OVERVIEW

You will read a real professional research report on species diversity.  Some are available only on campus computers or library terminals.  
Then you will answer questions to demonstrate how well you understood it.  You may work alone or with one or two partners who collaborate on one typed report, with all partners receiving equal grades.  You may work anywhere you wish, but the instructor will be available to answer questions and help you with this assignment only during scheduled lab hours.  

How to write the analysis

• *Decadal Change in Vegetation and Soil Phosphorus Pattern across the Everglades Landscape http://jeq.scijournals.org/cgi/content/full/32/1/344 Abstract:  Wetlands respond to nutrient enrichment with characteristic increases in soil nutrients and shifts in plant community composition. These responses to eutrophication tend to be more rapid and longer lasting in oligotrophic systems. In this study, we documented changes associated with water quality from 1989 to 1999 in oligotrophic Everglades wetlands. We accomplished this by resampling soils and macrophytes along four transects in 1999 that were originally sampled in 1989. In addition to documenting soil phosphorus (P) levels and decadal changes in plant species composition at the same sites, we report macrophyte tissue nutrient and biomass data from 1999 for future temporal comparisons. Water quality improved throughout much of the Everglades in the 1990s. In spite of this improvement, though, we found that water quality impacts worsened during this time in areas of the northern Everglades (western Loxahatchee National Wildlife Refuge [NWR] and Water Conservation Area [WCA] 2A). Zones of high soil P (exceeding 700 mg P kg^-1 dry wt. soil) increased to more than 1 km from the western margin canal into the Loxahatchee NWR and more than 4 km from northern boundary canal into WCA-2A. This doubling of the high soil P zones since 1989 was paralleled with an expansion of cattail (Typha spp.)-dominated marsh in both regions. Macrophyte species richness declined in both areas from 1989 to 1999 (27% in the Loxahatchee NWR and 33% in WCA-2A). In contrast, areas well south of the Everglades Agricultural Area, including WCA-3A and Everglades National Park (ENP), did not decline during this time. We found no significant decadal change in plant community patterns from 1989 and 1999 along transects in southern WCA-3A or Shark River Slough (ENP). Our 1999 sampling also included a new transect in Taylor Slough (ENP), which will allow change analysis here in the future. Regular sampling of these transects, to verify decadal-scale environmental impacts or improvements, will continue to be an important tool for long-term management and restoration of the Everglades.

• *Urban Bird Diversity and Landscape Complexity: Species–environment Associations Along a Multiscale Habitat Gradient http://www.consecol.org/vol7/iss1/art5/index.html ABSTRACT
  For birds in urban environments, the configuration of local habitat within the landscape may be as critical as the composition of the local habitat itself. We examined the relative importance of environmental attributes (e.g., tree cover, composition, and number of tree species) measured at different spatial scales in relation to urban bird species richness and abundance. We expected that some bird species and nesting guilds would have a closer association with landscape-level features (within 1000 m), such as proximity to large forested areas, than with local-scale habitat measures (within 50 m). To investigate this, avian community data were collected at 285 point-count stations in 1997 and 1998 along four roadside transects located in Vancouver and Burnaby, British Columbia, Canada. Transects (5–25 km in length) bisected three large parks (>324 ha) and proceeded along residential streets in urban and suburban areas. In total, 48 bird species were observed, including 25 common species. Species richness declined in relation to a gradient of increasing urbanization, as measured by local- and landscape-level habitat features. We further examined the significance and importance of local- vs. landscape-level habitat attributes using logistic regression and found that both scales explained the presence/absence distributions of residential birds. Local-scale habitat features such as large coniferous trees, berry-producing shrubs, and freshwater streams were of particular importance in estimating the likelihood of finding bird species. Landscape measures, particularly forest cover (within 500 m) and park area (measured at different scales as a function of distance from point-count stations) significantly improved likelihood estimations based solely on local-scale habitat features. Our results suggest that both local- and landscape-scale resources were important in determining the distribution of birds in urban areas. Parks, reserves, and the surrounding residential areas should be integrated into urban planning and development designs to maintain resident avifauna and overall species diversity in urban environments.

