Genus of Cucumbers and Pumpkins

[fresh_42]

I have a question regarding the genus of these:

Cucumber: Cucurbitaceae
The probable wild form of cucumber, the variety hardwickii, is native to India.

Pumpkin: Cucurbitaceae
The genus is originally native exclusively in America.

How can this be?

 

[jedishrfu]

Continental drift, bird transport or Amazon deliveries? I'm going with bird transport for now and Amazon seed delivery for later.

https://en.wikipedia.org/wiki/Cucurbitaceae

https://en.wikipedia.org/wiki/Pumpkin

https://en.wikipedia.org/wiki/Cucumber

 

[fresh_42]

Continental drift, bird transport or Amazon deliveries? I'm going with bird transport for now and Amazon seed delivery for later.

https://en.wikipedia.org/wiki/Cucurbitaceae

https://en.wikipedia.org/wiki/Pumpkin

https://en.wikipedia.org/wiki/Cucumber

I suspect that Cucurbitoideae are native to the Americas but not Cucurbitaceae, resp. that the deliberate classification has a flaw here. Wikipedia says nothing about genetics which would be relevant in this case: are cucumbers pumpkins or not? is the question which I really like to be answered.

If in doubt, I would favor convergent evolution over birds and amazon.

 

[jedishrfu]

I forgot the convergent evolution idea.

This article might explain it though as a complex genetic process with duplicate genes:

https://cosmosmagazine.com/biology/pumpkins-are-more-complex-than-you-think

They have some timelines too where melons and cucumbers split at 14 million years ago.

 

[jim mcnamara]

FWIW - Oak trees. Quercus robur, English Oak, brought over the ocean to Central Park in NYC, produced viable hybrid offspring with the local Quercus species.
They were separated for about 60 million years. This happens with geographically separated species sometimes. One tenets of the definition is fully functional hybrids are not supposed to happen, as taught in secondary school Biology. But they do.

Our definition of species arose from our need to cubbyhole living things, when in reality the definition of species sometimes has exceptions. And may get in the way of understanding what is going on. So could you say our species definition is "specious"?

 

[jedishrfu]

This is often true as science progresses we find better ways to categorize something or better ways to measure it.

The story of the thermometer is a case in point where different materials were used based on the their freezing / heating properties and different scales were used until we standardized on Celsius and even that one is not quite right once absolute zero was discovered and Kelvin became the measure.

Spoiler: addendum: for further info on thermometer history...

https://www.thoughtco.com/the-history-of-the-thermometer-1992525

Also as I recall, the Celsius scale was initially reversed:

http://www.todayifoundout.com/index.php/2014/12/fahrenheit-scale-isnt-arbitrary-seems/

and lastly, the Veritaseum talk on Fahrenheit:

 

[Ygggdrasil]

I have a question regarding the genus of these:

Cucumber: Cucurbitaceae
The probable wild form of cucumber, the variety hardwickii, is native to India.

Pumpkin: Cucurbitaceae
The genus is originally native exclusively in America.

How can this be?

Note that Cucubitaceae is a classification at the level of family, whereas statements about which crops are native to which regions refer to genuses or species, which are levels of classification below family (see https://en.wikipedia.org/wiki/Taxonomy_(biology)). It is certainly possible that the common ancestor of cucumber and pumpkins pre-dated the separation of the continents, and after separation of the continents, that common ancestor diverged to the various genuses and species of Cucurbitaceae found around the world.

Given that many Cucubitaceae are important food crops for humans, it is also possible that these plants spread with humans during human migration.

 

[BillTre]

I suspect that Cucurbitoideae are native to the Americas but not Cucurbitaceae, resp. that the deliberate classification has a flaw here. Wikipedia says nothing about genetics which would be relevant in this case: are cucumbers pumpkins or not? is the question which I really like to be answered.

