Finch 1: teeny beak--Species. Finch 2: micro-teenier beak--Diff. Species. But dogs is just dogs?

Factual Questions
1

Subject means:

I don’t know what this question belongs to in the study of evolution, and would like to know. I’ve read about the suggested processes of speciation, but clearly don’t understand it and how somebody/committee decides on calling it so.

Looking at finches, Darwin’s and otherwise, some visual typical phenotypes factor in, right? IAMNAEvolutionScientist, and in particular IANAFinchologist, but once pointed out I can see the visual markings distinguishing one finch species from another, and many of them are minute–to me, at least, if not to the finch race.

So why are all dogs dogs? I’ve read in many places something that “the greatest variation in any population” is evident among Canus lupus familiaris. Chihuahuas and mastiffs, etc.

Why do the finches get divided up so exquisitely and parceled into species and not dogs? Is it because of my throwaway comment above “…many of [the visual distinctions] are minute–to me, at least, if not to the finch race”?

2

I believe it has to do with the ability to reproduce…cross-species can’t reproduce I think. Whales and Lions can’t make baby Whions. The “liger” is a product of artificial insemination/genetic tinkering I think…

IANAFinchologist either. That’s just the way I understand it from school…

3

From der Wiki:

In 1753, the father of modern biological taxonomy, Carl Linnaeus, listed among the types of quadrupeds familiar to him, the Latin word for dog, canis. Among the species within this genus, Linnaeus listed the fox, as Canis vulpes, wolves (Canis lupus), and the domestic dog, (Canis canis; see File:Linnaeus - Regnum Animale (1735).png).

In later editions, Linnaeus dropped Canis canis and greatly expanded his list of the Canis genus of quadrupeds, and by 1758 included alongside the foxes, wolves, and jackals and many more terms that are now listed as synonyms for domestic dog, including aegyptius (hairless dog), aquaticus, (water dog), and mustelinus (literally “badger dog”). Among these were two that later experts have been widely used for domestic dogs as a species: Canis domesticus and, most predominantly, Canis familiaris, the “common” or “familiar” dog.[22]

The domestic dog was accepted as a species in its own right until overwhelming evidence from behavior, vocalizations, morphology, and molecular biology led to the contemporary scientific understanding that a single species, the gray wolf, is the common ancestor for all breeds of domestic dogs.[23][24][25] In recognition of this fact, the domestic dog was reclassified in 1993 as Canis lupus familiaris, a subspecies of the gray wolf Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists. C. l. familiaris is listed as the name for the taxon that is broadly used in the scientific community and recommended by ITIS, although Canis familiaris is a recognised synonym.[26]

Since that time, C. domesticus and all taxa referring to domestic dogs or subspecies of dog listed by Linnaeus, Johann Friedrich Gmelin in 1792, and Christian Smith in 1839, lost their subspecies status and have been listed as taxonomic synonyms for Canis lupus familiaris.[27]

So, in other words, a domestic dog refers to any “tame” wolf.

Looking at the taxonomy for finches, the definition of what is an isn’t a finch is apparently a frequent battleground for ornithologists:

The taxonomic structure of the true finch family, Fringillidae, has been fairly disputed in the past, with some upranking the Hawaiian honeycreepers (Drepanidinae) as family Drepanididae and/or uniting the cardueline and fringilline finches as tribes (Carduelini and Fringillini) in one subfamily; the euphonious finches (Euphoniinae) were thought to be tanagers due to general similarity in appearance and mode of life until their real affinities were realized. In particular, North American authors have often merged the buntings and American sparrow family (Emberizidae) – and sometimes the bulk of the nine-primaried oscines – with the split-up Fringillidae as subfamilies of a single massive family. But the current understanding of Passeroidea phylogeny is better reflected in keeping the fundamental nine-primaried oscine clades as distinct families. However, Przewalski’s “Rosefinch” (Urocynchramus pylzowi) is now classified as a distinct family, monotypic as to genus and species, and with no particularly close relatives among the Passeroidea.

Definitions of “what is a dog” and “what is a finch” are subject to change if a strong enough argument could be presented.

4

Yeah, I understood it from school that way too. The problem is this: Who did the research? I mean, who tested these two finch species to verify that they can’t reproduce with each other? Ditto for any two similar species of mosquitoes or whatever.

5

And equally, could, say, a great dane and a chihuahua actually reproduce? Let’s assume the physical act would be impossible, but if you artificially inseminated a chihuahau with great dane sperm, could it carry the resulting pup to term or would there be some horrible ripping sound part way through the pregnancy as the offspring grew larger than the mother?

6

The relevant finchologist here was John Gould. Darwin himself did not think the Galapagos finches he had seen were were of different species (varieties of a single species) until he showed the (dead) specimens he had collected to Gould, who was an expert on bird classification, and Gould got all excited. It was probably this experience with Gould that actually led Darwin to embrace evolution, and to start a deliberate search for a mechanism by which it could happen (Natural Selection, which he did not come up with for another few years). Darwin could not conceive why a rational God should have chosen to create so many species of finches, but no other land birds, just within the small area of the Galapagos Islands, but an evolutionary explanation of the situation made perfect sense.

What led Gould to his conclusion, I do not know, but my guess is that there was more to it than minor variations in markings and in beak size and shape. The point is, however, that Gould was a highly experienced ornithological taxonomist, and presumably knew by long experience just what sorts and levels of apparently superficial variation were likely to be correlated with species differences (lack of interbreeding) within birds in general, and within the finch family in particular. The levels of superficial variation that are sufficient to suggest a species difference may be quite different from one higher order taxonomic group to another. As you note, in dogs, there can be quite remarkably high levels of superficial differences in appearance that do not and should not suggest species differences at all. In finches, not so much (apparently), in octopuses it might be different again.

