Systematics and phylogeography of Lactarius subgenus Plinthogalus

Lactarius subgenus Plinthogalus, sometimes referred to as the velvety milkcaps, is a group within the genus of the milkcaps with a strong distribution in both temperate and tropical continents. So far, approximately 85 species have been assigned to this subgenus.

Their velutinous cap, most often in a brownish colour, makes them fairly easily recognisable. The surface colours may be a tad dullish, however this is not the case for the colour changes of their context or latex. Many species exhibit a pink or reddish colour in the context or latex when fractured, but in other species the context or latex can turn bright blue, purple, brown, yellow or even black. Microscopically the group stands out because of its spores bearing high ridges or crests, forming either a (partial) reticulum or a zebroid pattern. The ridges can reach up to 3 µm in height, making them not only the highest spore ornamentations in the entire genus but also a spectacular sight to see under the microscope.

Goals

Since this subgenus has a wide-spread distribution across the globe, it is an interesting test-case for a large-scale phylogenetic study, including species from different continents and various climates. The questions we focus on are: How are the species of this wide-spread subgenus interrelated? What is their place of origin and how has their distribution taken place? Is there an explanation for the species-richness in certain areas? Which characters are phylogenetically informative (give us information about their kinship)?

To answer these questions, we first obtained a dataset covering as much different areas as possible. Europe, Africa and the Americas are relatively well-studied. On the other hand, Southeast Asia has been a practically uncharted area concerning Russulaceae species. So with several expeditions and cooperations (Thailand, Malaysia) we attempted to establish a better knowledge of the species in this continent. This resulted in the publication of almost 15 new species since the start of this project. A thorough phylogenetic analysis is now in progress, including as many species as possible and using multiple genes.

Publications

Stubbe D. (2012). Systematics and phylogeny of Lactarius subgenus Plinthogalus sensu lato. Ghent University, PhD thesis.

Wang X.-H., Stubbe D., Verbeken A. (2012). Lactifluus parvigerardii sp nov., a new link towards the pleurotoid habit in Lactifluus subgen. Gerardii (Russulaceae, Russulales). Cryptogamie Mycologie 33 (2):181–190.

Stubbe D., Verbeken A., Wang X.-H. (2012). New combinations in Lactifluus. 2. L. subgenus Gerardii. Mycotaxon 119:483–485.

Stubbe D., Le H.T., Wang X.H., Nuytinck J., Van de Putte K., Verbeken A. (2012). The Australasian species of Lactarius subgenus Gerardii (Russulales). Fungal Diversity 52 (1):141–167.

Montoya L., Bandala V.M., Haug I., Stubbe D. (2011). A new species of Lactarius (subgenus Gerardii) from two relict Fagus grandifolia var. mexicana populations in Mexican montane cloud forests. Mycologia 104 (1):175-181. doi:10.3852/11-051

Verbeken A., Nuytinck J., Stubbe D. (2010). Type studies of six Australian and one New Zealand Lactarius species (Basidiomycota, Russulaceae). Cryptogamie Mycologie 31 (3):235-249.

Stubbe D., Nuytinck J., Verbeken A. (2010). Critical assessment of the Lactarius gerardii species complex (Russulales). Fungal Biol 114 (2-3):271–283.

Verbeken A., Stubbe D., Nuytinck J. (2008). Two new Lactarius species from Cameroon. Cryptogamie Mycologie 29 (2):137-143.

Stubbe D., Nuytinck J., Verbeken A. (2008). Lactarius subgenus Plinthogalus of Malaysia. Fungal Diversity 32:125-156.

Stubbe D., Verbeken A., Watling R. (2007). Blue-staining species of Lactarius subgenus Plinthogali in Malaysia. Belgian J Bot 140 (2):197-212.

Le H.T., Stubbe D., Verbeken A., Nuytinck J., Lumyong S., Desjardin D.E. (2007). Lactarius in Northern Thailand: 2. Lactarius subgenus Plinthogali. Fungal Diversity 27 (1):61-94.