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  Alocasia macrorrhizos and A. cucullata
From: LariAnn <AROIDIAN at worldnet.att.net> on 2009.09.04 at 23:35:08(19936)
Peter and fellow aroiders,

I need to jump in here and share what I've observed in my hybridization
work with all of the species mentioned in recent posts (A. macrorrhizos,
A. odora, and A. cucullata). Now, in my experience there are quite a
few A. macrorrhizos cultivars available, and one I know of seems to be,
as Peter mentiond, a culton of A. odora. However, most of the ones I
call "A. macrorrhizos" have significant differences in floral morphology
and in addition, are nearly genetically incompatible with what I have
come to call the A. odora group. This group includes A. odora, A.
gageana, A. odora 'Azurea', A. odora 'Indian' and A. cucullata. In
hybridizing with both groups, I have found, first, that a cross of A.
macrorrhizos and A. odora yields sterile offspring. A cross between A.
odora and A. cucullata yields fertile offspring. Likewise, a cross
between A. odora and either A. odora 'Azurea', or A. odora 'Indian'
yields fertile offspring. Crosses between cultivars or varieties of A.
macrorrhizos (such as blackstem, lutea, Borneo Giant, portei) yield
fertile offspring. It is my position that genetic work can indicate the
specific nature of various plants.



From: Peter Boyce <phymatarum at googlemail.com> on 2009.09.06 at 06:56:11(19945)
Hi LariAnn,

To re-iterate my reply to Tony, Certainly 'species' such as A. macrorrizos
and A. cucullata bend the boundaries a lot. What is of course interesting is
that A. macrorrhizos (notwithstanding its doubtful 'pure' species status) is
definitely related (and here we are talking molecularly) to some
unquestionably 'good' species, such as A. portei and A. flabellifer, which
poses even more difficulties. It is also problematic to talk about
utilization of cultivars, especially those that are selections of what may
themselves be cultivars, albeit so long-standing that they have effectively
stabilized and function as species, even to the extent that they have lost
the ability to hybridize with other elements of what was once a single gene

The bottom line is that, at present, we can only be sure that A.
macrorrhizos and A. cucculata are NEVER found away from human disturbance in
'habitat' and furthermore, away from the attentions of horticulturists are
remarkable morphologically stable.

As a final thought on this, it is also important to remember that species
framework, and the interspecific crossing is often in nature not just a
matter of 'incompatibility'. Distribution, flowering time even down to the
level of time of day, and how these barriers function to manage
pollinators, or select for a particular pollinator guild, are as much, if
not more, a barrier than simple unrelatedness. If ever an example was needed
of the role of pollinator guild niche selection, the orchids of the
Stanhopineae contain numerous examples.

Very best


From: LariAnn <AROIDIAN at worldnet.att.net> on 2009.09.06 at 18:01:41(19947)

Interesting thoughts - I would think that if a variety, cultivar or
hybrid has stabilized to such an extent that it comes true to seed and
functions as a species, as you described, then wouldn't that mean it has
actually become a new species, in effect? Isn't that one way that
speciation manifests itself? Whether it took 100 years or 1000 years,
that should not make it any less of a new species, should it?

Regarding the barriers to crossing, all of the barrier factors you
mentioned, with the exception of genetic incompatibility, are factors
that can be overcome by judicious hybridization work. I can preserve
pollen to make up for flowering time differences, I can grow the plants
together even though in habitat they may be very far away from each
other, I can do my pollinations at different times of day in order to
find the right time, and, of course, I can learn how to be the right
pollinator myself. What I cannot do in traditional hybridization is to
overcome a genetic or biochemical barrier to the production of viable
pollen or ovules, or to the growth of the pollen on the stigma. However,
as a result of my work, I've done some hybridizations that I actually
thought were genetically impossible. The most remarkable example is my
hybrid of A. odora and A. reginula. Predictably, the progeny are
sterile, but the plants are beautiful. Perhaps, in time, the plant may
stabilize genetically and manifest fertility.

Kind regards,

From: Peter Boyce <phymatarum at googlemail.com> on 2009.09.07 at 06:43:45(19952)

The answer to your first para is a definite yes, and in fact there is such a
category for such seemingly stable taxa where the hybridity is known or at
least heavily suspected - nothospecies (literally 'bastard' species). There
are a couple of Cryptocoryne (purpurea and the recently describe timahensis)
that are just this.

The problem with A. macrorrizos and A. cucullata is that the 'parentage', if
they are of hybrid origin, is unknown and short of an extensive set of
experiments with possible 'known suspects' (e.g., odora, navicularis, etc.)
will probably remain so unless there is a chance 'discovery' in the wild.

Very best


From: "mossytrail" <mossytrail at hctc.com> on 2009.09.09 at 01:56:07(19977)
So you are saying they appear to be cultigens? But cannot
cultigens have valid species names (e.g., Zea mays)? And in
that case, there can then be named cultivars of such
cultigens (e.g., Zea mays 'Ruby Queen').

Jason Hernandez

From: Peter Boyce <phymatarum at googlemail.com> on 2009.09.09 at 05:31:48(19980)
We don't know what they are.

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