Phylloporus is a fascinating genus I have mentioned a few times before here on Forest Floor Narrative. Like the title suggests, mushrooms in this genus are more commonly known as the gilled boletes. They are a fungal group nested within the family Boletaceae and they share some of the most defining characteristics other species from the same family do. For the most part, species of Phylloporus and other fungi within the Boletaceae, have robust cap surfaces and rigid stipes. Compared to many other fleshy gilled mushrooms, boletes are hardier and usually last a bit longer once they initially fruit. The first time I found a gilled bolete, I was perplexed to say the least. This fungus was rigid like many boletes I find, but it had gills like other agarics. Everything about this first specimen shouted bolete, except its gills. This gilled morphology reveals yet another example of convergent evolution, and reiterates that overtly successful traits will appear in distantly related species given enough time.
The first ever gilled boletes I found. Phylloporus rhodoxanthus. The white one is being parasitized by a species of Hypomyces.
Starting in 2016, three researchers started surveying tropical oak forests from central Veracruz, Mexico. Leticia Montoya, Edith Garay-Serrano and Victor M. Bandala found a few Phylloporus specimens that were likely undescribed. These two new specimens were collected beneath two native oaks in the area, Quercus oleoides and Quercus sapotifolia. Like other Phylloporus species, these fungi are mycorrhizal, delivering nutrients to compatible plants in return for a sugar reward. After a few years of amplifying and sequencing genetic material from these organisms, a molecular phylogenetic analysis supported their claim of finding two new species. It takes tedious work and a long time for scientific disciplines to accept new species. The work of Montoya, Garay-Serrano and Bandala has finally been published just earlier this year.
Phylloporus rimosus (Montoya 4834, holotype). a Basidiospores b hymenophoral trama c longitudinal section of pileipellis. Montoya et. al 2019.
It should be no surprise that more and more species of mycorrhizal fungi are being described from Mexico. Mexico truly is a mycological hotspot with its warm temperatures, seasonality, elevation gradients, and diverse plant assemblages. Additionally, Mexico has the highest diversity of oak species, with about 160 Quercus species of the total 500-600 species found worldwide. And it is these oaks that require a fungal symbiote to supplement their nutritional needs.
Research conducted by Montoya et al. describe two new gilled boletes named Phylloporus rimosus and Phylloporus quercophilus. Although they look quite similar, they are distantly related species that carry out quite similar ecological functions. We don’t have a time machine, but the common ancestor of these two species could have looked more like a regular, pore forming bolete. Over time, this lineage of fungi shifted to back to a gilled morphology. Gills are an evolutionary marvel that enhance fungal fitness in terrestrial environments. So much so, that some boletes reverted back to an even more ancestral trait even before boletes entered the scene.