Indirect interaction between two native thistles mediated by an invasive exotic floral herbivore

Spatial and temporal variation in insect floral herbivory is common and often important. Yet, the determinants of such variation remain incompletely understood. Using 12 years of flowering data and 4 years of biweekly insect counts, we evaluated four hypotheses to explain variation in damage by the Eurasian flower head weevil, Rhinocyllus conicus, to the native North American wavyleaf thistle, Cirsium undulatum. The four factors hypothesized to influence weevil impact were variations in climate, weevil abundance, phenological synchrony, and number of flower heads available, either on wavyleaf thistle or on the other co-occurring, acquired native host plant (Platte thistle, Cirsium canescens), or on both. Climate did not contribute significantly to an explanation of variation in R. conicus damage to wavyleaf thistle. However, climate did influence weevil synchrony with wavyleaf flower head initiation, and phenological synchrony was important in determining R. conicus oviposition levels on wavyleaf thistle. The earlier R. conicus was active, the less it oviposited on wavyleaf thistle, even when weevils were abundant. Neither weevil abundance nor availability of wavyleaf flower heads predicted R. conicus egg load. Instead, the strongest predictor of R. conicus egg load on wavyleaf thistle was the availability of flower heads on Platte thistle, the more common, earlier flowering native thistle in the sand prairie. Egg load on wavyleaf thistle decreased as the number of Platte thistle flower heads at a site increased. Thus, wavyleaf thistle experienced associational defense in the presence of flowering by its now declining native congener, Platte thistle. These results demonstrate that prediction of damage to a native plant by an exotic insect may require knowledge of both likely phenological synchrony and total resource availability to the herbivore, including resources provided by other nontarget native species

Plants Modify Biological Processes to Ensure Survival following Carbon Depletion: A Lolium perenne Model

BACKGROUND: Plants, due to their immobility, have evolved mechanisms allowing them to adapt to multiple environmental and management conditions. Short-term undesirable conditions (e.g. moisture deficit, cold temperatures) generally reduce photosynthetic carbon supply while increasing soluble carbohydrate accumulation. It is not known, however, what strategies plants may use in the long-term to adapt to situations resulting in net carbon depletion (i.e. reduced photosynthetic carbon supply and carbohydrate accumulation). In addition, many transcriptomic experiments have typically been undertaken under laboratory conditions; therefore, long-term acclimation strategies that plants use in natural environments are not well understood. METHODOLOGY/PRINCIPAL FINDINGS: Perennial ryegrass (Lolium perenne L.) was used as a model plant to define whether plants adapt to repetitive carbon depletion and to further elucidate their long-term acclimation mechanisms. Transcriptome changes in both lamina and stubble tissues of field-grown plants with depleted carbon reserves were characterised using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The RT-qPCR data for select key genes indicated that plants reduced fructan degradation, and increased photosynthesis and fructan synthesis capacities following carbon depletion. This acclimatory response was not sufficient to prevent a reduction (P<0.001) in net biomass accumulation, but ensured that the plant survived. CONCLUSIONS: Adaptations of plants with depleted carbon reserves resulted in reduced post-defoliation carbon mobilization and earlier replenishment of carbon reserves, thereby ensuring survival and continued growth. These findings will help pave the way to improve plant biomass production, for either grazing livestock or biofuel purposes

Genome-wide analysis identifies 12 loci influencing human reproductive behavior.

The genetic architecture of human reproductive behavior-age at first birth (AFB) and number of children ever born (NEB)-has a strong relationship with fitness, human development, infertility and risk of neuropsychiatric disorders. However, very few genetic loci have been identified, and the underlying mechanisms of AFB and NEB are poorly understood. We report a large genome-wide association study of both sexes including 251,151 individuals for AFB and 343,072 individuals for NEB. We identified 12 independent loci that are significantly associated with AFB and/or NEB in a SNP-based genome-wide association study and 4 additional loci associated in a gene-based effort. These loci harbor genes that are likely to have a role, either directly or by affecting non-local gene expression, in human reproduction and infertility, thereby increasing understanding of these complex traits