Abstract
A major aim in invasion biology is identifying traits distinguishing alien invasive and alien non-invasive plants. Surprisingly, this approach has been, so far, poorly used to understand why some arable weeds are abundant and widespread while others are rare and narrowly distributed. In the present study, we focused on the characteristics of successful weeds occurring in maize fields, one of the most important crops worldwide. Two national weed surveys conducted in France were used to identify increasing and decreasing species based on 175 and 484 surveyed fields in the 1970s and the 2000s, respectively. Weed trait values related to regional frequency, local abundance, and specialization to maize were identified with phylogenetic generalized least-squares (PGLS). We found a positive relationship between regional frequency and local abundance, i.e., the most widespread weeds were also locally more abundant. We highlighted that weeds with the C4 photosynthetic pathway and summer emergence were more abundant, more frequent, and more specialized to maize crops. More generally, we highlighted two successful strategies: On the one hand, traits related to a general weediness syndrome with rapid resource acquisition (high SLA and Ellenberg-N) and high colonization capacity (seed longevity, fecundity, and wind dispersal); on the other hand, traits related to specific adaptation to spring cultivation (thermophilous species with summer emergence, late flowering, and C4 photosynthetic pathway). Deviations from the abundancy–frequency relationships also indicated that species of the Panicoideae sub-family, species with Triazine-resistant populations, and neophyte species were more abundant than expected by their regional frequency. To some extent, it is therefore possible to predict which species can be troublesome in maize crops and use this information in weed risk assessment tools to prevent new introductions or favor early detection and eradication. This study showed how tools developed in functional and macro-ecology can be used to improve our understanding of weed ecology and to develop more preventive management strategies.
Highlights
Invasion ecology has a long tradition of searching for traits allowing to distinguish alien invasive and alien non-invasive plants [1,2]
The assessment of changes in weed species status was based on comparing the regional frequency and local abundance in 175 fields surveyed in the 1970s and 484 fields surveyed in the 2000s
Among common species already recorded in the 1970s, Solanum nigrum and Mercurialis annua were the only weeds significantly increasing in frequency, by +13% and +5%, respectively
Summary
Invasion ecology has a long tradition of searching for traits allowing to distinguish alien invasive and alien non-invasive plants [1,2]. Plants 2020, 9, 40 an ideal weed should possess to rapidly spread and occupy a new area or previously vacant ecological niche. Such approach has been so far poorly extended and used to understand why some arable weeds are regionally frequent or locally abundant in crop fields while other are not [5,6,7]. Chytry, and Kuhn [5] found that widespread arable weeds in cultivated fields of Czech Republic, mostly with winter cereals, were those flowering in pre-spring and early spring, adapted to low temperatures, relatively shade tolerant, and with high nutrient requirements. Chauvel, and Reboud [6] found that weeds that have increased in frequency in sunflower crops between the 1970s and the 2000s in France differed from decreasing weeds by high nutrient and light requirements, a lower sensitivity to sunflower herbicides, and a summer life cycle
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