• Long-term patterns of shrub expansion in a C₄-dominated grassland: fire frequency and the dynamics of shrub cover and abundance.  http://www.amjbot.org/cgi/content/full/90/3/423 Abstract:  Worldwide, grassland ecosystems have experienced a major shift in growth-form dominance as woody plant species have expanded and replaced native grasses. In the C4-dominated grasslands of central North America, a reduction in fire frequency is the most cited cause of this shift in growth forms as fire both enhances grass productivity and constrains the establishment and expansion of native woody vegetation. Using an 18-yr plant species composition data set, we quantified patterns of change in shrub cover, frequency, and species richness associated with three distinct fire regimes. During the study period (1983–2000), shrub cover increased most dramatically in sites in which the frequency of fire was once every 4 yr (intermediate frequency; 28.6%) followed by sites in which fire occurred only once during the 18-yr period (low frequency; 23.7%). Annual fire effectively prevented the recruitment of new woody species, but even with this high fire frequency, shrub cover increased slightly (3.7%). Comparatively, shrub species richness increased by three and six, respectively, in the intermediate- and low-frequency fire sites. These data indicate that within this grassland, periods without fire are necessary for recruitment of both new individuals and additional shrub species; however, once established, shrub cover will increase regardless of fire frequency and even annual fire will not reduce shrub abundance

• *Biodiversity, Community Structural Shifts, and Biogeography of Prokaryotes within Antarctic Continental Shelf Sediment.  16S ribosomal DNA (rDNA) clone library analysis was conducted to assess prokaryotic diversity and community structural changes within a surficial sediment core obtained from an Antarctic continental shelf area (depth, 761 m) within the Mertz Glacier Polynya (MGP) region. Libraries were created from three separate horizons of the core (0- to 0.4-cm, 1.5- to 2.5-cm, and 20- to 21-cm depth positions). The results indicated that at the oxic sediment surface (depth, 0 to 0.4 cm) the microbial community appeared to be dominated by a small subset of potentially r-strategist (fast-growing, opportunistic) species, resulting in a lower-than-expected species richness of 442 operational taxonomic units (OTUs). At a depth of 1.5 to 2.5 cm, the species richness (1,128 OTUs) was much higher, with the community dominated by numerous gamma and delta proteobacterial phylotypes. At a depth of 20 to 21 cm, a clear decline in species richness (541 OTUs) occurred, accompanied by a larger number of more phylogenetically divergent phylotypes and a decline in the predominance of Proteobacteria. Based on rRNA and clonal abundance as well as sequence comparisons, syntrophic cycling of oxidized and reduced sulfur compounds appeared to be the dominant process in surficial MGP sediment, as phylotype groups putatively linked to these processes made up a large proportion of clones throughout the core. Between 18 and 65% of 16S rDNA phylotypes detected in a wide range of coastal and open ocean sediments possessed high levels of sequence similarity (>95%) with the MGP sediment phylotypes, indicating that many sediment prokaryote phylotype groups defined in this study are ubiquitous in marine sediment.

• A Globally Consistent Richness-Climate Relationship for Angiosperms http://www.journals.uchicago.edu/AN/journal/issues/v161n4/010327/010327.html ABSTRACT: Species richness, the simplest index of biodiversity, varies greatly over broad spatial scales. Richness-climate relationships often account for >80% of the spatial variance in richness. However, it has been suggested that richness-climate relationships differ significantly among geographic regions and that there is no globally consistent relationship. This study investigated the global patterns of species and family richness of angiosperms in relation to climate. We found that models relating angiosperm richness to mean annual temperature, annual water deficit, and their interaction or models relating richness to annual potential evapotranspiration and water deficit are both globally consistent and very strong and are independent of the diverse evolutionary histories and functional assemblages of plants in different parts of the world. Thus, effects of other factors such as evolutionary history, postglacial dispersal, soil nutrients, topography, or other climatic variables either must be quite minor over broad scales (because there is little residual variation left to explain) or they must be strongly collinear with global patterns of climate. The correlations shown here must be predicted by any successful hypothesis of mechanisms controlling richness patterns.

