Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

There’s no such thing as a tree (phylogenetically)

eukaryotewritesblog.com

Post reply on HN
Print view View original

41–50 of 137 posts

Re: There’s no such thing as a tree (phylogenetically)

#41

Post by svara »

thaumasiotes wrote: post #32
samus wrote: post #15

Earlier quoted context omitted.

The phylogenetic tree of life is organized not on the characteristics, but on the evolutionary origin of species. Species are in a specific branch of that tree if they share a common ancestor species with the whole branch. Shared characteristica were a good proxy for ancestry back when the mechanism behind inheritance of genes was not discovered yet. Of course, the concept of a species is a bit fuzzy (even the possib…

> The phylogenetic tree of life is organized not on the characteristics, but on the evolutionary origin of species. My mother's old university biology textbook presents this as one of a few "equally valid" visions for how taxonomy should be organized. I agree with the modern view that it's the only valid vision, but it's interesting to see it presented in a "teach the controversy" way, and we can see from the comment…

Think of evolution as an optimization algorithm that finds organisms for ecological niches.

The monophyletic grouping approach tells you something about the path through solution space taken by the algorithm.

The paraphyletic approach instead focuses on properties of the solutions.

I think it's fine to think of those as equally valid.

Re: There’s no such thing as a tree (phylogenetically)

#42

Post by Groxx »

Rebelgecko wrote: post #38
yesenadam wrote: post #13

Well, I thought this was a fascinating and well-written article. p.s. I learnt not long ago that there's no such 'thing' as an antelope: "The term antelope is used to refer to many species of even-toed ruminant that are indigenous to various regions in Africa and Eurasia. Antelope comprise a wastebasket taxon (miscellaneous group) within the family Bovidae, encompassing all Old World ruminants that are not bovines, c…

What's the difference between a ruminant and an ungulate?

Broadly speaking: a ruminant is a subset of ungulates. Well, technically too.

Ungulates have hooves (horses, pigs, camels, cows, etc). Ruminants are ungulates that eat grasses in a somewhat unique way, by partially fermenting it in their gut, and horking it back up for another good chew or three (cows, giraffes, deer, antelopes, etc).

And I say "broadly" and "somewhat" because, to intentionally misrepresent the article's title, there's no such thing as a tree (of ancestry/relationships). Camels also ferment food in their gut but aren't ruminants, as do (I assume) other kinds of animals. There are a lot of parallel evolutions, genetic crossovers, and general muddying with any kind of attempted high-level grouping of creatures.

Did you know ungulates include whales, for instance? You know, those hoofed, herbivorous aquatic mammals that people are so fond of. But not seahorses. https://en.wikipedia.org/wiki/Ungulate

Taxonomies are weird. And it only gets weirder as we dig into them more and more, and keep making adjustments and corrections.

Re: There’s no such thing as a tree (phylogenetically)

#43

Post by metanomicon »

Shape seems to be a very superficial trait. One need only consider an elephant's trunk. In terms of shape and size, it has more in common with my leg, but ask anyone, "What is an elephant's trunk?" and they will immediately tell you "A nose!"

When it comes to examining various lifeforms and fossil remains to determine ancestory, it seems to be more a matter of homology - the relationships between parts. Whether it's the same part over long periods of time (ex. comparing differences in the thumb) or different parts within the same individual (ex. comparing the big toe and thumb) or interspecies similarities (ex. the similarities of hands, feet, paws and flippers), evolution is a story of relationships, not size or shape.

https://www.jstor.org/stable/2097084

https://en.wikipedia.org/wiki/Homology_(biology)

Re: There’s no such thing as a tree (phylogenetically)

#44

Post by k_sze »

Can we say the same about moths? I’m an avid participant on iNaturalist. I record lots of moth sightings because there really are many beautiful moths in Hong Kong.

There’s a “Hong Kong Moths” project on iNaturalist, but adding observations to that project can be very frustrating because the observation must be in one of the defined (sub)families.

