Lactocollybia is closely related to Hydropus (/Hydropoid clade, Agaricales). Macrocystidia has no relation with this clade and is included in the /Pluteoid clade, in a basal and somewhat ambiguous position (Matheny et al. 2006. Major

clades of Agaricales: a multilocus phylogenetic overview.

Mycologia 98: 982-995).

Thanks. Actually there is no apparent relationship of Lactocollybia with the Hydropoid clade (containing Clitocybula, Hydropus, Hydnopolyporus, Megacollybia, Mycena, Henningsomyces ) in their (Matheny et al. 2006 or Moncalvo et al. 2002) phylogenetic analyses. Probably Lactocollybia was not mentioned in the text as well.

This reference concerns the position of Macrocystidia. Actually only a few ITS sequences of Lactocollybia spp. are available in GenBank, and BLASts do not provide a clear answer about the phylogenetic position of the genus, but somewhere in the Marasmiaceae. Its relationships with Hydropus suggested by Singer have to be confirmed thus.

Hi, we are working on this genus. At the moment I have no final insights on his phylogenetic placement.

Thanks Pierre-Arthur Moreau and Alfredo Vizzini. Recently I've collected some basidiomata of Lactocollybia from Guangzhou, China and got nrLSU sequence from it. The nrLSU sequence doesn't apparently show any close sister genera to Lactocollybia. However, the ITS sequence of L. epia (KP840552) from Italy clusters with the sequences of Tricholoma sp. (KP155121) and Mycena sp. (KR154992) from India. Personally, I think the Indian taxa might be members of Lactocollybia rather than Mycena or Tricholoma. Another species from Australia named as Agaricales sp. MEL 2382868 (KP012742) is weakly supported as a close sister species or genus to Lactocollybia.   

I sequenced a specimen of Lactocollybia from Mexico that was deposited at TENN and it showed close affinities with Hydropus and Clitocybula, however I never had the chance to look at the morphological characters to confirm that it was correctly identified as Lactocollybia, the ITS sequence is already in Genbank (KP453707), but I also have LSU and rpb2 sequences, if you are interested I can send you those sequences.

Many thanks Marisol Sanchez-Garcia. The submitted sequence to GenBank (KP453707; TENN 055867) may not be a Lactocollybia species, it could be a Hydropus sp. or belongs to other genera, if the other ITS sequences deposited in GenBank are true Lactocollybia or  vice-versa. I had an opportunity to examine the morphology of the Chinese collection and this Chinese collection well fitted with the concept of Lactocollybia (presence of fusoid gloeocystidia in context of pileus, stipe and lamellae which is sharply tapering at both ends; common presence of clamp connection, etc.). Furthermore, nrLSU sequence from the Chinese collection nested with L. epia (GenBank KP840552) with maximum BS support. Based on ITS tree TENN 055867 collection nested with Hydropus and apart from other ITS sequences  (KU320581 and KP840552) of Lactocollybia epia. I would be very happy to have your nrLSU sequence, I will compare it with other nrLSU of Lactocollybia. 

Many thanks @ Pierre-Arthur Moreau, Marisol Sanchez-Garcia and Alfredo Vizzini for the discussion on this genus. We have little contribution on the genus Lactocollybia (see- http://www.mycosphere.org/pdf/Mycosphere_7_6_10.pdf)

Thanks Iqbal!