Lateral gene flow and arthropods

I’ve long been a fan of A Thousand Plateaus, the epic second volume of Capitalism and Schizophrenia by Gilles Deleuze and Félix Guttari, in good measure because it is a philosophical work that makes a number of statements directly relevant to evolutionary biology. In particular, Deleuze and Guttari spend some time criticizing the idea that the gene flow from parent to offspring (vertical gene flow) is far more important than any other form of gene flow. Instead, they argue that we should be paying more attention to lateral gene flow, the flow between organisms not involved in a parent-offspring relationship. 

While evidence of lateral gene transfer in micro-organisms is well accepted (think, for example, of plasmid transfer among bacteria by conjugation), there seems to remain some skepticism about the importance of this phenomenon in more complicated organisms. Despite this skepticism, Deleuze and Guttari’s suggestion that lateral gene flow is generally important was recently reinforced by a paper out of Yale describing the first evidence of de novo carotenoid synthesis in animals, effected by genes incorporated into the aphid genome from a probable fungal origin (Moran and Jarvik 2010). 

Fast forward to 2012 when two papers make this story a little longer, and a little more remarkable. First, the April issue of Biology Letters contained a paper by Altincicek et al. describing genes for carotenoid synthesis present in spider mites. These genes cluster phylogenetically close to the aphid carotenoid synthesis genes (and therefore are also likely to be of fungal origin). Second, an August 16th paper in Scientific Reports by Valmalette et al. suggests that the carotenoids in aphids may actually form a sort of photosynthetic system capable of reducing NAD+, and therefore fueling ATP synthesis. 

While the results are new, and therefore are sure to come with a number of unanswered questions, there is no denying that these papers are going to shake up our understanding of both ecology and evolution. First, the previously accepted wisdom that animals have to obtain carotenoids from their diet has been challenged in two disparate arthropod groups, which suggests that the power to synthesize these physiologically important pigments may actually be widespread. Second, we may have to abandon the notion that animals are not necessarily pure heterotrophs if they can perform some  photosynthesis-like process, which adds a whole new level of complexity to food webs. Finally, it may be time to begin accepting that lateral gene flow has relevance to metazoans, and at least sometimes in functionally important ways. 

When stressors collide

Though not exactly ecology, this week’s “HIV/AIDS in America” special issue in Science highlights an important trend that applies to all sciences involving the public well being: the extent to which economically marginalized communities bear the brunt of many challenges, be it the HIV/AIDS epidemic, or, as our lab has pointed out in the past, biodiversity loss.

This message about economic vulnerability and HIV is made clear in the issue’s news feature A Tale of 10 Cities by Jon Cohen, which does a nice job of highlighting how economic and social stability have major consequences for prevention and treatment of infection in individuals, and, one imagines, on the overall infection dynamics as well. While much of the the article’s focus is on prevention and treatment programs in cities across the United States, Cohen also describes how structures that uproot people, such as borders, can facilitate spread, whereas socially stabilizing structures can minimize it by facilitating access to treatment and acquisition of stable housing for the infected.

It should not come as a surprise that economically vulnerable individuals can be the hardest hit by medical or ecological stressors, but this unfortunate truth seems particularly germane to our present era of exceptional austerity and government cut backs. Economically it has been a tumultuous year across the globe, which has brought many governments to try and curtail long running deficits, yet there is also a much needed place for societal assistance to prevent the most vulnerable from being left behind. There is a role here for academia generally, and science specifically, to guide us through the challenges facing us, and we would all do well to remember that when deciding on the allocation of our limited resources.

