Field Notes: Why leaf quality is important to an insect ecologist.
Posted by: Judith Edwards
Jan. 17, 2017
When we hear the word “insect,” our minds often conjure up images of pesky buzzing creatures who sting or bite us, or destroy all of the vegetables in our garden.
But for Dr. Frances Sivakoff, a postdoctoral insect ecologist from Ohio State University, insects are not only her primary research focus, but also important players in our environment.
“I'm fascinated by insects because of their stunning diversity,” Dr. Sivakoff told us recently. “Not only their physical differences, but also their different life history strategies and behaviors. They are the most species-diverse group on the planet and play an important role in ecosystems.”
If you haven’t already put two and two together, insect ecologists study the way insects interact with the environment. Dr. Sivakoff, for example, is studying how environmental factors control the abundance and distribution of arthropods—those are animals that lack a spinal column and instead have an exoskeleton, segmented body, or jointed appendages.
From common agricultural pests to rare endangered butterflies, Dr. Sivakoff’s research covers arthropods across agricultural, natural and urban landscapes. “I am particularly interested in how changes in habitat quality, which often arise from habitat manipulation, affect species interactions, including those between plants and pollinators, plants and herbivores, and predators and prey.”
So, why would an insect ecologist need to measure leaf area?
The basic strategy for species conservation through habitat restoration usually goes something like this: increase the abundance of the species’ host plants and you’ll support the endangered species. Yet the quality of the host plants—including nutrient content, water content, and leaf toughness—is often overlooked, despite the fact that these factors have a direct impact on insect health.
In this study, the authors tested the impact of both tree removal and stream damming on the quality properties, both physical and chemical, of wetland sedge. Wetland sedge is the primary host consumed by the wetland butterfly, a threatened species, in its larval stage. Removing trees had a negative effect on the quality of the sedge, and in turn negatively impacted the fecundity of female butterflies raised in these plots. While stream damming did not reduce plant quality directly, butterflies raised in this environment showed a change in wing-to-body ratio, which likely led to an increase in the energetic cost of flying—a concept their recapture studies supported.
To quantify sedge leaf areas, Dr. Sivakoff used the CI-202 Laser Leaf Area Meter
to compare leaves grown in different restoration treatments to determine how restoration affects leaf physical characteristics. Using leaf area measurements taken with the CI-202 and dry weight of the leaves, Dr. Sivakoff calculated Specific Leaf Area (SLA) for each leaf.
What does Dr. Sivakoff hope to achieve with this research? “My long term goal as a scientist is to address basic ecological questions in applied systems and to improve the management of insect abundances, whether the goal is to increase them (in the case of species of conservation concern or beneficial species like pollinators) or decrease them (such as agricultural pests or insect vectors of disease).”
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