In mammals, intrinsic postzygotic isolation has been well studied in males but has been less studied in females, despite the fact that female gametogenesis and pregnancy provide arenas for hybrid sterility or inviability that are absent in males. Here, we asked whether inviability or sterility is observed in female hybrids of Mus musculus domesticus and M. m. musculus, taxa which hybridize in n...

Reciprocal crosses between species often display an asymmetry in the fitness of F1 hybrids. This pattern, referred to as isolation asymmetry or Darwin's corollary to Haldane's rule, is a general feature of reproductive isolation in plants, yet factors determining its magnitude and direction remain unclear. We evaluated reciprocal species crosses between two naturally hybridizing diploid species...

The competitive ability of hybrids, compared with their parental taxa, can cover a wide fitness range from poor to superior. For example communities of the Daphnia galeata-hyalina-cucullata species complex often show hybrid dominance. We tested whether taxa composition of 43 European lakes inhabited by this species complex can be explained by habitat characteristics (e.g. size descriptors, trop...

The synthesis of H(2)O-soluble and NaOH-hydrolyzable bound forms of indole-3-acetic acid (IAA) in petiole slices of Nicotiana glauca, Nicotiana langsdorffii, and their tumorous and nontumorous hybrids in the presence of exogenous (14)C-IAA was investigated. The synthesis of conjugates progressively increased during 6 hours of incubation in (14)C-IAA. The results showed that the rate of synthesi...

The benefits of composite rather than local seed provenances for ecological restoration have recently been argued, largely on the basis of maximizing evolutionary potential. However, these arguments have downplayed the potentially negative consequences of outbreeding depression once mixed provenances interbreed. In this study, we compared intraspecific F1 hybrid performance and molecular marker...

The inability of mouse cell hybrids derived from two malignant parental cells to produce tumors in syngeneic F1 hosts was analyzed. YC hybrids, derived from the fusion of C1.1D and L1210 clls, failed to induce any tumor in adult mice, while 91% of x-irradiated newborn mice developed tumors and died. Some telocentric chromosomes were lacking in hybrid tumors; however, none of the immunologically...

In Arabidopsis thaliana, significant efforts are under way to determine the extent of genomic variation between phenotypically divergent accessions, but virtually nothing is known about variation at the transcription level. We used microarrays to examine variation in transcript abundance among three inbred lines and two pairs of reciprocal F1 hybrids of the highly self-fertilizing species Arabi...

Drought is an abiotic environmental stress that can significantly reduce crop productivity. We examined the mode of inheritance for different biochemical traits including total soluble proteins, chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, total phenolic contents and enzymatic antioxidants (superoxide dismutase, peroxidase and catalase), and their relationship with Bacillus thu...

The mechanisms by which outbreeding depression leads to reduced fitness are poorly understood. We considered the hypothesis that outbreeding can depress fitness by increasing the susceptibility of hybrid individuals and populations to infectious disease. Competitive breeding trials in experimental ponds indicated that outbred largemouth bass ( Micropterus salmoides) crossed from two geographica...

Creating new apple cultivars largely depends on the availability of sufficient genetic diversity, while apple breeding has eroded in time the genetic base of domestic cultivars. The possibility to induce and exploit useful variability for selecting hybrids resistant to apple scab and powdery mildew attack was evaluated in interspecific descendants derived from five wild apple species (Malus cor...