Heterocarpy diversifies diaspore propagation of the desert shrub Ammopiptanthus mongolicus

Abstract

In the desert, plant diaspore spreading usually relies on both external vectors, such as wind, and internal factors, such as diaspore shape. Ammopiptanthus mongolicus is a heterocarpous shrub species in the cold desert in northwest China. Mature pods may have dehisced or not yet dehisced when abscising, and the dehiscent pods may be twisted or flattened. The propagation distances of diaspores might vary due to differences in their buoyancies in upward air and ground friction according to pod shape. The wind tunnel experiments were conducted to measure the horizontal displacement upon fruit dropping (D1) and the wind‐blown distance traveled by a fallen pod (D2) of A. mongolicus. A generalized linear mixed model and generalized linear model were used to test the effects of pod shape, release height, wind speed and ground substrate type on the spread distance of pods. D1 is jointly determined by the effects of release height and pod shape. Wind speed, pod shape and ground substrate type together affect D2. A twisted pod has higher dispersibility than a flat pod, and dehiscent pods spread further than indehiscent ones. The positive correlation of D1 and D2 indicates that the difference in pod shape additively broadens the range of seed‐spreading distance. Differential seed‐spreading properties could be adaptively advantageous to disperse the risks associated with diasporic dissemination compared with the maintenance of a single optimal dissemination characteristic. Thus, heterodiaspory is an advantageous adaptive characteristic for seed spreading in the windy, arid and harsh desert environment.

Functional packaging of seeds

“…Responsive encapsulations, on the other hand, typically remain attached to the plant as aerial seedbanks and are thus not dispersed (Fig. 1c), except when removed deliberately by animals (Talluto & Benkman, 2014) or accidentally by any means, or in rare cases by the plant itself via abscission (Abraham & Elbaum, 2013; Yang et al ., 2020). Close to maturity, most responsive encapsulations either open up to release seeds (dehiscence), or remain closed until environmentally stimulated, thereby delaying seed dispersal (stage 2 in Fig.…”

“…In different populations of the candlestick banksia ( Banksia attenuata ), plants develop follicles (responsive systems) with different valve curvatures along a climatic gradient, which results in higher levels of serotiny and higher opening temperatures in drier regions (Huss et al ., 2018). These morphological adaptations and the corresponding differences in physical dormancy and serotiny are often interpreted as bet‐hedging strategies to maximize survival in unpredictable environments (Clarke et al ., 2013; Arshad et al ., 2018; Yang et al ., 2020; Gianella et al ., 2021). In bet‐hedging species, dormancy appears to be linked to a higher polyphenol content in seed coats, resulting in darker morphs (Gianella et al ., 2021).…”

“…(2008)), storage periods before, during, or after dispersal, and germination. Particularly in regions with irregular rainfall, the seed stage often involves diaspore heteromorphism (Arshad et al ., 2018; Yang et al ., 2020; Gianella et al ., 2021), environmentally regulated dispersal (e.g. Seale & Nakayama, 2020), and extended storage periods in the canopy (termed serotiny; Lamont et al ., 2020) or in the soil (known as dormancy; Baskin & Baskin, 2014).…”

Parallel adaptation prompted core-periphery divergence of Ammopiptanthus mongolicus

“…Since precipitation varies with longitude in inland Asia, Du et al (2021) predicted different expansion routes of A. mongolicus under different warming scenarios: eastward under the mild warming scenario (greenhouse gas emission scenario RCP4.5) but westward under severe warming (RCP8.5) ( Du et al, 2021 ). Its heterocarpy (dehiscent-flat, dehiscent-twisted, and indehiscent-flat diaspores) ensures and diversifies propagation in deserts ( Yang et al, 2021 ). In addition to wind speed and ground substrate, which may affect spread distance ( Yang et al, 2021 ), the geographic distance ( Ge et al, 2005 ), and local environments (e.g., soil organic matter, total nitrogen, and summer rainfall) ( Liu et al, 2017 ; Jiang et al, 2019 ) also determine its spatial-genetic structure, i.e., isolation-by-distance (IBD) and isolation-by-environment (IBE).…”

Environmental Heterogeneity Leads to Spatial Differences in Genetic Diversity and Demographic Structure of Acer caudatifolium

“…For sessile organisms, dispersibility could be relatively important for range change. As representative sessile organisms, plants can overcome spatial constraints through seed dispersal with variable strategies [ 3 , 4 ]. Consequently, seed dispersibility is one of the determinants of the ability of plants to cope with climate change.…”