• Spatial Grain and the Causes of Regional Diversity Gradients in Ants http://www.journals.uchicago.edu/AN/journal/issues/v161n3/020069/020069.html   ABSTRACT: Gradients of species richness (S; the number of species of a given taxon in a given area and time) are ubiquitous. A key goal in ecology is to understand whether and how the many processes that generate these gradients act at different spatial scales. Here we evaluate six hypotheses for diversity gradients with 49 New World ant communities, from tundra to rain forest. We contrast their performance at three spatial grains from S_plot, the average number of ant species nesting in a m² plot, through Fisher's , an index that treats our 30 1-m² plots as subsamples of a locality's diversity. At the smallest grain, S_plot was tightly correlated (r² = 0.99) with colony abundance in a fashion indistinguishable from the packing of randomly selected individuals into a fixed space. As spatial grain increased, the coaction of two factors linked to high net rates of diversificationwarm temperatures and large areas of uniform climateaccounted for 75% of the variation in Fisher's . However, the mechanisms underlying these correlations (i.e., precisely how temperature and area shape the balance of speciation to extinction) remain elusive.

• Does Herbivore Diversity Depend on Plant Diversity? The Case of California Butterflies http://www.journals.uchicago.edu/AN/journal/issues/v161n1/020139/020139.html ABSTRACT: It is widely believed that the diversity of plants influences the diversity of animals, and this should be particularly true of herbivores. We examine this supposition at a moderate spatial extent by comparing the richness patterns of the 217 butterfly species resident in California to those of plants, including all 5,902 vascular plant species and the 552 species known to be fed on by caterpillars. We also examine the relationships between plant/butterfly richness and 20 environmental variables. We found that although plant and butterfly diversities are positively correlated, multiple regression, path models, and spatial analysis indicate that once primary productivity (estimated by a water-energy variable, actual evapotranspiration) and topographical variability are incorporated into models, neither measure of plant richness has any relationship with butterfly richness. To examine whether butterflies with the most specialized diets follow the pattern found across all butterflies, we repeated the analyses for 37 species of strict monophages and their food plants and found that plant and butterfly richness were similarly weakly associated after incorporating the environmental variables. We conclude that plant diversity does not directly influence butterfly diversity but that both are probably responding to similar environmental factors.

• Explaining Species Richness from Continents to Communities: The Time-for-Speciation Effect in Emydid Turtles http://www.journals.uchicago.edu/AN/journal/issues/v161n1/010178/010178.html  ABSTRACT: Speciation is the process that ultimately generates species richness. However, the time required for speciation to build up diversity in a region is rarely considered as an explanation for patterns of species richness. We explored this "time-for-speciation effect" on patterns of species richness in emydid turtles. Emydids show a striking pattern of high species richness in eastern North America (especially the southeast) and low diversity in other regions. At the continental scale, species richness is positively correlated with the amount of time emydids have been present and speciating in each region, with eastern North America being the ancestral region. Within eastern North America, higher regional species richness in the southeast is associated with smaller geographic range sizes and not greater local species richness in southern communities. We suggest that these patterns of geographic range size variation and local and regional species richness in eastern North America are caused by glaciation, allopatric speciation, and the time-for-speciation effect. We propose that allopatric speciation can simultaneously decrease geographic range size and increase regional diversity without increasing local diversity and that geographic range size can determine the relationship between , , and diversity. The time-for-speciation effect may act through a variety of processes at different spatial scales to determine diverse patterns of species richness.

