Natural selection drives chemical resistance ofDatura stramonium

Abstract

Plant resistance to herbivores involves physical and chemical plant traits that prevent or diminish damage by herbivores, and hence may promote coevolutionary arm-races between interacting species. Although Datura stramonium’s concentration of tropane alkaloids is under selection by leaf beetles, it is not known whether chemical defense reduces seed predation by the specialist weevil, Trichobaris soror, and if it is evolving by natural selection. We measured infestation by T. soror as well as the concentration of the plants’ two main tropane alkaloids in 278 D. stramonium plants belonging to 31 populations in central Mexico. We assessed whether the seed predator exerted preferences on the levels of both alkaloids and whether they affect plant fitness. Results show great variation across populations in the concentration of scopolamine and atropine in both leaves and seeds of plants of D. stramonium, as well as in the intensity of infestation and the proportion of infested fruits by T. soror. The concentration of scopolamine in seeds and leaves are negatively associated across populations. We found that scopolamine concentration increases plant fitness. Our major finding was the detection of a positive relationship between the population average concentrations of scopolamine with the selection differentials of scopolamine. Such spatial variation in the direction and intensity of selection on scopolamine may represent a coevolutionary selective mosaic. Our results support the view that variation in the concentration of scopolamine among-populations of D. stramonium in central Mexico is being driven, in part, by selection exerted by T. soror, pointing an adaptive role of tropane alkaloids in this plant species.

Genomic and chemical evidence for local adaptation in resistance to different herbivores in Datura stramonium

“…2004), whereas in Teotihuacán it is consumed mainly by the specialists beetles Lema daturaphila , Epitrix parvula , and the specialist seed predator Trichobaris soror (Bello‐Bedoy and Núñez‐Farfán 2010; Miranda‐Pérez et al. 2016). In fact, L. daturaphila is absent in the Ticumán population.…”

Selection on tropane alkaloids in native and non‐native populations of Datura stramonium

“…In the native range, scopolamine was positively selected in three populations. Previous evidence shows that this alkaloid is a component of resistance to herbivores of D. stramonium in its native range, though it does not account for all variation in resistance owing to spatial variation in the pressure exerted by specialist herbivores (see Castillo et al, 2014;Miranda-Pérez et al, 2016). For instance, the dietary specialist leaf beetle Lema trilineata daturaphila and the seed predator Trichobaris soror are absent in tropical, low altitude, locations of central Mexico (Castillo et al, 2014;J.…”

“…Weevils of the genus Trichobaris (Coleoptera: Curculionidae) are specialized seed predators of Datura (De‐la‐Mora et al, ). Trichobaris soror is tightly associated with D. stramonium along the Trans‐Mexican Volcanic Belt (De‐la‐Mora, Piñero, & Núñez‐Farfán, ) and exerts selection on plants' scopolamine concentration (Miranda‐Pérez et al, ).…”

“…Alkaloids are toxic to animals, affecting enzymes and altering different physiological processes; some have strong effects on the nervous systems (Mithöfer & Boland, 2012). Studies have shown selection on one or two tropane alkaloids of D. stramonium when consumed by dietary specialist or generalist herbivores (Castillo et al, 2014;Miranda-Pérez et al, 2016;Shonle & Bergelson, 2000).…”

Molecular genetic and biochemical evidence for adaptive evolution of leaf abaxial epicuticular wax crystals in the genus Lithocarpus (Fagaceae)

“…CER1 and CER3 , Table 3 ). The makeup of defensive chemicals usually directly reflects the herbivore stress of plants and reveals strong signs of positive selection [ 91 , 92 ]. Cuticular or epicuticular waxes of the leaf surface are suggested to play a role in physical defense [ 60 , 87 ].…”