In the previous post (was it really five weeks ago?), I described our project to try to see native species in 95% of the 252 or so of the native vascular plant families in North America (defined here as that part north of the U.S.-Mexican border). In that post I simplified things by saying that vascular plants were basically ferns, conifers, and flowering plants. But in this post I want to delve into that in greater detail, to provide context for one of our target families, and also comment on why it is interesting to focus on the family level.
Addressing the latter topic first, there are some groups that have few enough species in North America that it is possible to see the majority of them with sufficient effort. For example, there are around 700 species of regularly occurring bird species (plus a couple hundred rare strays from other parts of the world); a similar number of butterflies; about 450 mammals; and around the same number of odonates (dragonflies and damselflies). In contrast, there are on the order of 20,000 native vascular plant species in the same region. This is too many species to actively look for all of them. But to grasp the variety of plant life in the region, one might focus on a higher taxonomic rank.
On average, species within a genus are more similar to one another than to species in other genera, so trying to see at least one species in each genus would capture the bulk of the variation present. But this is still a large number — I don’t have a precise total but it is in the range of three thousand native genera. However, continuing the logic, genera within the same family are on average more similar than those in different families, so trying to see at least one species in each family would still sample much of the diversity. This proves to be more tractable, there being about 250 native vascular plant families in North America. This is the motivation for our tracking down families of native vascular plants we’ve not seen in North America. A similar approach has been adopted by quite a number of birders, who seek the roughly 250 families of birds worldwide, to appreciate the variation among the 10,000 plus species.
So what is a vascular plant? If you are about my age, you probably learned in grade school that living things were divided into three or four kingdoms: Animalia, Plantae, and one or two kingdoms of single-celled organisms. Animalia has remained pretty much unchanged since then, but there is a consensus that Plantae should be defined more narrowly, to exclude fungi (which become a separate kingdom) and also to exclude most algae. So defined, kingdom Plantae includes the informal groups of green algae; bryophytes (mosses and relatives); ferns and allies; gymnosperms (conifers, etc.); and angiosperms (flowering plants). Of these, the green algae and bryophytes do not possess a vascular system (xylem and phloem) and are largely the domain of specialists. In contrast, the remaining groups, in aggregate called vascular plants, are frequently treated together in reference books that are slightly less intractable, and so form a natural assemblage that is somewhat amenable to study.
To dig down one more level, in a widely accepted classification scheme, the vascular plants of the world comprise seven divisions, which are the botanical equivalent of phyla (for calibration, vertebrates all belong in a single phylum, Chordata, with a few other creatures). These divisions are: Lycopodiophyta (clubmosses, spikemosses, and quillworts); Pteridophyta (ferns); Ginkgophyta (a single extant species, the Ginkgo tree); Cycadophyta (cycads); Gnetophyta (Ephedra being the only genus in North America); Pinophyta (conifers); and Magnoliophyta (flowering plants). Most of these divisions are well represented in North America, but the Gingko is only native to China (though planted extensively elsewhere), and there is only a single cycad species occurring naturally in North America, in Florida and Georgia.
The point of all this taxonomic discussion is to understand the significance of our search for Zamia pumila, that lone cycad species. As we had seen many species in each of the other five North American divisions of vascular plants, Zamia represented the plant species we had not yet seen, which was least closely related to any plant species that we had seen. Restated, it was our target of “greatest uniqueness” compared to species we have seen previously. Although our first few months of this year’s travels have focused on new vascular plant families, here was a case of a new division, about three taxonomic levels above family (the intervening ranks being order and class). We would never have another opportunity to add this high a taxonomic rank within North American vascular plants.
Our hunt for Zamia, commonly known as Coontie (a corruption of its Seminole name), was complicated by two factors. First, information on locations for the species are actively suppressed because the plant is rare and because it is such an interesting addition to gardens that people frequently dig it up when they find it in the wild. For example, all sightings in iNaturalist, an on-line natural history record repository, have their detailed location information redacted. Second, it is planted as an ornamental everywhere, especially in state parks, where plantings can be old enough, and in wild enough areas, that it can be difficult to say whether the species is present naturally or through human intervention.
We had only one decent lead to follow up, a location I found in an on-line search of specimen labels in southeastern herbaria. Though nearly all such information was obscured, one collection from a smaller out-of-state source slipped through, and was only about a decade old. It was from a remote section of Ocala National Forest, where human introduction could be positively ruled out. So there we went, and despite all forest service roads having been renumbered in the interim, we located the area based on GPS coordinates. We split up and started walking zigzag search patterns through the pine woodland. Less than an hour later we independently found different plants at just about the same time! We ultimately located about 30 individuals; both male and female plants were in evidence, and the latter had brightly colored orange-red fruit. What a thrill!
To cap off an already outstanding afternoon, in this same area we heard and then saw a clan of Red-cockaded Woodpeckers, a federally endangered species endemic to the southeastern U.S. We boondocked right there, and as dusk descended, and we were sitting in our campsite recording bats, a Bachman’s Sparrow sang its hauntingly beautiful song. Unlike any other North American bird except Hermit Thrush, this sparrow delivers a series of songs at different pitches, seemingly randomly arranged, so that the listener is held in suspense, waiting to hear whether the next song will be higher or lower. The effect is exquisite, and this was the perfect ending to a perfect day.