Denny S. Fernandez (University of Puerto Rico – Humacao) firstname.lastname@example.org
Tom A. Langen (Clarkson University) email@example.com
Explaining Latitudinal Patterns of Species Diversity
Geographic patterns of biodiversity, especially species richness (the number of species in a locality, often
alternatively referred to as ‘species diversity’ or biodiversity), has fascinated ecologists since the time of
the great explorer and geographer Alexander von Humboldt. The species-area relationship (the larger the
island, the more species) has been known since Augustin de Candolle in 1820.
Latitude, a measure of distance from the equator (or toward the poles), has long been known to be
associated with species richness, at least for non-marine organisms. The lower the latitude (i.e. closer to
the equator) the more species at a location. Read the appropriate section of your text (e.g. Molles:
Ecology-Concepts & Applications, sections 22.3 & 22.4, pp 501-508). There are a number of alternative
hypotheses for what causes the latitudinal pattern in species richness, including the same factors that
account for geographic patterns of primary productivity and others that are related to time and area; for a
review of hypotheses for global patterns of species richness, see Gaston (2000) and Willig et al. (2003).
Note that species richness always increases with area sampled: bigger places span a larger range of
climatic conditions and contain more habitats. Thus, a comparison of places that differ greatly in size can
be misleading. Large countries (and large states) will have often have more species than small, even if
the small has far more species at any one point location. For geographic comparisons, it is always best to
compare localities that are similar in area.
The objectives of this activity are for you to begin to learn how to (1) search for publicly-available
ecological information using the web, (2) graph an outcome variable of interest (e.g. species richness)
against various putative predictors, and (3) evaluate alternative factors that may account for patterns of
Gaston KJ (2000) Global patterns in biodiversity. Nature 405:220227
Willig MR, Kaufman DM, Stevens RD (2003) Latitudinal Gradients of Biodiversity: Pattern, Process,
Scale, and Synthesis. Annual Review of Ecology, Evolution, and Systematics34 :273-309
Biological Inventories of the World’s Protected Areas
Conservation International Global Biodiversity Hotspots
NOAA National Climate Data Center http://www.ncdc.noaa.gov/oa/ncdc.html
1. You will be assigned a taxon to study (e.g. freshwater fish, birds, snakes, frogs, vascular plants,
2. With your group, make a list of plausible hypotheses that would account for patterns of global
variation of species richness of the taxon.
3. Collect a geographically diverse set of estimates of species richness (number of species). Your
group should have at least twenty data points (twenty different locations) that span at least 30
degrees in latitude.
a. Search (using Google, Google Scholar, JSTOR etc.) using the name of the taxon
(popular or scientific) + species richness, or species diversity or biodiversity or
species list. You may also add a geographical search term, e.g. Colombia, Mexico, New
b. Good sources of information include research papers (especially biological surveys or
biogeographical comparisons), international conservation organizations (e.g.
Conservation International, International Union for Conservation of Nature (IUCN), and
governmental agencies involved in conservation (e.g. US Fish & Wildlife Service,
c. Alternatively, use data on biodiversity of the world’s parks and protected areas at the
website Biological Inventories of the World’s Protected Areas . Make sure to check the
metadata to make sure that the data site is complete. Your instructor will help you with
this. You will need to use GoogleEarth to find the latitude.
4. Make a table that includes the following information: Species Richness, Location, Latitude, Data
a. You can find the latitude by entering the location in Google Earth.
5. Make a graph of species richness (y axis) against the absolute value of latitude (x axis).
a. Is there a relationship between latitude and species richness?
6. Collect data on one measure of precipitation (e.g. average monthly precipitation, number of
months with precipitation, total annual precipitation etc.) and one temperature related variable
(e.g. average monthly low temperature, average monthly high temperature, average temperature
a. I have added links on the course Moodle site that provide global data on precipitation and
b. Add your two climate variables onto your table
c. Graph species richness (y-axis) against each of your climate variables
d. What predictor variable (latitude, temperature, precipitation) is most strongly associated
with species richness? Why might that be?
