An active-learning pedagogy increased all students’ science self-efficacy, but this increase led to improved academic performance only for underrepresented minority students—an improvement that eliminated the performance gap present in the traditional lecture semester.

No abstract

The Robertsonian fusion is a common chromosomal mutation among mammal species and is especially prevalent in the West European house mouse, Mus musculus domesticus. More than 40 races of the house mouse exist in Europe, including the famous "tobacco mouse" (Poschiavo race) of Val Poschiavo, Switzerland. Documented here is the discovery of an extreme case of karyotypic variation in the neighboring Upper Valtellina, Italy. In a 20-km stretch of the valley, 32 karyotypes were observed, including five chromosomal races and 27 hybrid types. One previously unknown race is reported, the "Mid Valtellina" race, with a diploid number of 2n = 24 and the Robertsonian fusions Rb(1.3), Rb(4.6), Rb(5.15), Rb(7.18), Rb(8.12), Rb(9.14), Rb(11.13), and Rb(16.17). The Poschiavo race (2n = 26), Upper Valtellina race (2n = 24), Lower Valtellina race (2n = 22) and all-acrocentric race (2n = 40) were also present. The races form a patchy distribution, which we term a "mottled hybrid zone." Geographical position, isolation, extinction, recolonization, and selection against hybrids are all believed to be instrumental in the origin and evolution of this complex system. Previous studies of house mice from Upper Valtellina indicated that two of the races in the valley (the Upper Valtellina and Poschiavo races) may have speciated in the village of Migiondo. We discuss the possibility that there may have been a reinforcement event in this village.

Commensalism within anthropogenic environments has not been extensively discussed, despite its impact on humans, and there is no formal framework for assessing this ecological relationship in its varied forms. Here, we examine commensalism in anthropogenic environments in detail, considering both ecological and evolutionary drivers. The many assumptions about commensalism and the nature of anthropogenic environments are discussed and we highlight dependency as a key attribute of anthropogenic commensals (anthrodependent taxa). We primarily focus on mammalian species in the anthropogenic-commensal niche, but the traits described and selective pressures presented are likely fundamental to many species engaged in intense commensal relationships with humans. Furthermore, we demonstrate that this largely understudied interaction represents an important opportunity to investigate evolutionary processes in rapidly changing environments.

Restriction analysis had revealed only M u domesticus mtDNA in house mouse populations in northern Denmark, Sweden, and Finland, where the nuclear genomes are Mus mutculus. The goals of the present study were to (1) test the proposal that these Scandinavian musculus mice arose by a series of founder and island-hopping events from one or a few populations near the domesticus-musculus hybrid zone on the East Holstein Peninsula of northern Germany and (2) see whether more than the two types of domesticus mtDNA detected by restriction analysis existed among these musculus populations. Sequences of the 1 -kilobase mtDNA segment encompassing the entire control region and the flanking tRNAs were gathered from 217 domesticus and musculus mice. Included were 104 mice from 12 localities across a 120-km transect of the Holstein hybrid and adjacent zones, 56 animals from 12 localities in the musculus range of Scandinavia, 56 domesticus mice representing 46 localities in Europe, North Africa, the Middle East, and the Americas, and one musculus mouse from Czechoslovakia. Save for the Czech mouse, all individuals had domcslicus mtDNA, a total of 56 types being resolved and 10 of these being found among the Holstein mice. Electrophoresis of proteins encoded by nuclear loci along with assessment of external morphology and of skeletal, cranial, and dental traits revealed a transition from domesticus to musculus nuclear genomes over a distance of about 20-40 km in East Holstein. Ofthe 216 mtDNAs, 149 fall into a clade of 17 types characterized by the addition of an 1 l-bp direct repeat; included are all Swedish, Finnish, and northern Danish mtDNAs as well as 82 from the Holstein transect. Support for the previously proposed migration pathway from the European mainland to Scandinavia came from finding that on the domesticus side of the hybrid zone in Holstein a high proportion of mice carry the types of mtDNA found in the mice 85 0024-4066/93/010085 + 38 SOS.OO/O 0 1993 The Linnean Society of London 86 E.M. PRAGER ETAL.with rnwculw nuclear genomes. Sequencing revealed 1 I different mtDNAs in the + I I-bp clade among rnuscufus mice, one of these being widespread, seven others being confined to single localities, and one Danish collecting locality yielding five types. The mitochondria1 diversity uncovered among these mice leads to a reexamination ofsome aspects of the original model, notably with respect to the number of founding females, the possible role of selection, and the possibility of an accelerated rate of mtDNA evolution. This study also showed that for the mouse control region the transition/ transversion ratio is significantly lower than for the human control region and that small length mutations occur about as frequently as transversions during mouse control region evolution.