IAS Aroid Quasi Forum

About Aroid-L
 This is a continuously updated archive of the Aroid-L mailing list in a forum format - not an actual Forum. If you want to post, you will still need to register for the Aroid-L mailing list and send your postings by e-mail for moderation in the normal way.

  Re: [Aroid-l] Adelonema
From: Lars <larsmaillist at googlemail.com> on 2011.11.24 at 18:45:11(22408)
Hello everybody,

sorry for this mail coming a bit late. I wanted to add something to the
discussion of the aroid biogeography but had problems posting here on
the list.
Well, if you can read this, it means it finally worked. Thanks Steve for
figuring out the problem!

I am just working on the dating and biogeography of the family for my
phd. Basically, I use molecular data and assign fossil to certain nodes
in order to get minimum ages for all other nodes.
It also means, that I don't even have a glimpse of the deep
understanding in the ecology, morphology, and taxonomy of Tom and Peter
(and others), as I just work since a few years with Araceae and mainly
from a molecular point of view.

Having said that, here are some of my results.
(The ages are minimum ages and therefore might be considerably older.)

The spit between Adelonema and Homalomena is relatively young, at least
25 Ma. Maybe 40 Ma is more realistic, but I don't think it is much
older. Although I would like to explain it by vicariance (maybe in a
very warm period in the Paleocene, when there was subtropical climate in
Antarctica and a land connection to Australia). The direction would be
from South America to SE Asia, as Peter told me Philodendron is basal to
the two genera in his more detailed dataset. It is very unlikely that
they got dispersed over the pacific, but not impossible. There have been
some weird long distance dispersals.
If it would be 50-60 Ma a pathway through Antarctica and Australia could
have been possible.

The same young ages (20-30Ma) are in the disjunctions of the Lasioideae
and Monstera (which is in a South East Asian clade).
The split between Philonotion and the rest of the Schismatoglottideae on
the other hand is quiet some time older, at least 45 Ma. With the error
boundary and considering it as minimum a dispersal in the Paleocene
might have been possible.

The Bornean Nephthytis bintuluensis groups with Aglaonema and Aglaodorum
(both from SE Asia), while the rest of Nephthytis groups with Anchomanes
and Pseudohydrosme from Africa. The split between these two groups was
at ~40 Ma.

Rhaphidophora, Amorphophallus, and Arisaema went somewhen in the Miocene
to Africa.

Peltandra (eastern North America) and Typhonodorum / Arophyteae
(Madagascar) have spilt in the Eocene and have had ancestors in Asia
(good fossil record). So it must have been a relatively continuous
connection, or movement later to Africa at the one side and crossing the
Bering Strait at the other.

The Origin of the Araceae is a bit more difficult. The ages are not
really clear, as for the molecular dating with fossil assigned as
minimum ages you have to have a maximum bound at the base.
But they surely go back to the Early Cretaceous (fossil record), maybe
even Jurassic. The true Araceae (without Lemnoids and Proto-Araceae)
most probably come from Gondwana. But reconstructing the real origin it
has to be taken into account the free floating (and mostly world wide
distributed Lemnoids), the today probably only remnant basal
Gymnostachys (Australia) and Orontioideae (Laurasia), and the
Alismatales, the next sistergroup of the Araceae (many in the northern
hemisphere, or marine, or sweet water plants and world wide
distributed). That leaves everything open for speculation and any
reconstruction there is difficult, so to answer an earlier question of
No, there is no data robust enough to give an unambiguous result for the
origin (I guess that is what you mean with center of radiation).

At least that is what the molecules and some modern methods let suggest.

Very best,

Note: this is a very old post, so no reply function is available.