Gerwasia amphidasydis Q. F. Zhang, Q. Z. Wu & Q. R. Li 2025, sp. nov.

Gerwasia amphidasydis Q. F. Zhang, Q. Z. Wu & Q. R. Li sp. nov. Fig. 2 Type. China • Guizhou Province, Zunyi City, Kuangkuoshui Nature Reserve (28°12'40"N, 107°10'22"E), 2227 m a. s. l., on leaves of Rubus amphidasys. 1 November 2022, Q. Z. Wu and Q. F. Zhang (holotype GMB 4047, isotype KUN-HKAS 144247); Etymology. The epithet refers to the host species, Rubus amphidasys Focke ex Diels., from which the holotype was collected. Description. Spermogonia, Aecia, and Telia not found. Uredinia 0.2–0.8 mm diam. produced on the abaxial leaf surface, scattered to gregarious, hypophyllous, covered by peridium, small, rounded, light yellow, or orange-yellow. Urediniospores 29–41 × 22–29 μm (av. = 34 × 26 μm, n = 30), globose to subglobose or ovoid, golden, yellow-brown, wall 1.2–2.5 µm thick at sides, hyaline, prominent sparsely echinulate, markings elongated longitudinally, 1.3–3.1 µm in distance, pore obscure, germ pores inconspicuous. Pedicel broken; paraphyses not seen. Additional material examined. China • Guizhou Province, Zunyi City, Kuangkuoshui Nature Reserve, (28°12'38"N, 107°10'21"E) 2214 m a. s. l., on the leaves of Rubus amphidasys (Rosaceae). 1 November 2022, Q. Z. Wu and Q. F. Zhang (GMB 4076). Notes. Gerwasia amphidasydis was the first species of Gerwasia described on Rubus amphidasys. Our phylogenetic analyses showed that G. amphidasydis formed a separate branch (Fig. 1). Morphologically, G. amphidasydis and G. rubi exhibit similar spines. Moreover, the difference between G. amphidasydis and G. rubi is that the former has bigger urediniospores (29–41 × 22–29 μm vs. 22–33 × 16–26 µm) (Ito 1950; Hiratsuka et al. 1992). Gerwasia amphidasydis and G. guanganensis have similar uredinia and urediniospores; however, G. guanganensis has longer spine distances compared to G. amphidasydis (4.0–6.0 µm vs. 1.3–3.1 µm) (Zhao et al. 2021). Gerwasia amphidasydis is distinguishable from G. rubi-setchuenensise by having larger urediniospores (29–41 × 22–29 μm vs. 18–29 × 15–22 μm) and a thinner wall (1.2–2.5 µm vs. 2.1–3.2 μm) (Sun et al. 2024). Additionally, the LSU sequences of Gerwasia amphidasydis also differ from that of G. rubi with 93.74 % similarity and from G. rubi-setchuenensis with 90.56 % similarity. The ITS sequence for Gerwasia rubi is not available in the NCBI database, whereas the ITS sequence similarity between Gerwasia amphidasydis and G. rubi-setchuenensis is 98.56 %.