Category Archives: History

Laveran’s eye

The military hospital of Constantine, Algeria was a fitting place to view what must have seemed the Devil in microscopic form.

Stages of the malaria parasite drawn by Alphonse Laveran

An interesting look at using skeletal remains and historical reports to reconstruct the geographic distribution of a vector-borne disease.


England once looked very different. Much of southern Britain was marshland for most of the island’s occupied history. These bogs, fens, and marshes ensured that areas of virtual wilderness persisted  from before Roman Britain through the Norman period and beyond. Despite the difficulties of using fenlands, these areas were not only occupied throughout the Anglo-Saxon period, but important centers like Croyland, Bardney, and Ely eventually developed in the marsh.

The largest fenland region was known as ‘the Wash’.  This low-lying region drained four rivers into  a square bay of the North Sea that forms the corner between Lincolnshire and Norfolk. In Anglo-Saxon times, this tidal marsh and bog was a vast border region between the region of Lindsey and East Anglia.  Places like Croyland and Ely were islands in the wetlands.  The eighth century Life of Guthlac describes the environment of Croyland when Guthlac arrived:

There is…

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Visualizing trophic interactions in an urban aquatic mesocosm

Variations in how to display the trophic interactions of an ecosystem—the food web, the regulating pressures between organisms of a particular space—have existed since the roots of the idea in community ecology. Nature—or, in particular, the relationships between organisms—has long been described as a web by many. Take, for example, the now-classic food web of Bear Island, the southernmost island of the Norwegian Svalbard archipelago, by Victor Summerhayes and Charles Elton in their seminal 1923 paper. In their illustration below, organisms are grouped into functional clusters, and arrows depict one organism being consumed by another, outlining a basis from which these systemic illustrations would build upon for decades.

Victor Summerhayes and Charles Elton's 1923 food web of Bear Island, Norway.

But this depiction of life wasn’t quite so scientifically until Charles Darwin published his On the Origin of Species in 1859, in which he wrote,


Darwin also described this web of complex relations as an entangled bank, “clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth,” and he reflected on how each of these forms, different they may be, are dependent on one another in direct and indirect pathways while at the same time producing the kinds of ecological pressures that lead to adaptation and the rise—or elimination—of species.

A species web of a slightly different kind: Charles Darwin's 1837 sketch of an evolutionary tree.

On the Origin of Species and Darwin’s subsequent writings were foremost about natural selection, the non-random process by which biological traits become more or less common in a population. But Darwin’s idea can be, and was, applied the same to how organisms themselves become more or less common in an ecosystem—the question became the following: what are those forces and relationships that allow some species to foster in a particular environment, while others only play a minor role? Community ecologists divide these species into two initial groups: autotrophs, which produce organic matter from inorganic substance to compose the primary level of an ecosystem (the first trophic level), and the heterotrophs (1+ trophic levels), which cannot fix carbon and thus must consume organisms from the initial or subsequent trophic bases. In terms of the relationships between the autotrophs and heterotrophs, food web ecology polarizes the dynamic between which group regulates the other. In bottom-up control, also known as donor control, the autotrophs (i.e., plants and algae) produce the primary resources, thereby maintaing the nutrient availability that organisms at higher trophic levels are dependent upon. Contrasting bottom-up control is the top-down dynamic, also known as a trophic cascade, in which predation and herbivory are the factors that dominate whether a species will thrive in an environment. More typically, however, analyses in community ecology strive for some middle ground between the two.

While the organization of a food web is inherently more complex—incorporating the movement of energy and mineral nutrients; dividing the heterotrophs into carnivores, herbivores, decomposers; delineating even further between competitor species, generalist consumers, specialist predators, etc—this basic model holds steady. Because this organization is predominantly a visual one—spatial and temporal patterns and variations are a large part of community dynamics in ecological research, as outlined in a recent review by Massol et al.—an interesting aspect of studying trophic interactions lies in the possibilities for visualizing data. The first graphical interpretation of a food web was published in 1880 by Lorenzo Camerano, in a manuscript entitled “On the equilibrium of living beings by means of reciprocal destruction.” Frustrated by his time’s scientific divide over which animals are useful or beneficial to agriculture, Camerano wrote the following.

