Category Archives: Geology

When did the flowering plants evolve? Two new studies come to different conclusions

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The angiosperms (flowering plants) are far and away the most diverse group of plants ever to have evolved.  There are an estimated 350,000 to 370,000 species, more than all other groups of plants (ferns, conifers, cycads, mosses, etc.) combined, living and extinct.  The origin of the flowering plants was termed an “abominable mystery” by Charles Darwin – or perhaps it wasn’t: see this essay by Prof. Richard Buggs for an alternative view of what Darwin was describing, and this paper by Prof. William Friedman giving a different interpretation.

These disagreements about what Darwin meant are as nothing compared to disagreements about when the flowering plants actually evolved and how we interpret fossils and evidence from molecular phylogenies.  Two new studies illustrate this point: they use some of the same information to come to completely different conclusions.  I’ve copied the details and abstracts below, with links to the originals, and emphasised the areas of disagreement in bold text.  And I’m going to leave it at that; I don’t have a horse in this race and I have no idea which (if either) is correct.

There are, however, profound implications for understanding when and how relationships between flowering plants and their pollinators evolved, as I noted in my recent review of pollinator diversity.  If the much earlier, Triassic origin of the angiosperms is correct then perhaps the earliest flowering plants did not co-opt pollinators that were already servicing gymnosperms.  Perhaps the relationships between plants and pollinators originated with the (Triassic) angiosperms and the gymnosperms subsequently evolved to exploit this.  My feeling is that only more, better fossils will provide definitive answers.

Here’s the details of the studies:

Coiro et al. (2019) How deep is the conflict between molecular and fossil evidence on the age of angiosperms? New Phytologist

Abstract: The timing of the origin of angiosperms is a hotly debated topic in plant evolution. Molecular dating analyses that consistently retrieve pre‐Cretaceous ages for crown‐group angiosperms have eroded confidence in the fossil record, which indicates a radiation and possibly also origin in the Early Cretaceous. Here, we evaluate paleobotanical evidence on the age of the angiosperms, showing how fossils provide crucial data for clarifying the situation. Pollen floras document a Northern Gondwanan appearance of monosulcate angiosperms in the Valanginian and subsequent poleward spread of monosulcates and tricolpate eudicots, accelerating in the Albian. The sequence of pollen types agrees with molecular phylogenetic inferences on the course of pollen evolution, but it conflicts strongly with Triassic and early Jurassic molecular ages, and the discrepancy is difficult to explain by geographic or taphonomic biases. Critical scrutiny shows that supposed pre‐Cretaceous angiosperms either represent other plant groups or lack features that might confidently assign them to the angiosperms. However, the record may allow the Late Jurassic existence of ecologically restricted angiosperms, like those seen in the basal ANITA grade. Finally, we examine recently recognized biases in molecular dating and argue that a thoughtful integration of fossil and molecular evidence could help resolve these conflicts.

 

Li et al. (2019) Origin of angiosperms and the puzzle of the Jurassic gap. Nature Plants

Abstract: Angiosperms are by far the most species-rich clade of land plants, but their origin and early evolutionary history remain poorly understood. We reconstructed angiosperm phylogeny based on 80 genes from 2,881 plastid genomes representing 85% of extant families and all orders. With a well-resolved plastid tree and 62 fossil calibrations, we dated the origin of the crown angiosperms to the Upper Triassic, with major angiosperm radiations occurring in the Jurassic and Lower Cretaceous. This estimated crown age is substantially earlier than that of unequivocal angiosperm fossils, and the difference is here termed the ‘Jurassic angiosperm gap’. Our time-calibrated plastid phylogenomic tree provides a highly relevant framework for future comparative studies of flowering plant evolution.

 

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Filed under Biodiversity, Charles Darwin, Evolution, Geology, History of science

Silver Medal for the BES’s pollinator’s display at RHS Chelsea Flower Show!

RHS Silver Medal

An early train to London yesterday got me to the RHS Chelsea Flower Show in time for the gates opening at 8am.  I’d agreed to spend the day staffing the British Ecological Society’s Animal Attraction: The garden and beyond display, which deals with the relationships between plants and their pollinators – see my recent posts here and here.

The first thing I noticed as I approached the display was how impressive and well designed it looked, with some wonderful planting to complement the simple, bold scientific information.  The second thing I noticed was that we had won a Silver Medal!  The whole team was very pleased – it’s the third year that the BES has been represented at Chelsea, but the first time that it’s won a medal.  I’m proud to have made a small contribution to that by advising on the plants and the scientific content, but the main kudos goes to the BES’s staff and to the garden designer Emily Darby.

Over the course of a long day we talked to hundreds of visitors about the display, what it represented, and the different ways that flowers are adapted to their pollinators.  There was a huge amount of public interest and support, very gratifying to see.  Here’s some pictures from the day:

RHS display

RHS crowd

RHS crowd with fig

RHS Jeff

RHS display

 

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Filed under Bees, Biodiversity, Biodiversity and culture, Birds, British Ecological Society, Butterflies, Ecosystem services, Geology, Honey bees, Hoverflies, Pollination, Royal Horticultural Society, University of Northampton, Wasps

Something for the weekend #5

The latest in a regular series of posts to biodiversity-related* items that have caught my attention during the week:

  • The British Government’s official line on the impact of neonicotinoid pesticides on bee health is largely based on a widely criticised study conducted by the UK’s Food & Environment Research Agency (FERA) which concluded that there was no link to bumblebee pesticide exposure and colony performance.  Professor Dave Goulson at the University of Sussex has now reanalysed the original data and shown that in fact there was a significant effect of the pesticides on those nests.  You can read the study in full here.  How could the FERA scientists get it so wrong?  Were they influenced by Defra’s desire to come to a particular conclusion?
  • It will be interesting to see how FERA responds to this criticism of their work, though it may take a while to get a full answer: the lead scientist on the study now works for agrochemicals firm Syngenta….
  • The story has also been picked up by some media outlets, notably the Guardian.  Pity they confused honey bees with bumblebees though – managed honey bees use human-made hives; bumblebees use nests (even artificial ones).
  • The RSPB’s Big Garden Birdwatch, which I talked about in a post earlier this year, has reported its results.  There seems to be good news for some species, but for others it was bad: for example, there’s been an 80% drop in observations of starling since the scheme began in 1979.  Starlings are now RSPB Red Status due to their worrying decline; whilst they are still common, they are not anywhere near as common as they used to be.

Feel free to recommend links that have caught your eye.

*Disclaimer: may sometimes contain non-biodiversity-related links.

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Filed under Bees, Biodiversity, Birds, Geology, Honey bees, RSPB