The concept of Species has always been a little vague for me. I used to work with fresh water mussels and it would amaze me how two extremely similar blobs of tissue and shell were different species where as the extreme diversity of dog breeds were just one.
It was always explained to me that the species divider was one of reproduction where despite the physical similarities the two mussels would never cross breed.
so after seeing a couple articles about hundreds of new species found int he rain forests i wonder. how do they know?
did they follow the bugs around and make sure they never breed? did they run genetic comparisons and find different numbers of chromosomes. how can you find a bug in the middle of a jungle who looks a helluva lot like every other bug and say that its not a breed but a distinct species? same with bugs found in amber or the bones of dinosaurs.
if modern dogs lived millions of years ago and we dug up their bones would we be able to tell they were all the same species ?
The defining line for a species isn’t that they never interbreed. It’s that they rarely interbreed or that interbreeding does not produce viable offspring. Plenty of species interbreed in the wild, such as cattle and bison, or wolves and coyotes. Amongst the plants hybridisation is even more common. However in all these cases the hybrids are either rare or, where they are common, they are rarely fertile.
And no, they don’t follow the animals around. It’s a pretty good rule of thumb amongst wild species that if two groups of organisms look different then they are different species. If the two groups were commonly interbreeding then the mingling of genes would mean that one would commonly find individuals that intergrade between the two groups. This rule of thumb isn’t perfect however, and there have been plenty of cases where phenotypic differences have been misidentified as species.
Looking “a helluva lot like” another species by itself would tend to suggest that an insect was the same as that species. However there can be minor but key differences, especially in the sexual apparatus but also in the feet and other body parts, that mark two superficially similar species as distinct.
Possibly. They may differ a lot in some obvious ways thanks to human intervention, but feature that humans aren’t breeding for shouldn’t have that problem. Such a molar shape, which happens to be a common method of identifying species.* It would depend on someone noticing that these apparently very different skeletons all had something in common.
This is because molars have a raised pattern on them to aid in chewing; it’s genetically determined so is pretty much the same within a species. But while just having such ridges is useful, there isn’t any great advantage to any particular pattern so it tends to vary significantly between species since there’s no evolutionary pressure stopping it from doing so. Also teeth are durable and more likely to be fossilized.
Almost certainly not, unless we had DNA samples. It would be unheard of to have the size variation of, say, a chihuahua and a great dane in a wild mammalian species. If we had thousands of fossils showing a great continuum of sizes and shapes, then biologists would be scratching their heads and coming up with all kinds of wild hypothesis to explain something never seen in nature before. Or, they would decide it was a domesticated species.
Basically, it’s done by comparison with other known species. We know a lot about the typical way different kinds of animals vary between species. When we come up with a new specimen, or preferably several specimens, that’s outside the expected range of variation between species, we can name a new species. You don’t have to observe the breeding behavior of every new species.
The decision is easiest if the specimens come from the same locality. Say you collect 100 beetles, and they are all similar in a certain set of characters. Then you collect a new one from the same locality, and although similar it is outside the range of variation of the 100 previous specimens. It almost certainly represents a new species, although you will want to have several specimens of the same kind to be absolutely sure. If you collect 100 of the new kind, and there are clear and consistent differences from the first and no overlap, you certainly have a new species. Since the two kinds show no intermediates, then they are not hybridizing.
Things become more complicated when the similar species occurs in a different locality, since you don’t know if the two kinds might hybridize if they do come together. In this case the decision is usually made on the basis of whether the new kind has the same degree of difference from the first as is typically seen between species in the same group.