Fungual competition of Auriscalpium andStrobilurus on pinecones
Successive decomposition may be affected by fungul competition. Fungal
competitions of Auriscalpium and Strobilurus on substrates
correspond to the two functional types: primary resource capture and
secondary resource capture, respectively (Boddy, 2000), so that the two
genera appear orderly on the cones. On newly fallen cones, there may be
hundreds of fungi competing to colonize cones on the surface, which is
similar to the situation reported in woods (Coates & Rayner, 1985).
However, the most obvious obstacles for fungi on newly fallen cones are
the lack of easily assimilated nutrient matrixs such as lignin and
hemicellulose, and the presences of inhibitory substances such as resin,
etc. (Abad, Ansuategui, & Bermejo, 2006). Because of their ability to
breakdown these resistant substances, Auriscalpium can gain a
competitive edge with other microorganisms in microbial community on
newly fallen cones.
With the increase of the decomposition levels, the competitive pressures
on the cones gradually increase attributed to the disappearance or
reduction of antibacterial or antifungal substances. On one hand, the
cones decomposed by the Auriscalpium provide suitable conditions
for Strobilurus growth. During this period, the fruitbodies ofStrobilurus and Auriscalpium can co-exist on the same cone
(Figure S5f). On the other hand, fungi of Strobilurus , as
aggressive competitors, produce toxins (e.g. strobilurin) to enhance its
competitiveness with Auriscalpium and other microorganisms
(Figure S5a–f). For nutrients and spaces, the antagonists can either
interact directly with the competitors (Lima, Arru, De Curtis, & Arras,
1999), or secrete antibiotics to suppress competitors (Wilson et al.,
1991). Some studies on antifungal SMs and enzymes produced by fungi with
antagonists have been conducted extensively in vitro (Alves, Ferreira,
Martins, & Pintado, 2012; Jonkers et al., 2012). Through SM clusters
analyses, we find that the number of SM clusters of the genusAuriscalpium is fewer than that of Strobilurus (Table 3),
while all fungi of Strobilurus contain a fungicidal strobilurin
cluster whose derivatives have broad spectrum antifungal activity, and,
thus, are widely used as biological fungicide (Niego et al., 2021). In
addition, the number of NRPS-like in the genomes of Strobilurusis higher than those in Auriscalpium (Table 3). Most of the NRPS,
PKS and their combinations have antibacterial and antifungal activities
(Fernandes, Costa, Sousa, Zalocha, & Almeida, 2019), which indicates
that the fungi in Strobilurus have stronger antibacterial and
antifungal activities than those in Auriscalpium . Aside from the
SMs, other factors such as microclimate, the size and quality of
nutrient sources can shift the balance between fungal decomposer groups
(Boddy, 2000). Thus, in the natural environment, the outcomes of
interactions between fungi are variable, leading to differences in
community structures.