Implications of flower developmental stage, plant isolation and microclimatic condition on a hemiparasitic plant–avian pollinator interaction

Abstract

The pollination success of bird pollinated plants is determined by avian visits and duration of foraging which in turn have been shown to be regulated by several plant features. However, very few of these factors have been demonstrated on hemiparasitic plants under tropical African climate. This study, determined how three flower developmental stages (ripe, unripe and open flowers), plant isolation and microclimatic conditions (temperature and wind speed) influenced frequency of visits and duration of foraging by avian pollinators on the Loranthaceae mistletoe T. sessilifolius in a tropical savanna habitat in Nigeria, West Africa. One hour focal observations across 40 individuals of the study plant species was used to collect information on avian visits and duration of foraging. While numbers of flowers for the three flower developmental stages were obtained through direct counts. Results showed that increased number of closed ripe flowers on the study plant significantly attracted avian pollinators. This relationship between avian visitors and ripe flowers may be connected with the high nectar content of such flowers as reported in previous studies. Increased intensity of microclimatic factors; temperature (°C) and wind speed (m/s) however, negatively affected avian pollinators. This could be linked to their established effects of increasing avian thermoregulatory costs and mechanical inhibition of flight. These observations could potentially limit pollen deposition at stigma with consequences on plant fitness as shown in previous studies. The observations also give a picture of the potential effects of increasing temperatures in the face of global warming.

Keywords: flower, avian, plant-isolation, microclimate, hemiparasitic-plant, interaction