The existence of genetic variability for dispersal is a crucial issue for organisms facing increa... more The existence of genetic variability for dispersal is a crucial issue for organisms facing increased habitat fragmentation and climate change. We study the genetic basis and evolutionary potential for diaspore traits related to dispersal in Centaurea corymbosa. Using diaspores collected in natural conditions in four of the six extant populations of this narrow-endemic plant species and diaspores produced in a common garden experiment, we study the variation for pappus and achene sizes, and diaspore mass. Using a sample of achenes from the common garden experiment, we find that the best predictor of terminal velocity is a linear combination of pappus length, achene width, and achene weight. We find significant differences among populations for all traits in both conditions, as well as significant differences among families within population. Although the differences among populations for some traits are not exactly the same in controlled conditions compared to natural conditions, the ranking of populations according to their mean trait values is consistent in both conditions. Our study is therefore one of the first to show a correlation between phenotypic differentiation for dispersal traits in natural conditions vs. controlled conditions. We also show evidence of genetic variation for traits commonly thought to be involved in dispersal ability, suggesting the potential for evolutionary changes following environmental change and management actions.
One major challenge in parasitology and epidemiology is determining whether the richness of paras... more One major challenge in parasitology and epidemiology is determining whether the richness of parasitic and infectious diseases simply tracks host diversity or is largely determined by exogenous factors, such as climate-forced variables. We addressed this issue by analysing a 30-year survey of fungal diseases in French forests. We first combined generalized linear models and stepwise analyses to select the habitat descriptors that may account for variations in parasitic fungal species richness. Our results suggest that host species diversity is not a major determinant of parasite richness. Temperature seasonality, host abundance, and the composition of host species assemblages may play a greater role. Then we used structural equation modelling to investigate the links between these habitat descriptors and parasitic fungal species richness. Our results showed that climatic and host species descriptors had not only direct effects on species richness, but also indirect effects (via host species and sampling effort, respectively). Our results also showed that the direct effects of climate and host species were roughly equal. We therefore conclude that it is important to take into account exogenous factors when investigating the potential causes of spatial variation in the richness of parasitic diseases, in particular for plant diseases.
Variation in leaf development caused by water deficit was analysed in 120 recombinant inbred line... more Variation in leaf development caused by water deficit was analysed in 120 recombinant inbred lines derived from two Arabidopsis thaliana accessions, Ler and An-1. Main effect quantitative trait loci (QTLs) and QTLs in epistatic interactions were mapped for the responses of rosette area, leaf number and leaf 6 area to water deficit. An epistatic interaction between two QTLs affected the response of whole rosette area and individual leaf area but only with effects in well-watered condition. A second epistatic interaction between two QTLs controlled the response of rosette area and leaf number with specific effects in the water deficit condition. These effects were validated by generating and phenotyping new appropriate lines. Accordingly, a low reduction of rosette area was observed for lines with a specific allelic combination at the two interacting QTLs. This low reduction was accompanied by an increase in leaf number with a lengthening of the vegetative phase and a low reduction in individual leaf area with low reductions in epidermal cell area and number. Statistical analyses suggested that responses of epidermal cell area and number to water deficit in individual leaves were partly caused by delay in flowering time and reduction in leaf emergence rate, respectively.
• This study investigated the relationships between root structure and anatomy and whole-plant fu... more • This study investigated the relationships between root structure and anatomy and whole-plant functioning in herbaceous species.• Fourteen annual and perennial species representative of a Mediterranean old-field succession were grown in monocultures in a common-garden experiment. Whole-plant functioning was assessed by inherent relative growth rate (RGRmax), measured in standardized conditions, and maximum height (Hmax). Root tissue density (TMDr), considered as a major component of root structure, was measured on roots harvested within in-growth cores. Anatomical characteristics were analysed on cross-sectional areas (CSA).• TMDr was correlated positively with Hmax and negatively with RGRmax. Root CSA explained interspecific variation in Hmax but not that in TMDr and RGRmax. Root xylem CSA and xylem proportion in root CSA were positively correlated with TMDr and Hmax and negatively with RGRmax. Mean xylem vessel CSA did not account for variations in TMDr, Hmax and RGRmax.• These results suggested that RGRmax and Hmax are constrained by opposite root structural and anatomical traits, which have potential links with hydraulic conductance, support and longevity.This study investigated the relationships between root structure and anatomy and whole-plant functioning in herbaceous species.Fourteen annual and perennial species representative of a Mediterranean old-field succession were grown in monocultures in a common-garden experiment. Whole-plant functioning was assessed by inherent relative growth rate (RGRmax), measured in standardized conditions, and maximum height (Hmax). Root tissue density (TMDr), considered as a major component of root structure, was measured on roots harvested within in-growth cores. Anatomical characteristics were analysed on cross-sectional areas (CSA).TMDr was correlated positively with Hmax and negatively with RGRmax. Root CSA explained interspecific variation in Hmax but not that in TMDr and RGRmax. Root xylem CSA and xylem proportion in root CSA were positively correlated with TMDr and Hmax and negatively with RGRmax. Mean xylem vessel CSA did not account for variations in TMDr, Hmax and RGRmax.These results suggested that RGRmax and Hmax are constrained by opposite root structural and anatomical traits, which have potential links with hydraulic conductance, support and longevity.
