Intraspecific Competition and Mating Between Fungal Strains of the Anther Smut Microbotryum Violaceum From the Host Plants Silene Latifolia and S. Dioica

Abstract

We studied intraspecific competition and assortative mating between strains of the anther smut fungus Microbotryum violaceum from two of its host species, Silene latifolia and S. dioica. Specifically, we investigated whether strains from allopatric host populations have higher competitive ability on their native host species and show positive assortative mating. In general, strains isolated from S. latifolia outcompeted strains isolated from S. dioica on both host species, but in female hosts, heterotypic dikaryons (i.e., dikaryons composed of a haploid strain originating from S. latifolia and a haploid strain originating from S. dioica) were most successful in competition. Furthermore, the latency period was significantly shorter for heterokaryons that contained at least one strain originating from S. latifolia, compared to heterokaryons that only contained strains originating from S. dioica. The frequencies of conjugations between strains originating from S. latifolia were much higher than conjugation frequencies between strains originating from S. dioica. A significant positive correlation was detected between the relative success of strains in competition and in conjugation, suggesting that success of a strain in competition might be partly determined by its swiftness of mating. In addition, reciprocal differences within heterotypic crosses revealed a significant effect of fungal mating type, with mating type a1 being the main determinant of mating pace. The observed differences in infection success, conjugation rate, and latency period in favor of strains from S. latifolia relative to strains from S. dioica on both host species are discussed in an evolutionary context of opportunities for the maintenance of differentiation between different formae speciales upon secondary contact.

Evolution of Reproductive Isolation Within a Parasitic Fungal Species Complex

“…The full matrix of crosses was not performed because we could not obtain sporidia of both mating types for some species, probably due to mating‐type‐linked deleterious recessive mutations that occur commonly in lineages of this fungus (Hood and Antonovics 2000). Previous studies have shown that the addition of host extracts had no influence on the relative proportion of conjugations in vitro between different crosses (Kaltz and Shykoff 1999; Van Putten et al 2003), supporting a lack of this potential form of environmental influence. Sporidia were therefore suspended in 1 mL of sterile water.…”

Mating System of the Anther Smut Fungus Microbotryum violaceum : Selfing under Heterothallism

“…Studies have suggested a correlation between the rapidity of conjugation and competitive success (105). The developmental processes involved in mate recognition may therefore be of vital importance to the pathogen's life cycle.…”

Benefits and costs to pollinating, seed-eating insects: the effect of flower size and fruit abortion on larval performance

“…S. latifolia flowers from April to October; its white flowers open and start emitting scent at dusk (Jurgens et al 1996). Nocturnal (moths) and diurnal (e.g., hoverflies) pollinators visit the plant (Jurgens et al 1996;Shykoff and Bucheli 1995;Van Putten et al 2003;Young 2002). The moth Hadena bicruris Hufnagel (Lepidoptera: Noctuidae) is considered to be the main pollinator in the European native range (Brantjes 1976;Jurgens et al 1996).…”