This paper is a review of recent developments of a research line proposed on the turn of the decades, 1980s to 1990s. The
main results concern basic qualitative properties of nonlinear models of population biology, such as controllability and observability.
The methods applied are different for the density-dependent models of population ecology and for the frequency-dependent models
of population genetics and evolutionary theory. While in the first case the classical theorems of nonlinear systems theory
can be used, in the second one an extension of classical results to systems with invariant manifold is necessary.
Languages sometimes undergo major shifts, when multiple phenomena change together, often called catastrophes, phase transitions, or saltations. Recently Emonds and Faarlund (2014) argued for a major shift when the syntax of Middle English was largely replaced by Scandinavian syntax. Their proposal was met with hostility by historians of English, committed to the gradualness of change. However, if one thinks in terms of internal languages holding of individuals (‘I-languages’ in Chomsky 1986) and not of languages as wholes or Chomsky's ‘E-language’, we can follow the methods of population biology and understand better the mechanisms of such major shifts.
Population biology studies during 1966–2010 have revealed that the proportion of bisexual plants has declined in natural populations of Isoetes pantii at Narsinghgarh (Central India), where it has been growing with the parental species I. coromandelina L. and I. sampathkumaranii Rao. Since many fundamental discoveries have been observed from within the microsporangia (male sporangia) over four decades the decline of production of male sporangia by this species has been briefly presented in the light of chromosomal as well as ecological factors. Directional selection appears to have favoured this decline.
A review of Mathematical Models of Social Evolution: A Guide for the Perplexed by Richard McElreath and Robert Boyd. The University of Chicago Press (2007), 432 pages, £16.00 ($25.00), ISBN: 0226558274 (paperback); and Why Humans Cooperate: A Cultural and Evolutionary Explanation by Natalie Henrich and Joseph Henrich. Oxford University Press (2007), 272 pages, £20.00 ($35.00), ISBN: 0195314236 (paperback)
Casas, J. (2000): Host location and selection in the field. In: M. E. Hochberg and A. R. Ives (eds) (2000): Parasitoid PopulationBiology. Princeton University Press, Princeton and Oxford, pp. 19–21.