To sum up, our molecular data suggest that P. simile sp.
nov. and P. raistrickii have evolved, as the morphological
differences between these species suggest, and should be
treated as two closely related, though distinct entities (Fig.
3, Supplementary Figs S1 and S2). These two species of the
genus Penicillium are likely to have evolved recently from
a common ancestor as suggested by low genetic divergence
values. In particular, analyses of the b-tubulin and
calmodulin gene coding regions (similar exon sequences)
point to a recent speciation event within this monophyletic
group (Fig. 3, Supplementary Figs S1 and S2), in which P.
raistrickii appears to exhibit derived molecular traits
Supplementary Fig. S1); future studies are warranted to
determine whether they are biogeographically rare or widespread
strains. It is noteworthy, however, that the strains of
P. raistrickii displayed a certain degree of morphological
variability, which points to infraspecific genetic variation
(Fig. 3). Future taxonomic studies are needed to redefine the
specific structures of this species on the basis of all the
information available on taxa belonging to the species.