Contribution to the Knowledge of Three Indian Spermacoce L. (Rubiaceae) and Some Preliminary Information About Their Pollination Ecology
Total Page：16
File Type：pdf, Size：1020Kb
Anales de Biología 39: 111-126, 2017 ARTICLE DOI: http://dx.doi.org/10.6018/analesbio.39.13 Contribution to the knowledge of three Indian Spermacoce L. (Rubiaceae) and some preliminary information about their pollination ecology Aluri Jacob Solomon Raju & Janga Radhakrishna Department of Environmental Sciences, Andhra University, Visakhapatnam 530 003, India. Resumen Correspondence Contribución al conocimiento de tres especies indias de AJS. Raju Spermacoce L. (Rubiaceae) e información preliminar de su E-mail: [email protected] ecología de polinización. Received: 10 February 2017 Se han descrito caracteres taxonómicos no documentados para Accepted: 3 July 2017 Spermacoce hispida L. y Spermacoce articularis L. S. hispida es Published on-line: 25 July 2017 bimórfica. Las flores son débilmente protándrica, nectaríferas y au- to-polinizadoras. Las mariposas, las abejas y los trips son impor- tantes como polinizadores. El conjunto de fruta natural más eleva- do que se evidencia en estas especies se atribuye a autopoliniza- ción y entomofilia. Los frutos la dehiscencia es septicida en S. his- pida y S. articularis, y circunscisa en Spermacoce pusilla Wall. La dispersión de las semillas es anemo-, baro-, ombro- e hidrocórica. Estas especies ocupan diferentes hábitats para evitar la competen- cia por los polinizadores y maximizar la producción de semillas y ampliar su rango de distribución. Palabras clave: Bimorfismo, Taxonomía, Entomofilia, Dispersión de semillas. Abstract Undocumented taxonomic characters have been described for Spermacoce hispida L. and Spermacoce articularis L. S. hispida is bimorphic. The flowers are weakly protandrous, nectariferous and self-pollinating. Butterflies, bees and thrips are important as pollin- ators. The highest natural fruit set evidenced in these species is at- tributed to auto-selfing and entomophily. Fruits dehisce septicidally in S. hispida and S. articularis and circumscissile mode in Sperma- coce pusilla Wall. Seed dispersal is anemo-, baro-, ombro- and hy- dro-chorous. These species occupy different habitats to avoid com- petition for pollinators and maximize seed output and expand their distribution range. Key words: Bimorphism, Taxonomy, Entomophily, Seed dispersal. 112 AJS. Raju & J. Radhakrishna Anales de Biología 39, 2017 Introduction stigma lobes; (iii) pollen deposition on the outer side of the stigma; (iv) pollen deposition exclus- Rubiaceae is one of the five largest plant families ively, largely or partly on the receptive surface of with 611 genera and 13,143 species (Davis et al. the stigma. In types (ii) and (iii), the receptive 2009). It is a cosmopolitan family, predominantly areas are the inner sides of the stigma lobes or the pantropical, and with a small portion of species of furrows between two stigma lobes. At the time of extra-tropical distribution. Almost one half of the pollen deposition the stigma lobes are fused so species and one third of the genera occur in the that contact between self-pollen and the receptive Neotropics. The species of this family occur at all surfaces is improbable. Yeo (1993) and Castro et layers of tropical vegetation, with all kinds of al. (2008) suggested that protandry, herkogamy, habits, as herbs, shrubs, lianas, and from small and self-incompatibility are the primary means of trees to tall canopy trees (Delprete & Jardim avoiding self-interference in plants with secon- 2012). This family shows a wide spectrum of flor- dary pollen presentation. Ladd (1994) stated the al mechanisms characterized by different types of secondary pollen presentation has evolved to gynoecium and androecium organization (Castro increase the efficiency and accuracy of pollen & Paulo-Eugenio 2001). Robbrecht (1988) repor- transfer because of the close proximity of pollen ted heterostyly and secondary pollen presentation to the stigma while Webb & Lloyd (1986) stated as reproductive mechanisms in this family. The that the proximity of pollen and stigma, however, sexual systems include hermaphroditism, mono- could result in self-interference. Castro et al. ecy, polygamomonoecy, dioecy and heterostyly. (2008) suggested that the mechanism of second- Coelho & Barbosa (2003) mentioned that little is ary pollen presentation might be an accurate sys- known about the reproductive biology of most tem for pollen transport, but that it may also have species in this family, particularly from tropical its costs. regions. Robbrecht (1988) reported that pollina- Rubiaceae species with a wide range of flower tion in this family is entomophilous and its mech- forms, sizes and colours present a wide range of anism is conspicuously specialized via stylar floral visitors (Consolaro