A Paradigm Shift, or a Paradigm Adjustment? The Evolution of the Oleaceae Mating System as a Small-Scale Kuhnian Case Study

Abstract

Kuhn (1962) proposed an evolutionary model to explain how scientific knowledge is built, based on the concept of paradigm. Even though Kuhn's model is general, it has been applied to only a few topics in evolutionary biology, almost exclusively to broad-based paradigms. We analyze here, through the lens of Kuhn's theory, a small-scale paradigm change that occurred with the resolution of the controversy about the mating system of a Mediterranean shrub Phillyrea angustifolia (Oleaceae). We first summarize the different steps of the paradigm change and replace them in the more general context of sex ratio theory. Second, we show how the different steps of the paradigm change can be interpreted by Kuhnian concepts and tools. Finally, we discuss the actual and future status of the new paradigm.

The diallelic self-incompatibility system in Oleaceae is controlled by a hemizygous genomic region expressing a gibberellin pathway gene

“…A fascinating feature of the Oleaceae is the diversity of their mating systems (Francq et al 2023), ranging from no sexual differentiation (pure hermaphroditism) to full separation of sexual functions (dioecy), and comprising multiple instances of mating systems that are extremely rare in the rest of the living world, such as androdioecy (Charlesworth 1984, Pannell 2002, Wallander 2008). Here we focused on the DSI determinants, but our results open the way to more detailed studies on the relationship between DSI and mating systems (Francq et al 2023). An interesting case study of such interactions will be the universal compatibility of pollen produced by male individuals in P. angustifolia , which has been shown to be key to their evolutionary success (Saumitou-Laprade et al 2010).…”

“…The maintenance of only two S-alleles in the Oleaceae has been described as an evolutionary puzzle, and suggests a long-term evolutionary constraint on the diversification of S-alleles (Billiard et al 2011, Francq et al 2023). Strong natural selection in favor of the emergence of new S-alleles is expected to lead to the rapid diversification of S-allele lineages, especially when their number is low (Gervais et al 2011; Harkness et al 2021), and SI systems in most plant families typically indeed diversify to a spectacular extent (Lawrence 2000).…”