What is the oldest EXISTING species of butterfly?

[Chuck]

Geneticists use rate of mutation (AKA "voodoo") to estimate when taxa, such as subspecies, are significantly different enough to be recognized.

When the parental species becomes extinct, those subspecies become elevated to species status, and presumably continue to mutate.

But not all parental species are extinct. I wonder- does anyone know which species-level taxa that still exists is the oldest remaining?

If I'm reading Figure 4 of Condamine 2023 correctly, Papilio esperanza as a species dates to about 18 million years old.

[eurytides]

https://www.scielo.org.mx/scielo.php?sc ... 1000100340

[Chuck]

Ah, interesting it’s been long said it’s one of the oldest, so perhaps that confirms. I wonder what other regional taxa may also be that old. Figure, to continue for that many millions of years requires a specific environmental stability.

[adamcotton]

https://www.scielo.org.mx/scielo.php?sc ... 1000100340

I was going to reply Baronia brevicornis but you beat me to it with this paper about the species.

Adam.

[Jshuey]

Some semantics.

What do you mean - oldest species? All species are constantly evolving, Life emerged on the planet about 4.2 billion years ago, so we have the misconception that humans are the most evolved species. But Archeobacteria have been evolving the entire 4.2 billion years as well and are equally evolved. If you except that all species are the decedents of a single origin - then they are all equally evolved lineages. That is the key - every species on the planet traces back along a linage that is equally ancient. However, some lineages have changed quite a bit from those humble beginnings, while others have taken a more conservative path such that they are less changed through time.

But I suspect that you are asking what lineage represents the most basal split from the rest of the butterflies. That would be Papilionidae + Hesperiidae + Hedylidae from the Pieridae + Nympalidae + Riodinidae + Lycaenidae. But these two linages are equally old. And within that first split - Baronia is indeed on a unique path from the rest of the Papilionids. But that doesn't mean that there were not other Baronia related species (or even genera) along the way - just that one species remains from that particularly old lineage.

And don't forget that there are two recognized subspecies of Baronia - who is to say that these are not destined to become separate species from a very recent lineage split? Or maybe they are indeed already different species! If so, will one of these be considered "new" while the other is "old"?

Just messing with ya!

John

[eurytides]

Point taken. However, I think the prima facie interpretation of the question is, which extant species has been around the longest and is relatively unchanged. People often say that modern humans have been around for 200,000 years. We descended from animals that were around, say, 300,000 years ago. It’s a continuous lineage, but our ancestors that long ago are not considered modern humans because the fossils look a lot different than a “modern skeleton.” A coelacanth that hasn’t changed compared to fossils from 70 million years ago would be considered “older” than modern humans, even you as you pointed out, both can be traced back to something 4.2 billion years ago.

[Jshuey]

So - we are looking for species that retain the most "plesiomorphic" traits - right? My AI generator defines plesiomorphic as - In evolutionary biology, plesiomorphic refers to a trait or character state that is ancestral, meaning it is inherited from a common ancestor of a group of organisms. A plesiomorphic trait is the original, primitive version of a character, before any evolutionary changes occurred. (not bad for AI!)

Oldest species - meaning - a species that retains more plesiomorphic characters than others within a lineage...

Again - just messing with semantics!

John

[Chuck]

John, you may be "just messing" but your and eurytides' points are philosophically and scientifically interesting.

I did not define "oldest" so let me flip it around. There are species that are more recently evolved, and there are species for which the ancestral taxon is extinct. Those can be eliminated from competition.

As pointed out, even the test model Baronia brevicornis may be the remnant of a multitude of multiple taxa in that tree branch that still exists. Not unlike that one leaf on the one lower left branch of a mostly dead maple tree. Still, it exists and apparently has a [what's the term?] direct and discreet lineage that goes way back- as opposed to the more recently evolved taxa.

Or is it? As pointed out by eurytides, homo sapiens 200,000 years ago is not homo sapiens today. One would think that the current brevicornis has along the way also experienced significant (?? > 2% who knows) mutation, so in fact the ancestral species is extinct, thereby making it not as old as a genetics tree infers.

Or, maybe brevicornis has for whatever reason NOT experienced significant mutation. If a design works, there is less induced need to change, and presumably less change. Contrast that to Papilio glaucus, which Scriber showed experiences environmentally induced mutation which is inheritable; this I take to mean a higher rate of mutation. Like the Coelacanth and gars (for both of which it should be acknowledged that the current taxa are not the same as the fossil taxa) the genus at least works well and has experienced very limited mutation over many millions of years. Perhaps Baronia has had no need to change? How would we know?

I was just looking at the length of the branches in Condamine, which may infer that a taxon is very, very old. It may have, and probably has, experienced mutation but not much, making it the leader in plesiomorphic success. Sadly, our snapshot of evolution is such a small window.