Cody H via pbs
Sat, 13 Mar 2021 08:35:49 PST

The real problem with genera like Lysimachia is that (plant) evolution is
not as simple as we were led to believe. In this case, the former generic
concept for Lysimachia does not appear to actually map to a coherent
lineage of plants.

I’ve attached a screenshot (I hope) from one of the more recent (2008)
phylogenetic studies on the group that I found with a cursory Google
scholar search. If anybody knows of a better/more recent one, by all means
please share it. A link to the study (open access) is here:…

What you can see in the screenshot is that “Lysimachia”—which I am assuming
represents the species included in the former generic concept—is all over
the place in the diagram, indicating that these species are (likely) not
all as closely related to one another as their morphology alone would
suggest. Another problem is that there is a severe lack of resolution along
the part of the phylogeny that systematists often refer to as the
“backbone”—indicated in the diagram by many groups branching from the same
(long) vertical in the tree, the interpretation of which is “the
data/analysis are insufficient to clarify the relationships are among these
various groups”. This is a common problem in groups of organisms that have
experienced rapid diversification in the distant past, because there is
often not sufficient time for the signature of the important population
splitting events to be recorded in the plants’ genetics, and morphology
(perhaps obviously in this case) usually presents an equally confusing
story. The take home message here is that all these various genera
(Lysimachia, Anagallis, Trientalis, etc.) are very unlikely to really be
the separate lineages we thought they were. More likely, their histories
and evolutionary relationships interweave in complex ways.

The vast majority of modern systematists (a.k.a. taxonomists) place high
value on producing classifications (a.k.a. taxonomy) that are consistent
with evolutionary history. The most important reason for this is well
summed up by the title of a famous paper by Dobzhansky, which is “Nothing
in biology makes sense except in the light of evolution”. Since taxonomic
classifications provide the structure upon which pretty much all other
discussions of organisms depend, it makes a lot of sense to try and make
the classification match the evolutionary history, so that all the
dependent discussions also make sense. In the case of Lysimachia, lumping
all those other interwoven genera into a single generic concept presents a
view that is more consistent with the evolutionary picture that is coming
into focus.

I agree that it is inconvenient when the evolutionary history doesn’t match
familiar morphological concepts, but that is actually the point of the
reclassification. It removes the veil from the statue, so to speak, and
opens your eyes to what’s underneath. In this case, I would suggest that
the most important conclusion is that “Lysimachia” as you thought you knew
it, isn’t really the same kind of thing as other familiar genera like
Narcissus or Calochortus or Galanthus (which to my knowledge, do correspond
to coherent lineages). In reality, the story of Lysimachia is likely much
more complex and nuanced than you were led to believe. The reclassification
is just the mechanism by which systematics has clarified that reality.

That said, classifications are constantly evolving as new data and analyses
continue to improve our understanding of the evolutionary history of life
on earth. Based on the papers I saw, the classification of Lysimachia is
far from complete. Maybe the next breakthrough in this group will vindicate
some of your misgivings about the current one. Either way, I think these
kinds of taxonomic stories are fascinating, since they do such an
outstanding job of illustrating how much we still have to learn about
evolution and plant diversity.

And, Campanula is a mess, isn’t it? If only the main problem faced by
systematists these days was too much time on their hands. (If it were, I
might still be one.) Unfortunately, not enough funding (or time for that
matter) is more of an issue. But considering that it took hundreds of
millions of years for all this diversity to evolve in the first place, I
suppose we are doing alright for having been studying it for only a few
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