Biodiversity spiders

timer Asked: Oct 28th, 2018
account_balance_wallet $30

Question description

In this spider data analysis exercise, that is divided into three parts, you will classify and analyze data on spider communities to explore the concept of biological diversity and experience its application to decision-making in biological conservation. This week you will complete part 1 (sorting and classification) and part 2 (sample comprehensiveness) of this exercise.

Please use the Spider Data Analysis Worksheet [DOC, File size 2.7 MB] to complete and submit your work. Make sure to save a copy of it to your computer before working.

Just part one and two need to be completed.

BIO 340 Spider Data Analysis Worksheet Excelsior College M1A2: What is Biodiversity? A Comparison of Spider Communities Spiders are a species-rich group of invertebrates that exploit a wide variety of niches in virtually all the earth’s biomes. Some species of spiders build elaborate webs that passively trap their prey whereas others are active predators that ambush or pursue their prey. While spiders are all in one taxonomic group, they represent useful indicators of environmental change and community level diversity because they are taxonomically diverse, with species inhabiting a variety of ecological niches, and they are easy to catch. In the first part, you will identify, sort, and describe the set of characteristics of each individual group of spiders included in Site 1 collection of 50 spiders. You will present the information in a table. In the second part of the spider assignment, you will investigate whether the Site 1 spider collection adequately represents the true diversity of spiders in the forest patch at the time of collection. Were most of the species present sampled or were many likely missed? This is always an important question to ask to ensure that the sample was adequate and hence can be legitimately contrasted among sites in order to, for example, assign areas as low versus high diversity sites. To do this you will perform a simple but informative analysis that is standard practice for conservation biologists who do biodiversity surveys. This analysis involves constructing a so-called “species accumulation,” or “collector’s curve” (Colwell and Coddington, 1994). These curves plot the cumulative number of species observed against the cumulative number of individuals collected and classified. The slope of the species accumulation curve will decrease as more individuals are classified and as fewer species remain to be identified. More information was provided in the required reading from the Princeton Guide to Ecology (Colwell, 2012). See also Figure 3 in this guide for an example of a species accumulation curve. This activity measures Module Outcome 3. Please follow the instructions for Parts 1 and 2 below. Part 1: Sorting and classifying a spider collection For this assignment, you will use this Spider Data Analysis Worksheet. Make sure to save it to your computer before beginning your work. When you have completed Parts 1 and 2 of this assignment, you will submit this worksheet to your instructor. 1. You will investigate a spider collection from a forest patch in Africa. The spiders were captured by a biologist traveling along transects through the patch, stroking a random series of 100 tree branches. a. All spiders that were dislodged and fell onto an outstretched sheet were collected and preserved in alcohol. They have since been spread out on a tray for you to examine. b. Look at Spider Specimens image. The illustrations of the spiders are aligned in rows and columns so that, if desired, you can print a second copy and cut them out with scissors for sorting and identification. Note: printing and cutting are optional. The Spider Specimens are on the next page. 1 BIO 340 Spider Data Analysis Worksheet Excelsior College 2 BIO 340 Spider Data Analysis Worksheet Excelsior College 2. The next task is for you to identify and sort the spiders. You are provided with a high-resolution copy of an identification key to help you identify all the specimens in the collection. Use the Family Key image below. a. To classify the spiders, look for external characteristics that all members of a particular group of spiders have in common but that are not shared by other groups of spiders. b. For example, look for characteristics such as leg length, relative size of body segments, or abdomen patterning and abdomen shape. 3 BIO 340 Spider Data Analysis Worksheet Excelsior College For the next several questions, you will complete the Spider Collection Observation Table with information from your observations. It is located on the next page after Step 5. 3. After you have completed #2 above, now look for groups of morphologically indistinguishable spiders, and describe briefly the set of characters unique to each group. These descriptions will be included in the table under “Distinguishing Characteristics.” Please restrict the descriptions to 15 words. a. These “operational taxonomic units” that you define will be considered separate species. b. To assist you in classifying these organisms, a diagram of key external morphological characteristics of spiders is provided. Note that most spider identification depends on close examination of spider genitalia. For this exercise, however, we will be examining only general external morphological characteristics of different species. Use the Key Spider Characteristics image below. 