Many couples would probably agree that deciding on a place to live together is about as easy as tying your shoes using one hand and one foot- and that’s when the two parties are both human. Consider what life is like for a lichen, a creature made up of organisms from two different kingdoms of life. A lichen is a fungus that obtains nutrients from an algae growing inside of it- a symbiotic lifestyle that benefits the fungus, but not necessarily the algae.
It the past, biologists thought that it was the fungal partner who determined where the lichen grew, since it is the fungus that makes up most of the body of the lichen. However, a new study in Molecular Ecology adds to the growing body of evidence that, it may actually be the algae who hold the reins.
What this shows is that different algal species have preferences for different environments and if a fungal partner wants to live in a particular environment, it has to ally itself with an alga that also wants to live in that environment. If the fungus attempts to grow somewhere that the alga doesn’t like, the alga will probably die, taking the fungus along with it.
Why is this biogeography? Scale up the microclimatic preferences of the algae to the macroscale patterns of climate found across the earth. Different algae have been found in lichens from the tropics versus the temperate zone versus more polar regions; and on a smaller scale, different algae are found in lichens at the tops of mountains than at their bases. To figure what causes a lichen to live where it does, the most pertinent question may be, “Who’s your alga?”
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PEKSA, O., & ŠKALOUD, P. (2011). Do photobionts influence the ecology of lichens? A case study of environmental preferences in symbiotic green alga Asterochloris (Trebouxiophyceae) Molecular Ecology, 20 (18), 3936-3948 DOI: 10.1111/j.1365-294X.2011.05168.x