• *Beta-Diversity in Tropical Forest Trees (http://www.sciencemag.org/cgi/content/full/295/5555/666 ) abstract:  The high alpha-diversity of tropical forests has been amply documented, but beta-diversity--how species composition changes with distance--has seldom been studied. We present quantitative estimates of beta-diversity for tropical trees by comparing species composition of plots in lowland terra firme forest in Panama, Ecuador, and Peru. We compare observations with predictions derived from a neutral model in which habitat is uniform and only dispersal and speciation influence species turnover. We find that beta-diversity is higher in Panama than in western Amazonia and that patterns in both areas are inconsistent with the neutral model. In Panama, habitat variation appears to increase species turnover relative to Amazonia, where unexpectedly low turnover over great distances suggests that population densities of some species are bounded by as yet unidentified processes. At intermediate scales in both regions, observations can be matched by theory, suggesting that dispersal limitation, with speciation, influences species turnover. (NOTE:  Sciencemag articles are not formatted in regular report form; you have to figure out the sections for yourself.)
• *Tree Diversity in Tropical Rain Forests: A Validation of the Intermediate Disturbance Hypothesis http://www.sciencemag.org/cgi/content/full/294/5547/1702?ijkey=rWZGw900o/8o.   Abstract:  The "intermediate disturbance hypothesis," which postulates maximum diversity at intermediate regimes of disturbance, has never been clearly proved to apply to species-rich tropical forest tree communities and to local-scale canopy disturbances that modify light environments. This hypothesis was tested on a sample of 17,000 trees in a Guianan forest, 10 years after a silvicultural experiment that added to natural treefall gaps a wide range of disturbance intensities. Species richness, standardized to eliminate density effects, peaked at intermediate disturbance levels, particularly when disturbance intensity was estimated through the percentage of stems of strongly light-dependent species.  (NOTE:  Sciencemag articles are not formatted in regular report form; you have to figure out the sections for yourself.)
• *Metabolic biochemical hypothesis to explain the latitude rule http://www.sciencemag.org/cgi/content/full/297/5586/1545 (very challenging, lots of math) ABSTRACT: The latitudinal gradient of increasing biodiversity from poles to equator is one of the most prominent but least understood features of life on Earth. Here we show that species diversity can be predicted from the biochemical kinetics of metabolism. We first demonstrate that the average energy flux of populations is temperature invariant. We then derive a model that quantitatively predicts how species diversity increases with environmental temperature. Predictions are supported by data for terrestrial, freshwater, and marine taxa along latitudinal and elevational gradients. These results establish a thermodynamic basis for the regulation of species diversity and the organization of ecological communities  (NOTE:  Sciencemag articles are not formatted in regular report form; you have to figure out the sections for yourself.)
• Coexistence in Metacommunities: The Regional Similarity Hypothesis http://www.journals.uchicago.edu/AN/journal/issues/v159n4/010041/010041.html Abstract excerpts:       Species richness has historically been studied with a separation between small- and large-scale processes. Species diversity has been approached, on the one hand, from a local perspective, based on niche theory and on the other hand, from a regional perspective, through island biogeography (MacArthur and Wilson 1967), with no strong interactions between these two levels. At the local scale, interactions between competing species constrain diversity, and coexistence is a function of niche dimensions and resource heterogeneity (MacArthur and Levins 1967) or differences in species life-history traits as in colonization-competition trade-off models (Hastings 1980; Tilman 1994). At the regional scale, the theory of island biogeography (MacArthur and Wilson 1967) ignores local dynamics and considers local diversity as the result of regional processes such as chance events of immigration and extinction. There are no limits to diversity except those arising from the size of the regional species pool (continent size) and the constraints on immigration events (continent-island distance). This apparent contradiction has been named "MacArthur's paradox" (Schoener 1983; Loreau and Mouquet 1999) because MacArthur's contribution has been central in both niche theory (MacArthur and Levins 1967) and island biogeography theory (MacArthur and Wilson 1967).
       Despite this arbitrary separation of scales, many authors have pointed out that both regional and local processes are acting together to structure local species diversity (see Ricklefs 1987; Zobel 1997 for reviews). In a previous article we studied the influence of immigration (regional scale) on the dynamics of local plant communities. We showed that immigration can be a key factor determining local species richness by maintaining a high diversity in communities in which a single species would persist if they were closed. Immigration intensity also had a considerable effect on species relative abundances and community properties.
       In this article, we go further and study a network of communities linked by dispersal, in which each community acts as a source of immigrants for other communities in the region. Thus, immigration becomes an explicit function of emigration from other communities. Such a network is called a "metacommunity" (Wilson 1992; Holt 1997). We describe the environmental conditions and constraints on species parameters that promote coexistence in such a system. Finally, we investigate the dynamics of species diversity depending on the relative importance of dispersal between communities. Our approach potentially concerns any ecological system in which the dispersal dynamics leads to a spatial structure that permits a distinction between local and a regional dynamics. However, for simplicity we describe our model in terms that concern sessile organisms such as plants.

