Endangered native finds reproductive success in numbers.
By Beth Goulart
Like blades of Johnson grass in a flooded backyard, leaves of Zizania texana wave below the surface of the San Marcos River, occasionally reaching their green tips up into the air. When it flowers, the plant’s feathered stalks peek above the ripples, too. The endemic species, commonly known as Texas wild rice, joined the federal register of endangered species in 1982, and today it grows only along a 2-mile stretch of the San Marcos River in Hays County. According to F.M. Oxley, a conservation biologist at Austin’s Lady Bird Johnson Wildflower Center, only around 2,000 individual plants exist in the wild today. When a plant’s numbers get that low, conservationists start to talk about reintroduction — growing specimens in captivity, then planting them in the wild to increase the population. That’s exactly what Oxley and others would like to do. First, though, they need to know a bit about how the plant works. For instance, how close together should they sow plants to maximize their chances of survival?
Texas wild rice, like many flowering plants, reproduces sexually via pollen and ovules. One grain of pollen from one plant must reach one female flower of another plant so that fertilization can occur, resulting in a seed. How far pollen can travel, then, determines how close together the plants should be. A study Oxley recently published with several colleagues revealed just how close Z. texana likes its neighbors: A significant proportion of its wind-borne pollen, it turns out, travels less than 75 centimeters from the flower that releases it. So if there’s no flower to pollinate within a few feet, chances are that a grain of pollen is doomed — it will likely never reach a flower and produce seed. The takeaway? When reintroducing Texas wild rice, “we need to put lots and lots and lots of plants out in a particular place,” says Oxley, “close enough so that pollen can get from one plant to the next.”
Texas wild rice is technically edible, but it’s not often eaten. It’s in the same family as the familiar white rice consumed around the world and shares the same genus with the nuttier, darker colored “wild” rice at the health-food store. Although it’s unlikely to become the next overnight food sensation, there’s still reason to save it from extinction. “If Texas wild rice goes away,” says Oxley, “we know that it’ll impact things like habitat for the fountain darter,” an endangered fish that lives among the rice plants. “Could the fountain darter find another plant to use as habitat? Maybe. We don’t know.” Reintroduction plans are underway, but no firm dates are in place yet. For the time being, recreationists on the San Marcos River can help Texas wild rice rebound by paddling clear of it. Floating over it in tubes, kayaks and canoes doesn’t bother it, but it can uproot easily if grabbed or pulled by feet walking through. And if you see flower stalks above the surface, veer the other way. Submerging may prevent flowers from pollinating at all.