Mirror-image flowers without buzz pollination in the Asian endemicHiptage benghalensis(Malpighiaceae)

Abstract

Mirror‐image flowers represent a highly specialized pollination system that is normally associated with poricidal anthers and buzz pollination (pollen can be only released from anthers via pollinator vibration). In the Asian endemic Hiptage benghalensis (Malpighiaceae), mirror‐image flowers were found with longitudinally dehiscing anthers and such floral syndromes are firstly reported in the family. We investigated the floral biology and frequencies of left‐ and right‐styled flowers of H. benghalensis in Hainan Island, southern China. We conducted pollination manipulations to determine breeding systems and studied the pollination mechanism. We also examined the compositions of the secretions of the calyx gland. Controlled pollinations revealed that H. benghalensis is self‐compatible. Left‐ and right‐styled flowers are produced in the same inflorescence and a 1:1 ratio is found at both plant and population levels. Flowers have extremely reflexed petals, zygomorphic corollas and a single but oversized calyx gland. This gland secretes sugars and mainly attracts ants and wasps in both blooming and fruiting periods. Heteranthery is obvious with one large stamen producing more viable pollen than the nine small stamens. All anthers dehisce longitudinally and pollen grains readily adhere to floral visitors without the need of buzz pollination. The unusual association of mirror‐image flowers with longitudinal anthers probably reflects an adaptation to local pollen‐collecting (but non‐buzzing) honeybees such as Apis dorsata. These results indicate that floral syndromes and pollination adaptation in H. benghalensis differ completely from the New World Malpighiaceae and may help to explain evolutionary adaptations of the family during its long‐distance dispersals from the New World to Asia. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 764–774.

Two new species of Hiptage (Malpighiaceae) from Yunnan, Southwest of China

“…The zygomorphic or mirror-image flower of the Hiptage is a unique feature of evolutionary and biological importance that enhances adaptations (Ren et al 2013, Qian et al 2016). The presence or absence of calycinal glands calyx is an important characteristic and feature of the glands’ shape and number, and whether it is adnate to pedicel or not is also a key diagnostic for species identification (Sirirugsa 1991, Srivastava 1992, Chen and Funston 2008).…”

“…(Gaertner 1791) is one of the largest genera of Malpighiaceae with about 30 species of woody lianas and shrubs growing in forests of tropical South Asia, Indo-China Peninsula, Indonesia, Philippines and Southern China, including Hainan and Taiwan islands (Chen and Funston 2008, Ren et al 2013). There are currently ten species of Hiptage recorded in Thailand (Sirirugsa 1987, 1991), ten species with seven endemic ones in China (Chen and Funston 2008) and 9 species in India (Srivastava 1992).…”

“…a larger middle wing and two smaller lateral wings, sometimes the dorsal wing is absent or present as a small crest, most species bear an elongated commissural gland on the calyx (Srivastava 1992, Anderson et al 2006). Hiptage is also unique for having mirror-image flowers, with 1 long and 9 short unequal stamens (Ren et al 2013, Qian et al 2016). H.benghalensis (L.) Kurz is the most well-known species due to its attractive and fragrant flowers; it is often cultivated as a tropical ornamental plant in gardens (Anderson et al 2006).…”

A new species of Hiptage (Malpighiaceae) from Nujiang Gorge, southwest China

“…The calyx gland is a unique floral trait in Malpighiaceae (Anderson , , Ren et al ) and is important for taxonomical studies of the family (Anderson et al , Cappellari et al , Ren et al ). In Hiptage , calyx glands produce nectar (Ren et al ) and the number of calyx glands is greatly reduced as compared with American members of the family, in which the calyx glands secrete oils (Anderson , Davis and Anderson ). In most Hiptage species, no or only one calyx gland is present (Chen and Funston , Ren et al , Ren ), but in H. lushuiensis two obvious calyx glands are visible and in some individuals additional smaller calyx glands can be found (Fig.…”

A botanical Christmas stocking

“…A third paper on reproductive biology concludes the issue. This paper by Ren, Zhong & Song () relates to the mirror image flowers of a species of Hiptage Gaertn. (Malpighiaceae).…”