Thursday, October 1, 2020

Is Distichlis spicata (Saltgrass) precocious at Cheesequake State Park?

Distichlis spicata (Saltgrass)

During my last trip to Cheesequake State Park, I noticed that in the area closest to the entrance of the walkway to the Crabbing Bridge, there were quite a lot of dried up small seedheads poking out from the grass.

Not knowing what they were I used my macro to take a few photos of the seedheads (amazingly enough, the macro could focus on faraway and smaller items).

Distichlis spicata (Saltgrass)

When I got home, I was delighted to find out that the grass was another of the common species inhabiting salt marshes. Distichlis spicata is a small-sized perennial that is extremely salt tolerant, and can expand via both stolons and rhizomes. It tends to be found in the high marsh, and the interesting thing about the species is that it is dioecious, with male and female flowers residing on separate plants.

Although such an arrangement is common in animals, in sessile plants this might mean that population growth in the species is slower because the plants cannot self-pollinate. There is also 50% less pollen in the population, and the direction of travel of pollen makes a difference. If pollen goes from one male plant to another male, then it is wasted, although this can be somewhat negated by using vectors such as insect pollinators that can be pushed in one direction.

Distichlis spicata (Saltgrass)

Nevertheless, many species of plants are dioecious, so the mechanisms by which they compete against monoecious plants have been investigated.

Some studies have suggested that long lived perennials achieve this by the dioecious female producing many more seeds than their competitors. Another possible mechanism is to flower earlier during the lifecycle, so that the population size grows incrementally faster, and some papers have seen this happen as well.

As a wind-pollinated grass with no insect pollinators, one has to wonder whether D. spicata uses one mechanism or the other (or maybe both), but some studies show this species has low seed production. So the question is whether D. spicata flowers earlier in its development, or whether its ability to spread and dominate an area comes through some third option. Perhaps vegetative reproduction through rhizomes is the secret weapon that it uses to overcome the dioecious dilemma.

There's so much we don't know about our fellow inhabitants on Earth! 

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