Narrow genetic base in forest restoration with holm oak (Quercus ilex L.) in Sicily

In order to empirically assess the effect of actual seed sampling strategy on genetic diversity of holm oak (Quercus ilex) forestations in Sicily, we have analysed the genetic composition of two seedling lots (nursery stock and plantation) and their known natural seed origin stand by means of six nuclear microsatellite loci. Significant reduction in genetic diversity and significant difference in genetic composition of the seedling lots compared to the seed origin stand were detected. The female and the total effective number of parents were quantified by means of maternity assignment of seedlings and temporal changes in allele frequencies. Extremely low effective maternity numbers were estimated (Nfe $\approx$ 2-4) and estimates accounting for both seed and pollen donors gave also low values (Ne $\approx$ 35-50). These values can be explained by an inappropriate forestry seed harvest strategy limited to a small number of spatially close trees

Cascading host-associated genetic differentiation in parasitoids of phytophagous insects

The extraordinary diversity of phytophagous insects may be attributable to their narrow specialization as parasites of plants, with selective tradeoffs associated with alternate host plants driving genetic divergence of host-associated forms via ecological speciation. Most phytophagous insects in turn are attacked by parasitoid insects, which are similarly specialized and may also undergo host-associated differentiation (HAD). A particularly interesting possibility is that HAD by phytophagous insects might lead to HAD in parasitoids, as parasitoids evolve divergent lineages on the new host plant-specific lineages of their phytophagous hosts. We call this process ‘cascading host-associated differentiation’ (cascading HAD). We tested for cascading HAD in parasitoids of two phytophagous insects, each of which consists of genetically distinct host-associated lineages on the same pair of goldenrods (Solidago). Each parasitoid exhibited significant host-associated genetic divergence, and the distribution and patterns of divergence are consistent with divergence in sympatry. Although evidence for cascading HAD is currently limited, our results suggest that it could play an important role in the diversification of parasitoids attacking phytophagous insects. The existence of cryptic host-associated lineages also suggests that the diversity of parasitoids may be vastly underestimated

Data from: Nutrient supply alters goldenrod’s induced response to herbivory

Recent interest in using trait-based approaches to understand and predict ecosystem processes and evolutionary responses to environmental change (both biotic and abiotic), highlights the need to understand the relative importance of genetic and environmental sources of intraspecific trait variation within local populations of dominant species. Here, I combine plant defense theory with functional approaches to quantify genetic trait variation and phenotypic trait plasticity of nine goldenrod (Solidago altissima) genotypes derived from a local field population in Connecticut, USA to herbivory along a nutrient supply gradient. I found that increasing nutrient supply changed the dominant plant defense strategy from tolerance to induced resistance. Induced resistance was detected through decreased herbivore growth rates and a behavioral feeding shift of grasshoppers to older leaf tissue. This could not be fully accounted for through stoichiometric changes in leaf tissue quality. A multi-dimensional phenotype approach revealed that abiotic and biotic environments (nutrients and herbivory) accounted for almost as much whole-plant trait variation (31%) as did plant genotype (36%). Increasing nutrient supply and herbivory resulted in independent and differential effects on whole-plant trait expression. Increasing both treatments concurrently produced a unique plant phenotype with increased leaf carbon content and allocation to asexual reproduction (ExE). Notably, individual genotypes exhibited different magnitudes of multivariate trait plasticity to nutrient and herbivory gradients. However, the population of genotypes as a whole within a given environment expressed an approximately equal magnitude of trait variation across both permissive (high nutrient, no herbivory) and stressful (low nutrient, high herbivory) environments. Quantifying plasticity in defensive strategy in concert with correlated whole-plant trait expression changes across multiple abiotic and biotic factors may be key to providing a mechanistic understanding of how heterogeneous landscapes impact community interactions and ecosystem processes