To have an exact and clear idea, I repeat, of the relations between, for example, insectivorous birds and phytophagous insects, and between these and plants, these groups cannot be studied separately. Rather it is necessary to study each in relation to all other animals to see the general laws governing the equilibrium of animal and plant species.

While Camerano’s reasoning for the paper, published in the Accademia delle Scienze di Torino, was particular and applied towards the practical, his ultimate goal in the article and its resulting visualization was of general and theoretical concern.

Plate 1, Camerano 1880. Theoretical web of plant and animal interactions.

Compare that template of trophic relationships among organism groups—including primary producers, predators, ectoparasites, endoparasites, and carnivores—with a particular illustration of an ecological community of individual species with regard to enemies of a specific phylogenetic order, Coleoptera.

Plate 2, Camerano 1880. Web of interactions between Coleoptera, enemies of Coleoptera, and ecological enemies of those enemies.

In the former, more-theoretical visualization, Camerano sides with the theory of bottom-up control—vegetation is the base layer of the trophic sphere, with interactions between higher trophic levels expanding in outward rings. In the latter, allying with top-down ideas of control, complex relations are derived not from primary production, but rather from multiple pressures of predation, forming direct and indirect influences between heterotrophs. It is the latter depiction—with its emphasis on predator–prey relationships and linear–nonlinear associations between species—that has most influenced how many visualizations of trophic dynamics are drawn. In Summerhayes and Elton’s depiction of Bear Island, the first illustration in this article, the ecologists organized the biota with priority on that relationship between predator and prey—protozoa eat the bacteria, polar bears eat seals. Even where nutrients and zooplankton entered the situation, their connection to the rest of the system was given within the framework of consumption dynamics—bacteria consume nitrogen, worms eat dead plants, algae take in mineral salts.

And nor is this choice of visualization a poor or incorrect one. However, an interesting note lies in the shift between how to organize a food web in the 19th and early 20th centuries  and what kind of information should and can be included in more sophisticated images now. When one adds in the more quantitative turn in food web analysis—such as with ecological pyramids and trophic dynamics, both of which incorporate the second law of thermodynamics to consider how energy is conserved or lost as it passes between organisms—the complexity inherent in the early food webs above exponentially increases in magnitude.

The question in producing a food web is, then, how to produce a visualization of that complexity without overwhelming our perception of reality. Sacrifice quantitative rigor, and the illustration instead appears as illusion, an over-simplification. Introduce too much information, and the traceable dissolves into surplus. Such are the balancing acts Edward Tufte outlines in his 1983 The Visual Display of Quantitative Information. In the book, the statistician argues that good information design reveals the greatest number of ideas in the shortest time, with the least ink, in the smallest amount space, akin to what Italo Calvino described as lightness in literary prose—both must, in the end, tell not only a good story, but a proper one, without sacrificing either extreme of this information equilibrium.

As some of the first illustrations of food webs came from aquatic systems, bodies of water, as simultaneously self-contained microcosms and hubs in ecological networks, are good places to look for growing trends in data visualizations. An interesting and successful  update on the classic food web comes from a paper by Kevin Caillouët et al. in a 2008 paper on enclosed aquatic communities in New Orleans, Louisiana. After Hurricane Katrina flooded 80% of the city in August of 2005, floodwater from Lake Pontchartrain to the north inundated the urban terrain for over three weeks. By completely covering most regions of the city in brackish water, flooding resulted in the production of novel aquatic habitats in lowlands, depressions, and artificial containers, to name a few. Much as a forest fire produces a blank template from which previously occupied niches can be reclaimed and monocultures overthrown, Hurricane Katrina produced a blank template from which new food webs—new trophic interactions, in new magnitudes and organizations—could be drawn. In particular, on the back of research suggesting correlations between flooding and increased mosquito populations, Caillouët et al. sought to examine how these new aquatic communities would work for or against local mosquito populations, and how this in turn could influence the human risk of mosquito-borne diseases such as that caused by West Nile virus. In particular, the team examined the quasi-contained ecosystem of abandoned swimming pools, the largest of artificial containers and one of the most prone habitats to support mosquito larval development.

