Growth traits in simple crossbreeding among dam and sire lines

Twenty-five genetic groups were produced following a diallel-crossbreeding scheme among five lines: three dam and two sire lines belonging to two Spanish Research Institutions (UPV and IRTA). A total of 2773 young rabbits from 525 kindlings were controlled in different seasons. Growth traits were evaluated during the fattening period lasting from five to nine weeks. On average, genetic groups coming from lines selected for growth rate were heavier (+57 g at weaning and 311 g at 60 days), had a faster growth rate (+9g/d) and a realised higher daily feed intake (+12.9 g/d), improving feed conversion ratio (-0.21), than the groups originated from crosses among lines selected for litter size. Crossbreeding parameters were estimated using the Dickerson model. Maternal genetic and heterosis effects were close to 0 or very low. Direct genetic effects mainly regulated expression of these traits

Temperature-specific competition in predatory mites: Implications for biological pest control in a changing climate

Climate change is affecting the future of sustainable agriculture, because increasing temperatures may interfere with the functioning of natural enemies that are used in biological pest control. In this work, we examined the role of abiotic conditions in shaping the structure of a simple agricultural community that is dominated by two species of predatory mites (i.e., Eusieus stipulatus and Eusieus scutalis) competing for resources. Population and community dynamics experiments were carried out at two abiotic conditions mimicking local climates in a Mediterranean region, to estimate the population cariying capacity (k) and interspecific competition (a) for each predatory mite species. Subsequently, we used this data to parameterize a competition model, thereby predicting species dominance at each abiotic condition. To test our model predictions, we sampled several orchards located in areas influenced by each of the local climates, to determine the abundance of each species of natural enemy. Results showed that the outcome of the competitive interactions between predatory mites was strongly affected by abiotic conditions, leading to temperature-dependent changes in the community structure. Furthermore, the pattern of species dominance found in the field agreed with the model predictions built upon our laboratory experiments. We therefore emphasize that, in a changing climate, if we are to guarantee the successful use of biocontrol agents, we need to account for the effect of temperature upon biotic interactions. (C) 2015 Elsevier B.V. All rights reserved