Explosive pollen release, stigma receptivity, and pollen dispersal pattern of Boehmeria caudata Sw. (Urticaceae) in a Brazilian rain forest

Abstract

Male flowers of the wind-pollinated, dioecious shrub Boehmeria caudata Sw. release pollen explosively, possibly stimulated by anther dehydration in response to temporarily dry conditions coupled with hydrostatic pressure in the filament. In the Brazilian Atlantic rain forest, the daily frequency of male flower anthesis peaked between 1000–1200 h (GMT −3) and was positively correlated with rising temperature, wind currents, and direct insolation, but negatively correlated with relative humidity. A generalized linear mixed model predicts the probability of pollen release under different conditions of relative humidity and wind. Receptive stigmas on female flowers were found at any time of day: individual stigmas were receptive (H2O2 test) for at least two days. Beetles and halictid bees were observed feeding on pollen from staminate flowers, but probably did not affect pollination because they did not seem to visit pistillate flowers. Individual plants of this apparently ruderal species grow along road edges and show aggregated (clumped) spatial dispersion. The overall sex ratio we found was 29 females to 43 males, with one monoecious plant in a total transect distance of 6319 m. Pollen traps were placed on the female plants to measure pollen arrival. Pollen capture was higher on the more exposed road-facing side and positively related to male plant density.

Landscape Features and Climatic Forces Shape the Genetic Structure and Evolutionary History of an Oak Species (Quercus chenii) in East China

“…Highland habitats are characterized by significantly lower temperature of spring, and a wetter environment surrounded by montane landscapes (Wang et al, 2010). These factors can influence the asynchronism of reproductive phenology, e.g., the timing of flowering and pollen release (Montoya-Pfeiffer et al, 2016), and then increase the effects of IBE through nonrandom mating due to climatic differences along altitudinal gradients. Finally, highland populations exhibited stronger differentiation and much lower within-population diversity than those in lowland areas ( Table 2 and Figure 3 ), suggesting that the species may have experienced genetic drift and long-term fragmentation among multiple island-like highland habitats, probably a consequence of historical colonization along altitudinal gradients and following ecological isolation (Qiu et al, 2009a; Wang et al, 2017).…”

Ecological Factors Generally Not Altitude Related Played Main Roles in Driving Potential Adaptive Evolution at Elevational Range Margin Populations of Taiwan Incense Cedar (Calocedrus formosana)

“…Habitat-associated microclimate is also found to have a relationship with elevation (Clinton, 2003;Bell et al, 2014;Sunday et al, 2014). A single environmental factor is not always sufficient to explain local vegetation penology (Hwang et al, 2011) and it is probable that elevation, slope, and aspect in combination can have influence on tree structure and growth (Turner et al, 2001;Montoya-Pfeiffer et al, 2016;Hu et al, 2018), and increase the effects of IBE contributing to the geographic patterns of climatically and ecologically structured genetic variation.…”

Comparative analysis of pollen release biomechanics in Thalictrum: implications for evolutionary transitions between animal and wind pollination

“…A mechanism similar to the one investigated here occurs in Halophytum ameghinoi (Halophytaceae) but involves movements of the anther instead of the filament (Pozner & Cocucci, ). An alternative mechanism in Cornus canadensis (Cornaceae; Whitaker et al ., ), Morus alba (Moraceae; Taylor et al ., ) and Boehmeria caudata (Urticaceae; Montoya‐Pfeiffer et al ., ) involves stamens developing under increasing elastic tension that when released catapults pollen from anthers.…”