[HN Gopher] Ancient lineage of small fungi upends ideas about it...
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Ancient lineage of small fungi upends ideas about its genetic
relationships
Author : wglb
Score : 29 points
Date : 2022-10-27 01:27 UTC (3 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| jeffhwang wrote:
| One of the joys of the last 50 years of biology is learning how
| evolutionary relationships we long took for granted need
| revision.
|
| First it was confirmation about Margulis' endosymbiotic origin of
| mitochondria and chloroplasts. Then the discovery and
| classification of archaea. Now it's upending our understanding of
| fungal phylogenetics! For people interested in biology, it's a
| wonderful time! (Well except for massive species die-off, loss of
| biodiversity, destruction of ecosystems, etc...)
| beambot wrote:
| > First it was confirmation about Margulis' endosymbiotic
| origin of mitochondria and chloroplasts. Then the discovery and
| classification of archaea.
|
| Sounds neat. Can you elaborate on these two topics or provide
| links digestible for a layperson?
| adrian_b wrote:
| Regarding the "confirmation about Margulis' endosymbiotic
| origin of mitochondria and chloroplasts", I assume that OP
| has meant that after this event (her paper was published in
| 1967) it became clear that the original view of the evolution
| of the living beings as along a tree has been overly
| simplistic.
|
| Even if the most common form of evolution is the appearance
| of several new species by differentiation from a common
| ancestor, there are also many cases when a new species
| appears as a hybrid of 2 previously distinct species.
|
| This hybridization happens most frequently between closely
| related species, by the normal process of syngamy between
| reproductive cells (i.e. fusion of gametes), and this does
| not change much the form of the evolution tree, but in a few
| cases the hybridization has occurred between extremely
| distantly related living beings, as a consequence of the
| evolution of a symbiosis relationship towards the integration
| of 2 distinct cells, until they have merged into a hybrid
| cell, which reproduces as a unit and which can no longer be
| separated into the former independent constituents without
| causing death.
|
| Because of these very long range hybridization cases, the
| evolution tree has merged branches, so it is no longer a tree
| in the graph theory sense, even if most smaller parts of it
| are still trees.
|
| Besides these cases of complete hybridization, the form of
| the evolution tree is complicated by partial hybridizations,
| i.e. by the so-called lateral transfer of genes, which is
| frequently mediated by viruses, between unrelated species,
| e.g. between snakes and frogs, as reported right now in
| another thread on HN.
|
| So, like in a code repository, in the evolution of the DNA
| the most frequent event is creating forks, which are then
| edited separately (i.e. separate DNA mutations in distinct
| species), the next most frequent event is to copy and paste
| some code fragment from a branch to another branch (i.e.
| lateral transfer of genes between distinct species), and the
| least frequent event is the merge of 2 distinct branches,
| which is less and less frequent the more the branches have
| diverged since forking, because that increases the chances of
| fatal bugs in the merged code (i.e. species hybridization
| events).
|
| It should be noted however, that while Margulis' supposition
| about the endosymbiotic origin of mitochondria and
| chloroplasts has been confirmed beyond any reasonable doubt,
| she got carried away by the enthusiasm of understanding these
| important events in the history of the living beings and she
| had also made a third proposal, that also the flagella of the
| eukaryotes are the result of an endosymbiotic event. This
| third supposition was wrong.
| alehlopeh wrote:
| The merging of separate evolutionary branches makes sense
| to me on a cellular level, but how does a species propagate
| from a single individual?
| chc wrote:
| Binary fission.
| agarsev wrote:
| Mutations also happen in one individual. This gene then
| enters the pool of the population, and it can spread. The
| genes from a hybrid individual diffuse into the
| population when it reproduces. Speciation happens when a
| population accumulates enough changes to be distinct from
| other populations of the same original species.
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