Trichome production and variation in young plant resistance to the specialist insect herbivore Plutella xylostella among natural populations of Arabidopsis lyrata

Abstract

The strength of plant-herbivore interactions varies spatially and through plant ontogeny, which may result in variable selection on plant defense, both among populations and life-history stages. To test whether populations have diverged in herbivore resistance at an early plant stage, we quantified oviposition preference and larval feeding by Plutella xylostella (L.) (Lepidoptera: Plutellidae) on young (5-6 weeks old) Arabidopsis lyrata (L.) O'Kane & Al-Shehbaz (Brassicaceae) plants, originating from 12 natural populations, six from Sweden and six from Norway. Arabidopsis lyrata can be trichome-producing or glabrous, with glabrous plants usually receiving more damage from insect herbivores in natural populations. We used the six populations polymorphic for trichome production to test whether resistance against P. xylostella differs between the glabrous and the trichomeproducing morph among young plants. There was considerable variation among populations in the number of eggs received and the proportion of leaf area consumed by P. xylostella, but not between regions (Sweden vs. Norway) or trichome morphs. Rosette size explained a significant portion of the variation in oviposition and larval feeding. The results demonstrate that among-population variation in resistance to insect herbivory can be detected among very young individuals of the perennial herb A. lyrata. They further suggest that trichome densities are too low at this plant developmental stage to contribute to resistance, and that the observed among-population variation in resistance is related to differences in other plant traits.

Costs associated with the evolution of selfing in North American populations of Arabidopsis lyrata?

“…Trichomes have been shown to be important in resistance against herbivores in the European subspecies of A. lyrata (Clauss et al 2006;Kivimaki et al 2007;Loe et al 2007;Sletvold et al 2010), and trichome density is highly variable within and between popu lations (Karkkainen and Agren 2002;Vergeer and Kunin 2011;Puentes and Agren 2013). Our results also revealed high variation in trichome density both within and among pop ulations of the North American subspecies (Fig.…”

“…2c), but trichome density did not affect the performance of M. brassicae caterpillars. Trichome densities were of comparable magnitude to European populations (e.g., see Puentes and Agren 2013). However, unlike in the European range ), we found no glabrous morphs within populations, although plants from the LPT population had less trichomes than any of the other popu lations (Fig.…”

“…We tested whether these selfing populations (that have outcrossing rates t m ranging from 0.09 to 0.41; Table 1) show a reduced performance in traits with a direct effect on fitness, i.e., life history traits (germination, early growth), and in terms of traits potentially involved in plant defence, which are expected to only affect fitness in the presence of herbivores. For the latter, we specifically looked at trichome density, specific leaf area (SLA) and leaf dry matter content (LDMC), all traits that are known to vary within and between populations (own observations; Karkkainen and Agren 2002;Puentes and Agren 2013), and to be involved in defence against herbivores (Vergeer and Kunin 2011). Furthermore, we tested for general defence costs associated with selfing by comparing the performance of cater pillars of the generalist herbivore Mamestra brassicae (L.) on plants from selfing and outcrossing populations.…”

Evaluation of wild tomato accessions (Solanum spp.) for resistance to two-spotted spider mite (Tetranychus urticae Koch) based on trichome type and acylsugar content

“…L. trifolii), tomato fruit worm (Helicoverpa armigera) and armyworm (Spodoptera litura). Resistance to each insect may depend on the susceptibility of the targeted insect to acylsugars and the levels and types of acylsugars produced, presence of other, non-acylsugar based insect resistance, glandular trichomes, coverage of foliar tissue (abaxial and adaxial leaf surfaces), effects of plant age, temperature, light intensity and other environmental factors on accumulation of acylsugars (Gurr and McGrath 2001;Kang et al 2010, Lucatti et al 2013Puentes and Å gren, 2013). Although breeders would be interested to know the minimum acylsugar levels required for spider mite resistance, these cannot be determined from this study.…”

Associational effects against a leaf beetle mediate a minority advantage in defense and growth between hairy and glabrous plants

“…Biomass and flowers were evaluated 4, 6, and 7 months after transplant, where the biomass was estimated on the basis of plant allometry (see ''Materials and method'' section for details). Estimated biomass 1 or 4 months after transplant was used as the initial biomass for the analyses of biomass or flowers, respectively Trichome density is often high on young leaves (e.g., Chu et al 2001;Yamawo et al 2012), and consequently, leaf age can influence the effectiveness of trichomes as a defense against herbivory (Chu et al 2001;Puentes and Å gren 2013). In our study, the pattern that less abundant hairy plants suffered less herbivory was the most prominent for the young leaves because the young leaves of hairy plants produced denser trichomes than those of mature leaves.…”