Ant species range shift may impact forest ecology

It is a well-established fact that all a round the world, animals, plants, fungi, bacteria and viruses are undergoing biological and/or phenological range shifts due to anthropogenic driven climate change. I have a number of references here on this blog that demonstrate these changes. Here I highlight yet another one, this time in an ant specie, but what is important I think about the following study is the very important question raised about broader secondary ecological impacts that may occur when species move rapidly. I suspect it is only a matter of time before we start seeing a raft of ecology papers  demonstrating and discussing this issue.

The Appalachian Mountains in Georgia, USA

Aphaenogaster ant species are ecologically extremely important in eastern North American forests as the central and most effective plant seed dispersers and as potential forest ecosystem dynamics regulators. While there is some overlap between species many appear to have distinct ranges delineated by climate. A 2012 study, accepted for publication this year in Global Change Biology by Robert Warren and Lacy Chick investigates thermal tolerances and the range shifts in two species of Aphaenogaster ant in the Appalachian Mountains in Georgia, USA.  A. picea and A. rudis are two species that have overlapping ranges however, the range of A. picea extends further north and at higher altitudes than A. rudis. Minimum daily temperatures have been found to be the key deciding factor for when these species of ant break dormancy and begin foraging in spring with A. rudis requiring temperatures 6 degrees C higher than its neighbour. 38 years of data reveals a range expansion of A. rudis into its neighbour’s territory where it has completely replaced the previous occupier probably through direct competition.

In order to determine the driving factor behind the shifting ranges, Warren and Chick collected ants from each species and subjected them to thermal testing and found  that A. rudis consistently became incapacitated at minimum and maximum temperatures 2 degrees C higher than A.picea  allowing them to move upwards in altitude with rising regioanl minimum temperatures, and displace the latter species. Here is the important part…

Given that Aphaenogaster ants are the dominant woodland seed dispersers in eastern deciduous forests, and that their thermal tolerances drive distinct differences in temperature-cued synchrony with early blooming  plants, these climate responses not only impact ant-ant interactions, but might have wide implications for ant-plant interactions.

In other words, research will need to be done to see if the shift upwards in altitude by A. rudis will result in the lower woodland species of early blooming plants are dragged along for the ride, resulting in more dramatic changes to the ecosystem overall.

Aphaenogaster picea is being displaced by the warm tolerant Aphaenogaster rudis in the Appalachian Mountains, in Georgia.

For some of the most amazing photographs of ants and various other insects, please visit Alexander Wild’s site here.

 

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