The megadiverse genus Carex (c. 2000 species, Cyperaceae) has a nearly cosmopolitan distribution, displaying an inverted latitudinal richness gradient with higher species diversity in cold‐temperate areas of the Northern Hemisphere. Despite great expansion in our knowledge of the phylogenetic history of the genus and many molecular studies focusing on the biogeography of particular groups during the last few decades, a global analysis of Carex biogeography and diversification is still lacking. For this purpose, we built the hitherto most comprehensive Carex‐dated phylogeny based on three markers (ETS–ITS–matK), using a previous phylogenomic Hyb‐Seq framework, and a sampling of two‐thirds of its species and all recognized sections. Ancestral area reconstruction, biogeographic stochastic mapping, and diversification rate analyses were conducted to elucidate macroevolutionary biogeographic and diversification patterns. Our results reveal that Carex originated in the late Eocene in E Asia, where it probably remained until the synchronous diversification of its main subgeneric lineages during the late Oligocene. E Asia is supported as the cradle of Carex diversification, as well as a “museum” of extant species diversity. Subsequent “out‐of‐Asia” colonization patterns feature multiple asymmetric dispersals clustered toward present times among the Northern Hemisphere regions, with major regions acting both as source and sink (especially Asia and North America), as well as several independent colonization events of the Southern Hemisphere. We detected 13 notable diversification rate shifts during the last 10 My, including remarkable radiations in North America and New Zealand, which occurred concurrently with the late Neogene global cooling, which suggests that diversification involved the colonization of new areas and expansion into novel areas of niche space.
Phylogenetic studies of Carex L. (Cyperaceae) have consistently demonstrated that most subgenera and sections are para-or polyphyletic. Yet, taxonomists continue to use subgenera and sections in Carex classification. Why? The Global Carex Group (GCG) here takes the position that the historical and continued use of subgenera and sections serves to (i) organize our understanding of lineages in Carex, (ii) create an identification mechanism to break the~2000 species of Carex into manageable groups and stimulate its study, and (iii) provide a
Changes in holocentric chromosome number due to fission and fusion have direct and immediate effects on genome structure and recombination rates. These, in turn, may influence ecology and evolutionary trajectories profoundly. Sedges of the genus Carex (Cyperaceae) comprise ca. 2000 species with holocentric chromosomes. The genus exhibits a phenomenal range in the chromosome number (2n = 10 − 132) with almost not polyploidy. In this study, we integrated the most comprehensive cytogenetic and phylogenetic data for sedges with associated climatic and morphological data to investigate the hypothesis that high recombination rates are selected when evolutionary innovation is required, using chromosome number evolution as a proxy for recombination rate. We evaluated Ornstein-Uhlenbeck models to infer shifts in chromosome number equilibrium and selective regime. We also tested the relationship between chromosome number and diversification rates. Our analyses demonstrate significant correlations between morphology and climatic niche and chromosome number in Carex. Nevertheless, the amount of chromosomal variation that we are able to explain is very small. We recognized a large number of shifts in mean chromosome number, but a significantly lower number in climatic niche and morphology. We also detected a peak in diversification rates near intermediate recombination rates. In combination, these analyses point toward the importance of chromosome evolution to the evolutionary history of Carex. Our work suggests that the effect of chromosome evolution on recombination rates, not just on reproductive isolation, may be central to the evolutionary history of sedges.
Cyperaceae (sedges) are the third largest monocot family and are of considerable economic and ecological importance. Sedges represent an ideal model family to study evolutionary biology due to their species richness, global distribution, large discrepancies in lineage diversity, broad range of ecological preferences, and adaptations including multiple origins of C 4 photosynthesis and holocentric chromosomes. Goetghebeur′s seminal work on Cyperaceae published in 1998 provided the most recent complete classification at tribal and generic level, based on a morphological study of Cyperaceae inflorescence, spikelet, flower, and embryo characters, plus anatomical and other information. Since then, several family-level molecular phylogenetic studies using Sanger sequence data have been published. Here, moreThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Editor: Erika EdwardsPremise of research. The Schoenoxiphium clade (Carex, Cyperaceae) exhibits a high species diversity in South Africa and a complex taxonomy. Previous phylogenetic studies did not resolve the species relationships within the Schoenoxiphium clade due to the lack of informative characters in DNA markers used. Our aim is to resolve the species relationships within the Schoenoxiphium clade by adding information from more markers and more samples to information from previous studies.Methodology. We sampled 19 out of 20 recognized species in the former genus Schoenoxiphium. Four DNA regions (two nuclear ribosomal: internal transcribed spacer, external transcribed spacer; two plastid: matK and rps16) were sequenced for 134 samples. Phylogenetic reconstruction was performed using Bayesian inference and maximum likelihood analyses.Pivotal results. The monophyly of the Schoenoxiphium clade was confirmed. Five main clades with strong support were retrieved in congruence with a previous phylogeny. Although species relationships within these clades are still partially unresolved, our phylogeny highlights the need for the description of at least two new species in this group.Conclusions. The monophyly of the former genus Schoenoxiphium, taken together with its morphological synapomorphies and the recent phylogenetic studies and subsequent recircumscription of the genus Carex to include all nested genera, advises the consideration of this clade as a section (Carex sect. Schoenoxiphium Baillon). Additional investigations based on genomic sequencing are needed to fully resolve the species relationships within each of the five main clades.
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