Convolvulaceae (or Cuscutaceae)
John is on the road so George used the weekly botany trip to reconnoiter Sandhill Crane Park past the west edge of Palm Beach Gardens for an upcoming “Horticultural Taxonomy” class field trip. This small park set among wet marshy-flatwoods alongside the C-18 Canal has a boat launch, and maybe boat activity adds a little botanical kick, including more different grasses and sedges than you find in other postage stamp parks. One of the interesting life forms present is Dodder (Cuscuta), a dandy example of convergent evolution.
Convergent evolution occurs when two unrelated plants or animals evolve similarities independently. For example, porpoises resemble sharks despite absence of relationship, or in our green world, many Euphorbs (Spurges) resemble Cacti to the point of being called “Cacti,” having adapted similarly to harsh desert existence. Now to the point, South Floridians are accustomed to seeing masses of an orange-yellow-greenish parasitic spaghetti vine festooned over other plants. This is the native Love Vine (Cassytha filiformis) CLICK ….(or is it?). Dodder (species of Cuscuta) can look nearly indistinguishable at a casual glance. I’m sure I’ve seen Dodder and thought “Love Vine.”
To make up a figure, precisely 99.8703% of the living spaghetti around here is Love Vine, but biomass is not everything. Dodder is the majority parasite in terms of biodiversity, with at least three species here in Palm Beach County. These doppelgangers confuse many observers, and would be more confusing if Dodders were more common here. (There are plenty in other regions. Over a hundred species.) Don’t take this too much to heart, but to my imperfect eye, Love Vines seem to prefer on average larger woodier prey, and Dodder on average tilts toward lower more herbaceous victims, but both have broad tastes, and overlap undermines that feeble distinction.
The two are unrelated. Love Vine is in the Cinnamon Family (Lauraceae). Lauraceae often have a spicy aroma when crushed, and Love Vine crushes a wee bit fragrant, at least to the gullible or to those with super noses. Flowers of the Lauraceae are unusual for dicots by having flower parts in multiples of 3 (CLICK), which helps distinguish Love Vine from Dodder with its 5 petals.
In the Lauraceae, including Love Vine, the anthers open via little flaps instead of splitting open like garden-variety anthers; the flaps are true of Love Vine, but you need a magnifier to see them. Try it—you can succeed. Dodder traditionally resides in the Morning Glory Family (Convolvulaceae). Like most Morning Glories, its fruits are dry, although otherwise variable depending on the species. (Love Vine has a fleshy fruit.)
Thinking back in evolutionary time, it seems obvious, maybe inevitable, that the Morning Glory Family would spawn parasitic members. Anyone who has ever weeded gardens knows the intimate twining relationships between various weedy “Morning Glories” and the plants they love. It is only a small step for the twining vine to discover the easy life by penetrating the host to extract the host’s fluids. Dodders have not gone completely down that road; some (all?) still retain a slight ability to make their own chlorophyll.
Botany has an “oh my” side: the Secret Lives of Plants: bloodthirsty carnivores, terrorist poisons, bombastic fruits, murdered pollinators, and secret symbioses. An oh my in the air these days is the ability of plants to “smell.” Outside the blogosphere and into actual plant physiology, plants can truly use chemical signals in the air. The more we learn about the fine fine fine aspects of gene control, probably the more of that we’ll sniff out. For example aspirin was originally derived from the plant hormone salicylic acid, a plant-to-plant airborne hormone. Dodder has garnered attention as a green bloodhound recently for what seems to be an ability to find and even select a host by sniffing. Just ask YouTube. CLICK and also CLICK
I wonder what a Dodder does when it smells a Love Vine.