It sounds this might interest you:

These data have allowed to infer evolutionary relationships in the family. The major phylogenetic structure of the family is now clear, and this chapter includes an up-to-date phylogenetic scheme with the placement of all genera. The Cucurbitaceae clade originated in mainland Southeast Asia sometime in the Late Cretaceous, and the five deepest evolutionary divergences in the family all date to the Late Cretaceous, 70–80 Ma. Two of these ancient clades, the Gomphogyneae and Actinostemma, are now almost restricted to Asia. A third ancient group, the Triceratieae, is mainly Neotropical, except one African genus; other clades and tribes are more widespread.

Which came from the abstract of: Phylogeny and Evolution of Cucurbitaceae (in Genetics and Genomics of Cucurbitaceae pp 13-23;) which is behind a paywall here, thus I have not read the whole article. (You might be able to search the web for the autors/title or go to their academic websites and get free copies somewhere).

The abstract indicates a current view of this group and its origins include:
The group originated in SE Asia, and made its 5 deepest lineage splits, in the late Cretaceous (Maybe 25 MYA before the dinosaur killing meteor impact, 90.5 - 65.5 MYA).
Earth, 66 MYA from the Ancient Earth webpage:

The Indian sub-continent is moving north (toward about 1 o'clock and will eventually smash into the area that will become Tibet (among other things).
Australia and Antarctica are still close together.
Africa is moving North towards Southern Europe.
Mediterranean is not yet enclosed.
Alaska and Siberia have a relationship similar to today's.

At 105 MYA, Africa and South America were just separating:

Two deep clades are "largely" restricted to Asia.
One group is Neotropical (largely South America).
Other groups are more widespread.

The distributions of different clades don't seem to match up with landmass separations as absolute restrictions to movement. Africa and the Americas were separate from Asia when the Neotropical group would have had to have gotten from the familly's place of origin in SE Asia to S. America (via Africa?).

As was already mentioned, other methods of plant distribution could be involved:

• bird transport or Amazon deliveries? I'm going with bird transport for now

• possible that these plants spread with humans during human migration.

• Another possibility is the fruit/seeds floating across bodies of water (coconuts do this, pumpkins probably not though).

 

[fresh_42]

Thanks for the information. This makes the cucumber part plausible, however, leaves the question how their relatives (pumpkins) became native to the Americas.

I read this as (disregarding the deliberate names): Pumpkins (later) are cucumbers (SE Asia) but not the other way around. As we humans arrived far later on the timescale, the human migration can only explain pumpkins formerly known as cucumbers aka hardwickii . If this is roughly correct, then a closer look should bear insights on possible migration paths across the pacific! That's just an idea, since I cannot really imagine the seeds would have survived the long route along the Bering strait and down the Andes.

 

[BillTre]

Pumpkins (later) are cucumbers (SE Asia) but not the other way around.

Or the pumpkin group is a sub-set of the larger cucumber group.

That's just an idea, since I cannot really imagine the seeds would have survived the long route along the Bering strait and down the Andes.

The seeds might get eaten by birds in one continent and then pooped out in another.

 

[fresh_42]

The seeds might get eaten by birds in one continent and then pooped out in another.

I have thought about this, but the poor bird would have suffered a severe constipation regarding the distances! AFAIK there is a hypothesis of a migration wave across the Pacific to Southern America (over Easter Island). It's certainly easier to transport seeds in a boat by island hopping than by foot over ten thousands of miles, especially as it is assumed that it was along the coastlines due to the supply of fish - in other words: it wasn't agriculture which made the route possible, but meat. Plus that pumpkins don't grow very well in the Northern part of the continents.

 

[BillTre]

North-South migration patterns of birds between continents seem common, but East-West migrations, not so much.
Check out the many migration patterns Google found here.
Almost all the birds in a particular species do this each year, so they are kind of made for it.
The seeds of the ancestral plants were probably not as big as pumpkin seeds. Cucumber seeds, for example, are reasonably small.
The bird mediated distribution process would have depended upon the evolution of birds that could undertaken the migrations. This would have had to occur after the dinosaur meteor impact (65 MYA).

