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Flowers on the tree of life
\"Genetic and molecular studies have recently come to dominate botanical research at the expense of more traditional morphological approaches. This broad introduction to modern flower systematics demonstrates the great potential that floral morphology has to complement molecular data in phylogenetic and evolutionary investigations. Contributions from experts in floral morphology and evolution take the reader through examples of how flowers have diversified in a large variety of lineages of extant and fossil flowering plants. They explore angiosperm origins and the early evolution of flowers and analyse the significance of morphological characters for phylogenetic reconstructions on the tree of life. The importance of integrating morphology into modern botanical research is highlighted through case studies exploring specific plant groups where morphological investigations are having a major impact. Examples include the clarification of phylogenetic relationships and understanding the significance and evolution of specific floral characters, such as pollination mechanisms and stamen and carpel numbers\"-- Provided by publisher.
Book
Flowers on the Tree of Life
Genetic and molecular studies have recently come to dominate botanical research at the expense of more traditional morphological approaches. This broad introduction to modern flower systematics demonstrates the great potential that floral morphology has to complement molecular data in phylogenetic and evolutionary investigations. Contributions from experts in floral morphology and evolution take the reader through examples of how flowers have diversified in a large variety of lineages of extant and fossil flowering plants. They explore angiosperm origins and the early evolution of flowers and analyse the significance of morphological characters for phylogenetic reconstructions on the tree of life. The importance of integrating morphology into modern botanical research is highlighted through case studies exploring specific plant groups where morphological investigations are having a major impact. Examples include the clarification of phylogenetic relationships and understanding the significance and evolution of specific floral characters, such as pollination mechanisms and stamen and carpel numbers.
eBook
Evolutionary history of Coleoptera revealed by extensive sampling of genes and species
Beetles (Coleoptera) are the most diverse and species-rich group of insects, and a robust, time-calibrated phylogeny is fundamental to understanding macroevolutionary processes that underlie their diversity. Here we infer the phylogeny and divergence times of all major lineages of Coleoptera by analyzing 95 protein-coding genes in 373 beetle species, including ~67% of the currently recognized families. The subordinal relationships are strongly supported as Polyphaga (Adephaga (Archostemata, Myxophaga)). The series and superfamilies of Polyphaga are mostly monophyletic. The species-poor Nosodendridae is robustly recovered in a novel position sister to Staphyliniformia, Bostrichiformia, and Cucujiformia. Our divergence time analyses suggest that the crown group of extant beetles occurred ~297 million years ago (Mya) and that ~64% of families originated in the Cretaceous. Most of the herbivorous families experienced a significant increase in diversification rate during the Cretaceous, thus suggesting that the rise of angiosperms in the Cretaceous may have been an ‘evolutionary impetus’ driving the hyperdiversity of herbivorous beetles.
The phylogeny of beetles, which represent ~25% of known extant animal species, has been a challenge to resolve. Here, Zhang et al. infer a time-calibrated phylogeny for Coleoptera based on 95 protein-coding genes in 373 species and suggest an association between the hyperdiversification of beetles and the rise of angiosperms.
Journal Article
Reconstructing the ancestral angiosperm flower and its initial specializations
Increasingly robust understanding of angiosperm phylogeny allows more secure reconstruction of the flower in the most recent common ancestor of extant angiosperms and its early evolution. The surprising emergence of several extant and fossil taxa with simple flowers near the base of the angiosperms—Chloranthaceae, Ceratophyllum, Hydatellaceae, and the Early Cretaceous fossil Archaefructus (the last three are water plants)—has brought a new twist to this problem. We evaluate early floral evolution in angiosperms by parsimony optimization of morphological characters on phylogenetic trees derived from morphological and molecular data. Our analyses imply that Ceratophyllum may be related to Chloranthaceae, and Archaefructus to either Hydatellaceae or Ceratophyllum. Inferred ancestral features include more than two whorls (or series) of tepals and stamens, stamens with protruding adaxial or lateral pollen sacs, several free, ascidiate carpels closed by secretion, extended stigma, extragynoecial compitum, and one or several ventral pendent ovule(s). The ancestral state in other characters is equivocal: e.g., bisexual vs. unisexual flowers, whorled vs. spiral floral phyllotaxis, presence vs. absence of tepal differentiation, anatropous vs. orthotropous ovules. Our results indicate that the simple flowers of the newly recognized basal groups are reduced rather than primitively simple.
Journal Article
ACANTHACEAE, AN ADDITIONAL FAMILY OF ANGIOSPERMS WITH STAMINAL LEVERS
Reportamos por primera vez un mecanismo de palanca staminal en Acanthaceae. Presionar el apéndice staminal en dos especies de Justicia causó que la antera descendiera en una forma similar al género Salvia. Movimiento de las anteras con una palanca puede afectar donde el polen es depositado en el cuerpo de potenciales polinizadores. Acanthaceae es una de las pocas familias donde se han reportado palancas estaminales, y la mayoría de las familias están en el orden Lamíales.
Journal Article
Coordination between compound-specific chemistry and morphology in plant roots aligns with ancestral mycorrhizal association in woody angiosperms
• Recent studies on fine root functional traits proposed a root economics hypothesis where adaptations associated with mycorrhizal dependency strongly influence the organization of root traits, forming a dominant axis of trait covariation unique to roots. This conclusion, however, is based on tradeoffs of a few widely studied root traits. It is unknown how other functional traits fit into this mycorrhizal-collaboration gradient. Here, we provide a significant extension to the field of root ecology by examining how fine root secondary compounds coordinate with other root traits.
• We analyzed a dataset integrating compound-specific chemistry, morphology and anatomy of fine roots and leaves from 34 temperate tree species spanning major angiosperm lineages.