Your group will make a 5 minute presentation on your study. Make sure to explain (1) what taxon you
were assigned, (2) major plausible hypotheses that could account for geographic patterns in species
richness, (3) present your three graphs and explain what they show, and (4) explain what you conclude
about patterns of species richness. (5) What would be the best next variable to graph against species
richness if you want to continue to test the most plausible hypotheses?
Written reports will be done by each individual, not as a group. Make sure it has (1) a brief Introduction.
This intro will provide an intro to what taxon you were assigned to study, and major candidate
hypotheses for geographic patterns of this taxon. (2) Methods. Provide your data sources, and how you
located them. What (if any) were your rules for including or excluding studies/data? (3) Results. Include
your data table and the three graphs (Make sure figures have legends and the table has a header). Make
sure to state what (if anything) you can infer from each figure. (4) Discussion. What can you conclude, if
anything, about the causes or correlates of geographic patterns in species richness. What problems with
the data you used (if any) could have obscured real patterns or created spurious ones? If you were to
continue to test hypotheses about the causes of geographic patterns of your taxon, what one potential
predictor variable would you next want to evaluate?
You will be graded on both your written report and the oral presentation. Both will be evaluated for
scientific understanding, completeness, and clarity. 65% of your grade is based on the written report, 35%
on the oral report. I will grade the written reports. I am a stickler for clear, clean prose – you should plan
to visit the writing center if your writing is poor. Although this is not a lab, you may want to look at my lab
writeup template, posted on Moodle, to get an idea of the kinds of things I look for. Late written reports
will be docked 5% each week they are late. Oral presentations will be evaluated by both the class and me
(50% grade based on class judgment, 50% by the professor).
To detect ‘free-riders’, I will ask each of you to assess the relative efforts of all group members on the oral
presentation. For example, in a group of 5, if in your judgment everyone contributed equally, than each
would be credited with 20% effort but if one person did the lions-share, you might credit that person with
80% and the other four with 5% effort each. I will use the median score of all of the group members’
rankings to weight the oral presentation grade. Thus someone who works less than other group members
will be penalized, someone who works relatively more will be rewarded.
Title: Explaining Latitudinal Patterns in Species Diversity
Author(s): Denny S. Fernández & Tom Langen
Institution(s): University of Puerto Rico at Humacao, Humacao, Puerto Rico - Clarkson
University, Potsdam, New York
The Ecological Question:
General: What causes patterns in species richness?
More specific: What causes latitudinal gradients in biodiversity?
distribution of organisms
What Students Do:
1. Use and process data on the geographical (latitudinal) distribution of
2. Graph data, and examine to look for patterns.
3. Propose mechanisms/hypotheses to explain latitudinal gradients of
biodiversity (i. e.: species richness.)
4. Select mechanisms/hypothesis to be tested.
5. Look for data to compare/correlate with the biodiversity distribution
6. Use provided data to compare/correlate with the biodiversity distribution
7. Perform statistical (at least exploratory) analyses to test the explanatory
8. Discuss alternative mechanisms/hypotheses, multiple or concurrent
effects, regional or local effects, for biodiversity patterns (see Faculty
It is suggested to incorporate, along the implementation of the activity, a student-
active teaching approach with the 5Es format (Engagement, Exploration, Explanation,
Elaboration, Evaluation). The following are examples of this approach within this
● Engagement - Brainstorming on main ecological concepts (i. e.:
● Exploration - Using GoogleEarth to map biodiversity using georeferenced
species’ image collages, hot spots, et c.
● Explanation - Informal groupwork will generate questions and formulate
hypotheses/predictions about information previously presented in the
22 March 2011
exploration phase (biodiversity map, for example.). During the assigment
the explanatory phase will be fully developed.
● Elaboration - As part of an assignment and oral presentation, the students
will formulate alternative hypothesis on the relationship of biodiversity
and abiotic variables and/or ecological processes or interactions. Open-
ended inquiry to formulate questions/ explanations/hypothesis on diverse
biodiversity related questions.
