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The Mass Media

The Mass Media

Tough Talk On Plants

In its series of lectures, the science departments at UMass Boston continue to bring renowned scientists to UMB to deliver challenging lectures on innovative science. Last Friday was no exception.

Benjamin Bolker, a self-described mathematician/biologist/ecologist, addressed a full house for a discussion on the tough world of plant competition. Bolker uses mathematical models to predict species’ survival and proliferation. He employs a relatively new method of using mathematical formulas that ecologists and others can use in planning and aiding habitats.

Bolker comes from an eclectic academic background. He’s studied mathematics, physics, zoology, and biology; he earned a master’s, doctorate, and post-doctorate degrees. He spoke with fervor on his specialty, mathematical ecology.

While much of the discussion flew above the head of this reporter, several ideas managed to take shape. Using a speedy slide show and the space of an hour, Bolker explained some “simplified” and salient points of his method of studying plant data. Bolker showed several models of formulas and diagrams to illustrate his data gathering and informational graphing techniques.

The dominant result sought seemed to be the quest to predict the causes and effects of the “trade-off [amongst plants] between competition and colonization” or “CC.” Very simply put that means that a specific species of plants is either better at competing with other species through a high “birth” rate and/or dispersal of seeds and spores or is better at colonizing – adapting to the environment. All plant species possess both talents but are better at one of them.

Bolker showed graphs depicting the migration of an “invading” plant species into an area already populated by another “native” plant species. Several possible outcomes loom when such migration occurs in the wild. The two species can reach an equilibrium state where both reasonably thrive – barring periodic, outside catastrophes – in the same locale. One can plant species could thrive at the expense of the other. The two plant species may coexist in a segregated region – where each species cluster in groups of their own. Or they may coexist in an integrated region, where plant species A is as likely to have as its neighbor plant species B as it is to live next to one of its own.

Several factors serve as variables in the equation of which possibility is most likely to actually occur. The results depend on the species involved and certain endogenous traits of the plants. Endogenous qualities include fertility and dispersal rates of each plant. It also includes the capacity to adapt quickly to new or changing environments. For example, a plant that can develop the ability to withstand lack of resources in a region that experiences periodic drought would have an edge over ones that cannot.

The exogenous variables include the environment itself, climate, other types of vegetation present, available resources. All plants need nitrogen, water, and sunlight but vary in the amounts they need to survive. Blights, fungi, plant epidemics, natural disasters fall into the category of exogenous forces. Exogenous forces interact with the endogenous. A blight that can migrate into an area and the plants own capacities for resisting the spread of that blight serves as an example.

Bolker specializes in creating something he calls “moment equations” to measure such variables and predict outcomes. One of the studies he’s been involved with aims to see whether invading species can grow and spread in a mono-culture (single species) of a different resident plant. Some of his findings included the fact that invader species in these cases actually hurt themselves by clustering with their own species. Such clustering leads to competition among the same species for the same resources. Inversely, invading species are helped by resident species’ clustering because such spotting provides bare niches for the invading species to take hold.

The resulting fractions of different species inhabiting the same area depends on each species ability to reproduce. It also depends on its ability to disperse itself or to move, its strategy of avoiding other species or coexisting with them, and whether the species benefits or not from high or low density of itself and other species.

Bolker can apply his formulas to the spread of disease among plants. He asks questions such as “how does one cluster of infected plants affect the rest [of the region’s plants]?” Bolker admits to “a little bit of bias” when his data and equations lead him to conclude that plants with short dispersal ranges have a better long-term chance of surviving with a cluster arrangement in partially infected regions. Such plants have a better chance of remaining in a healthy, uninfected environment because they can’t traject their seeds far enough to land in infected clusters farther away. He adds the caveat however, that so far, this tendency is known to occur with predictability only in areas with very little competition between species.

Several UMass Boston students and faculty members peppered Bolker with intelligent questions at the end of his talk. Refreshments were served.