Mechanistic Levels, Reduction, and Emergence

We sketch the mechanistic approach to levels, contrast it with other senses of “level,” and explore some of its metaphysical implications. This perspective allows us to articulate what it means for things to be at different levels, to distinguish mechanistic levels from realization relations, and to describe the structure of multilevel explanations, the evidence by which they are evaluated, and the scientific unity that results from them. This approach is not intended to solve all metaphysical problems surrounding physicalism. Yet it provides a framework for thinking about how the macroscopic phenomena of our world are or might be related to its most fundamental entities and activities

Revision of the South African endemic bee genus Redivivoides Michener, 1981 (Hymenoptera: Apoidea: Melittidae)

The South African endemic bee genus Redivivoides Michener, 1981 is revised and redefined. The genus comprises seven species, six of which are described here as new: Redivivoides capensis sp. nov. ♀♂, R. eardleyi sp. nov. ♀, R. kamieskroonensis sp. nov. ♀, R. karooensis sp. nov. ♀♂, R. namaquaensis sp. nov. ♀♂ and R. variabilis sp. nov. ♀♂. A key to species is provided

Mechanisms in Dynamically Complex Systems

In recent debates mechanisms are often discussed in the context of ‘complex systems’ which are understood as having a complicated compositional structure. I want to draw the attention to another, radically different kind of complex system, in fact one that many scientists regard as the only genuine kind of complex system. Instead of being compositionally complex these systems rather exhibit highly non-trivial dynamical patterns on the basis of structurally simple arrangements of large numbers of non-linearly interacting constituents. The characteristic dynamical patterns in what I call “dynamically complex systems” arise from the interaction of the system’s parts largely irrespective of many properties of these parts. Dynamically complex systems can exhibit surprising statistical characteristics, the robustness of which calls for an explanation in terms of underlying generating mechanisms. However, I want to argue, dynamically complex systems are not sufficiently covered by the available conceptions of mechanisms. I will explore how the notion of a mechanism has to be modified to accommodate this case. Moreover, I will show under which conditions the widespread, if not inflationary talk about mechanisms in (dynamically) complex systems stretches the notion of mechanisms beyond its reasonable limits and is no longer legitimate

Capalictus, a new subgenus of Lasioglossum Curtis, 1833 from South Africa, with description of three new species (Hymenoptera, Apoidea, Halictidae)

Capalictus, a new subgenus of Lasioglossum Curtis, 1833 (Hymenoptera, Apoidea, Halictidae), endemic to the South African Cape Province, is described. The type species is Halictus mosselinus Cockerell, 1945. Evylaeus (Sellalictus) fynbosensis (Pauly et al., 2008) is a new junior synonym of L. (C.) mosselinum. Three new species are described: Lasioglossum (Capalictus) hantamense sp. nov., L. (C.) tigrinum sp. nov. and L. (C.) timmermanni sp. nov. DNA sequence data from three nuclear genes support morphologically-determined species limits. Capalictus is a basal clade of the Hemihalictus series of Lasioglossum