the timing of flower abortion in Tilia japonica. .  Plant Species Biology. (2000);  15 179-186
• 22 Janoušek B., Široký J., Vyskot B.. Epigenetic control of sexual phenotype in a dioecious plant, Melandrium album. .  Molecular Genetics and Genomics. (1996);  250 483-490
• 23 Jausoro M., Galetto L.. Estudio comparativo de nectario y néctar en flores perfectas y estaminadas de Caesalpinia gilliesii (Fabaceae, Caesalpinoideae).  Boletín de la Sociedad Argentina de Botánica. (2000);  35 107-114
• 24 Jausoro M., Galetto L.. Producción de flores y frutos en una especie andromonoica: Caesalpinia gilliesii (Fabaceae).  Kurtziana. (2001);  29 15-25
• 25 Koelewijn H. P., Hunscheid M. P. H.. Intraspecific variation in sex allocation in hermaphroditic Plantago coronopus (L.).  Journal of Evolutionary Biology. (2000);  13 302-315
• 26 Krupnick G. A., Weis A. E.. Floral herbivore effect on the sex expression of an andromonoecious plant, Isomeris arborea (Capparaceae).  Plant Ecology. (1998);  134 151-162
• 27 Lewis G., Gibbs P.. Reproductive biology of Caesalpinia calycina and C. pluviosa (Leguminosae) of the caatinga of north-eastern Brazil.  Plant Systematics and Evolution. (1999);  217 43-53
• 28 Lloyd D. G.. Sexual strategies in plants I. An hypothesis of serial adjustment of maternal investment during one reproductive session.  New Phytologist. (1980);  86 69-79
• 29 Machon N., Deletre-Le Boulc'h V., Rameau C.. Quantitative analysis of sexual dimorphism in Asparagus. .  Canadian Journal of Botany. (1995);  73 1780-1786
• 30 Manicacci D., Després L.. Male and hermaphrodite flowers in the alpine lily Lloydia serotina. .  Canadian Journal of Botany. (2001);  79 1107-1114
• 31 Méndez M.. Sexual mass allocation in species with inflorescences as pollination units: A comparison between Arum italicum and Arisaema (Araceae).  American Journal of Botany. (2001);  88 1781-1785
• 32 Motten A. F., Stone J. L.. Heritability of stigma position and the effect of stigma- anther separation on outcrossing in a predominantly self-fertilizing weed, Datura stramonium (Solanaceae).  American Journal of Botany. (2000);  87 339-347
• 33 Murcia C.. Effect of floral morphology and temperature on pollen receipt and removal in Ipomoea trichocarpa. .  Ecology. (1990);  71 1098-1109
• 34 Ramírez N., Sobrevila C., de Enrech N. X., Ruiz-Zapata T.. Floral biology and breeding system of Bauhinia benthamiana Taub. (Leguminosae), a bat-pollinated tree in Venezuelan “llanos”.  American Journal of Botany. (1984);  71 273-280
• 35 Shaw R. G., Mitchell-Olds T.. Anova for unbalanced data: an overview.  Ecology. (1993);  74 1638-1645
• 36 Sokal R. R., Rohlf F. J.. Biometry. New York; Freeman and Company (1995)
• 37 Solomon B. P.. Sexual allocation and andromonoecy: resource investment in male and hermaphrodite flowers of Solanum carolinense (Solanaceae).  American Journal of Botany. (1986);  73 1215-1221
• 38 Spielman M., Vinkenoog R., Dickinson H. G., Scott R. J.. The epigenetic basis of gender in flowering plants and mammals.  Trends in Genetics. (2001);  17 705-711
• 39 Thomson J. D., Stratton D. A.. Floral morphology and cross-pollination in Erythronium grandiflorum (Liliaceae).  American Journal of Botany. (1985);  72 433-437
• 40 Tucker S. C.. The developmental basis for sexual expression in Ceratonia siliqua (Leguminosae: Caesalpininoideae: Cassieae).  American Journal of Botany. (1992);  79 318-327
• 41 Ushimaru A., Nakata K.. Evolution of flower allometry and its significance for pollination success in the deceptive orchid Pogonia japonica. .  International Journal of Plant Sciences. (2001);  162 1307-1311
• 42 Ushimaru A., Nakata K.. The evolution of floral allometry in selfing species.  Evolutionary Ecology Research. (2002);  4 1217-1227
• 43 Ushimaru A., Itagaki T., Ishii H. S.. Variation in floral organ size depends on function: a test with Commelina communis, an andromonoecious species.  Evolutionary Ecology Research. (2003 a);  5 615-622
• 44 Ushimaru A., Itagaki T., Ishii H. S.. Floral correlations in an andromonoecious species, Commelina communis (Commelinaceae).  Plant Species Biology. (2003 b);  18 103-106
• 45 Vaughton G.. Nonrandom patterns of fruit set in Banksia spinulosa (Proteaceae): interovary competition within and among inflorescences.  International Journal of Plant Science. (1993);  154 306-313
• 46 Whalen M. D., Costich D. E.. Andromonoecy in Solanum in Solanaceae: Biology and Systematics. D'Arcy, W. G., ed. New York; Columbia University Press (1986): 285-302
• 47 Zhou Q., Wang Y., Jin X.. Ontogeny of floral organs and morphology of floral apex in Phellodendron amurense (Rutaceae).  Australian Journal of Botany. (2002);  50 633-644

Editor: J. T. M. Elzenga