# What genus has the most species? The fewest? **URL:** \ **Category:** Factual Questions\ **Created:** [October 14, 2009, 6:01pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814 "2009-10-14T18:01:59Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [October 14, 2009, 6:01pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/1 "2009-10-14T18:01:59Z")
There’s probably a list of this somewhere, but I can’t find it. What genus has the most species? In another thread it was mentioned that there are over 40,000 species of spiders. I sort of remember hearing that crabs have about 20,000, as do orchids. What about beetles? Pines? And what genus has the fewest? The one I can think of is elephants, with only two. Is there a genus with only one? ---
**Author:** ![twickster](https://avatars.discourse-cdn.com/v4/letter/t/ec9cab/32.png) [@twickster](https://boards.straightdope.com/u/twickster)\ **Post date:** [October 14, 2009, 6:06pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/2 "2009-10-14T18:06:00Z")
I’m pretty sure most is beetles. Dunno about least – do you wish to include only current species? Because some of the megafauna have higher counts if you include their extinct kin. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [October 14, 2009, 6:07pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/3 "2009-10-14T18:07:24Z")
There are hundreds of genera with only one species. Plenty of families with only one species. Even orders with only one species. Heck, there are phyla that have only one species. ETA: Also “spider” or “crab” wouldn’t be examples of genera, but rather orders: order Areana within class Arachnidia within phylum Arthropoda, and order Decapoda within class Crustacea within phylum Arthropoda. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [October 14, 2009, 6:09pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/4 "2009-10-14T18:09:35Z")
Are there any other extant species in Homo? That’s the genus I think of first. ---
**Author:** ![cmkeller](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmkeller/32/118_2.png) [@cmkeller](https://boards.straightdope.com/u/cmkeller)\ **Post date:** [October 14, 2009, 6:15pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/5 "2009-10-14T18:15:05Z")
Well, at least in fossils, there’s homo habilis and homo erectus. I believe the Aardvark is the only member of its family, order, and genus, and I don’t think there are even fossil relatives considered to be members of the family. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [October 14, 2009, 6:16pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/6 "2009-10-14T18:16:10Z")
ISTR they found a water cave critter that was a new genus, and I suspect it is still the only one. It might have even been a level or two up, making it really special, if not exactly what the OP is asking. I’ll let the google fu experts and biolgists find that one. ---
**Author:** ![lissener](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lissener/32/6139_2.png) [@lissener](https://boards.straightdope.com/u/lissener)\ **Post date:** [October 14, 2009, 6:21pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/7 "2009-10-14T18:21:30Z")
There is one living species in the order [Sphenodontia](http://en.wikipedia.org/wiki/Sphenodontia). ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [October 14, 2009, 6:22pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/8 "2009-10-14T18:22:48Z")
> [@twickster](#): > > Dunno about least – do you wish to include only current species? For the sake of simplicity, yes. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [October 14, 2009, 6:26pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/9 "2009-10-14T18:26:51Z")
> [@lissener](#): > > There is one living species in the order [Sphenodontia](http://en.wikipedia.org/wiki/Sphenodontia). Two, according to [Wikipedia](http://en.wikipedia.org/wiki/Tuatara). The first example of a single-species genus that comes to my mind is the Venus Flytrap, [_Dionaea muscipula_](http://en.wikipedia.org/wiki/Dionaea). The order that contains it also has things like carnations and spinach, as well as more closely related carnivorous plants. By the way, the name you are looking for is “monotypic” genera. Wikipedia has a list of [over 1,000 of them](http://en.wikipedia.org/wiki/Category:Monotypic_genera). ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [October 14, 2009, 6:27pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/10 "2009-10-14T18:27:00Z")
> [@cmkeller](#): > > Well, at least in fossils, there’s homo habilis and homo erectus. Maybe extant doesn’t mean what I think it means. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [October 14, 2009, 6:27pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/11 "2009-10-14T18:27:35Z")
There are probably more monospecific genera than polyspecific genera. So we could list thousands of them. > **[Monotypic taxon](https://en.wikipedia.org/wiki/Monospecificity)** > > In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispecific" or "monospecific" is sometimes preferred. In botanical nomenclature, a monotypic genus is a genus in the special case where a genus and a single species are simultaneously described. In contrast, an oligotypic taxon contains more than one but o Just ... ---