• Our data uncovered previously undocumented coordination where root chemistry, morphology and anatomy covary with each other. This coordination, aligned with mycorrhizal colonization, reflects tradeoffs between chemical protection and mycorrhizal dependency, and provides mechanistic support for the mycorrhizal-collaboration gradient. We also found remarkable phylogenetic structuring in root chemistry. These patterns were not mirrored by leaves. Furthermore, chemical protection was largely decoupled from the leaf economics spectrum.
• Our results unveil broad organization of root chemistry, demonstrate unique belowground adaptions, and suggest that root strategies and phylogeny could impact biogeochemical cycles through their links with root chemistry.
Journal Article
From one side to two sides
The functions of stomata have been studied for a long time; however, a clear understanding of the influences of stomatal distribution on photosynthesis, especially the CO₂ diffusion, is still unclear.
Here, we investigated the stomatal morphology, distribution on leaf surfaces, vein traits and gas exchange parameters of 61 species, of which 29 were amphistomatous, spanning 32 families.
Photosynthesis (A) was tightly coupled with operational stomatal conductance (g
s) and mesophyll conductance (g
m) regardless of whether phylogenetic relationships were accounted for. Although the enhancement of g
s from ferns and gymnosperms to angiosperms could largely be explained by the increase in leaf vein density (VLA) and stomatal density (SD), the g
s was decoupled from VLA and SD across angiosperm species. Instead, A in angiosperms was further influenced by the allocation of stomatal pores on leaf surfaces, which dramatically increased g
s and g
m. Moreover, the ratio of g
s to anatomically based maximum g
s was, on average, 0.12 across species.
Our results show that the shift of stomatal pores from one leaf side to both sides played an important role in regulating CO₂ diffusion via both stomata and mesophyll tissues. Modifications of stomata distribution have potential as a functional trait for photosynthesis improvement.
Journal Article
Nested whole-genome duplications coincide with diversification and high morphological disparity in Brassicaceae
Angiosperms have become the dominant terrestrial plant group by diversifying for ~145 million years into a broad range of environments. During the course of evolution, numerous morphological innovations arose, often preceded by whole genome duplications (WGD). The mustard family (Brassicaceae), a successful angiosperm clade with ~4000 species, has been diversifying into many evolutionary lineages for more than 30 million years. Here we develop a species inventory, analyze morphological variation, and present a maternal, plastome-based genus-level phylogeny. We show that increased morphological disparity, despite an apparent absence of clade-specific morphological innovations, is found in tribes with WGDs or diversification rate shifts. Both are important processes in Brassicaceae, resulting in an overall high net diversification rate. Character states show frequent and independent gain and loss, and form varying combinations. Therefore, Brassicaceae pave the way to concepts of phylogenetic genome-wide association studies to analyze the evolution of morphological form and function.
As one of the most successful angiosperm clades with ~4000 species, the mustard family has been diversifying into many evolutionary lineages. Here, the authors construct plastid-based phylogeny and show nested whole-genome duplications coincide with diversification and high morphological disparity.
Journal Article
Ancestral Gene Flow and Parallel Organellar Genome Capture Result in Extreme Phylogenomic Discord in a Lineage of Angiosperms
While hybridization has recently received a resurgence of attention from systematists and evolutionary biologists, there remains a dearth of case studies on ancient, diversified hybrid lineages—clades of organisms that originated through reticulation. Studies on these groups are valuable in that they would speak to the long-term phylogenetic success of lineages following gene flow between species. We present a phylogenomic view of Heuchera, long known for frequent hybridization, incorporating all three independent genomes: targeted nuclear (∼400,000 bp), plastid (∼160,000 bp), and mitochondrial (∼470,000 bp) data. We analyze these data using multiple concatenation and coalescence strategies. The nuclear phylogeny is consistent with previous work and with morphology, confidently suggesting a monophyletic Heuchera. By contrast, analyses of both organellar genomes recover a grossly polyphyletic Heuchera, consisting of three primary clades with relationships extensively rearranged within these as well. A minority of nuclear loci also exhibit phylogenetic discord; yet these topologies remarkably never resemble the pattern of organellar loci and largely present low levels of discord inter alia. Two independent estimates of the coalescent branch length of the ancestor of Heuchera using nuclear data suggest rare or nonexistent incomplete lineage sorting with related clades, inconsistent with the observed gross polyphyly of organellar genomes (confirmed by simulation of gene trees under the coalescent). These observations, in combination with previous work, strongly suggest hybridization as the cause of this phylogenetic discord.
Journal Article
Pollinator shifts, contingent evolution, and evolutionary constraint drive floral disparity in Salvia (Lamiaceae)
Switches in pollinators have been argued to be key drivers of floral evolution in angiosperms. However, few studies have tested the relationship between floral shape evolution and switches in pollination in large clades. In concert with a dated phylogeny, we present a morphometric analysis of corolla, anther connective, and style shape across 44 % of nearly 1000 species of Salvia (Lamiaceae) and test four hypotheses of floral evolution. We demonstrate that floral morphospace of New World (NW) Salvia is largely distinct from that of Old World (OW) Salvia and that these differences are pollinator driven; shifts in floral morphology sometimes mirror shifts in pollinators; anther connectives (key constituents of the Salvia staminal lever) and styles co-evolved from curved to linear shapes following shifts from bee to bird pollination; and morphological differences between NW and OW bee flowers are partly the legacy of constraints imposed by an earlier shift to bird pollination in the NW. The distinctive staminal lever in Salvia is a morphologically diverse structure that has evolved in concert with both the corolla and style, under different pollinator pressures, and in contingent fashion.
Journal Article