et al. 2005). Most of the modifications for passive pollen presentation. An- pollinators include insects while birds and bats derson (1973) reported that heterostyly in this play a minor role in pollination. Among insects family consists basically of a balanced poly- also, bees are important pollinators especially for morphism in which some plants bear flowers ha- small-flowered species; the showy large-flowered ving the receptive stigmas above the level of the species are adapted for pollination by butterflies anthers (pin flowers) and the other plants bear and hawk-moths. The butterflies are pollinators flowers having the receptive stigmas below the for scentless flowers while hawkmoths for long- anthers (thrum flowers). This difference is often tubed fragrant flowers (Puff et al. 2005). Different accompanied by differences in corolla tube length, workers documented that the family as a whole filament length, pollen and stigmatic papillae size. shows a great diversity of pollination syndromes In hermaphroditic isostylous flowers, protan- involving butterfly (Hamilton 1990), moth (Nils- dry is predominant; the pollen matures early and son et al. 1990), bee (Hamilton 1990) and bird is shed at or soon after anthesis. Before anthesis pollination (Sobrevilla et al. 1983; Ree 1997). and in some cases for a period after anthesis, the Anemophily is rare and restricted to more elongation of the style is arrested, the immature advanced members (Bawa & Beach 1983). stigmas are temporarily retained within the tube of The genus Spermacoce L. comprising 275 spe- the corolla, below the level of the anthers. During cies of perennial or annual herbs is distributed in and/or after the release of the pollen the style tropical and sub-tropical America, Africa, Aus- elongates, eventually equalling or surpassing the tralasia and Australia (Dessein et al. 2006). In anthers, and the stigmas belatedly mature. Puff et India, three Spermacoce species, Spermacoce al. (2005) stated that protandry in isostylous stricta L.f., Spermacoce ocymoides Burm.f. and flowers is associated with secondary pollen Spermacoce hispida L. have been reported by presentation. These authors recognized four types Hooker (1881) and other early authors of Indian secondary pollen presentation according to the Floras. Sivarajan et al. (1987) reported that Sper- presenting area and receptive surfaces: (i) pollen macoce has nine species in India but they named deposition on the style only; (ii) pollen deposition only seven species, Spermacoce confusa Rendle., on the style and outside of the non-receptive Spermacoce podocephala DC., Spermacoce Anales de Biología 39, 2017 Contribution to the knowledge of three Indian Spermacoce 113 mauritiana Gideon., Spermacoce pusilla Wall., 2014-2016 in Visakhapatnam and its surroun- Spermacoce latifolia Aubl., Spermacoce hispida dings, Andhra Pradesh, India (17°42’N Latitude L. and Spermacoce articularis L. Deb & Dutta and 82°18’E Longitude). The inflorescence type (1984) mentioned that these species are important and the number of flowers per inflorescence were constituents of herbaceous layer in open habitats, noted using twenty individual plants. Ten inflores- roadsides and agricultural fields. Dessein et al. cences on five individual plants were tagged prior (2008) stated that the taxonomy of many species to commencement of their flowering and followed of Spermacoce is still in great confusion, espe- daily for recording the flowering duration of the cially for paleotropical species. Further, these inflorescence. Twenty five fresh flowers from five authors explained the use of certain characters individual plants for each species were used to re- such as general habit, indumentum features, leaf cord the floral details such as flower shape, col- morphology, inflorescence position, calyx and our, odour, sex, symmetry, floral mechanism, ca- corolla morphology, and types of fruit dehiscence lyx, corolla, stamens and style and stigma, ovule for species delimitation within Spermacoce. Des- number, fruit and seed characters in order to give sein et al. (2005) reported that the Spermacoce clarity to certain taxonomic characters especially species producing small pollen grains might be for S. hispida and S. articularis. These characters adapted to specific pollinators and such species were used to classify two morphs in S. hispida. bear flowers with very short corolla tubes and the Ten inflorescences from five individual plants, anthers and style included in the tube. In most which have not initiated flowering were tagged other Spermacoce species the anthers and style are and followed daily to record the duration of exserted; those species with short tubes and flowering, anthesis schedule and the timing of an- included anthers and style have different pollen ther dehiscence. Twenty five fresh flowers from vectors. Punt