**Author:** ![lissener](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lissener/32/6139_2.png) [@lissener](https://boards.straightdope.com/u/lissener)\ **Post date:** [October 14, 2009, 6:31pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/12 "2009-10-14T18:31:41Z")
> [@Colophon](#): > > Two, according to [Wikipedia](http://en.wikipedia.org/wiki/Tuatara). That’s what I get. I originally wrote “two” but then misread a Wiki entry and corrected it to “one.” I stand by my first post. 🆒 ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [October 14, 2009, 6:31pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/13 "2009-10-14T18:31:42Z")
Extant is the antonym of extinct. An extant taxon is one that has living members. There is only one extant species of the genus Homo: _Homo sapiens_. Unless we want to go all radical and lump chimpanzees into Homo. That would invalidate all sorts of genera for extinct hominids. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [October 14, 2009, 6:35pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/14 "2009-10-14T18:35:39Z")
As for the most, my Googling isn’t coming up with much. The greatest number I’ve found so far is _Acacia_ which has somewhere north of 1300 species. “Orchids” and “beetles” etc comprise loads of genera. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 14, 2009, 6:40pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/15 "2009-10-14T18:40:34Z")
The modern elephants are actually in two different genera: Loxodonta and Elephantus. Elsewhere in the animal kingdom, the two species of tuatara are the only member of their class, order, family, and genus. But including all living things, I think the champion is probably the ginkgo tree, with only one extant species (Ginkgo biloba) in the entire division (equivalent to phylum). ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [October 14, 2009, 7:17pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/16 "2009-10-14T19:17:32Z")
Taxonomists are almost always willing to split a genus if its member list is growing to an unwieldy size. Heck, most of them are willing to name a new genus if it can get them another paper published. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [October 14, 2009, 7:22pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/17 "2009-10-14T19:22:58Z")
1. There are literally hundreds of monospecific genera (genus-es with only one species). 2. I have no clue as to what genus actually has the most species. Some WAGs: – among all life, probably _Bacillus_, the capsule-shaped bacteria. – among plants, genus Poa, the common grasses, probably far exceeds any other genus in number of species – among insects, _Musca_, the houseflies and allies. While there are more species of beetles than almost anything else you can name, there are a lot of beetle genera, none of which to my knowledge have a large number of species. – among mammals, my guess would be _Mus_ or _Rattus_. – among birds, _Passer_, the sparrows, with at least 27 distinct species. While there are dozens of species of warblers, they belong to a wide assortment of nont-particularly-closely-related genera. 1. **Lemur** is correct that crabs are by no means a single genus, but true crabs constitute Infraorder Brachyura, with hermit, coconut, and king crabs in the separate Superfamily Paguroidea in a different Infraorder. > [@cmkeller](#): > > I believe the Aardvark is the only member of its family, order, and genus, and I don’t think there are even fossil relatives considered to be members of the family. 1. The aardvark is indeed the only extant member of genus Orycteropus, family Orycteropodidae, and order Tubulidentata, but there are extinct aardvark allies known from fossils. > [@Chronos](#): > > The modern elephants are actually in two different genera: Loxodonta and Elephantus. 1. Elephas, not Elephantus, but otherwise accurate. Taxonomists are divided as to whether there are one or two species of Loxodonta, FWIW. As for the ginkgo, it’s definitely monospecific, and that quite far up the taxonomic hierarchy. But depending on who’s doing the classifying, Ginkgoformes may be only an order among Gymnosperma. ---
**Author:** ![EdwardLost](https://avatars.discourse-cdn.com/v4/letter/e/bbe5ce/32.png) [@EdwardLost](https://boards.straightdope.com/u/EdwardLost)\ **Post date:** [October 14, 2009, 9:13pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/18 "2009-10-14T21:13:52Z")
I was thinking of Formica - but on checking I see that there are fewer than 200 species. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [October 14, 2009, 9:32pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/19 "2009-10-14T21:32:04Z")
> [@Polycarp](#): > > Some WAGs: > > – among all life, probably _Bacillus_, the capsule-shaped bacteria. > > – among plants, genus Poa, the common grasses, probably far exceeds any other genus in number of species. Wikipedia says _Poa_ has only about 500 species, less than half that of _Acacia_. In fact there are said to be almost 1000 species of _Acacia_ in Australia alone. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 14, 2009, 9:36pm UTC](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814/20 "2009-10-14T21:36:27Z")
> [@](#): > > Taxonomists are divided as to whether there are one or two species of Loxodonta, FWIW. Really? I hadn’t even heard that there were two distinct subspecies of African elephant (presumably, the two species some are arguing for are at least widely recognized as subspecies, right?). [Next page](https://boards.straightdope.com/t/what-genus-has-the-most-species-the-fewest/513814.md?page=2)