Most flowering stalks reach 7-8 feet but some are 3-4 feet tall with nothing observed of intermediate length. Shaw's agave is endemic to Southern California and Northern Mexico. It is considered endangered for several reasons. First, it has an inefficient reproductive strategy. Second, its habitat was threatened by erosion and by the border fence. Third, the indigenous people used to eat the reproductive parts of the plant thus interfering with its proliferation. One challenge of studying Shaw's is that the best examples grow on federal land, much of which is restricted to the public. Another problem is that few seem to care about the future of the plant. I have studied the morphology, distribution and life cycle of Shaw's agave for many years but I have more questions than answers. Can anyone help?
Kalidass, thank you for your answer. The observations have been with the same populations in the same locations, some of them not more than three or four feet away. I can go back to my notes and count the number of short stalks, but the long stalks seem to predominate. I have studied Shaw's agave in two locations - the Cabrillo National Monument, and at The Space and Naval Warfare Systems Center, seaside location on Point Loma, which has the most spectacular growing population of Shaws agave. The Navy lab is off limits to the general public and even the Cabrillo National Monument has restricted access and kept viewers at a distance so that close measurements cannot be made without prior arrangement. The two populations are related because when some plants were falling off a eroded cliff at the Navy lab, the park rangers rescued them and transplanted them at the National monument. That was around 1975 before I started my study.
I am not sure what you mean by "long stalk at base short stalk in the top" I measured the total height above ground level of both types of flowering stalks. Notably the short stalks do not flower like the long stalks do. The horizontal branches are quite truncated with hardly any seed production compared to the long stalk flowers. I have hypothesized that the dimorphism is related to the existence of male and female plants, but have no way to prove this.
first i would like to ask you is the species is dioecious or monoecious. secondly if the flowers borne on both the type of stalks are hermaphrodites you can check the dimorphism in traits like fertlity of pollen grains, pollen production and flower display per day in a reproductive season etc. If these characters are significantly varying then you can comment on dimorphism. I'll suggest you read articles by SCH Barrett. Definitely you'll get the idea.
Kalidass and Yash, thank you for your answers. Unfortunately I have moved away from the area where Shaw's agave grows and genetic studies seem not to be possible for me at this time. I agree that it would be a very interesting study to sample genetic material from various individual plants as a function of location and determine the genetic distributions.
The Agave americana, or century plant, which is another species of the same genus as Shaw's agave, is monoecious. So far, I have not been able to determine if Shaw's is dioecious or monoecious.
Yash, thank you for the suggestion on the SCH Barrett articles.
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