Diversity Dynamics of Silurian–Early Carboniferous Land Plants in South China

Abstract

New megafossil and microfossil data indicate four episodes in the diversification of Silurian–Early Carboniferous land plants of South China, a relatively continuous regional record. Plant diversity increased throughout, but the rising curve was punctuated by three major falls. There were peaks of origination in the Ludlow–Pragian, Givetian, late Famennian and Visean and peaks of extinction in the Pragian–Emsian, Givetian and early Tournaisian. Speciation and extinction rates were highest in the Lochkovian–Pragian and became progressively lower in subsequent stages. High correlation coefficients indicate that these events are associated with the availability of land habitat contingent on eustatic variations and increasing numbers of cosmopolitan genera. Meanwhile, proportions of endemic genera declined gradually. Due to less endemism and more migrations, both speciation and species extinction rates reduced. The changes of diversity and the timing of the three extinctions of land plants in South China are similar to those known already from Laurussia. However, the largest events in the Lochkovian–Pragian and subsequent smaller ones have not been seen in the global pattern of plant evolution. These land plant events do not correspond well temporally with those affecting land vertebrates or marine invertebrates. In South China, the diversity curve of land plants is generally opposite to that of marine faunas, showing a strong effect of eustatic variations. The increasing diversity of both land vertebrates and plants was punctuated above the Devonian–Carboniferous boundary, known as Romer's Gap, implying common underlying constraints on macroevolution of land animals and plants.

Stepwise evolution of Paleozoic tracheophytes from South China: Contrasting leaf disparity and taxic diversity

“…Green flags indicate the position of South China. (B) Plant diversity in South China (Xiong and Wang, 2011;Xiong et al, 2013), and in North America, Europe, and Russia (Niklas, 1988). (C) Representative plant types.…”

“…Tracheophytes are abundant and diverse in late Paleozoic strata of South China (Gu and Zhi, 1974;Li et al, 1995;Xiong and Wang, 2011;Hao and Xue, 2013a;Xiong et al, 2013) and have been documented extensively in recent compendia (Xiong and Wang, 2011;Xiong et al, 2013). Usually, the organs of Paleozoic tracheophytes (e.g., stems, seeds, roots, and leaves) are found disarticulated and might be ascribed to different fossil-taxa (Cleal and Thomas, 2010a,b).…”

“…Age attributions follow the international stratigraphic subdivisions and are based on previous synoptic reviews Xiong and Wang, 2011;Xiong et al, 2013). The Early and Middle Devonian are combined into a single time bin because only a small number of euphyllophytes from these time periods show leaves (Hao and Xue, 2013b).…”

“…10B) (Niklas et al, 1985;Knoll et al, 1984;Niklas, 1988;Wang et al, 2010;Xiong et al, 2013). This phase witnessed the rise and decline of the eophytic flora (e.g., Zosterophyllopsida, Trimerophytopsida, and early Lycopsida) in the Early-Middle Devonian and the expansion of the paleophytic flora in later times, with the introduction of heterospory among the spore producing plants, and of early gymnosperms (Wang et al, 2010;Cleal and Cascales-Miñana, 2014).…”

“…In this paper, we explore new databases of tracheophyte fossilspecies (sensu Cleal and Thomas, 2010a,b) based on the well documented and well sampled Paleozoic record from South China (Figs S1, 10A; Datasets S1-S3) (Gu and Zhi, 1974;Li et al, 1995;Wu, 1995;Xiong and Wang, 2011;Hao and Xue, 2013a;Xiong et al, 2013). South China was an important center of radiation and dispersal for Paleozoic tracheophytes (Hao and Xue, 2013a;Xue and Hao, 2014).…”