The existence of genetic variability for dispersal is a crucial issue for organisms facing increa... more The existence of genetic variability for dispersal is a crucial issue for organisms facing increased habitat fragmentation and climate change. We study the genetic basis and evolutionary potential for diaspore traits related to dispersal in Centaurea corymbosa. Using diaspores collected in natural conditions in four of the six extant populations of this narrow-endemic plant species and diaspores produced in a common garden experiment, we study the variation for pappus and achene sizes, and diaspore mass. Using a sample of achenes from the common garden experiment, we find that the best predictor of terminal velocity is a linear combination of pappus length, achene width, and achene weight. We find significant differences among populations for all traits in both conditions, as well as significant differences among families within population. Although the differences among populations for some traits are not exactly the same in controlled conditions compared to natural conditions, the ranking of populations according to their mean trait values is consistent in both conditions. Our study is therefore one of the first to show a correlation between phenotypic differentiation for dispersal traits in natural conditions vs. controlled conditions. We also show evidence of genetic variation for traits commonly thought to be involved in dispersal ability, suggesting the potential for evolutionary changes following environmental change and management actions.
One major challenge in parasitology and epidemiology is determining whether the richness of paras... more One major challenge in parasitology and epidemiology is determining whether the richness of parasitic and infectious diseases simply tracks host diversity or is largely determined by exogenous factors, such as climate-forced variables. We addressed this issue by analysing a 30-year survey of fungal diseases in French forests. We first combined generalized linear models and stepwise analyses to select the habitat descriptors that may account for variations in parasitic fungal species richness. Our results suggest that host species diversity is not a major determinant of parasite richness. Temperature seasonality, host abundance, and the composition of host species assemblages may play a greater role. Then we used structural equation modelling to investigate the links between these habitat descriptors and parasitic fungal species richness. Our results showed that climatic and host species descriptors had not only direct effects on species richness, but also indirect effects (via host species and sampling effort, respectively). Our results also showed that the direct effects of climate and host species were roughly equal. We therefore conclude that it is important to take into account exogenous factors when investigating the potential causes of spatial variation in the richness of parasitic diseases, in particular for plant diseases.
Variation in leaf development caused by water deficit was analysed in 120 recombinant inbred line... more Variation in leaf development caused by water deficit was analysed in 120 recombinant inbred lines derived from two Arabidopsis thaliana accessions, Ler and An-1. Main effect quantitative trait loci (QTLs) and QTLs in epistatic interactions were mapped for the responses of rosette area, leaf number and leaf 6 area to water deficit. An epistatic interaction between two QTLs affected the response of whole rosette area and individual leaf area but only with effects in well-watered condition. A second epistatic interaction between two QTLs controlled the response of rosette area and leaf number with specific effects in the water deficit condition. These effects were validated by generating and phenotyping new appropriate lines. Accordingly, a low reduction of rosette area was observed for lines with a specific allelic combination at the two interacting QTLs. This low reduction was accompanied by an increase in leaf number with a lengthening of the vegetative phase and a low reduction in individual leaf area with low reductions in epidermal cell area and number. Statistical analyses suggested that responses of epidermal cell area and number to water deficit in individual leaves were partly caused by delay in flowering time and reduction in leaf emergence rate, respectively.
• This study investigated the relationships between root structure and anatomy and whole-plant fu... more • This study investigated the relationships between root structure and anatomy and whole-plant functioning in herbaceous species.• Fourteen annual and perennial species representative of a Mediterranean old-field succession were grown in monocultures in a common-garden experiment. Whole-plant functioning was assessed by inherent relative growth rate (RGRmax), measured in standardized conditions, and maximum height (Hmax). Root tissue density (TMDr), considered as a major component of root structure, was measured on roots harvested within in-growth cores. Anatomical characteristics were analysed on cross-sectional areas (CSA).• TMDr was correlated positively with Hmax and negatively with RGRmax. Root CSA explained interspecific variation in Hmax but not that in TMDr and RGRmax. Root xylem CSA and xylem proportion in root CSA were positively correlated with TMDr and Hmax and negatively with RGRmax. Mean xylem vessel CSA did not account for variations in TMDr, Hmax and RGRmax.• These results suggested that RGRmax and Hmax are constrained by opposite root structural and anatomical traits, which have potential links with hydraulic conductance, support and longevity.This study investigated the relationships between root structure and anatomy and whole-plant functioning in herbaceous species.Fourteen annual and perennial species representative of a Mediterranean old-field succession were grown in monocultures in a common-garden experiment. Whole-plant functioning was assessed by inherent relative growth rate (RGRmax), measured in standardized conditions, and maximum height (Hmax). Root tissue density (TMDr), considered as a major component of root structure, was measured on roots harvested within in-growth cores. Anatomical characteristics were analysed on cross-sectional areas (CSA).TMDr was correlated positively with Hmax and negatively with RGRmax. Root CSA explained interspecific variation in Hmax but not that in TMDr and RGRmax. Root xylem CSA and xylem proportion in root CSA were positively correlated with TMDr and Hmax and negatively with RGRmax. Mean xylem vessel CSA did not account for variations in TMDr, Hmax and RGRmax.These results suggested that RGRmax and Hmax are constrained by opposite root structural and anatomical traits, which have potential links with hydraulic conductance, support and longevity.
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Papers by Denis Vile