How populations persist when asexuality requires sex: the spatial dynamics of coping with sperm parasites

The twofold cost of sex implies that sexual and asexual reproduction do not coexist easily. Asexual forms tend to outcompete sexuals but may eventually suffer higher extinction rates, creating tension between short- and long-term advantages of different reproductive modes. The ‘short-sightedness’ of asexual reproduction takes a particularly intriguing form in gynogenetic species complexes, in which an asexual species requires sperm from a related sexual host species to trigger embryogenesis. Asexuals are then predicted to outcompete their host, after which neither species can persist. We examine whether spatial structure can explain continued coexistence of the species complex, and assess the evidence based on data on the Amazon molly (Poecilia formosa). A modification of the Levins metapopulation model creates two regions of good prospects for coexistence, connected by a region of poorer patch occupancy levels. In the first case, mate discrimination and/or niche differentiation keep local extinction rates low, and most patches contain both species; the other possibility resembles host–parasite dynamics where parasites frequently drive the host locally extinct. Several dynamical features are counterintuitive and relate to the parasitic nature of interactions in the species complex: for example, high local extinction rates of the asexual species can be beneficial for its own persistence. This creates a link from the evolution of sexual reproduction to that of prudent predation

Data in Antarctic science and politics

The internationalization of Antarctica as a continent for science with the Antarctic Treaty (1961) was heralded as bringing about international cooperation and the free exchange of data. However, both national rivalry and proprietorship of data, in varying degrees, remained integral to Antarctic science and politics throughout the 20th century. This paper considers two large field-surveys in Antarctica: first, an aerial photographic survey carried out by the Ronne Antarctic Research Expedition of 1946—8; and second, the Scott Polar Research Institute's radio-echo sounding survey of 1967—79. Both surveys involved geoscientific data but the context in which the investigations and the exchanges of their results took place changed. We argue that the issue of control of data remained paramount across both cases despite shifting international political contexts. The control of data on Antarctic territory, once framed in terms of geopolitics and negotiated between governments, became a matter of science policy and credit to be negotiated among scientific institutions. Whereas the Ronne data were of potential strategic value for reinforcing national territorial claims, the radio-echo sounding data contained information of potential economic and environmental value

New developments in vertebrate cytotaxonomy III. Karyology of bony fishes: A review

[No abstract available