• Contrasting Effects of Plant Richness and Composition on Insect Communities: A Field Experiment http://www.journals.uchicago.edu/AN/journal/issues/v158n1/000196/000196.html  Abstract:  We experimentally separated the effects of two components of plant diversityplant species richness and plant functional group richnesson insect communities. Plant species richness and plant functional group richness had contrasting effects on insect abundances, a result we attributed to three factors. First, lower insect abundances at higher plant functional group richness were explained by a sampling effect, which was caused by the increasing likelihood that one low-quality group, C₄ grasses, would be present and reduce average insect abundances by 25%. Second, plant biomass, which was positively related to plant functional group richness, had a strong, positive effect on insect abundances. Third, a positive effect of plant species richness on insect abundances may have been caused by greater availability of alternate plant resources or greater vegetational structure. In addition, a greater diversity of insect species, whose individual abundances were often unaffected by changes in plant species richness, may have generated higher total community abundances. After controlling for the strong, positive influence of insect abundance on insect diversity through rarefaction, insect species richness increased as plant species richness and plant functional group richness increased. Although these variables did not explain a high proportion of variation individually, plant species richness and plant functional group richness had similar effects on insect diversity and opposing effects on insect abundances, and both factors may explain how the loss of plant diversity influences higher trophic levels.

• Ecological Biogeography of Southern Ocean Islands: The Importance of Considering Spatial Issues http://www.journals.uchicago.edu/AN/journal/issues/v158n4/000146/000146.html ABSTRACT: Understanding patterns of among-island variation in species richness has long been an important question in ecology and biogeography. However, despite the clear spatial nature of the data used for such investigations, the spatial distribution of the different sampled locations is rarely explicitly considered, which may be critical for statistical and biological reasons. In a recent study, Chown et al. (1998) investigated the relationships between species richness of different indigenous and introduced taxonomic groups and a variety of variables characterizing Southern Ocean islands, and here, we use these data to address spatial issues. As predicted, we found spatial autocorrelation in species richness for terrestrial taxa with high dispersal ability or for terrestrial taxa that had time to disperse locally (introduced land birds and indigenous taxa) but not for taxa that had low opportunity to disperse to nearby islands (introduced plants, insects, and mammals), which suggests that colonization from nearby islands has played an important role in shaping present-day patterns of among-island variation in species richness. Interestingly, in several cases, the estimated effect of variables changed when spatial covariance was incorporated. Moreover, the absence of autocorrelation of some variables allowed us to confirm some important results of Chown et al. (1998), notably those involving the potential impact of human presence on the biodiversity of these islands. Overall, our results illustrate the importance of considering spatial structures in ecological studies. This is notably the case when dispersal processes can be expected to explain some of the observed patterns.
• *Winter Responses of Forest Birds to Habitat Corridors and Gaps (http://www.consecol.org/Journal/vol2/iss2/art13/)
  excerpt from the abstract:  "Forest fragmentation and habitat loss may disrupt the movement or dispersal of forest-dwelling birds."     "We studied the movement of wintering resident birds, lured by playbacks of mobbing calls, to compare the willingness of forest birds to travel various distances in continuous forest, along narrow corridors (fencerows), and across gaps in forest cover."  " ... to cross gaps when alternative forested detour routes were available. "
• A Comparison of the Taxonomic Richness of Vascular Plants in China and the United States 
  (http://www.journals.uchicago.edu/AN/journal/issues/v154n2/980341/980341.html)
  ABSTRACT excerpt: "Numbers of taxa at the level of order, family, genus, and species were tabulated for ... groups of vascular plants in ... China and the United States. Analysis of these data showed that the flora of China is significantly more diverse than that of the United States."   "We conclude that the patterns of diversity of Chinese and U.S. vascular plants have been influenced by the longer and more open access of temperate eastern Asia to tropical regions, the presence in southern China of a larger area of subtropical climate with complex topography, and the reduced impact of late Tertiary climate cooling in eastern Asia compared to North America."    "Understanding the relative diversity of two regions requires an appreciation of the historical development of the floras in the context of large-scale processes and events."
• *Latitudinal gradients of species richness in the deep-sea benthos of the North Atlantic www.pnas.org/cgi/doi/10.1073/pnas.050589497     abstract:
  Latitudinal species diversity gradients (LSDGs) in the Northern Hemisphere are the most well established biogeographic patterns on Earth. Despite long-standing interest in LSDGs as a central problem in ecology, their explanation remains uncertain. In terrestrial as well as coastal and pelagic marine ecosystems, these poleward declines in diversity typically have been represented and interpreted in terms of species richness, the number of coexisting species. Newly discovered LSDGs in the bathyal (500-4,000 m) benthos of the North Atlantic may help to resolve the underlying causes of these large-scale trends because the deep sea is such a physically distinct environment. However, a major problem in comparing surface and deep-sea LSDGs is that the latter have been measured differently, by using species diversity indices that are affected by both species richness and the evenness of relative abundance. Here, we demonstrate that deep-sea isopods, gastropods, and bivalves in the North Atlantic do exhibit poleward decreases in species richness, just as those found in other environments. A comprehensive systematic revision of the largest deep-sea gastropod family (Turridae) has provided a unique database on geographic distributions that is directly comparable to those used to document LSDGs in surface biotas. This taxon also shows a poleward decline in the number of species. Seasonal organic enrichment from sinking phytodetritus is the most plausible ecological explanation for deep-sea LSDGs and is the environmental factor most consistently associated with depressed diversity in a variety of bathyal habitats.
  