● Evaluation - A short presentation/essay to review and assess the
process/activity, and it use in other subjects/context for a continuous
learning (life-long learning.)
Main learning/research skills that the students will practice:
○ search for data sets (use of search engines and navigation through
○ evaluation and selection of reliable information,
○ organize data for exploratory analysis (spreadsheet,)
○ construction and interpretation of graphs (spreadsheet, R,)
○ map interpretation and measurements (maps, R, GIS,)
○ data management (database) and statistical analysis (correlation and
Assessable Outcomes and Methods of Assessments:
Pre- and post-test with rubric (Student Assessment of their Learning Gains:
Classroom Assessment Techniques, for activity knowledge and skills, from:
Transferable to specialized courses like: Ecosystem Ecology, Global Changes,
Biogeography, Conservation, but also serves as a research assignment in non-specialized
courses, like: Environmental Studies, Introductory Ecology. With proper guidance may
be used in pre-college (high school). Geographical location is not important to
implement the activity, and any college student capable of using a computer connected to
internet may be prepared to do the activity.
(For an updated and interactive list of databases please link to:
○ Papers with datasets on taxonomic richness (example: Monjeau et al. 2009
Latitudinal Patterns of Species Richness Distribution in South American
22 March 2011
○ Websites of conservation organizations, natural reserves, government
agencies in charge of wildlife, USGS, Forest Service
○ wolframalpha.com (for climate data from specific geograpical locations.)
○ cdiac.ornl.gov/climate/temp/temp_table.html (for temperature data).
○ rredc.nrel.gov/solar/pubs/redbook/ (for solar radiation.)
○ http://nsidc.org/data/nsidc-0272.html (GLIMS glacier database - for
extension and frequency of glaciations.)
○ http://www.climatediagrams.com/countrylist (Climate diagrams of the
world, more than 3000) – to assess latitudinal climate variation and
correlate with biodiversity.
The main purpose of this activity is to expose the student to a research question that
requires the use of large scale datasets. It will not be an exclusive answer for the question
on what determine the latitudinal gradient of biodiversity - some variables are indeed
correlated among them (i. e.: temperature-radiation) - but part of the exercise is to
evaluate alternative explanations and to confront with the complexity of ecological
3. The Data Sets
At least one dataset for species richness and variables that may explain biodiversity
distribution will be available in case the time separated for the activity does not allow for
searching the internet. What follows is a link to a data set for South American carnivores
from Monjeau et al., 2009:
More database links can be found in the activity’s spreadsheet of databases (see Source.)
4. Student Instructions:
I. For introductory discussion:
You should come prepared to discuss the following concepts: biodiversity,
species richness, hot spots
II. For the assignment (writing report):
1. You will be assigned a taxon to study (e.g. freshwater fish, birds, snakes, frogs,
vascular plants, rodents, et c.)
2. Collect a geographically diverse set of estimates of species richness (number of
species). Your group should have at least twenty data points (twenty different
locations) that span at least 30 degrees in
22 March 2011
a. Search (with Google, Google Scholar, JSTOR etc.) using the name of
the taxon (popular or scientific) + species richness, or species diversity or
biodiversity or species list. You may also add a geographical search term,
e.g. Colombia, Mexico, New York.
b. Good sources of information include research papers (especially
biological surveys or biogeographical comparisons), international
conservation organizations (e.g. Conservation International, International
Union for Conservation of Nature (IUCN), and governmental agencies
involved in conservation (e.g. US Fish & Wildlife Service, Environment
3. Make a table that includes the following information: Species Richness,
Location Name, Latitude, Data Source.
a. You can find the latitude by entering or looking for the location in
Google Earth. You may use a band (range of latitude) if your location
areas are big.
4. Make a graph of species richness (y axis) against the absolute value of latitude
a. Is there a relationship between latitude and species richness?
5. With your group, make a list of plausible hypotheses that would account for
patterns of latitudinal/geographical variation of species richness of the taxon.
a. Include in your hypotheses two about temperature and precipitation
variations and their correlation with species richness.
