Cities are often perceived as biodiversity wastelands. Adding to that perception is the common result of research surveys of urban biodiversity, which often report limited and declining numbers of species (1). Concealed by that preconception, however, is the extraordinary undiscovered biodiversity that still exists, even in the most urban of environments. Much of this biodiversity is cryptic, defined as “invisible to the naked eye, dormant species, and other species present in such low numbers that they go undetected” (2). Urban biodiversity goes under-recognized both in these small, rare, or morphologically confusing groups and because the assumption is often that nothing is to be found.
Contradicting this perspective are new results from a unique urban biodiversity study that has yielded dozens of new species of flies in the family Phoridae from a mere three months of sampling in backyards in Los Angeles, California (3). The findings come from a project called “BioSCAN” (Biodiversity Science, City and Nature), conducted by the Natural History Museum of Los Angeles County (4). The intent of the project is to inventory the insect biodiversity of Los Angeles. The study focuses on insects because their small size, relatively sedentary habits, and life history diversity could reasonably be expected to make them sensitive responders to varying urban conditions (5, 6).
BioSCAN is based on thirty sampling sites, each with a tent-like Malaise trap and a microclimate weather station, arrayed from the urban core of Los Angeles out to the nearby less-urbanized foothills. Each trap’s sampling bottle is changed weekly, and the study will sample for three years. The diversity data, in conjunction with physical measurements from the microclimate stations and landscape parameters (e.g. local percentage of hardscape, plant species adjacent to the trap, population density, proximity to roads and highways) will be used to develop mechanistic hypotheses about the causes of differences in biodiversity across these conditions.
Access for sampling is a major challenge in urban areas. It is logistically and bureaucratically impractical to deploy thirty sampling stations for three years in urban public or agency land with reasonable security. The solution was to situate most of BioSCAN’s thirty sampling sites in the backyards of volunteers, taking advantage of personal commitments of private property. Involving fewer than thirty families, this is not a typical crowd-sourced “citizen science” program. The intimate involvement between site hosts and researchers, however, has injected science and biodiversity appreciation into the daily life of the site hosts and grounded the researchers in the public life of their city.
Where is previously unknown diversity showing up in the urban environment? Unsurprisingly, it is in the world of small insects — what Piotr Nasrecki has termed “the smaller majority” (7). Like other current research exploring the biodiversity of human-dominated spaces, such as assessments of urban ants through the School of Ants project (8) and bees and butterflies of the Bronx and East Harlem (9), cryptic biodiversity abounds. So far, the BioSCAN survey has yielded at least eighty species in the single phorid fly genus Megaselia, of which thirty are new to science (3). Phoridae is the first taxon that the researchers have examined in depth. Even in one of the most heavily studied insect groups in the world, the drosophilid fruit flies, the survey has yielded unsuspected new finds (10). Finding such undescribed diversity strongly suggests that further exploration will yield dozens of new species across the insect taxa.
Although it would be efficient and ultimately necessary to discern the full range of insect biodiversity through genetic techniques (11), the early results rely on traditional taxonomy, with Hartop and colleagues illustrating the diagnostic differences in genitalia of the thirty new species in careful hand-drawn figures (3). The illustrations highlight the craftsman-like dedication required of traditional insect taxonomy and will be an irreplaceable educational tool in educating Los Angeles schoolchildren how 30 different kinds of flies could be so similar and yet different.
The results from Los Angeles are establishing baselines of species distribution. Not enough is known about these groups to even predict whether the species are native and continue to thrive in the urban forest of Los Angeles neighborhoods or whether they represent cosmopolitan species that might be found in other cities. Documenting and understanding patterns of seemingly inconsequential species groups is important, as shown by the utter lack of knowledge about the prior distributions of emerging pathogens such as the fungi Batrachochytrium dendrobatidis, which was cryptic biodiversity until it was identified as a pathogen responsible for decline and extinction of amphibians (12, 13) and Geomyces destructans, responsible for white nose syndrome and resulting collapse of bat populations in North America (14). If we know more about the nature of the surface of the moon than we do of the microbes and microscopic insects of our cities — and we do — society will remain vulnerable to the unintended consequences of global homogenization and transportation of that biota. And urban planning cannot fully incorporate biodiversity unless we actually how the full range of biodiversity is affected by urbanization.
The study of urban ecology also inevitably involves working with the people living in the research area. Rather than being seen as a challenge, that is a strongly positive benefit of urban work. People who experience nature care more about conserving it (15). Conservation of worldwide biodiversity, even outside of urban areas, depends on large numbers of people caring about it. Paradoxically, therefore, the fate of global biodiversity conservation rests on how city dwellers — now a majority group — experience urban nature (16, 17).
- M. L. McKinney, Effects of urbanization on species richness: A review of plants and animals. Urban Ecosystems 11, 161-176 (2008).
- G. F. Esteban, B. J. Finlay, Conservation work is incomplete without cryptic biodiversity. Nature 463, 293 (2010).
- E. A. Hartop, B. V. Brown, R. H. L. Disney, Opportunity in our ignorance: urban biodiversity study reveals 30 new species and one new Nearctic record for Megaselia (Diptera: Phoridae) in Los Angeles (California, USA). Zootaxa 3941, 451–484 (2015).
- B. V. Brown, A. Borkent, R. Wetzer, D. Pentcheff, New types of Inventories at the Natural History Museum of Los Angeles County. Am. Entomol. 60, 231–234 (2014).
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- P. Naskrecki, The smaller majority: the hidden world of the animals that dominate the tropics. (Harvard University Press, 2005).
- A. Lucky et al., Ecologists, educators, and writers collaborate with the public to assess backyard diversity in The School of Ants Project. Ecosphere 5, 78 (2014).
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- D. Grimaldi et al., Strange little flies in the big city: exotic flower-breeding Drosophilidae (Diptera) in urban Los Angeles. PLoS ONE, (in press).
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