Isolation from the natural world and our perception of biodiversity

Why doesn’t society value and effectively protect biodiversity?  As a “biodiversity scientist” this question often occupies my thoughts, especially when I contemplate the current rates of human-caused biodiversity loss and environmental degradation.  Two recent papers point towards a couple of potential causes:

(1) The increasing isolation of human populations from the natural world

(2) People’s relatively poor ability to perceive the actual level of biodiversity in the environment around them

Children's picture books that depict
the natural environment, like these,
are becoming more rare

(1) One of the first ways we're exposed to important social issues is through children's picture books.  The stories we tell our children are often designed to teach important moral lessons, as well as entertain.  A recent paper in Sociological Inquiry by Williams et al shows that depictions of the natural world in children’s books have declined over the past forty years.  This despite increasingly serious and widespread environmental problems and a highly public environmental movement.  Their study examined 296 children’s picture books from 1938 to 2008 that won Caldecott awards for illustration.They found that depictions of the natural environment in children’s picture books peaked in the 1960s and 1970s, but have since declined.  Depictions of built environments (anything constructed by humans) have increased since the 1970s.  Likewise, pictures of interactions between humans and the natural environment or between humans and animals, also declined, reaching their lowest levels during the past ten years.  While the authors caution that their study cannot say that these changes are directly caused by our increasing isolation from the natural world, or that environmentalism is not taught through other media, it does suggest that young children are less and less exposed to the connections that exist between human society and the natural environment.  I read with surprise that this mirrors other studies that have found similar declines of environmental issues in children’s science textbooks, television entertainment, news programs and magazines.  One possible consequence of this lack of early exposure to environmental issues may be a subsequent lack of understanding of environmental issues, like the consequences of biodiversity loss.

How much biodiversity we perceive in a
landscape influences our well-being,
but how good are we at perceiving the bio-
diversity around us?

(2) Society derives a multitude of benefits, both material and emotional, from the biodiversity that makes up the natural world.  Apart from essential ecosystem goods and services, these benefits can include improved psychological well being, increased cognitive functioning, and lower stress.  Dallimer et al (2012) set out to investigate whether psychological well-being of park visitors was positively correlated with the actual species richness (plant, butterfly and bird) of riparian greenspaces around the city of Sheffield, England.  They found no consistent relationships between actual biodiversity and human well-being, but a positive link between the perceived level of biodiversity and well-being.  Essentially, people were unable to accurately identify the actual level of biodiversity present in the greenspaces around them, leading to a mis-match between reality and perception.  However, if they perceived a high level of biodiversity this had a positive effect on their well-being, irregardless of the actual level of diversity.  People’s well-being was instead better predicted by the “greenness” or tree cover of the greenspace, similar to a recent study of urban areas in Australia (Luck et al 2011).  Park visitors also had poor species identification skills, with many unable to identify a single common bird, butterfly or plant species from pictures.  These results could have important conservation implications.  If the areas the public perceives as biodiverse and lobby for protection aren’t the same areas that contain actual biodiversity, conservation programs may be unable to effectively conserve biodiversity and the ecosystem services it provides.

So what can be done to improve people’s understanding of our connections with nature and perception of the biodiversity around them?  In general, the scientific community (myself included) could do a much better job at communicating the importance of biodiversity to the public.  This doesn’t mean that we all have to write children’s books and teach people to identify plants or insects, although these might help at a small scale.  Instead, new and innovative ways to communicate science need to be developed, including research-based communication initiatives, greater participation in public forums, digital science news communities (blogging, video posts, etc.) and involving the public in biodiversity research (see Groffman et al 2010 for a discussion).  Increased training for graduate students and young scientists in public communication should also be encouraged in our universities.  Programs like Let’s Talk Science, the new TerreWEB program at the University of British Columbia, and the Biodiversity Education and Awareness Network (BEAN) in Ontario are all good starts, but require all of us to be engaged and involved in communicating our research and knowledge of biodiversity and human well-being.

References

(1) Williams, JA et al. 2012. The human-environment dialog in award-winning children’s picture books. Sociological Inquiry 82(1): 145-159.
(2) Dallimer, M et al. 2012. Biodiversity and the feel-good factor: Understanding associations between self-reported human well-being and species richness. BioScience 62(1): 47-55.
(3) Luck, GW et al. 2011. Relations between urban bird and plant communities and human well-being and connection to nature. Conservation Biology 25(4): 816-826.
(3) Groffman, PM et al. 2010. Restarting the conversation: challenges at the interface between ecology and society. Frontiers in Ecology and the Environment 8(6): 284-291.