4. Assign each species a working name, preferably something descriptive. For example, you might call a particular species "small, spotted abdomen" or "short legs, spiky abdomen." These working names will be included in the table under “Species Name.” Please restrict the names to 5 words. a. Just remember that the more useful names will be those that signify to you something unique about the species. b. While working on the identification, label each distinct species of the picture collection on your personal copy using the Species ID (e.g., A, B, C, and so one) corresponding to each ‘Species Name’ in the table. (Hint: there are 50 individuals belonging to 13 distinct species at ‘Site 1’) c. The first individual in the upper left corner will belong to species A; work your way left to right, and then down to the next row. The next spider to the right of the first one, being different from the first one, will belong to species B and so on (Hint: species A has 7 individuals). 5. You will use these data for part 2 of this assignment. Complete Table 1 (20 points) listing each species, its distinguishing characteristics, the name you have applied to it, and the number of individuals of the species in this collection. 4 BIO 340 Spider Data Analysis Worksheet Excelsior College Spider Collection Observation Table (For use with Steps 3 – 5) Species ID A Species name Distinguishing characteristics Number of individuals B C D E F G H I J K L M Part 2: Assessing the comprehensiveness of the collection Using the spider collection from forest Site 1, create a graph that depicts the species accumulation curve. Refer to Figure 3 in the Princeton Guide to Ecology (Colwell, 2012) for an example of a species accumulation curve. The y-axis values are number of species observed. 6. What variable will go on the x-axis? (5 points) Species Accumulation Curve 5 BIO 340 Spider Data Analysis Worksheet Excelsior College 7. Using the graph template on the next page, draw a graph (20 points), label axes x (5 points) and y (5 points) and add a caption in the space provided under the graph (5 points). Also answer the questions that follow for the graph Instructions on creating a curve To construct the species accumulation curve for this spider collection, choose a specimen on the Site 1 spider collection sheet at random. This will be your first data point, such that X = 1 and Y = 1, because after examining the first individual you have also identified one new species! Next move consistently in any direction to a new specimen and record whether it is a member of a new species. In this next step, X = 2, but Y may remain as 1 if the next individual is not of a new species or it may change to 2 if the individual represents a new species different from individual 1. Repeat this process until you have proceeded through all 50 specimens on your Site 1 sheet and construct the collector’s curve from the data obtained (just plot Y versus X) As you will see, the species accumulation curve is an increasing function with a slope that will decrease as more individuals are classified and as fewer species remain to be identified. If sampling stops while the curve is still rapidly increasing, sampling is incomplete and many species likely remain undetected. Alternatively, if the slope of the collector’s curve reaches zero (flattens out), sampling is likely adequate as few to no new species remain undetected. Please also answer the following questions: 8. Does the curve for forest Site 1 flatten out? (10 points) 9. If so, after how many individual spiders have been collected? If not, is the curve still increasing? (10 points) 10. Based on the shape of your species accumulation curve, do you feel this spider collection is an adequate representation of spider diversity at the site? Please explain your answer. (20 points) If you have any questions or concerns about any of the tasks associated with this activity, please get in touch with me and your peers in the Course-Related Questions discussion. 6 BIO 340 Spider Data Analysis Worksheet Excelsior College X-axis label: Y-axis label: Caption: References Berland, L. 1955. Les arachnides de l'Afrique noire française. Dakar, IFAN, 130 p. Coddington, J. A. and H. W. Levi. 1991. Systematics and evolution of spiders (Araneae). Annual Review of Ecology and Systematics 22:565-592. Stiassny, M.L.J. 1997. Systematics and conservation. In G.K. Meffe and R.C. Carroll (eds.) Principles of Conservation Biology, Second Edition, pp. 7072. Sinauer Associates, Inc., Sunderland, MA. Stiassny, M.L.J. and M. de Pinna. 1994. Basal taxa and the role of cladistic patterns in the evaluation of conservation priorities: a view from freshwater. In P.L. Forey, C.J. Humphries, and R.I. Vane-Wright (eds.), Systematics and Conservation Evaluation, pp. 235-249. Clarendon Press, Oxford. Gibbs, J. P., Ian J. Harrison, I. J., & Jennifer Griffiths, J. Adapted by Bravo, A. & Porzecanski, A. (2013). What is Biodiversity? A Comparison of Spider Communities. Retrieved from “Copyright 2011, by the authors of the material, with license for use granted to the Center for Biodiversity and Conservation of the American Museum of Natural History. All rights reserved.” Modified by Dana Ghioca-Robrecht (2017) Image credits: CDC Gibbs, J.P., Harrison, I.J., and Griffiths, J. (2013). What is Biodiversity? A Comparison of Spider Communities [Data Analysis Exercise 2]. Retrieved from 7

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