TGIFF, thank goodness it’s FUNGI FRIDAY!
What you see in front of you is and ugly looking, black ascocarp of a saprobic fungus. Bulgaria inquinans is its name, and if you google it, you won’t find much. All you will see is what types of trees it decomposes and its distribution. It seems like this species has nothing ecologically significant or exciting to offer. Like most fungi, we don’t have any direct evidence of its origins (unless it is encapsulated in amber) because the soft tissues associated with fruiting bodies degrade before sediments set and its fine details can become preserved through fossilization. However, we can assume a rough time frame of a species origin if they specialize in breaking down a type of tree.
I found this species doing field work last summer in the Southern Appalachia. It was happily feeding on a large oak stump. After researching this species, I found out that Bulgaria inquinans specialized in oak, tanoak, and beech degradation. Although they also decompose birch and hornbeams, interestingly, most of their diet is composed of trees within the same family- the Fagaceae. So, without using direct fossil evidence I hypothesize the origin of Bulgaria inquinans indirectly, by looking at the geneses of the Fagaceae.
Fossils discovered in Georgia represent the earliest evidence of this family of trees. Around 85 million years ago, these large woody trees began to transform the forest floor. With all of the new carbon rich organic debris, an entirely new niche for saprotrophic fungi became pried opened. Oaks didn’t appear in the fossil record until nearly 50 million years later.
The fact holds that Bulgaria inquinans is found mostly on oaks, but can still decompose the wood of the oaks more ancient relatives in the Fagaceae. Because of this, I predict that this fungus evolved after the origins of Fagaceae, but before oaks. The ancestors of this fungus went through a series of adaptations in order to access the new pool of nutrients presented by the Fagaceae. Many fungi can degrade, parasitize and form mutualisms with closely related trees because they contain a similar chemical makeup, so the transition to becoming more specialized on oaks was smooth.
The ancestors of Bulgaria inquinans enhanced their ability to break down woody substrate from this family of trees. Once oaks evolved, they began dominating the landscape. As acorns littered the forest floor, this species of fungus, driven by selection, fine-tuned its ability to become more specialized in decomposing oaks. I tentatively predict that this species of fungi originated 10 million years before the first oaks, about 43 million years ago. Clearly, more genetic testing needs to be carried out to confirm this, but this story is a lesson in reading the signs of the environment. We can infer a lot about a species evolution indirectly, by looking into the species they specialize in.