• Fluctuating Environments and PhytoplanktonCommunity Structure: A Stochastic Model http://www.journals.uchicago.edu/AN/journal/issues/v155n4/990014/990014.html
  NOTE: "stochastic model" means they are including random luck and chance in their explanations.    "Temporal heterogeneity" means that conditions (including resources) change or fluctuate with time.
  
  ABSTRACT: Spatial heterogeneity in organism and resource distributions can generate temporal heterogeneity in resource access for simple organisms like phytoplankton. The role of temporal heterogeneity as a structuring force for simple communities is investigated via models of phytoplankton with contrasting life histories competing for a single fluctuating resource. A stochastic model in which environmental and demographic stochasticity are treated separately is compared with a model with deterministic resource variation to assess the importance of stochasticity. When compared with the deterministic model, the stochastic model allows for coexistence over a wider range of parameter values (or life-history types). The model suggests that demographic stochasticity alone is far more important in increasing the possibility of coexistence than environmental stochasticity alone.
  However, the combined effects of both types of stochasticity produce the largest
  likelihood of coexistence. Finally, the influence of relative nutrient levels and nutrient pulse frequency on these results is addressed. We relate our findings to variable environment theory with evidence for both relative nonlinearity and the storage effect acting in this model. We show for the first time that temporal dynamics generated by demographic stochasticity may operate like the storage effect at particular spatial scales.
  
• * Evidence for edge effects on multiple levels in tallgrass prairie.
  Abstract: We tested how edges affect nest survival and predator distribution in a native tallgrass prairie system in southwestern Missouri using artificial nests, natural nests of Dickcissels (Spiza americana) and Henslow's Sparrows (Ammodramus henslowii), and mammal track stations. Survival of artificial nests was lower within 30 m of forest edge. Nesting success of Dickcissels and Henslow's Sparrows was lower within 50 m to a shrubby edge than at greater distances, whereas fates of nests were not related to distances to roads, agricultural fields, or forests. Evidence from clay eggs placed in artificial nests indicated that mid-sized carnivores were the major predators within 30 m of forest edges. Furthermore, mid-sized carnivores visited track stations most frequently within 50 m of forest edges. Because proximity of woody habitat explained more variation in nest
  survival and mammal activity than did fragment size, it appears that edge effects were more pronounced than area effects. Edge effects appeared to be caused mainly by greater exposure of nests to mid-sized carnivores. We argue that, based on edge avoidance behavior, "grassland-interior" species such as the Henslow's Sparrow respond to edge effects mainly by a decrease in density, whereas habitat generalists such as the Dickcissel are affected mainly by a decrease in nesting success.
  
