Plants of Southern California: Malacothamnus enigmaticus Project Timeline

For much of my botanical career, I have been confused by the Malacothamnus species in southern California, finding the keys and descriptions challenging to work with. So I was ecstatic when I found Tracey Slotta's 2004 thesis, on the genus Malacothamnus and related genera, online in 2010, hoping to find enlightenment there. Her thesis was filled with information. The historical review in the thesis was fantastic, especially the 1995 comment that "75% of the described taxa are referred to as taxonomically uncertain". I was glad to find I was not alone in finding Malacothamnus mysterious.

I had hoped that she had analyzed the plants called "M. aboriginum" from San Diego County, since I had long suspected these plants were not actually M. aboriginum. The San Diego County plants are disjunct by 540 km (330 miles) from the closest specimen of the population that actually was M. aboriginum, associated with the type specimen for that species. I suspected the only reason the San Diego County "M. aboriginum" had not been described as a new species was that it was so hard to separate Malacothamnus species that no one wanted to take up the challenge to add yet another species to make the task even more difficult.

Unfortunately, Tracey did not measure any of those San Diego County "M. aboriginum" plants, possibly because she was unable to get to most of San Diego County for collecting.

Then in January 2011, I found that M. aboriginum was no longer given as being in San Diego County in the new Jepson Manual Second Edition draft treatment by Tracey! I was left wondering what had happened for several years.

In mid-2014, Keir Morse and I started to discuss Malacothamnus. Keir was also interested in what happened to the "M. aboriginum" plants in San Diego County, and asked what it would take to find out. I said "Measure up a number of plants, and I'll put it in a Principal Components Analysis". We spent the next year noting where we had seen populations in the field, with Keir taking photographs of the ones he saw.

In mid-2015, Keir made the first measurements on 15 fresh specimens that he collected, 19 separate measurements, and I ran the first PCA which immediately classified the specimens into two species, M. fasciculatus and M. densiflorus, which matched quite well what Keir had decided the specimens were by looking at them. This made both of us anxious to find and measure some "M. aboriginum".

To get an idea of where to look, I made voucher plots of the distribution of the three species in San Diego County, and put them online so we could easily consult them. (That original webpage was deleted since we now have a much better map of Malacothamnus in San Diego County.)

Within a few days, Keir had found and measured some "M. aboriginum" specimens. The PCA plot was somewhat ambiguous; one could interpret it as showing three separate species, or that "M. aboriginum" was just an extreme form of M. densiflorus. In addition, there appeared to be structure within the M. fasciculatus plants by themselves, which might simply have been an artifact of having few samples. We concluded we needed more samples, and measurements of additional characteristics that might separate the species better.

In August 2015, Keir started going to herbaria to measure voucher specimens. It took 30 minutes to do all the measurements on a single specimen. He measured two specimens of the real M. aboriginum from San Benito County, and the PCA revealed it was "off the charts" different from any of the San Diego County plants. The additional specimens from San Diego County Keir measured, with the new additional measurements, clearly revealed that the "M. aboriginum" plants in San Diego County were an undescribed species.

We then came up with a list of things we needed to do before we could publish it as a new species, items that we would need for the paper (description of the new species; a map of its geographic range and that of the other species in San Diego County; a key to identify specimens; and the myriad other things that go into a paper), and to make sure we understood everything in our analysis. Keir continued to measure more specimens to give us a more robust data set. We spent a lot of time in the rest of 2015 working on all those things. We also issued a request to our close colleagues for any locations of any Malacothamnus in the Lagunas and Anza-Borrego Desert State Park, so we could analyze specimens from different areas.

We also found a small bias between measurements made from fresh specimens, and measurements from vouchers, so Keir went back and re-measured his specimens after they had been pressed for a month.

Field work prevented us from working further on Malacothamnus for the first part of 2016, with work resuming in August 2016, continuing through December 2016. We started writing the paper in November 2016.

Field work again caused a cessation of work in 2017, with work resuming in September 2017. The first draft of the paper was finally done on 9/30/17. We worked pretty hard on the paper trying to get it in reviewable form for the next three months, and finally had it ready in January 2018.

After a nine month break where we got comments and suggestions on the paper from others, we decided to submit the paper to Madrono. It took most of a month to put the paper in Madrono format, and to do final critical reads and make changes. We submitted the paper on 27 September 2018.

A manuscript number was not assigned until 20 December 2018, and we received the referee reports on 1 April 2019. We spent several weeks revising the paper, and resubmitted it on 30 April 2019. The paper was accepted on 8 May 2019.

We received a copy-edited version of our paper on 14 June 2019, made changes and resubmitted it on 20 June 2019. The paper was available electronically on 1 October 2019, and the print version was received a few weeks later.

This analysis, and writing the paper, was a massive effort, requiring much more of our time than either of us ever expected when we started, and spanning a much longer time interval than we ever dreamed of. But many good projects are like this, so our story is far from unique.

Go to:

• The Malacothamnus Species of San Diego County
• Native and Introduced Plants of Southern California