Maliau insect visitation project (proposal)

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Insect visitors and petal coloration in a Lamiaceae of Maliau Basin, Borneo

Introduction

Animal vectors are an important vehicle for pollen movement in many angiosperms. Organisms such as bees, wasps, ants and birds play a large role in moving around the pollen of sessile plants. There are a multitude of specific characteristics that angiosperm flowers exhibit to attract these specific organisms. Some such cues include flower shape, color, odor and production of nectar (Ruane). Another factor that has been shown to influence composition of stingless bee visitors in a high-sun habitat vs. a high-shade habitat in Lambir Hills [1]. In a single species of angiosperm found in the Maliau Basin Study Center of Sabah, Borneo, multiple insect visitors were observed to interact with the flowers in both high-sun and high-shade habitats.

These flowers have white petals, are approximately 1.25cm in diameter, and 1.50cm tall from the bottom of the ovary to the flower opening. They are dicots that exhibit bilateral symmetry. They have 5 petals, the top two on both sides are completely white, while the bottom 'lip' petal has a bright purple dotted-line leading into the center of the flower. Previous studies have suggested that such coloration is often a 'nectar guide' for pollinators [2]. The flowers also occur in both high sunlight and covered shady areas. After a preliminary hour-long observation, stingless bees, ants, and butterflies were observed to visit (and possibly pollinate) this angiosperm species. The butterflies observed were of the Eurema and Celaenorrhinus genera, but the other species remain unidentified at this time.

Questions

  1. Does the purple coloration pattern on the bottom petal of the species of examination play an important role in attracting insect pollinators and visitors? If the purple coloration is covered, will the composition or frequency of insect visitors change as compared to non-manipulated flowers?
  2. Is there a significant difference in frequency or composition of insect visitors in a high-sun vs. high-shade habitat?

Hypotheses

  1. We hypothesize that the frequency of visitation overall will decrease in the flowers that have the purple coloration covered and that the altered flowers will have a more narrow composition of visitors. Particularly, there may be a reduction in those insect visitors that use visual cues as their primary guidance for reward collection.
  2. We hypothesize that those flowers in the high-shade will have a lower frequency of overall visitors. (Based on a preliminary investigation).

Methods

  1. There will be 3 flower groups: Natural (non-manipulated), covered (purple coloration painted over with white paint) and uncovered (white paint painted onto the upper right petal to control for effects of the painting).
  2. For each of the 3 groups, 4 flowers will be observed for 10 minutes each, 3 times a day. From 9-10am, from 2-3pm and from 5-6pm. Flowers will be chosen at random while walking along the roads and trails of Maliau Basin. Because of difficultly with predicting shade in the extremely variable weather here, rather than choose specific shade vs. sun sites, we will simply record the light condition at the time of observation and attempt to get a variety of light conditions.
  3. 4 sites will be chosen per day with 1 of each flower type (natural, covered, uncovered) roughly together at each site. Sites will be at least 2m apart to reduce the risk of pseudo-replication.
  4. Time, date, and light habitat will be recorded for each flower and during each observation segment, all insect visitors will be recorded (at least to common name) and a few will be captured when possible to be identified to genus and/or species. An 'insect visitors' will be defined as any insect that lands on flower for a full second.
  5. Observations will be collected for three consecutive days, with each observer focusing on four flowers of a different single data type each day (in an attempt to reduce observer bias).

Total number of flowers observed will be 36. There will be 12 control flowers, 12 covered flowers, and 12 uncovered flowers (with an attempt to get around half in the sun, and half in the shade of each type). Each flower will be observed three times in a single day. 12 flowers will be observed per day, 4 by each of the 3 observers.

Analysis

T-test will be run to see if there is a significant difference in the frequency of visitation between the control, covered, or uncovered sites. T-tests will also be run to see if there is a significant difference between the sun and shade sites within each flower group.

Another test will be used to see if there is a significant difference in the species composition between the control, covered, or uncovered sites. The same will be done for each flower type in the sun vs. shade habitats.

It is also possible to analyze differences in frequency or composition of insect visitors at our 3 different data collection times.