Origins: From Australasia/Antarctica to Europe ?

[Croquin]

Iridaceaes are believed to be a branch diverging from the Doryanthaceaes about 82 million years ago, in Australasia and Antarctica (Goldblatt, Peter; Rodriguez, Aaron; Powell, M.P.; Davies, Jonathan T.; Manning, John C.; van der Bank, M.; Savolainen, Vincent, 2008. Iridaceae 'Out of Australasia'? Phylogeny, Biogeography, and Divergence Time Based on Plastid DNA Sequences. Systematic Botany, Volume 33(3), pp. 495-508).

Crocuses distribution is centered on Greece-Turkey expanding northwestward to the Atlantic ocean and northeastward to western China, and hardly present in northern Africa.

I am missing something in the history of iridaceaes: from their appearance date in late cretaceous to the appearance of the crocuses branch, how were they travelling from Australasia and Antarctica to the European continent ?

[arisaema]

Continental drift, perhaps.

[Croquin]

Some insights from outside the box:


There would be 3 possible paths from there to here/now :

• from eastern China
• from southern India
• from southern Africa

Nevertheless, something is missing: I'm stuck !

[Lesley Cox]

If all this is correct - and I don't doubt it for a minute - I take it as a personal insult that THERE ARE NO IRISES as such anywhere in the southern hemisphere, even though there are many Iridaceae. A few could have stuck around, surely.

[Croquin]

It seems that Iridaceae have spread all over the world, and that there is an important concentration in the south of Africa, which sounds OK with the continental drift/earth expansion theories - contrary to the biogeography of crocuses.
And now you add the irises issue (which I know nothing about - where are they distributed ?), which will surely bring additional cues to understand this question.

[Lesley Cox]

While Iridaceae are distributed world-wide, the genus Iris is entirely confined to the Northern Hemisphere.

[Croquin]

According to the reference I mentioned earlier in this thread, Iris is an Eurasian/north American offspring appearing between 45 and 50 mi. y.

After contemplating a little more the problem, I think that I start to get the picture for crocuses.

Their ancestors did not travel from Australasian/Antarctica through China or India, but most probably through Africa (crocuses are alleged to be of African origin - still the same ref).
The earth surface and climatic conditions have changed so dramatically that this was unclear.
Indeed, the Mediterranean sea is a recent opening which has split the landmass into Europe and Africa and will continue to grow.
And the Sahara desert was green just few millenia ago.
The appearance of both the Mediterranean sea and the Sahara desert represent a major ecological catastrophe resulting in mass extinctions in this whole area.
The current Crocus genus may only be the surviving end of a branch.

We can speculate that the birth place of crocuses is not Turkey/Greece, but rather an area including this zone as well as part of the Mediterranean bottom floor (hence including Mediterranean islands), which is a very conservative hypothesis.
Another hypothesis is that crocuses birthplace is somewhere further south than Turkey/Greece, i.e. Mediterranean bottom floor/north of Africa.

Does that sound congruent with other knowledge?

[Janis Ruksans]

Usually the place where greatest number of taxa of some genus occur is regarded as Centre of distribution and origin of Genus. For Tulips such is Central Asia, regarded as primary centre of distribution, and Caucasus as secondary centre of distribution (M. Hoog). For Crocuses such center definitely is Turkey, may be SW Turkey (see several publications of Pasche & Kammerlander).
Janis

[Croquin]

I agree.
But this is only true if no dramatic geographical or climatic changes occurred, which is not the case in this area of the world (opening of more than one sea plus significant degradation of the climate).

Crocuses and south African Syringodea share a common ancestry 12 mi.y ago and are remarkably similar morphologically.
It can only mean that the origin of crocuses is not Turkey, except - maybe - in very recent times for the newest evolved species.

Additionally, one need to explain, if Turkey is the birth place of crocuses, how did they jump to northern Lybia or to the Mediterranean islands.
Can it be through migrating birds having ingested seeds ?
Or are these isolates due to the opening of the Mediterranean sea after crocuses had populated the whole area from Eurasia to North Africa ?

I was trying to take a look at the history of the tree, crocuses is only the end of a branch.
Please, if what I wrote is unclear somewhere just ask me - I was going a bit fast.

[Janis Ruksans]

There are no problems to travel around Mediterranean sea by earth > Turkey-Syria-Lebanon-Israel-Egypt-Lybia. B the way - Mediterranean sea is not so old formation (by geological terms).
Janis

[Croquin]

But we have no travelling pattern around the Mediterranean sea, although we have for sure some diffusion pattern in the north of the Mediterranean sea across Eurasia, which is what you mentionned.
And what about the travelling pattern from the south of Africa where the sister genus Syringodea lives to Eurasia ??!!
I hope that you see something is missing here ?

[Tom Waters]

Just a thought on this - it seems the simplest explanation is that the ancestors of Crocus and Syringodea were widespread throughout east Africa and adjacent areas of Eurasia. The desertification of the Sahara is thought to have begun c. 7 million years ago (see http://www.sciencemag.org/content/311/5762/821.full), and this would have isolated the northern and southern populations, with the northern group (Crocus) being concentrated on the northern fringe of the deserts, i. e., Turkey.

BTW, the reference you cited in the original post makes the suggestion that the early Iridaceae migrated to Africa across the Indian ocean, perhaps using India as a stepping stone, and from Africa radiated north and east into Eurasia. Another branch of the family (to be Sisyrinchium and relations) went from Antarctica directly to South America, the two continents still being in close proximity then.

I've read that the cretaceous flora were quite widely dispersed, with many families being essentially global in distribution. It was a time of generally moderate, warm and moist climate, presenting fewer barriers to dispersal of plants than currently.

Regards, Tom

[Lesley Cox]

This discussion makes me think of a programme aired on our TV last night, called "Primeval New Zealand" and very interesting it was too, except that apparently it can be shown that "our" iconic birds, the moa, the kakapo and particularly the kiwi, all originated in AUSTRALIA!!!. We will never live this down! When they flew, as much bigger birds over to NZ as it was at that time many millions of years ago, (part of the breaking-up Gondwanaland) they evolved quickly into the birds we know today as smaller (the moa is extinct) and ground dwelling, flightless and nocturnal.

[fermi de Sousa]

This discussion makes me think of a programme aired on our TV last night, called "Primeval New Zealand" and very interesting it was too, except that apparently it can be shown that "our" iconic birds, the moa, the kakapo and particularly the kiwi, all originated in AUSTRALIA!!!. We will never live this down! When they flew, as much bigger birds over to NZ as it was at that time many millions of years ago, (part of the breaking-up Gondwanaland) they evolved quickly into the birds we know today as smaller (the moa is extinct) and ground dwelling, flightless and nocturnal.

Makes you wonder what the Magpie and the Possum will evolve into! (apart from very warm scarves and jumpers!)
 
cheers
fermi

[Croquin]

How do you think crocuses migrate ?
I mean: the mechanism.