Temperature fine-tunes Mediterranean Arabidopsis thaliana life-cycle phenology geographically.

To understand how adaptive evolution in life-cycle phenology operates in plants, we need to unravel the effects of geographic variation in putative agents of natural selection on life-cycle phenology by considering all key developmental transitions and their co-variation patterns. We address this goal by quantifying the temperature-driven and geographically varying relationship between seed dormancy and flowering time in the annual Arabidopsis thaliana across the Iberian Peninsula. We used data on genetic variation in two major life-cycle traits, seed dormancy (DSDS50) and flowering time (FT), in a collection of 300 A. thaliana accessions from the Iberian Peninsula. The geographically varying relationship between life-cycle traits and minimum temperature, a major driver of variation in DSDS50 and FT, was explored with geographically weighted regressions (GWR). The environmentally varying correlation between DSDS50 and FT was analysed by means of sliding window analysis across a minimum temperature gradient. Maximum local adjustments between minimum temperature and life-cycle traits were obtained in the southwest Iberian Peninsula, an area with the highest minimum temperatures. In contrast, in off-southwest locations, the effects of minimum temperature on DSDS50 were rather constant across the region, whereas those of minimum temperature on FT were more variable, with peaks of strong local adjustments of GWR models in central and northwest Spain. Sliding window analysis identified a minimum temperature turning point in the relationship between DSDS50 and FT around a minimum temperature of 7.2 °C. Above this minimum temperature turning point, the variation in the FT/DSDS50 ratio became rapidly constrained and the negative correlation between FT and DSDS50 did not increase any further with increasing minimum temperatures. The southwest Iberian Peninsula emerges as an area where variation in life-cycle phenology appears to be restricted by the duration and severity of the hot summer drought. The temperature-driven varying relationship between DSDS50 and FT detected environmental boundaries for the co-evolution between FT and DSDS50 in A. thaliana. In the context of global warming, we conclude that A. thaliana phenology from the southwest Iberian Peninsula, determined by early flowering and deep seed dormancy, might become the most common life-cycle phenotype for this annual plant in the region.

Clover and cress as indicator species of impacts from limed sewage sludge and landfill wastewater land application.

This study evaluated the performance of cress and clover as bioindicators to evaluate the impact of limed sewage sludge and landfill wastewater application on soil. The use of these two species, and the subsequent parameters measured, were also compared for their effectiveness in evaluating potential effects. Sewage sludge was added to the soil at a rate of 23 mg ha-1 and also at twice this dose. Wastewater was added at a level of 2 and 10% of the soil volume. Germination rate, height increase per week and final dry biomass were measured for both species. Heavy metal (Cd, Pb, Fe, Cu, Ni, and Zn) concentration was determined only for the shoot and root of clover. In general, the results showed that, compared to the control, the overall performance improved for plants exposed to both treatments. However, plants appeared to respond better to the wastewater addition than the sewage sludge amendment. The germination rate as well as other traits indicate that clover may be more sensitive to these fertilizers than cress. The lime addition did not appear to influence growth, nor heavy metal accumulation in clover. There were major differences in heavy metal accumulation in the root vs. shoot of clover. Hence, the concentrations of Cd, Cu, Fe, Zn, and Pb did not vary in the shoots of the plants under either treatments. The concentrations of the heavy metals in the roots however, greatly varied according to the type of metals. The concentrations of these metals appeared to increase with the increase of the addition treatments. The results suggest that for both species, the levels of fertilizers used in the present study were below the toxicity levels. Since the types of soils and the doses of fertilizers influence the rate of heavy metal absorption and their effects on plants, methods for rapid evaluation/monitoring as well as the types of indicators used should be explored as in the present study.

Genetic differences among language families in Europe.

We investigated whether 59 allele frequencies and 10 cranial variables differed among speakers of the 12 modern language families in Europe. Although this is a classical analysis of variance design, special techniques had to be developed for the analysis because of spatial autocorrelation of both biological and language data. The method examines pooled sums of squares within language families. These are compared with the same quantities obtained by randomly partitioning the available data points in Europe into internally cohesive subsets representing the same sample sizes for each language family as in the originally observed data. Our results suggest that for numerous genetic systems, population samples differ more among language families than they do within families. These findings are considered in relation to two contrasting models: a model of random spatial differentiation of gene frequencies unrelated to language and a model of aboriginal genetic differences among speakers of different language groups. Our observed findings suggest partial validity of both models.