Patterns in fish radiation are compatible with Pleistocene desiccation of Lake Victoria and 14 600 year history for its cichlid species flock

Geophysical data are currently being interpreted as evidence for a late Pleistocene desiccation of Lake Victoria and its refilling 14 600 years ago. This implies that between 500 and 1000 endemic cichlid fish species must have evolved in 14 600 years, the fastest large-scale species radiation known. A recent review concludes that biological evidence clearly rejects the postulated Pleistocene desiccation of the lake: a 14 600 year history would imply exceptionally high speciation rates across a range of unrelated fish taxa. To test this suggestion, I calculated speciation rates for all 41 phylogenetic lineages of fish in the lake. Except for one cichlid lineage, accepting a 14 600 year history does not require any speciation rates that fall outside the range observed in fishes in other young lakes around the world. The exceptional taxon is a lineage of haplochromine cichlids that is also known for its rapid speciation elsewhere. Moreover, since it is unknown how many founding species it has, it is not certain that its speciation rates are really outside the range observed in fishes in other young lakes. Fish speciation rates are generally faster in younger than in older lakes, and those in Lake Victoria, by far the largest of the young lakes of the world, are no exception. From the speciation rates and from biogeographical observations that Lake Victoria endemics, which lack close relatives within the lake basin, have such relatives in adjacent drainage systems that may have had Holocene connections to Lake Victoria, I conclude that the composition of the fish assemblage does not provide biological evidence against Pleistocene desiccation. It supports a hypothesis of recent colonization from outside the lake basin rather than survival of a diverse assemblage within the basin.

Multigrade teaching in primary education as a promising pedagogy for teacher education in Austria and Finland

This chapter focuses on teaching practices used in multigrade classes and the importance of them being incorporated in teacher education as promising pedagogies for future use. Multigrade classes - defined as classes in which two or more grades are taught together - are common worldwide. Hence, there is a need for teacher candidates to become familiar with how to teach in split grade classrooms. However, research on multigrade teaching as well as its development in teacher education studies has been neglected, even though multigrade teachers need special skills to organize instruction in their heterogeneous classrooms. We argue that in successful multigrade teaching practices, the heterogeneity of students is taken into account and cultivated. Based on content analysis of teacher interviews conducted in Austrian and Finnish primary schools, we recommend teaching practices such as spiral curricula, working plans, and peer learning as promising teacher education pedagogies for future multigrade class teaching. We also suggest that the professional skills required in high-quality teaching practices in multigrade teaching should be further studied by researchers and educators.