Until fairly recently, and the advent of DNA analysis, biological taxonomy was an arcane art that relied almost entirely on the expertise and trained intuition of people, such as Gould, who had essentially devoted their life, or much of it, to the study and taxonomy of some particular biological group (birds, in this case). Having such deep expertise was what won you respect as a biologist. After conceiving of evolution and natural selection, Darwin then set out to make himself such such an expert on a particular taxon, so that people would take him seriously as a biological thinker. Over about ten years of intense study, he turned himself into the world’s leading expert on the barnacles and their taxonomy. (He chose barnacles, so it seems, simply because no-one else had already done them, or wanted to.)

Of course, Leo, your creator James Joyce also devoted much of his life to a close study of the barnacle. :wink:

7

This exact same question was asked around here almost exactly ten years ago!

CrazyCatLady responded:

Given that a purebred Great Dane newborn is only about twice as long as a purebred Chihuahua newborn anyway, and that the pups in question would be 50% Chihuahua, I think your hypothesized Alien-style scenario is definitely way too drastic.

8

Heh.
hihuahua + St. Bernard = ???
Breed Great Dane to Chihuahua = Exploded Chihuahua?
Can a G. Dane have a Chihuahua’s pups?
Whaddya get when you cross a St Bernard with a Chihuahua?
What would happen if a Chihuaha was bred with a Great Dane?
What Would Happen if a Chiuaua was Inseminated with a Great Dane?

and just for added variety,

Could you breed a group of chihuahuas back into wolves given enough time?

ETA: Kimstu cross-posted ::sob:: …but MfM provides the volume!

9

Coupla things:

-Usually, whether two individuals can theoretically produce offspring is less important than whether or not they actually do interbreed in the wild. So lions and tigers can make ligers and tigons when we force them to mate, but since they live on different continents in the wild, they normally don’t do that, hence, different species.

-One of the best ways to turn one species into multiple species is to completely isolate small populations, as happened on the Galapagos with the finches. Beak shape variation is evidence of adaptation, not speciation, as you correctly deduced, but when you have small populations scattered across various islands with little to no intercommunication, you’ll get species pretty quickly (evolutionarily speaking).

-Dogs are weird. They can take on a wider variety of forms than any other animal we know of. A lot of that has been driven by breeding via artificial selection, but they do see to have some underlying genetic weirdnesses that let them tolerate a lot of shapes. We have identified some genes involved, but we still don’t fully understand it.

-All dogs are the same species, even if they cannot physically manage the act of mating and reproduction, because you can get constant gene flow from one end of the size range to the other. A mastiff can mate with a collie, a collie can mate with a terrier, and a terrier can mate with a chihuahua. It doesn’t take many generations for some of the DNA from the mastiff to meet some of the DNA from the chihuahua. Dogs are a bit like a ring species in that respect.

10

The taxonomic classification of species is an attempt to impose a tidy compartmentalism on a system that is not in reality as granular as we would like.

In general, two populations that don’t interbreed may be considered different species - for example, a population of apple-tree moths that has undergone a mutation so that they now only live on pear trees, would probably be a new species - even if they are technically still completely capable of interbreeding.

But it’s not always so cut-and-dried as all that - because you can have whole chains of populations that can (and do) interbreed with their nearest neighbour, but not the next-door-but-one population (this phenomenon is called 'ring species)

11

I can hear his thinking now: “there’s foxes and wolves and, you know, dog dogs.”

12

Just to further expand on the whole “different phenotype = different species” thing…

Picture two Galapogos islands with finches on them both. Finches on island A need big beaks to eat, I don’t know, big food, and on island B, they need small beaks for small food. If the islands are separated enough that there’s no migration between them, we know what’ll happen: two species, one with big beaks, one with small beaks.

Now, let’s say that the two islands are close enough that birds flit back and forth fairly regularly. There’s gene flow between the two islands. What would we expect? They’re not going to be able to develop big and little specialized beaks. Because either phenotype can be found on either island, selection is going to tend to keep the beaks intermediate - not great on either island, but good enough to get by. There are ways around this, like sexual selection - if the island A finches suddenly decide that big beaks are super sexy and start their own little interbreeding population, for instance.

The point is that when you see different phenotypes in different populations that otherwise seem to be the same species, that’s at least a hint that the populations don’t interbreed very much. If they were interbreeding, those differences would tend to be evened out over time. That’s why “this bird looks different from that bird” is actually a fairly reasonable way to separate species, particularly in the days before genetic sequencing was so easy. And still now, when no one has enough money to sequence everything they’d like.

13

Thanks for the replies. I’m just checking in, will answer and ask more when I’m awake.

njtt, I’m glad you’re not mad at me for my snark in the “Jewish Oven” thread.* Those Galway girls are hot. Beef to the heels.
*Those two words I had to force myself to write just now. FWIW, as a kid, I never said it–and used “stove” instead–and for years always misunderstood at first when kids or adults talked about “camp,” because I had grown up hearing it at the dinner table with my family, with only one, different meaning.)

ETA: open to all: Which animal has the longest penis relative to body size? And this is a zōothread, doubly appropriately enough.

14

The barnacle.

15

Yeah, but what if they’re doing it on a treadmill?

16

Am I the only one who is disappointed that the Doper who goes by Darwin’s Finch didn’t show up in this thread?

17

Now that’s…um…not at all hawt, actually. :frowning:

18

One could simply make sure that the mother is the larger breed.

19

Why do people always ask this question as if the Chihuahua couldn’t be the male?

20

…on stilts. :wink:

Actually, just down the street from my grandmother were a litter of doberman dachshunds. Not quite the size difference, but considerable. The bitch was the doberman. She, uh, took it lying down.