• Ecological Biogeography of Southern Ocean Islands: The Importance of Considering Spatial Issues 
  ABSTRACT:   Understanding patterns of among-island variation in species richness has long been an important question in ecology and biogeography. However, despite the clear spatial nature of the data used for such investigations, the spatial distribution of the different sampled locations is rarely explicitly considered, which may be critical for statistical and biological reasons. In a recent study, Chown et al. (1998) investigated the relationships between species richness of different indigenous and introduced taxonomic groups and a variety of variables characterizing Southern Ocean islands, and here, we use these data to address spatial issues. As predicted, we found spatial autocorrelation in species richness for terrestrial taxa with high dispersal ability or for terrestrial taxa that had time to disperse locally (introduced land birds and indigenous taxa) but not for taxa that had low opportunity to disperse to nearby islands (introduced plants, insects, and mammals), which suggests that colonization from nearby islands has played an important role in shaping present-day patterns of among-island variation in species richness. Interestingly, in several cases, the estimated effect of variables changed when spatial covariance was incorporated. Moreover, the absence of autocorrelation of some variables allowed us to confirm some important results of Chown et al. (1998), notably those involving the potential impact of human presence on the biodiversity of these islands. Overall, our results illustrate the importance of considering spatial structures in ecological studies. This is notably the case when dispersal processes can be expected to explain some of the observed patterns.
  
• Contrasting Effects of Plant Richness and Composition on Insect Communities: A Field Experiment 
  ABSTRACT: We experimentally separated the effects of two components of plant
  diversity plant species richness and plant functional group richness on insect communities.
  Plant species richness and plant functional group richness had contrasting effects on insect
  abundances, a result we attributed to three factors. First, lower insect abundances at higher
  plant functional group richness were explained by a sampling effect, which was caused by the increasing likelihood that one low-quality group, C4 grasses, would be present and reduce average insect abundances by 25%. Second, plant biomass, which was positively related to plant functional group richness, had a strong, positive effect on insect abundances. Third, a positive effect of plant species richness on insect abundances may have been caused by greater availability of alternate plant resources or greater vegetational structure. In addition, a greater diversity of insect species, whose individual abundances were often unaffected by changes in plant species richness, may have generated higher total community abundances. After controlling for the strong, positive influence of insect abundance on insect diversity  through rarefaction, insect species richness increased as plant species richness and plant functional group richness increased. Although these variables did not explain a high proportion of variation individually, plant species richness and plant functional group richness had similar effects on insect diversity and opposing effects on insect abundances, and both factors may explain how the loss of plant diversity influences higher trophic levels.
• *Remotely sensed habitat diversity predicts butterfly species richness and community similarity in Canada 
  Abstract
  Although there is no shortage of potential explanations for the large-scale patterns of biological
  diversity, the hypothesis that energy-related factors are the primary determinants is perhaps most
  extensively supported, especially in cold-temperate regions. By using unusually high-resolution
  biodiversity and environmental data that have not previously been available, we demonstrate that
  habitat heterogeneity, as measured by remotely sensed land cover variation, explains Canadian
  butterfly richness better than any energy-related variable we measured across spatial scales. 
  Although species-richness predictability declines with progressively smaller quadrat sizes, as expected, we demonstrate that most variability (>90%) in butterfly richness may be explained by habitat heterogeneity with secondary contributions from climatic energy. We also find that patterns of community similarity across Canada are strongly related to patterns of habitat composition but not to differences in energy-related factors. Energy should still be considered significant but its main role may be through its effects on within-habitat diversity and perhaps, indirectly, on the sorts of habitats that may be found in a region. Effects of sampling
  intensity and spatial autocorrelation do not alter our findings. 
• *Butterfly Species Richness Patterns in Canada: Energy, Heterogeneity, and the Potential Consequences of Climate Change    
  ABSTRACT.  The distributions of most pollinator species are poorly documented despite their importance in providing ecosystem services.  While these and other organisms are threatened by many aspects of the human enterprise, anthropogenic climate change is potentially the most severe threat to pollinator biodiversity. Mounting evidence demonstrates that there have already been biotic responses to the relatively small climate changes that have occurred this century. These include wholesale shifts of relatively well-documented butterfly and bird species in Europe and North America. Although studies of such phenomena are supported by circumstantial evidence, their findings are also consistent with predictions derived from current models of spatial patterns of species richness. Using new GIS methods that are highly precise and accurate, I document spatial patterns of Canadian butterfly diversity. These are strongly related to contemporary climate and particularly to potential evapotranspiration. An even more noteworthy finding is the fact that, for the first time, habitat heterogeneity, measured as the number of land cover types in each study unit, is proven to be an equally strong predictor of butterfly richness in a region where energy alone was thought to be the best predictor of diversity. Although previous studies reveal similar relationships between energy and diversity, they fail to detect the powerful link between richness and habitat heterogeneity. The butterflies of Canada provide a superb baseline for studying the effects of climate on contemporary patterns of species richness and comprise the only complete pollinator taxon for which this sort of analysis is currently possible. 
• *Physical stress and diversity-productivity relationships: The role of positive interactions 
  Abstract
  If environmental stress provides conditions under which positive relationships between plant
  species richness and productivity become apparent, then species that seem functionally redundant under constant conditions may add to community functioning under variable conditions. Using
  naturally co-occurring mosses and liverworts, we constructed bryophyte communities to test
  relationships between species diversity (1, 2, 4, 8, 16, 24, or 32 species) and productivity under
  constant conditions and when exposed to experimental drought. We found no relationship between species richness and biomass under constant conditions. However, when communities were exposed to experimental drought, biomass increased with species richness. Responses of individual species demonstrated that facilitative interactions rather than sampling effects or niche complementarity best explained results survivorship increased for almost all species, and those species least resistant to drought in monoculture had the greatest increase in biomass. Positive interactions may be an important but previously underemphasized mechanism linking high diversity to high productivity under stressful environmental conditions. 
• Other choices may be available by lab time.
  
