Seed dispersal of wild radishes and its association with within-population spatial distribution

Abstract

Background: The wild radishes, Raphanus raphanistrum and R. pugioniformis (Brassicaceae) are native to the East Mediterranean region. However, whereas R. raphanistrum is widely distributed worldwide, the endemic R. pugioniformis is limited to specific habitats. In R. raphanistrum the diaspores of the indehiscent fruits comprise glabrous, light, single-seeded segments, whereas the intact fruits of R. pugioniformis are heavy and covered with spiny backwardpointing trichomes. We aimed to investigate whether the structure of the diaspores was directly associated with longand short-range dispersal in R. raphanistrum and R. pugioniformis, respectively. We further surveyed within-population spatial distributions, to test the hypothesis that short-and long-range dispersal contribute to a patchy vs. uniform distribution patterns of R. pugioniformis and R. raphanistrum, respectively. Results: The results indicated that dispersal by wind and runoff water was substantially lower for diaspores of R. pugioniformis than for those of R. raphanistrum diaspores. Supporting the hypothesis that backward-pointing trichomes promote adherence to soil particles, the displacement on soil surface of R. pugioniformis fruits depended on their orientation relative to wind direction. Furthermore, trichome removal from fruits of R. pugioniformis significantly reduced wind velocity needed to remove fruits that were placed on soils typical of the species' natural habitats. The spatial-distribution survey results indicated a patchy distribution of R. pugioniformis populations as compared with the more uniform arrangement in the studied populations of R. raphanistrum; consistent with the unidirectional vs. homogeneous wind dispersal of the respective diaspores, with respect to wind direction. In addition, R. pugioniformis population sizes changed less between years than those of R. raphanistrum. Conclusions: Overall, our results indicate that fruit structure is strongly linked to dispersal ability and spatial distribution of the two closely related wild radish species. Whereas R. raphanistrum inhabits homogenous sandy soil habitats, the distribution range of R. pugioniformis includes heterogeneous environments in which growth niches are scarcer. We suggest that the different modes of dispersal have evolved as adaptive traits appropriate to the species' specific habitats.

Phenotypic Variation in Two Wild Radishes: Raphanus pugioniformis and Raphanus raphanistrum in Field and Common Gardens in Palestine

“…pugioniformis, an endemic species of the eastern Mediterranean [6], has received limited research attention. The relationships among these species remain largely unresolved [7]. However, a cDNA sequence analysis conducted on one population from each of eight Raphanus taxa (excluding R. pugioniformis) provided compelling evidence supporting the monophyly of the crop cultivars and the native and weedy forms of R. r. raphanistrum [2].…”

“…Weedy R. r. raphanistrum is frequently found as a troublesome invader in small grain fields and is widely recognized as one of the most significant agricultural weeds globally [7][8][9]. Weedy radish has been extensively utilized in ecological and evolutionary research, specifically for investigating plant-insect interactions [10][11][12][13][14][15][16], and possesses valuable genomic resources that render it an ideal system for studying the origins and adaptations of agricultural weeds, enabling researchers to address pertinent questions in this field [17].…”

‘Root of all success’: Plasticity in root architecture of invasive wild radish for adaptive benefit

“…In contrast, its close relative, Raphanus pugioniformis DC. ( Rp ) is endemic to northern Israel, southern Lebanon, and Syria, growing on Terra Rossa and basaltic soil ( Ziffer-Berger et al., 2020 ). This species is not studied as well as Rr due to its lower distribution range and not interfering with agriculture.…”

“…R. raphanistrum occurs mainly on sandy soils of coastal plains (=Calcisol), while R. pugioniformis is restricted to mountainous areas in north-eastern Israel on Terra Rossa (=Luvisol) and basaltic (=Vertisol) soils. (B) R. raphanistrum scattered worldwide (pale blue areas on the world map; ( Holm et al., 1997 )) from its native distribution area of the Mediterranean basin (highlighted by dark blue; ( Ziffer-Berger et al., 2020 )). R. pugioniformis is restricted to northern Israel, southern Lebanon, and Syria.…”

Effect of different growing media on selected growth performance parameters of Raphanus pugioniformis and Raphanus raphanistrum

“…Weedy radish belongs to the family Brassicaceae genus Raphanus and is a native population in the Mediterranean region (Conner et al 2011;Al-Shehbaz 2012;Conner et al 2014;Klinger et al 1991). Raphanus sativus comprise four major types including two fruit crops (Oilseed and edible pod Rat-tail) and two root crops (European radish and Asian daikon) but the relationships among these species are not well known (Ziffer-Berger et al 2020). According to the Campbell et al, (2006) cDNA sequence of Raphanus taxa revealed monophyly of native and weedy R. raphanistrum.…”