Tulostoma is a unique genus that I’ve been intrigued with since I first learned about its existence. Different species of these stalked puffballs are found all over the planet, but they are actually quite rare. Additionally, many Tulostoma species are found in more demanding habitats, places the aspiring mycologist would overlook. There are less rare temperate species that fruit from rich organic layers of the forest floor, but also psammophilous species that inhabit sandy, arid regions as well as clay loving, terricolous species. The newly described species featured in today’s edition of Fungi Friday is one of those psammophilous species.
Just a few months ago, some of Mexico’s leading mycologist found this new Tulostoma species. Eduardo Hernández-Navarro and his team later described published their new finding in the mycological journal, Mycotaxon. These researchers set off to survey a series of elevated geologic formations known as the Madrean Sky Islands. These biodiverse regions are comprised of around 40 mountains starting in southeastern Arizona and southwestern New Mexico, extending down to northwestern regions of Mexico. In the lower elevation regions surrounding these Madrean Sky Islands, arid to semiarid ecosystems persist, making up parts of the Sonoran and Chihuahuan deserts.
The high elevation Madrean Sky Islands provide refugia for temperate pine-oak forests that once dominated the area during the last Ice Age. So many times, we are reminded of the importance of ecological refugia. These areas support a subset of the descendants that once dominated the region. The island-like biogeography also promotes diversification, as species are more likely to remain isolated. Without outside genes infiltrating their isolated gene pool, species follow unique evolutionary trajectories, and diversification tends to occur.
Tulostoma rufescens can be found in the lower elevation regions of the Madrean Sky Islands, which is dominated by subtropical scrub vegetation. The habitat heterogeneity of these regions is quite intense, as two separate ecoregions (temperate ecosystems and arid scrublands) grow right next to each other. Tulostoma rufescens fruits from these more arid regions, and in every picture I’ve found, the fungus is covered with sand. Psammophilous species are unique to the fungal realm. Fruiting bodies and moist environments go hand in hand, but there are a handful of species that have evolved adaptations to allow them to exist in more demanding, arid environments. Since this species was just described, there’s little information regarding the adaptations involved with its success.
We truly are only scratching the surface of fungal diversity, and each and every month, mycologists around the world find and describe fungal species new to science. One of my all-time life goals is to describe a new species of fungus. A fantastic place to look for undescribed species are places like the Madrean Sky Islands. Species native to these isolated places that provide ecological refugium have been on a separate evolutionary trajectory for millions of years. Enough time has passed in these biodiverse regions for speciation to occur. In places of ecological refugia, several lineages of fungi, plants and animals have diverged into diverse array of species that we possibly haven’t described yet.