  

• Skim the report, noting mentally how it compares to the report forms  you have been using all semester to write your own lab reports and summaries of research news.  If you have no clue what the professional report is about, you might consider choosing another report.
• Read the report more carefully:  
  • Focus on what the report says about species diversity.  Remember,   many factors have been proposed to "cause" species richness.  Review them from Chapter51, Lab 8 and Lab 4.
  • Skip the technical parts about statistical analysis only. 
  • Try to understand the biological technical parts, the parts concerning species diversity. If you have no clue what it's about, you might consider choosing another report.   
    

HAND IN AN EXPERIMENT SUMMARY FORM.  Most research reports have one main hypothesis. These reports all have at least part of the hypothesis devoted to species diversity.  Find the main hypothesis.  Write it down.  Then re-write it (if necessary) so that is focuses only on species diversity in this form:  "Factor x causes species diversity to increase," or "Factor z causes species diversity to decrease."  Try to get the main points of the experimental design and results; then use your own words to finish the experiment summary form. 

Do not try to hide your confusion by using technical phrases copied from the professional report; using your own words is your best evidence of achieving a reasonable level of comprehension.

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What you need to know from this lab for future tests and labs

• Which factors seem to be related to species diversity?
• How do scientists design experiments to test species diversity hypotheses?
• How to analyze any research report, even identifying problems if it's bad science.
• How to write your own research reports.
• On upcoming quizzes and the final exam, you must be able to write and explain experiment summaries.
• Be able to comment on the value of peer review in scientific writing.   "Peer-reviewed" means that a report is not published (even on the good internet sites) unless it has been approved by a trained editor and at least one scientist (usually at least two) who is in expert in this area of research. The "bad science" reports are both from what is sometimes called gray literature, which means articles of questionable reliability or "fringe science."  Scientific "gray literature" usually is not peer-reviewed.