Dichelostemma--Themidaceae?

These changes are based on multiple gene sequences that clearly show that
Alliaceae+Amaryllidaceae+Agapanthaceae represent a very well-supported unit,
while the former Alliaceae tribe Brodieeae (I can never spell that
correctly) of Alliaceae is sister group to the Hyacinthaceae. Yes, Muilla
(I agree about the irony) is part of Themidaceae.

Thus, it has much less to do about morphology. There are not a great number
of good morphological characters to separate the group, but the lack of
bracteoles in Alliaceae, and the gynophores and articulate pedicels in many
Themidaceae are good characters. Though we wish that the DNA sequences were
always backed up by lots of morphological or anatomical characters (and
sometimes they are, especially when we go back and look carefully), that is
not always the case. And sequence phylogenies are the arbiters these days
of phylogenetic relatiionships.

Alan
-----------------------------
Alan W. Meerow, Ph.D., Research Geneticist, Systematist and Curator
USDA-ARS-SHRS, National Germplasm Repository
13601 Old Cutler Road, Miami, FL 33158 USA
voice: (305) 254-3635 fax: (305) 969-6410
email: miaam@ars-grin.gov
WWW page: http://ars-grin.gov/ars/SoAtlantic/…

----- Original Message -----
From: <Antennaria@aol.com>
To: <pbs@lists.ibiblio.org>
Sent: Tuesday, May 27, 2003 11:29 PM
Subject: Re: [pbs] Dichelostemma--Themidaceae?

Comments on several respondents offerings on this topic:

Mark:

Try these. Looks can be deceiving.

Alan

Thanks Alan,
I shall give these a lookup sometime. Until such time that I get a

chance,

can you summarize, is Muilla now in the Themidaceae? If it is, it's

ironic

n'est pa?

Mar Sue, thanks for the paragraph summarizing the differences between
Alliaceae and Themidaceae. Some comments:

Alliaceae have a true bulb (composed of
swollen leaf bases) with a membranous
coat, but the storage organ in
Themidaceae is a corm (composed
of stem tissue.)

This is a gross generalization. Many alliums do not have a recognizeable
bulb whatsoever
. many Chinese species, such as A. wallichii, have nothing more that a
ever-so-slightly thickened leaf base, and some fleshy white roots, nothing

that

you'd remotely call a bulb, but indeed merely a rhizome, and even

questionably at

that. A large number of species do not have membranous bulb coats... some
do, some have fibrous bulbs coats, some have no recognizeable bulb coats
whatsoever.

I do agree that Trits and Brodes have corms, but some Geranium species, as
well as some Pelergoniums, have bulbs or bulb-like storage structures

whereas

most are fibrous rooted perennials. Are they removed into their own

genus?

Alliums can have true bulbs, rhizomes (whole sections named after this

feature),

or a combination of vestigial bulb and rhizome. Should the different

groups

be separated into their own genera? Many genera exhibit similar rootstalk
diversity, such as Corydalis... should these be separated out into their

own

family?

Most, if not all, Themidaceae lack the onion odor."

Some major sections of the genus Allium also lack the characteristic onion
odor. Should these non-alliaceous-scented alliums be split off into their

own

genus, or a new family perhaps.

While Alliaceae have a pair of bracts that
encloses the flower buds, Themidaceae have
several bracts that do not enclose the young
flowers.

Alliums have *one* to *many* bracts that enclose the flower buds, not

always

a pair as described above. The number of spathe or bract segments, and
whether the segments are persistent or not, play a role in species

determination.

In some species the spathe is so short and ephemeral (dropping off) that

the

buds can appear as not being enclosed. The genus Muilla is described as

having

buds enclosed in several spathe segments. What am I missing?

Alan writes:

No South American Themidaceae. Strictly
Southwestern and Western U.S. andMexican.
There is no true Brodiaea in Chile. All the Chilean
onions are still onions.

Way back when, many S. American plants now known as Tristagma, Ipheion,
Nothoscordum, and others, were listed as Brodiaeas, even a few as Allium.

Alan is

quite right, there are no true Brodiaea in Chile and these genera names

were

misapplied. When it is said "all Chilean onions are still onions", I

assume

what is meant by that is that all Chilean Alliaceae are still Alliaceae,

because

there are no true onions (Alliums) in South America.

But this Themidaceae separation has me wondering... was the division

largely

devised based on Western American and Mexican taxa... if so, therein lies

the

conventional flaw in not looking "big picture". Most American Allium fall
into a single type with bulbs. Consider the genus Allium in it's holistic

sense,

including Chinese Allium, the "rhiziridium" section of Allium, the
stoloniferous Alliums, alliums with varying bract structure, rootstalk

structure, even

onion smell, and tell me that Themidaceae is justified. I just want to be
convinced. I'm not adverse to sensible change, but this one really has me
wondering.

Mark McDonough Pepperell, Massachusetts, United States
antennaria@aol.com "New England" USDA Zone 5
==============================================

web site under construction - http://www.plantbuzz.com/ <<

alliums, bulbs, penstemons, hardy hibiscus, western
american alpines, iris, plants of all types!
_______________________________________________
pbs mailing list
pbs@lists.ibiblio.org
http://www.pacificbulbsociety.org/list.php