Pollination of Aosa rupestris (Hook.) Weigend (Loasaceae): are stamen movements induced by pollinators?

Abstract

Inducement to stamen movement by oligolectic bees has been reported for some Loasaceae species; however, detailed research studies on the pollination ecology of species in the genus Aosa are absent. In this study, we analyzed the floral biology and breeding system of Aosa rupestris (Hook.) Weigend, focusing on the role of pollinators in inducing stamens' movements. We described the anthesis, the behavior of floral visitors, and carried out reproductive experiments in a population in a dry forest (''caatinga'') area in Northeastern Brazil. We carried out four experiments and one control to establish whether the interval between the movements of two successive stamens is regulated by pollinator visits. Anthesis lasted for 3-4 days. Stamens (102 ± 12.57) remained with closed anther inside petals early in the anthesis, after which they moved to the center of the flower and presented its pollen (male phase). After all stamens have reached the center of the flower, the female phase started. Bicolletes nordestina Urban, 2006 was the only floral visitor to A. rupestris flowers, drinking nectar, collecting pollen, or sleeping on the flowers. Aosa rupestris was autogamous, but fruit set was higher under natural conditions. The interval between movements of two successive stamens was not different among experiments. Therefore, stamen movements were spontaneous and did not respond to pollinator visits, in contrast to the pattern of stamen movements observed in other Loasaceae species. Although A. rupestris is autogamous, floral structure and behavior of the oligolectic bee pollinator ensured the highest level of fruit set in this species.

A case of behavioural diversification in male floral function – the evolution of thigmonastic pollen presentation

“…For A . rupestris , stamen presentation has already been reported to only be autonomous 103 . Interestingly, stamen presentation in respective sister taxa of these non-thigmonastic species is thigmonastic ( P .…”

Effects of continuous variation in vertical and lateral herkogamy on reproductive success in Euphorbia fischeriana (Euphorbiaceae)

“…Morphological or spatial–temporal variation in stigma or stamen movement is important in the sexual interference and reproduction of flowering plants (Abdusalam & Tan, 2014 ; Bynum & Smith, 2001 ; Dole, 1990 ; He et al, 2006 ; Lloyd, 1992 ; Wang et al, 2017 ; Ye et al, 2019 ). The degree of spatial and temporal separation of floral sexual organs (herkogamy and dichogamy, respectively) affects male and female fitness of bisexual flowers, prevents self‐pollination, and reduces interference between male and female organ functions (Barrett, 2002a ; Leite et al, 2016 ; Ren & Tang, 2012 ; Wang et al, 2017 ). Herkogamy is mainly thought to reduce interference between male and female functions for plants with homostylous flowers (Barrett, 2002a , 2002b ; Li et al, 2013 ; Lloyd & Webb, 1986 ; Webb & Lloyd, 1986 ).…”

Pollination adaptations of group-by-group stamen movement in a meadow plant with temporal floral closure

“…Morphological or spatial–temporal variation of stigma or stamen movement is important in the sexual interference and reproduction of flowering plants ( Dole, 1990 ; Lloyd, 1992 ; Bynum and Smith, 2001 ; He et al., 2006 ; Abdusalam and Tan, 2014 ; Wang et al., 2017 ; Ye et al., 2019 ). The degree of spatial–temporal separation of floral sexual organs (herkogamy and dichogamy, respectively) can enhance male and female fitness in hermaphroditic flowers by preventing self-pollination and reducing interference between the functions of male and female organs ( Barrett, 2002 ; Ren and Tang, 2012 ; Leite et al., 2016 ; Wang et al., 2017 ). The dramatic movements of floral structures that can separate male and female organs, such as flexistyly (e.g., the two phenotypes of Alpinia Roxb.…”

“…Floral movements include both passive (non-directional and independent of ecological factors) and initiated (oriented response) movements ( Ichmura and Suto, 1998 ; He et al., 2006 ; Ren and Tang, 2012 ; Wang et al., 2017 ), and they differ in function and adaptation in male-female reproduction and fitness ( Ren and Tang, 2012 ; Abdusalam and Tan, 2014 ; Leite et al., 2016 ). Movement of flower parts can reduce inter- or intra-sexual interference ( Ren and Bu, 2014 ; Wang et al., 2017 ; Ye et al., 2019 ), influence mating patterns (increase the delay of self-pollination or cross-pollination) ( Grant et al., 1979 ; Taylor et al., 2006 ; Du et al., 2012 ; Ren and Tang, 2012 ; Abdusalam and Tan, 2014 ; Wang et al., 2018 ), increase pollen transfer ( Lewis, 1982 ; Lloyd, 1992 ; He et al., 2006 ; Song et al., 2013 ), and protect male and female organs under harsh environmental conditions ( Schlindwein and Wittmann, 1997 ; Ren and Tang, 2012 ; Abdusalam and Tan, 2014 ).…”