Abstract
Capture-recapture models are important in ecology to understand the populations size of a particular species. It requires a capture and tagging of a population then recapturing them to understand the dynamics. There are several different models to do mark and recapture consisting of open and closed models. A model is a better fit depending depending on the population being used. The Lincoln-Peterson method is a closed model (where population is assumed to not change at each sampling event) that is good for large samples. Here mark and recapture was performed on a population of field crickets Gryllus assimilis nearing an industrialized zone. Trace elements were utilized to which enabled us to easily mark the crickets in the first sample and find marked crickets in the second sample. The methods are explained.
Capture-recapture models are common among ecologists to determine the population size of a particular species. A small but significant portion of the population are captured, marked then released. To estimate and predict the different species it is a problem in ecology. Several models depend on whether it is assumed that the population is open (additions and deletions) or closed (no change because of mortality and emigration). Models like Survival- Cormack-Jolly- Seber use an open system whereas the Lincoln-Peterson model is a closed model. For studying populations of insects a relatively large number of insects can be captured and tagged and then recaptured. A passive diffusion model can also be used where the environment is similar and constant and the individuals are identical (Kareiva, 1983). A closed model is a realistic model that allows the a population to be monitored over a period of time.
Insect movement is important for understanding the migration patterns of the insect and monitoring the environment. Different insect populations have giving insight to the environment (Rosenberg, 1986). Newly urbanized zones might change the habitat of the most vulnerable inhabitants within the region. As insects can be quite flexible we can monitor how quickly they adapt to their surrounding environment. Using mark and recapture methods on a wide area near an industrialized zones we can get a good idea whether these cricket can adapt to urban sprawl. Within this study we are doing a mark and capture experiment using Jamaican Field Cricket Gryllus assimilis. This field cricket only endemic to two regions in the United States specifically, Southern Texas and Southern Florida. They were likely flew to Florida from the West Indies. These crickets are lighter than other Florida crickets with a dense brown pronotum and light yellow eyes. They are also bigger than most other cricket species endemic to North America. Due to their relative small habitat, and larger size this cricket species was a good choice to look at population models in urbanized zones. Although they are within urbanized areas like on roadsides it is interesting to study their behavior when new urbanized areas come about (Alexander, 1962; Weissmann, 2009).
Methods
New techniques have evolved to track crickets within their natural habitat. Markers like fluorescent dust, radioactive tracers, typewriter correction fluid and other paint have been used (Rost, 1987). However, many of these may not be effective small crickets or may interfere with its normal biology. A marker should be easy to use, cost effective and easy to document. Trace elements do not interfere with the insects biology (Armes, 1989) and are retained within the insect tissues without causing toxicity. In this study significant amounts of trace elements rubidium was applied to foliage to 50% of the burrows near urbanized area and and another element cesium (Toal, 1999) was applied to burrows further outside the industrialized zone (Anderson, 1999). The amount of rubidium was monitored by using atomic absorption spectrometry (Berry, 1972).
Study plots for Gryllus assimilis the sampling was located 50 km south of (Southern Florida, FL) in a 10 hectare dry field where a new industrial park was being built on one side from April 15, 2014 - June 15, 2014. The five hectares was divided into five areas and their burrows were marked both with global positioning system (GPS ) and with small flags. This method allowed boundaries where we could work (Rost, 1987). Over the course of the three months there was warm and sunny days (15-25 degrees). We sampled from 11 a.m. to 18:00 five days during the week using atomic spectrometry to observe the trace elements. The markings were recorded to observe the interaction between the different burrows. This traditional method marked part of the different burrows close to the urban zone and observed whether they could be collected within other regions outside the urbanized zone (Joron, 2003)
Lincoln-Peterson model:
N - Population size; n1 - No. of marked animals in the population; n2 - Sample size; m2 - No. of marked animals in sample
Sample, (m 2 /n 2 ) ≈ (n 1 /N), Population
Nˆ =n1n2/m2
Over the sample period we captured at least 50 crickets to see if there was trace elements. The burrows, elements and population within these regions were calculated. The different GPS coordinates were logged and an average distance distance travelled estimated whether urbanization affected the cricket population.
References
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