LOVING the emphasis on invertebrates on this blog. Quite often the human-world forgets that over 95% of the organisms on this planet are spineless! I recently read a paper in my favorite journal, Behavioral Ecology and Sociobiology, which emphasizes the complexity and sophistication of invertebrates.
One of the most profound biological disasters affecting British Columbia, Canada (the province where I live) is the infestation of our forests with the mountain pine beetle (Dendroctonus ponderosae). Over 14 million hectares of forest is infested with the pine beetle, causing massive destruction of our forests (trees infected with beetles are eventually killed). A combination of warm winters and prevention of natural wildfires has made our mature lodgepole pine forests an easy target. Most people think about the wrath of the pine beetle at the large scale of its devastation, however, very few think about the beetles as individuals.
What a mistake!
It turns out that the colonization of a new tree is a very complicated process at the level of the individual. When organisms live in groups and forage in groups (as the beetles do), there are individuals that rist being the first one to attack a new prey item or to colonize a new site. These ‘pioneer’ individuals often face some kind of adversity for being the first to investigate a new site. For the pine beetles the first individual to attack a new tree often suffers a greater risk of mortality (from the trees’ defenses) and a decreased reproductive rate. In a set of detailed experiments, investigators found that beetles with an intermediate body condition were the most likely candidates to pioneer a new site. Those in great condition opted out, as did those in poor condition. This provides support for the ‘desperation’ hypothesis, where individuals base their foraging decisions on their current needs. The new pioneers still had the physical ability to move to a new site (unlike individuals in poor condition) BUT they weren’t in good enough shape to simply sit back and wait for someone else to do it (a luxury enjoyed by the individuals in great condition). In addition, beetles were more likely to pioneer to new sites based on the time of year (and hence the liklihood of being followed to a new site by members of their group) and the overall size of the tree.
So, far from being ‘just another pest’, the mountain pine beetle displays a complex sophistication when it comes to decision making. Time for the Homo sapiens to display a little humility!
Reference: Bark Beetle Who Goes First]]>