6. Collect data on one measure of precipitation (e.g. average monthly
precipitation, number of months with precipitation, total annual precipitation et c.)
and one temperature related variable (e.g. average monthly low temperature,
average monthly high temperature, average temperature et c.) You may include
other variables, according to your hypotheses.
a. Add your two climate variables (and others) onto your table.
c. Graph species richness (y-axis) against each of your added variables.
d. What predictor variable (latitude, temperature, precipitation, others) is
most strongly associated with species richness? Why might that be?
III. For the oral presentation:
Students with the same taxon will form a group.
Your group will make a five minute presentation on your study. Make sure to
a. what taxon you were assigned,
b. major plausible hypotheses that could account for geographic patterns
in species richness,
c. present your three graphs and explain what they show, and
d. explain what you conclude about patterns of species richness.
22 March 2011
e. What would be the best next variable to graph against species richness if
you want to continue to test the most plausible hypotheses for your data?
f. Are there other similar studies in different continents? At a more
5. Faculty Notes:
Pre-test (if adopted)
A class session is used to engage students in the activity, and to explain the subsequent
components of the activity (assignment and oral presentation.)
a. Introducing the concept of biodiversity. A concept map is recommended to
build a working definition of biodiversity. Once students suggest words related
to biodiversity, the teacher provides help to construct different definitions. Try to
reach (or propose, without forcing) a general and flexible concept, like:
“biodiversity is the variety of life, in all its manifestations” (Gaston & Spicer,
2004.) Discuss the different ways that “variety of life” may be expressed
(ecological, organismal, genetic.)
b. Present species richness (part of organismal diversity) as the common way to
measure biodiversity. Guide the students on the discussion of at least one of the
following issues regarding the use of species richness (from Gaston & Spicer,
i.number of species and dissimilarity among them (in the number of
individuals per species, for example.) The concept of evenness and its
inclusion on the measurement of diversity indexes.
ii.valuing biodiversity for conservation decisions. Is species richness more
important than ecosystems diversity?
iii.definition of species. There are at least seven species concepts (but the
morphological species concept is widely used for most organisms.)
iv.different kinds of diversity. Is an assemblage of two species of rodents
equally diverse compared to an assemblage, equivalent in size, of a
species of rodent and a species of shrimp? In general, species richness is
a good surrogate for biodiversity at other taxon level.
c. Show an interactive map (GoogleEarth) with tagged locations (the tag may
show number of species of a selected taxon, and pictures.) Ask the students to
infer patterns of species richness distribution. The students may take note
of the numbers in different localities and make tables in the blackboard.
Explain the use of GoogleEarth to obtain latitude and longitude
d. Explain the assignment. Although the description of the assignment will
be given in writing, some specifications on the components of the
assignment may require detailed explanation:
i.The students must be clear on the identity and components of the
22 March 2011
ii.A list of general biological databases must be listed in the written
iii.Explain where and how to collect climate variable data.
iv.Advice on the use of software and format of the documents to be
produced and how to be delivered.
v.Explain the format that you want for the report.
vi.Describe how is going to be done the evaluation of the assignment,
and the weight of each part.
vii.Time to complete the assignment must be at least two weeks. Tell
them if you are willing to review drafts of the final report.
e. Explain the oral presentation. The oral presentation is a group task by
all the students with the same taxon (not more than five, but if there are
more students for the same taxon, then subdivide them.) Stress out the
timing (five minutes plus two questions) and the minimum requirement of
information. Explain the elements of the presentation that you are going
to evaluate with the rubric. The oral presentation may be scheduled one
week after the assignment report due date, and may include some feedback
from the professor, based on the report.
Post-test (if adopted)
Comments on Challenges to Anticipate and Solve:
1. Many [data] students lack the skills [ability?, knowledge?] to construct [make?]
an appropriate graph for a [specific] purpose. Diagnostic and solutions:
a. Pre-assessment of graphing abilities (in the context of any course topic.)
b. Workshop, module, or lab on interpreting and creating graphs.
2. Lack of training on effective (?) web searching. Inappropriate (for this activity)
use of search engines. Solution:
a. Short exercise on database search [class or lab?]
