Searching for the bull’s eye: agents and targets of selection vary among geographically disparate cyanogenesis clines in white clover (Trifolium repens L.)

Kooyers, N. J.; Olsén, K. Håkan

doi:10.1038/hdy.2013.71

Cited by 40 publications

(71 citation statements)

References 57 publications

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“…Cyanogenic clover plants are differentially protected against a variety of small generalist herbivores (reviewed in Kooyers et al ., ). At the same time, acyanogenic plants predominate at higher latitudes and elevations, and climate‐associated cyanogenesis clines have evolved in native and naturalized populations worldwide (e.g., Daday, ,b, ; Kooyers & Olsen, , ; Thompson et al ., ). Glasshouse experiments indicate that there are energetic costs associated with the production of the cyanogenic components (Kakes, ; Kooyers et al ., ); acyanogenic plants may therefore have a competitive advantage in cooler climates if fewer herbivores are present in these locations.…”

Section: Discussionmentioning

confidence: 99%

Micro‐ and macroevolutionary adaptation through repeated loss of a complete metabolic pathway

Olsen

Small

2018

New Phytologist

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There is growing evidence for the convergent evolution of physically linked gene clusters encoding chemical defense pathways. Metabolic clusters are proposed to evolve because they ensure co-inheritance of all required genes where the defense is favored, and prevent inheritance of toxic partial pathways where it is not. This hypothesis rests on the assumption that clusters evolve in species where selection favors intraspecific polymorphism for the defense; however, they have not been examined in polymorphic species. We examined metabolic cluster evolution in relation to an adaptive polymorphism for cyanogenic glucoside (CNglc) production in clover. Using 163 accessions, we performed CNglc assays, BAC sequencing, Southern hybridizations and molecular evolutionary analyses. We find that the CNglc pathway forms a 138-kb cluster in white clover, and that the adaptive polymorphism occurs through presence/absence of the complete cluster. Component genes are orthologous to those in the distantly related legume Lotus japonicus. These findings provide empirical support for the co-inheritance hypothesis, and they indicate that adaptive CNglc variation in white clover evolves through recurrent deletions of the entire pathway. They further indicate that the shared ancestor of many important legume crops was likely cyanogenic and that this defense was lost repeatedly over the last 50 Myr.

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Section: Discussionmentioning

confidence: 99%

Micro‐ and macroevolutionary adaptation through repeated loss of a complete metabolic pathway

Olsen

Small

2018

New Phytologist

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“…Indeed, numerous biological studies have detected clinal variation in traits across altitudinal gradients (Barber & Jackson, ; Pitchers, Pool, & Dworkin, ). Recent studies have further suggested that the presence of replicated clines across independent geographical systems can strengthen inferences regarding the “agents and targets” of natural selection (Kooyers & Olsen, ).…”

Section: Introductionmentioning

confidence: 99%

Ecological gradients drive insect wing loss and speciation: The role of the alpine treeline

et al. 2019

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Alpine ecosystems are frequently characterized by an abundance of wing‐reduced insect species, but the drivers of this biodiversity remain poorly understood. Insect wing reduction in these environments has variously been attributed to altitude, temperature, isolation, habitat stability or decreased habitat size. We used fine‐scale ecotypic and genomic analyses, along with broad‐scale distributional analyses of ecotypes, to unravel the ecological drivers of wing reduction in the wing‐dimorphic stonefly Zelandoperla fenestrata complex. Altitudinal transects within populations revealed dramatic wing reduction over very fine spatial scales, tightly linked to the alpine treeline. Broad biogeographical analyses confirm that the treeline has a much stronger effect on these ecotype distributions than altitude per se. Molecular analyses revealed parallel genomic divergence between vestigial‐winged (high altitude) and full‐winged (low altitude) ecotypes across distinct streams. These data thus highlight the role of the alpine treeline as a key driver of rapid speciation, providing a new model for ecological diversification along exposure gradients.

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“…; Caradus & Forde ; Majumdar et al . ), as well as in regions where white clover has been introduced and naturalized, such as the central United States (Daday ; Kooyers & Olsen ), New Zealand (Kooyers & Olsen ) and the U.S. Pacific Northwest (Ganders ; Kooyers & Olsen ). For example, in the central United States, we have documented that the frequency of cyanogenic plants steadily decreases over a ~900km latitudinal transect from 86% in southern Louisiana to 11% in northern Wisconsin (Kooyers & Olsen ).…”

Section: Introductionmentioning

confidence: 99%

Aridity shapes cyanogenesis cline evolution in white clover (Trifolium repens L.)

et al. 2014

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Adaptive differentiation between populations is often proposed to be the product of multiple interacting selective pressures, although empirical support for this is scarce. In white clover, populations show adaptive differentiation in frequencies of cyanogenesis, the ability to produce hydrogen cyanide after tissue damage. This polymorphism arises through independently segregating polymorphisms for the presence/absence of two required cyanogenic components, cyanogenic glucosides and their hydrolysing enzyme. White clover populations worldwide have evolved a series of recurrent, climate-associated clines, with higher frequencies of cyanogenic plants in warmer locations. These clines have traditionally been hypothesized to reflect a fitness trade-off between chemical defence in herbivore-rich areas (warmer climates) and energetic costs of producing cyanogenic components in areas of low herbivore pressure (cooler climates). Recent observational studies suggest that cyanogenic components may also be beneficial in water-stressed environments. We investigated fitness trade-offs associated with temperature-induced water stress in the cyanogenesis system using manipulative experiments in growth chambers and population surveys across a longitudinal precipitation gradient in the central United States. We find that plants producing cyanogenic glucosides have higher relative fitness in treatments simulating a moderate, persistent drought stress. In water-neutral treatments, there are energetic costs to producing cyanogenic components, but only in treatments with nutrient stress. These fitness trade-offs are consistent with cyanogenesis frequencies in natural populations, where we find clinal variation in the proportion of plants producing cyanogenic glucosides along the precipitation gradient. These results suggest that multiple selective pressures interact to maintain this adaptive polymorphism and that modelling adaptation will require knowledge of environment-specific fitness effects.

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Searching for the bull’s eye: agents and targets of selection vary among geographically disparate cyanogenesis clines in white clover (Trifolium repens L.)

Cited by 40 publications

References 57 publications

Micro‐ and macroevolutionary adaptation through repeated loss of a complete metabolic pathway

Micro‐ and macroevolutionary adaptation through repeated loss of a complete metabolic pathway

Ecological gradients drive insect wing loss and speciation: The role of the alpine treeline

Aridity shapes cyanogenesis cline evolution in white clover (Trifolium repens L.)

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