The evolutionary history of the Central Asian steppe-desert taxon Nitraria (Nitrariaceae) as revealed by integration of fossil pollen morphology and molecular data

Abstract

The transition from a greenhouse to an icehouse world at the Eocene-Oligocene Transition (EOT) coincided with a large decrease of pollen from the steppe-adapted genus Nitraria. This genus, now common along the Mediterranean coast, Asia and Australia, has a proposed coastal origin and a geographically widespread fossil record. Here we investigated the evolution, taxonomic diversity and morphological disparity of Nitraria throughout the Cenozoic by integrating extant taxa and fossil palynological morphotypes into a unified phylogenetic framework based on both DNA sequences and pollen morphological data. We present the oldest fossil pollen grain of Nitraria, at least 53 Myr old. This fossil was found in Central Asian deposits, providing new evidence for its origin in this area. We found that the EOT is an evolutionary bottleneck for Nitraria, coinciding with retreat of the proto-Paratethys Sea, a major global cooling event and a turnover in Central Asian steppe vegetation. We infer the crown age of modern Nitraria spp. to be significantly younger (Miocene) than previously estimated (Palaeocene). The diversity trajectory of Nitraria inferred from extant-only taxa differs markedly from one that also considers extinct taxa. Our study demonstrates it is therefore critical to apply an integrative approach to fully understand the plant evolutionary history of Nitrariaceae.

Deep learning approaches to the phylogenetic placement of extinct pollen morphotypes

“…This approach differs from existing total evidence analyses of pollen, e.g. ( 42 ), in that our morphological features are continuous and quantitative, and the original molecular data are intrinsic to the selection of our phylogenetic embedding features and the training of our MLP neural networks. While this specific study uses a reference phylogeny derived exclusively from molecular data, the embedding model could utilize any well-supported tree, including total evidence phylogenies constructed using both molecular and morphological data.…”

Genetic Innovations Underpin Morphological Diversity and Radiation in Teleost Fish

“…We estimated the timing of taxon radiations using fossil records spanning from approximately 430 Ma to 12 Ma (Supplementary Table 6). Furthermore, we assessed the diversity trajectories of ray-nned sh by evaluating 13,194 Actinopterygii fossil records (Supplementary Table 7).…”

“…Diversity trajectory of sh using fossil sampling data A total of 13,194 Actinopterygii fossil records were used, of 9,841 were Teleostei fossil records (Supplementary Table 7). The were collected from the DeepBone database (https://www.deepbone.org).…”

“…Several researchers have emphasized the importance of integrating fossil data in understanding macroevolutionary processes 6,7 to address this limitation. By integrating phylogenetic studies with fossil records, a new perspective for studying the radiation of evolutionary history emerges, enabling detailed analysis of the genetic basis of adaptation and complex relationships among species [8][9][10][11][12][13] .…”

Relict Plants Are Better Able to Adapt to Climate Change: Evidence from Desert Shrub Communities

“…Zhang et al [45] considered that Nitraria first appeared between the Cretaceous and the Early Paleocene and hypothesized an Early Paleogene (65 Mya) origin of Nitraria based on molecular data. Amber Woutersen et al [46] found the oldest fossil pollen grain of Nitraria, at least 53 Myr old, and dated it to the Paleogene based on its characteristics. Reaumuria songarica is an ultra-xerophyte with strong stress resistance [47].…”