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Fine ‐ scale frequency differentiation along a herbivory gradient in the trichome dimorphism of a wild Arabidopsis

View Article: PubMed Central - PubMed

ABSTRACT

Geographic variation is commonly observed in plant resistance traits, where plant species might experience different selection pressure across a heterogeneous landscape. Arabidopsis halleri subsp. gemmifera is dimorphic for trichome production, generating two morphs, trichome‐producing (hairy) and trichomeless (glabrous) plants. Trichomes of A. halleri are known to confer resistance against the white butterfly, cabbage sawfly, and brassica leaf beetle, but not against flea beetles. We combined leaf damage, microclimate, and microsatellite loci data of 26 A. halleri populations in central Japan, to explore factors responsible for fine‐scale geographic variation in the morph frequency. We found that hairy plants were less damaged than glabrous plants within populations, but the among‐site variation was the most significant source of variation in the individual‐level damage. Fixation index (Gst″) of a putative trichome locus exhibited a significant divergence along population‐level damage with an exception of an outlier population, inferring the local adaptation to herbivory. Notably, this outlier was a population wherein our previous study reported a balancing role of the brassica leaf beetle Phaedon brassicae on the morph frequency. This differentiation of the trichome locus was unrelated to neutral genetic differentiation (evaluated by Gst″ of microsatellite loci) and meteorological factors (including temperature and solar radiation). The present findings, combined with those of our previous work, provide suggestive evidence that herbivore‐driven divergence and occasional outbreak of a specific herbivore have jointly contributed to the ecogeographic pattern in the frequency of two morphs.

No MeSH data available.


Locality and climatic variation in the present study. (a) Map showing locations of study sites and their frequency of hairy and glabrous plants. The size of pie charts reflects the total number of plants at each site. The site IDs (1–26) correspond to those listed in the Tables S1 and S2. (b) Summary of the principal component analysis (PCA) for eight meteorological variables. Red arrows show contributions of each climatic factor to the first and second principal component, PC1 and PC2
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ece32830-fig-0002: Locality and climatic variation in the present study. (a) Map showing locations of study sites and their frequency of hairy and glabrous plants. The size of pie charts reflects the total number of plants at each site. The site IDs (1–26) correspond to those listed in the Tables S1 and S2. (b) Summary of the principal component analysis (PCA) for eight meteorological variables. Red arrows show contributions of each climatic factor to the first and second principal component, PC1 and PC2

Mentions: This study aimed to address the following two specific questions. (1) To what extent does leaf damage to A. halleri individuals differ among the trichome phenotypes (hairy or glabrous) and study sites? (2) What kinds of ecological factors are responsible for fine‐scale geographic variation in the morph frequency? In this study, we first compared the leaf damage in hairy and glabrous plants among 26 populations in Japan, which were separated from each other by less than 200 km in distance (Figure 2). Then, we evaluated genetic differentiation of a putative trichome locus along gradients of ecological factors, such as herbivory and microclimatic conditions, by incorporating neutral genetic variation as another correlative factor.


Fine ‐ scale frequency differentiation along a herbivory gradient in the trichome dimorphism of a wild Arabidopsis
Locality and climatic variation in the present study. (a) Map showing locations of study sites and their frequency of hairy and glabrous plants. The size of pie charts reflects the total number of plants at each site. The site IDs (1–26) correspond to those listed in the Tables S1 and S2. (b) Summary of the principal component analysis (PCA) for eight meteorological variables. Red arrows show contributions of each climatic factor to the first and second principal component, PC1 and PC2
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383478&req=5

ece32830-fig-0002: Locality and climatic variation in the present study. (a) Map showing locations of study sites and their frequency of hairy and glabrous plants. The size of pie charts reflects the total number of plants at each site. The site IDs (1–26) correspond to those listed in the Tables S1 and S2. (b) Summary of the principal component analysis (PCA) for eight meteorological variables. Red arrows show contributions of each climatic factor to the first and second principal component, PC1 and PC2
Mentions: This study aimed to address the following two specific questions. (1) To what extent does leaf damage to A. halleri individuals differ among the trichome phenotypes (hairy or glabrous) and study sites? (2) What kinds of ecological factors are responsible for fine‐scale geographic variation in the morph frequency? In this study, we first compared the leaf damage in hairy and glabrous plants among 26 populations in Japan, which were separated from each other by less than 200 km in distance (Figure 2). Then, we evaluated genetic differentiation of a putative trichome locus along gradients of ecological factors, such as herbivory and microclimatic conditions, by incorporating neutral genetic variation as another correlative factor.

View Article: PubMed Central - PubMed

ABSTRACT

Geographic variation is commonly observed in plant resistance traits, where plant species might experience different selection pressure across a heterogeneous landscape. Arabidopsis halleri subsp. gemmifera is dimorphic for trichome production, generating two morphs, trichome‐producing (hairy) and trichomeless (glabrous) plants. Trichomes of A. halleri are known to confer resistance against the white butterfly, cabbage sawfly, and brassica leaf beetle, but not against flea beetles. We combined leaf damage, microclimate, and microsatellite loci data of 26 A. halleri populations in central Japan, to explore factors responsible for fine‐scale geographic variation in the morph frequency. We found that hairy plants were less damaged than glabrous plants within populations, but the among‐site variation was the most significant source of variation in the individual‐level damage. Fixation index (Gst″) of a putative trichome locus exhibited a significant divergence along population‐level damage with an exception of an outlier population, inferring the local adaptation to herbivory. Notably, this outlier was a population wherein our previous study reported a balancing role of the brassica leaf beetle Phaedon brassicae on the morph frequency. This differentiation of the trichome locus was unrelated to neutral genetic differentiation (evaluated by Gst″ of microsatellite loci) and meteorological factors (including temperature and solar radiation). The present findings, combined with those of our previous work, provide suggestive evidence that herbivore‐driven divergence and occasional outbreak of a specific herbivore have jointly contributed to the ecogeographic pattern in the frequency of two morphs.

No MeSH data available.