Floral and pollination biology, breeding system and nectar traits of Callistemon citrinus (Myrtaceae) cultivated in India

CHAUHAN, S.; CHAUHAN, SVS; GALETTO, L.

SOUTH AFRICAN JOURNAL OF BOTANY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 111 p. 319 - 325

0254-6299

This study reports the influence of habitat on floral (flower and nectar characteristics, phenology) and pollinationbiology (flower visitors and breeding system) on Callistemon citrinus (syn. Callistemon lanceolatus), an Australianspecies of family Myrtaceae. In India, this small ornamental tree is cultivated in gardens, avenues and road sidesand flowers throughout the year. At Agra (Uttar Pradesh, northern India) this species flowers twice a year(February?May and August?November). Flowers open early in the morning and can be characterized asprotandrous for a brief period. Fresh open flowers presented ca. 25% of total produced nectar. Nectar sugar compositionconsisted of only glucose and fructose. A wide array of visitors (honey bees (Apis dorsata), butterflies,wasps, ants, moth, hover flies, several birds and Indian palm squirrel) visit flowers either for pollen or nectaror for facilitating self- and cross-pollination by their intra- and inter-tree movements. Among these, honeybees are dominant in number and in the amount of pollen on their body,while butterflies, ants, wasps, sunbirds,parrots, oriental white-eye sparrow and squirrels forage only for nectar and can be considered occasional pollinatorsor nectar thieves. Although flowers are highly visited, nectar in standing crop showed that flower visitorsdid not consume the total nectar produced. Nectar replenishment decreased with age in both bagged- andexposed flowers, showing the capability of secreting nectar after removal during the entire flower lifetime.Experimental hand-pollinations showed that naturalized C. citrinus fruits matured through autogamy,geitonogamy or xenogamy as was reported for native Australian populations. C. citrinus displays an interestingreproductive strategy, shows phenotypic plasticity of flowering periodicity and interacts with a generalized pollinatorsystem, attracts a wide array of animal species with a conspicuous amount or replenished nectar after removals,and uses both compatibility strategies ? xenogamy and autogamy ? to ensure successful pollination andseed production at native or naturalized habitats.