Adaptive fruit colour variation along an elevational gradient in a colour-polymorphic plant

Abstract

Many plants produce colour polymorphic fruits. However, the processes responsible for the evolution and maintenance of fruit colour polymorphisms are poorly understood. We investigated the fruit colour polymorphism in Gaultheria depressa var. novae-zealandiae (Ericaceae), a predominantly bird-dispersed, alpine shrub from New Zealand, by testing whether colour morph frequencies vary geographically to maximise fruit-foliage colour contrasts. We also conducted a seed germination experiment to test whether fruit colour morphs vary in their susceptibility to UV damage. Results showed that ‘red’ fruits were more abundant at lower elevations, while ‘white’ fruits were predominant at higher elevations. Leaf colours shifted from ‘green’ in appearance at lower elevations to ‘red’ at higher elevations. Analyses of fruit-foliage colour contrasts showed that ‘red’ fruits were more conspicuous at lower elevations, and ‘white’ fruits being more conspicuous at higher elevations, which was consistent with the hypothesis that colour morph frequencies vary geographically to maximise their conspicuousness to dispersers. However, ‘red’ fruits were generally more conspicuous than ‘white’ fruits, regardless of elevation, indicating that the maintenance of the polymorphism could not be attributed to fruit-foliage colour contrasts alone. The seed germination experiment showed that ‘white’ fruits were more resistant to UV damage, suggesting the preponderance of ‘white’ fruited individuals in the landscape results from a greater degree of protection from UV damage. The fruit colour polymorphism in Gaultheria depressa var. novae-zealandiae therefore appears to be maintained by trade-offs between conspicuousness to dispersers and tolerance to UV damage, advocating a pluralistic approach to the problem in the future.

Proteomic and Physiological Signatures of Altitude Adaptation in aMyrsine coriaceaPopulation under Common Garden Conditions

“…Plant populations occurring along an altitudinal gradient can vary in their morpho-anatomical and physiological characteristics (Ahmad et al ., 2016; Rahman et al ., 2020). While physiological variations occurring in plants with increasing altitude are well described (Ahmad et al ., 2016; Hniličková et al ., 2016; Ibañez et al ., 2017; Liu et al ., 2020; Lim and Burns, 2022), the underlying processes leading to these phenotypic variations are not clearly understood. The continuous challenge lies in identifying the molecular pathways and genes of adaptive significance in this context.…”