Macbrideola gallicola G. Moreno, Seraoui, Mar. Mey. & López-Vill., 2023

Moreno, G., Seraoui, El-Hacène, Meyer, M. & López-Villalba, Á., 2023, A new species of Macbrideola on galls of Rosaceae, Phytotaxa 613 (2), pp. 180-186 : 181-182

Macbrideola gallicola G. Moreno, Seraoui, Mar. Mey. & López-Vill. , sp. nov. Fig. 1

MycoBank: MB847112

Etymology: gallicola refers to the unusual and new habitat discovered for myxomycetes—galls of Rosaceae .

Material studied: FRANCE: Gaillard-L’Arve, Haute-Savoie, 395 m, on Rosa canina galls ( Diplolepis rosae ) collected on 13-VI-2021, start of the moist chamber on 14-VI-2021, specimens collected on 24-VI-2021, Mc 1096 duplo AH 51482. Le Buëch, towards Aspremont, on the way to Dignes, 810 m, on Rosa canina galls, galls collected on 01-V-22, start of the moist chamber on 12-V-22, specimens collected on 23-V-22, Mc 1140 duplo AH 51483 Holotype. MONTENEGRO: Cetinje, Lovćen National Park, 1340 m, on Rosa canina galls collected on 17-VI-2022, start of the moist chamber on 22-VI-2022, specimens collected on 6-VII-2022, Mc 1154. Vusanje, 1000 m, Diplolepis rosae galls collected on 17-VI-2022, start of the moist chamber on 22-VI-2022, specimens collected on 05-VII-2022, Mc 1157.

Sporocarps shortly stipitate, scattered to clustered, 0.4–0.9 mm high. Hypothallus membranous, dark. Stalk 0.15–0.3 mm high, dark, thickened, hollow, and reddish at the base, tapering towards the apex. Sporotheca 0.2–0.5 x 0.15–0.20 mm, ellipsoidal, cylindrical, rarely subglobose. Peridium non-persistent, not attached to the capillitium. Capillitium scarce to abundant, loose, flexuous, with main branches emerging along the columella, sometimes bifurcated. Columella 0.15–0.25 mm high, tapered and curved towards the apex, with remnants of a collar. Spores dark to pale brown in mass, pale violaceous-brown under transmitted light, globose to subglobose, 9.5‒11.5 × 9.5‒11.5 µm, av. 10.5 × 10.5 µm, Q av = 1 (n = 25), with spines. Under SEM, the spines are loosely arranged, smooth on the base, but with a helix of denticules towards the apex.

Remarks: Macbrideola gallicola is characterized by fructifying on Rosaceae galls created by the gall wasp Diplolepis rosae , a stalk that can reach even half of the height of the sporocarp, the absence of peridium, the spiny spores, large for the genus (9.5‒11.5 µm diam.), and by the spines of the spores with a helix of denticules towards the apex.

Accompanying species that appeared in the moist chamber cultures together with the new Macbrideola were Arcyria cinerea (Bull.) Pers. , A. globosa Schwein. , Craterium concinnum Rex , Diachea leucopodia (Bull.) Rostaf. , Paradiachea cf. caespitosa (Sturgis) Hertel ex H. Neubert, Nowotny & K. Baumann , and Physarum bivalve Pers.

Other species of Macbrideola with spiny spores are: Macbrideola spinosispora L.M. Walker, G. Moreno & S.L. Stephenson , Macbrideola herrerae Lizárraga, G. Moreno & Illana , Macbrideola lamprodermoides G. Moreno, Lizárraga & Illana , Macbrideola ovoidea Nann. -Bremek. & Y. Yamam., and Macbrideola brevipes Lizárraga & G. Moreno.

Macbrideola spinosispora can be distinguished by the globose to subglobose sporotheca, violet shades, and the sporocarps are found on leaf litter ( WALKER et al. 2014). The ornamentation of the spores is similar to M. gallicola , but the diameter of the spores is smaller (8–9 µm de diam.).

Macbrideola herrerae can be distinguished by the abundant, rigid capillitium that does not create a net, dark brown to blackish, with parallel main branches emerging along the columella, and by the spores with thick spines that are smooth at the apex. Another difference is that the sporocarps are found on leaf litter ( LIZÁRRAGA et al. 2006).

Macbrideola lamprodermoides can be distinguished by the persistent peridium, dark and abundant capillitium creating a net, spores with thick spines, and the sporocarps are found on leaf litter ( MORENO et al. 2006).

Macbrideola ovoidea ( Fig. 2 ) can be distinguished by the sinuous capillitium with free endings that do not create a net and by the spiny spores which have denticules arranged in a crown at the tip. The sporocarps were originally found fruiting on inflorescences of Quercus serrata Murray (NB 12860) ( NANNENGA-BREMEKAMP & YAMAMOTO, 1983), however, one of the authors (Marianne Meyer) found M. ovoidea at the type locality but fruiting on inflorescences of Castanea crenata Siebold & Zucc. (MM 769).

Macbrideola brevipes can be distinguished by the persistent peridium, short stalk (0.12–0.15 mm), densely spiny spores, and because the sporocarps fruit on bark of Juniperus sp. ( LIZÁRRAGA & MORENO, 2021).

Another morphologically similar species is Comatricha rutilipedata H. Marx. Although the spore ornamentation is similar to that of Macbrideola gallicola sp. nov., C. rutilipedata can be distinguished by the 6–7.5 µm diam. spores, the dense, sinuous capillitium, and the fructifications generally developed on cone-like female strobili of Alnus spp. Due to the presence of a hollow base on the stalk and the absence of fibres, we propose the inclusion of this species in the genus Macbrideola .

Figures

FIGURE 1. Macbrideola gallicola a–d. Sporocarps AH 51483, e. Detail of the columella and threads of the capillitium AH 51483, f. Detail of the sporotheca AH 51482, g–i. Sporocarp and view of the hollow base of the stalk AH 51483, i. Stalk and columella AH 51482, j. Spores AH 51482, k–l. Capillitium AH 51483, m–o. Spores AH 51483, p. Detail of the denticulate helix at the apex of the spines AH 51483. Scale bars: a–d = 0.5 mm, e–i = 0.1 mm. j–l = 10 µm, m–o = 2 µm, p = 1 µm.

FIGURE 2. Macbrideola ovoidea a. Sporocarps, capillitium and spores NB12860 (typus), b. Sporocarps MM574, c. Sporocarp YY3159, d. Detail of the sporotheca YY3159, e. Stalk YY3159, f. Spore YY3159, g. Detail of the spore ornamentation YY3159. Scale bars: b = 0.5 mm, c = 100 µm, d–e = 100 µm, f = 2 µm, g = 1 µm.