Abstract:

Aims Our objective was to assess the floral biology, breeding system and reproductive success in the naturally isolated population of Sinojackia huangmeiensis, an endangered plant in a fragmented habitat, in order to develop successful conservation strategies for this species.

Methods We conducted field observations and artificial pollination experiments on the floral biology, pollination process and breeding system of S. huangmeiensis in southern Hubei Province.

Important findings The flowers of S. huangmeiensis were bisexual and protandrous, with two to six in a raceme on the top of lateral branches. The life span of a single flower was approximately 5-7 days. The viable pollen persistence of a single flower was prolonged because of asynchronous dehiscing of anthers. The styles were always longer than the anthers in the opening flowers. Self-pollination was partially avoided by temporal and spatial isolation of male and female organs within the same flower. However, autogamous and geitonogamous selfing is unavoidable because of the large number of flowers on a single tree and the action of pollinators or wind on pollen dispersal. Our experiments indicated that no apomixis occurred, the breeding system was outcrossing with partial self-compatibility and pollinators were needed. The most frequent floral visitors were flies (Epistrophe balteata) and bees (Apis cerana and Habropoda sinensis). Fruit set and seed set in natural condition were 10.33% and 0.387, respectively. Lack of pollination insects, low pollination efficiency, deposition of self pollen and partial self-compatibility may account for the low fruit set and seed set. However, the large number of flowers in a single plant ensured production of fruits and seeds, which contributed to the natural population regeneration. From the evolutionary perspective, the partial self-compatibility may provide reproductive assurance and evolutionary potential, which was important to adapt to the fragmented habitat. We recommend recovery of the natural ecological system of pollinators to conserve the remnant population of S. huangmeiensis.

Key words: habitat fragmentation, floral biology, breeding system, reproductive success, pollination, Sinojackia huangmeiensis