AN ARGUMENT FOR THE POSSIBILITY THAT I. CRISTATA IS A HYBRID OF I. LACUSTRIS

I make no claims that my argument has been scientifically established as fact and I have no formal training in any of the scientific fields. The reasoning is mine as are any mistakes I may have made in interpreting the data. A majority of my assumptions are based on observations of my own inter-specific and inter-series crosses and the mechanisms I have used to obtain them. I use the Ensiberians as examples here since these were some of the first and have produced the most data. I hope by the suggestions made here that others might delve more deeply into the possibilities of hybridization between species as the origin of new forms.

Current information is that Lacustris is a threatened species and the lack of genetic diversity in existing populations supports this.

Assumptions have been made that Lacustris is a subspecies descended from a limited population of cristata based on identical chromosome counts of 2n=32, similar appearance, and the lower genetic diversity of Lacustris. In addition, the assumption that cristata is the older of these is based on the fact that a more diverse gene pool is evidence of a source species and would make sense IF Lacustris and Cristata are subspecies and species. I believe this is a mistake.

If Cristata is a hybrid of Lacustris, and an additional species then cristata should show more genetic diversity.

Kohlein's book 'Iris' lists Cristata as 2n=24 as well as 2n=36. If all three C counts are accurate and Cristata is indeed a hybrid, this suggests the other parent would have a C count of around 2n=42. I. verna is a likely candidate due to a reported count of 2n=42, current location, and a similar appearance. Since it is the only possible candidate I'm able to find so far, I use it as example.

If some of the mechanics of reduction in meiosis are governed by inheritance, it's not unlikely individuals from a pairing of 2n=42 and 2n=32 might show these reported counts of 2n=24, 2n=32, and 2n=26.

Iris verna as a parent species of cristata is also likely since in a cross with Lacustris, the resulting hybrid should be 2n=37. Since an unpaired chromosome can and should be shed if the plant is to be viable, the resulting entity would show 2n=36 and be both stable and fertile. It's also my hunch that based on this, the most likely initial pairing would have been I. lacustris X I. verna.

The count of 2n=32 in Cristata may also be possible if, as in a few Ensiberians*, some plants shed any extra numbers of chromosomes reverting to that of the pod parent. IMHO, another indication I.lacustris may have been the pod parent.

*Of the first four chromosome counts made on the seedlings from JI X Siberian, three plants showed 2n=26 and one showed only 2n=24 yet all exhibited clear signs (to me, anyway) of being hybrid.

The lack of genetic diversity in Lacustris can be easily explained as a species in decline due to inbreeding. As any population ages and individuals are lost the gene pool is depleted. With each generation the remaining gene pool would become more homogenized with the effect escalating as more genes are lost in propagation by seed.

Interestingly, Kohlein mentions a mountain form of Iris verna with noticeably different features suggesting another species. Since the reported range of this atypical I. verna overlaps that of Cristata (South Carolina and West Virginia), a chromosome count may shed light on a possible relationship to I. cristata. (*The Ensiberians initially showed a resemblance to one parent or the other but no blended forms.) A count of 2n=36 would hint that it may be a second surviving form of a hybrid between I. lacustris and I. verna.