Caillouët et al. sample a flooded abandoned swimming pool in the Lakeview neighborhood of New Orleans.

By sampling pools in two flooded neighborhoods of New Orleans near the 17th Street Canal levee breach, the researchers were looking at this artificial environment as a mesocosm of sorts. Unlike the simplified microcosm, a controlled, laboratory-based ecosystem used to simulate and predict the behavior of its natural counterpart, a mesocosm instead brings the natural under controlled conditions, providing a link between observational field study and the artificiality of the laboratory. These mesocosms, which were being colonized by various invertebrates, fish, and mosquito species, allowed the team to ask the following questions about the composition of these new and temporary environments: if mosquito larvae were using the pools for development; if fish moved in from Lake Pontchartrain and were able to establish populations; if predatory invertebrates migrated to and colonized pools; and, lastly, if and to what extend these latter organism groups regulated mosquito populations.  To explore how these questions translate into science, Caillouët et al. relied on a conceptual model, the first step in transforming idea into design, the prerequisite for collecting and interpreting data.

Models and interpretations of aquatic community colonization post-Hurricane Katrina. Caillouët et al. 2008.

The conceptual model (A) of Caillouët et al. is not all too different, as a theoretical insight, from the initial plate by Camerano in 1880. Just as Camerano endeavored to clearly illustrate the relationships that draw together insectivorous birds and phytophagous insects, and between these and plants, the modern model food web illustrates the general relations between four main groups of organisms: the top predators, the specialist predators, the competitor species, and the prey. Much as Summerhayes and Elton used arrows in their 1923 depiction of an aquatic food web to illustrate the direction of the relationship between two or more organisms, the above model demonstrates a direct (and negative) effect of one group on another with solid lines, while dotted lines indicate an indirect (and therefore positive) effect. Continue reading

Beetles, form, art







Stag beetle, Pavel Krasensky (2007).



A gallery and a drawing

A recent gallery review in the New York Times asked the following question: are killer viruses, rendered in glass, also things of beauty? The exhibit, by Britain’s Luke Jerram, is showing in Manhattan from June 4th to July 31st, 2010. In it, Jerram has produced several infectious microbes out of glass, a step that the reviewer, the science journalist Donald G. McNeil Jr., questions and feels troubled by. As someone who reports on the global impact of infectious diseases, McNeil Jr. and his review both find troublesome depicting death as art and attempt to reconcile this bias. From the view of the artist, Jerram’s work attempts to reconcile the arts and the sciences, to illuminate cultural biases in biology and medicine’s depiction of pathogens, and to showcase his own agenda and position. I found the exhibit a success. But to get there, I need to stop, reflect, and return to the work of Ernst Haeckel and others if I wish to problematize McNeil Jr.’s critique.

Can art and science meet? Robert Hooke’s Micrographia serves as one example of this merger, and I can think of no better progression of the kind of polymath Robert Hooke embodied than in Ernst Haeckel. If Hooke had begun bridging the arts (drawings and sketches) with scientific rigor (microscopy), then it was Haeckel who took this task to another level. His Kunstformen der Natur, images of which were shown in an earlier post, not only was popular, but also embodied what Haeckel saw as scientific truths. If anything else, the prints of various organisms embody Haeckel’s scientific beliefs, his view of the world, which was often contested by the wider scientific community. In line with other mergers of art and science in 16th to 19th century Europe, Haeckel’s prints are about symmetry, about perfection, about order. Much like Robert Hooke’s Micrographia, in Kunstformen der Natur, something Platonic, some higher ideal, perhaps unobtainable by humans, existed in the natural world.
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