But to an amateur like me, a moth is a moth is a moth. Sometimes even the machine identification is way off and I know it’s a moth because of the general body features.

And I wouldn’t want to put it in a random (sub)family just to get the observation included in the project. I’d have to @mention some moth expert (e.g. @hkmoths, Dr. Roger Kendrick) to help me ID the observation first.

Re: There’s no such thing as a tree (phylogenetically)

#45

Post by ckastner »

This reminded me of the fascinating obversation of convergent evolution, the "independent evolution of similar features in species of different periods or epochs in time" [1].

For example, the concept of flight has evolved independently numerous of times (insects, birds, pterosaurs, and bats), so it would not be unreasonable to assume that it would evolve again, were life to start over from scratch.

[1] https://en.wikipedia.org/wiki/Convergent_evolution

Re: There’s no such thing as a tree (phylogenetically)

#46

Post by causi »

inglor_cz wrote: post #37
causi wrote: post #21

" Tree is not a distinct clade" is the version of the title that isn't clickbait horseshit.

How many people know what clade means, though? I had a pretty rigorous and extensive course of biology in high school, we spent a lot of time poring over various details, but the word clade never even fell. (Granted, that was 1992-1996, so things might have changed.) I only met the expression cladistics and clade much later in some popsci literature.

Most HN readers I'd wager. Regardless, "Trees are not a distinct evolutionary group" or "Trees are not all related to each other" or any number of other accurate or semi-accurate headlines are better than "There's no such thing as a tree".

Re: There’s no such thing as a tree (phylogenetically)

#48

Post by t786342723 »

Areibman wrote: post #34
yesenadam wrote: post #13

Well, I thought this was a fascinating and well-written article. p.s. I learnt not long ago that there's no such 'thing' as an antelope: "The term antelope is used to refer to many species of even-toed ruminant that are indigenous to various regions in Africa and Eurasia. Antelope comprise a wastebasket taxon (miscellaneous group) within the family Bovidae, encompassing all Old World ruminants that are not bovines, c…

The term for these sorts of categories is called "Wastebin Taxon"

The posh word is "polyphyletic"

Re: There’s no such thing as a tree (phylogenetically)

#49

Post by thaumasiotes »

svara wrote: post #41
thaumasiotes wrote: post #32

Earlier quoted context omitted.

> The phylogenetic tree of life is organized not on the characteristics, but on the evolutionary origin of species. My mother's old university biology textbook presents this as one of a few "equally valid" visions for how taxonomy should be organized. I agree with the modern view that it's the only valid vision, but it's interesting to see it presented in a "teach the controversy" way, and we can see from the comment…

Think of evolution as an optimization algorithm that finds organisms for ecological niches. The monophyletic grouping approach tells you something about the path through solution space taken by the algorithm. The paraphyletic approach instead focuses on properties of the solutions. I think it's fine to think of those as equally valid.

> I think it's fine to think of those as equally valid.

Only for extremely limited purposes. Both approaches are about properties of the organism as it currently exists. The paraphyletic approach will let you know about similarity in maybe three dimensions of a ten-thousand-dimensional space. The monophyletic approach captures the other 9,997.

Re: There’s no such thing as a tree (phylogenetically)

#50

Post by 2-718-281-828 »

This is also a thing with mushrooms.

The Common Earthball [1] f.x. is more related to a Porcino [2] than to a Meadow Puffball [3] which itself is related to the Field Mushroom [4].

Seems like genes are more like a toolbox where evolution takes from what it needs. After all we share a significant amount of common genes with totally different animals like flies.

1: https://en.wikipedia.org/wiki/Scleroderma_citrinum

2: https://en.wikipedia.org/wiki/Boletus_edulis

3: https://en.wikipedia.org/wiki/Lycoperdon_pratense

4: https://en.wikipedia.org/wiki/Agaricus_campestris

Post reply on HN