New insights into Silurian-Devonian palaeophytogeography

The Silurian-Devonian plant radiation was an event triggered by the progressive colonization of subaerial habitats. Nevertheless, it is still unclear whether this radiation was globally uniform or whether alternative diversification scenarios emerged depending on the geographical context. Here, we report on early land plant diversity patterns across different previously defined palaeogeographical units (i.e., Laurussia, Siberia, Kazakhstania, NE, NW and South Gondwana). Results reveal apparent diachronous events of diversification and extinction partly resulting from uneven sampling effort, especially in Gondwana. Global diversity patterns are most similar to the Laurussian curve suggesting that the observed global dynamics are mostly controlled by the historically best-sampled continents. Nevertheless, changes in floral composition through time become less prone to sampling biases, and reveal geographical disparities that indicate a non-random distribution of the Silur-ian-Devonian vegetation. Consequently, we further performed a set of multivariate analyses to revisit the palaeophytogeographical signal through four time-intervals (i.e., Silurian-Lochkovian, Pragian-Emsian, Middle and Late Devonian), which revealed that spatial differentiation of vegetation was mainly controlled by climatic conditions and to a lesser extent geographical barriers. Most importantly, we find the maximum provincialism during cooler periods such as during the Silurian-Lochkovian and Middle Devonian, whilst warmer periods (Pragian-Emsian and Late Devonian) coincided with increased cosmopolitanism among early land plants.

Automated summary

The Silurian-Devonian plant radiation was triggered by the colonization of subaerial habitats. The diversity patterns of early land plants varied across different palaeogeographical units, with apparent events of diversification and extinction. Global diversity patterns are mostly similar to the historically best-sampled continent, but changes in floral composition through time reveal geographical disparities.