3. Lack or poor computing abilities to manage databases [or their formats] to obtain
useful data or information. Solution:
a. Exercise with databases with different formats and more data than
necessary for a specific purpose.
4. Resistance to (or lack of confidence with) new or different evaluation methods.
a. Explain the purpose, objective, and goals of the activity.
b. Present the added value for their future professional development [ ? ], in
terms of learning new skills.
c. Offer bonuses/recognition for best reports/presentations, or efforts beyond
22 March 2011
5. Hard to find or disperse data for some groups of organisms. Solutions:
a. Do your own research to show/guide the students with troubles [?] with
6. Lack of standardization of the data. Diverse methodologies, and sampling efforts.
a. Explain how to standardize the data, in general and using examples with
Comments on the Activity Description:
Comments on Introducing the Activity to Your Students:
What follows are suggested clarification issues that may be discussed during introduction or as
the students come with doubts:
1. To explain diverse measurements of biodiversity (Magurran 2004 – Measuring
2. To clarify and agree on the proper terms and units for abiotic variables.
3. To explain the concept of species density as a way to avoid the effect of sampling
area and its bias in the comparison between locations.
Comments on the Data Collection and Analysis Methods Used in the activity:
Depending on the infrastructure of each institution, the students may require a training section on
the use of literature databases and obtaining specific references.
If you know that students may have not all access to Excel (Microsoft), you can introduce them to
the use of OpenOffice (Sun Microsystems) that is free, as well as GoogleDocs
It is recommended to use a common platform to share data and documents (Blackboard,
The type and depth of statistical analyses to test the hypotheses will depend on the level and
preparation of the students. The minimum requirement is to construct a graph and have a
notion on correlation among variables.
Comments on Questions for Further Thought:
Alternative activities for the assignment:
● to correlate species richness (or other indicator of biodiversity) from different
locations (according the latitudinal gradient) with solar radiation.
22 March 2011
● to obtain information on the temperature (or energy) requirements (ranges) of
diverse taxonomic groups and relate to their geographical (latitudinal)
distribution, and discuss theories that explain the distribution of organisms.
● to correlate biodiversity with latitudinal/regional variations in:
resource/energy availability (primary productivity, decomposition rates),
climatic variation (seasonality, extremes), geological events (glaciation)
● to formulate other/new hypothesis on the causes of organism distribution on
the planet. Other factors that are to be considered? Differences between
terrestrial and marine environments?
Comments on the Assessment of Student Learning Outcomes:
1. IRB exception
2. Pre- and post-tests, with rubric. Analysis
3. Classroom and activity assessment tools
4. Rubric for the oral presentation
5. Reflective essay
Comments on how using large datasets can be more effective in teaching selected
1. “Field work” like research (field is the planet).
2. Use of real data, that will give the experience of dealing with variability, lack
of fit, and uncertainty.
3. Working with public large datasets facilitates the teaching of connected (or
supposedly connected) concepts in ecology, under different conditions at a large
geographic scale (biodiversity and food webs, primary productivity and decomposition, et
4. Connections with geography, biogeography, geology, economics, et c.,
introduce the interdisciplinary character of ecological science.
Comments on Translating the Activity to Other Institutional Scales or Locations:
Gaston, K. J. and J. I. Spicer. 2004. Biodiversity. An Introduction, 2nd ed. Blackwell
Publ., Malde, MA, USA
Kaufman, D. 1995. Diversity of New World mammals: universality of the latitudinal
gradients of species and bauplans. J. Mammalogy, 76(2):322-334
22 March 2011
Monjeau, J. Adrián; et al. 2009. Latitudinal patterns of species richness distribution in
South America carnivores. Mastozoologia Neotropical, in press
Sax, D. F. 2001. Latitudinal gradients and geographic ranges of exotic species:
implications for biogeography. J. Biogeography, 28:139-150
Willig, M. & M. Gannon. 1997. Gradients of species density and turnover in marsupials:
a hemispheric perspective. J. Mammalogy, 78(3(:756-765
22 March 2011