Some thoughts on ecology, evolution and economics

Flower power

canadaarms1957The floral emblem of Canada – you know, the little garland at the bottom of the coat of arms – has four species.  Each species represents an ancestral homeland of the first settlers of Canada: England (rose), Scotland (thistle) , Ireland (shamrock), and France (lily).  Of course, the coat of arms also has maple leaves which dominated the lands that were originally settled – or at least the St. Lawrence vallley and lower Great Lakes.  That these species had meaning for the people who established Canada goes without saying but I am struck by how representative these plants are of the major groups of flowering plants.

As we discussed last time, the broad-leaved plants or dicots are divided into two major groups, the rosids and the asterids. This division came after the split with the narrow-leaved plants or monocots. A still deeper split occurred among the flowering plants early in their evolution, producing the magnoliids. Of these four groups, three are represented on the Canadian coat of arms, The distinction between monocots (3 & 6 petal flowers) and dicots (4 & 5 petal flowers) is well known. Grains and some root vegetables are monocots while fruits and trees are generally dicots. The distinction between asterids (fused petals, more petals than stamens) and rosids was known to botanists before DNA evidence was available but this advance in evolutionary  science helped confirm and clarify relationships.  The magnoliids ( of which the magnolia tree is the standard bearer) are a newly recognized group that share a common heritage and a distinct kind of pollen.

flower powerRoses and shamrocks are rosids, as is the maple tree. The thistle is an asterid, actually in the same family as the sunflowers and asters from which the group gets its name. The lily is a monocot. Looking across the flowering plants, about 30 % are rosids, a quarter of the species are monocots  and another quarter are asterids. So, perhaps  it is not unexpected that they all be represented on the coat of arms of one country.  There are only 250 species among the magnoliids.   I have included a brief sketch of the relationships among some of our most familiar plants. Most temperate trees are rosids, ash trees being one exception.  Our foods seem evenly divided among the three major groups with the magnoliids claiming the avocado and a few spices.

The species that come to be important in our lives have poetic and/or economic value. Through evolution and biogeography they come to take on historic significance.

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