 

[fresh_42]

North-South migration patterns of birds between continents seem common, but East-West migrations, not so much.

Sorry, for causing confusion. I meant a human west - east migration of Polynesians. A Chilean anthropologists investigates this possibility.

The bird solution would imply, that they "plant" along their routes, but I cannot imagine, that this will work for subtropical fruits along the Bering Strait and Canada.

 

[Ygggdrasil]

From the link @BillTre posted:

Cucurbitaceae apparently originated in Asia sometime in the Late Cretaceous (Schaefer et al. 2009). The five deepest evolutionary divergences in the family all date to the Late Cretaceous, 70–80 Ma. Two of these ancient clades [the Gomphogyneae (I) and Actinostemma (IV) clade; Fig. 1] are now almost restricted to Asia. A third, the Triceratieae (II), is mainly Neotropical, except for a small African genus, Cyclantheropsis. The ancestors of another early-diverging clade (Fig. 1), the Zanonieae (III), apparently reached the African continent early, and from there dispersed to Madagascar (the early Eocene Xerosicyos lineage). Later, in the Oligocene, at least two long-distance dispersal events brought two members of this clade, the Siolmatra lineage, to America, and the Zanonia lineage, back to tropical Asia. The younger tribes towards the top of the tree (Coniandreae, Benincaseae, Cucurbiteae) in Fig. 1 all have relatively large geographic ranges that they often extended by transoceanic dispersal (Schaefer et al. 2009). Striking examples of such transoceanic dispersal are found in the sponge gourd genus, Luffa, three of whose eight species occur in the New World, four in tropical and subtropical Asia, and one in northern Australia (Telford et al. 2011a, b; Filipowicz et al. 2014), and in Sicyos, which has 14 species, all descending from a single ancestor that arrived c. three million years ago, two species on Galapagos that arrived independently, and three species in Australia and New Zealand (Sebastian et al. 2012; Telford et al. 2012). Finally, the bottle gourds, Lagenaria, are of African origin but very likely arrived in Central America with sea currents and were domesticated there some 10.000 years ago (Clarke et al. 2006; Kistler et al. 2014).

South America has about 360 species of Cucurbitaceae that descend from just a few transoceanic dispersal events, mostly from Africa to South America. These events involved the ancestors of the Cucurbiteae, lineages of the Sicyoeae, part of the Coniandreae, and Melothria, Lagenaria, and Luffa (see under these genera). For Melothria, it appears that its ancestors came across the Pacific, since the sister group of Melothria, Indomelothria, is endemic in Southeast Asia. North American cucurbits descend from seven expansions of Central and South American lineages that occurred at widely different times (Schaefer et al. 2009).

The Schaefer et al. 2009 papers appears to be freely available online: https://royalsocietypublishing.org/doi/10.1098/rspb.2008.1447

 

[BillTre]

The Schaefer et al. 2009 papers appears to be freely available online: https://royalsocietypublishing.org/doi/10.1098/rspb.2008.1447

Cool.

leaves the question how their relatives (pumpkins) became native to the Americas

The paper claims that one or more LDD events (Long Distance Distribution) were required to explain the distributions of particular taxonomic groups.
Their favored explanation is transoceanic LDD's. To me that sounds like floating across the ocean.
I don't know what the seed containers of the ancestral plants of this group had, but its not out of the question that they might have had dried light weight thick skinned gourds that could get across the proto-ocean pretty well.
Between 66 and 105 MYA ago Africa and South America were separating, but not that far apart.
There was also (presumably) the outflow of two great rivers (Congo, Amazon (the river) or their equivalents) flowing toward their opposite coasts. This might aid transfers between the two continents.
Unusually large storms could additionally increase the odds of transfer. Freshwater cichlid fish are now thought have gotten from Africa to South America after the two continents split apart, as well as some mammals.