Simplicillium formicae D. P. Wei & K. D. Hyde
Year: 2026
Type: article
Abstract: Simplicillium formicae D. P. Wei & K. D. Hyde, MycoKeys 60: 78 (2019) Fig. 2 Synonym. Simplicillium puwenense Hong Yu bis, Y. L. Lu & Jing Zhao, MycoKeys 115: 187–208 (2025), syn. nov. Type. Thailand • Chiang Mai Province, Mushroom Research Centre, on an adult ant, April 2018, Deping Wei (holotype: HKAS 102459; ex-type living culture: MFLUCC 18–1379). Note. The description and illustrations are based on specimens and their derived isolates of Simplicillium formicae collected from the Lancang – Mekong River Basin, including the type locality in Thailand and additional localities in China and Laos. Description. Sexual morph. Undetermined. Asexual morph. Hyphomycetous. Mycelium rarely septate, hyaline, smooth-walled, covering the entire body of ant host. Phialides 19.8–87.2 × 0.6–1.5 μm (x ̄ = 42 × 0.9 μm, n = 30), arising from procumbent hyphae or synnemata, blastic, enteroblastic, phialidic, monophialidic, discrete, terminal, unbranched, solitary, aseptate, hyaline, smooth-walled, slender, occasionally with a swollen node. Conidia 1.5–2.5 × 1.1–1.8 μm (x ̄ = 1.8 × 1.5 μm, n = 30), globose to ellipsoidal, hyaline, aseptate, smooth-walled, rounded at both ends, aggregated in slimy heads at the tips of phialides. Culture characteristics. Colonies on PDA attaining a diameter of 3.6–4.0 cm (x ̄ = 3.8 cm, n = 10) after 14 days at 25 ° C, circular with entire margins, white and velvety on the surface, with raised margins; reverse dark yellow, with radial cracks. Host. Adult ants (Wei et al. 2019; this study) and spiders (Shahbaz et al. 2026). The known host range of Simplicillium formicae therefore includes insects and arachnids, with records from different geographical regions and ecological settings. Additional material examined. Thailand • Chiang Mai Province, Mushroom Research Centre (19°07'N, 98°44'E, 670 m above sea level), on adult ants, May 2023, Yao Wang (GMB 3237, GMB 3242; living culture: GMBC 3237); Laos • Vientiane Province (17°58'N, 102°36'E, 177 m above sea level), on an adult ant, May 2024, Yao Wang (GMB 3238; living culture: GMBC 3238); CHINA • Yunnan Province, Pu’er City, Lancang Lahu Autonomous County (22°38'N, 99°51'E, 1143 m above sea level), on an adult ant, June 2025, Hui Chen (GMB 3239; living culture: GMBC 3239). Notes. Multilocus phylogenetic analyses (Fig. 1) resolved our isolates GMBC 3237 –3239 in a highly supported monophyletic clade together with the ex-type strain of S. formicae (MFLUCC 18–1379; Wei et al. 2019) and two Malaysian isolates reported by Shahbaz et al. (2026). The ITS sequences of GMBC 3237 –3239 share 99.8 % identity (550 / 551 bp) with that of the ex-type strain, differing by a single thymine insertion at alignment position 449. This minor sequence variation, together with the morphological and multilocus phylogenetic evidence, supports the conspecificity of these isolates. Morphologically, the newly collected isolates conform to the protologue of S. formicae by producing solitary, slender phialides and globose to ellipsoidal conidia aggregated in slimy heads. Their conidia (1.5–2.5 × 1.1–1.8 μm) are slightly smaller than those of the ex-type (2.0–3.5 × 1.5–2.5 μm), a discrepancy regarded as intraspecific morphological variation. The Malaysian specimens also align with the protologue, with only marginally wider phialides that fall within the normal range of intraspecific variation (Shahbaz et al. 2026). The type strain of S. formicae was originally isolated from an ant in Chiang Mai (Wei et al. 2019), Thailand. Our new collections extend its known distribution to Vientiane (Laos) and Lancang, Yunnan (China), spanning the upper and middle Lancang – Mekong River basin and retaining a consistent host association with Hymenoptera. In contrast, the Malaysian isolates were recovered from a spider (Shahbaz et al. 2026), expanding the documented host range of S. formicae to Arachnida. We further reassessed the molecular circumscription of S. formicae by re-evaluating all publicly available sequence data for the ex-type strain. Wei et al. (2019) described S. formicae in the same study that reported S. lanosoniveum strain MFLUCC 18–1385 as a new record. The published rpb 1 sequence of the S. formicae ex-type (MK 882623) is 100 % identical (661 / 661 bp) to that of S. lanosoniveum MFLUCC 18–1385 and 99.7 % identical (659 / 661 bp) to S. lanosoniveum CBS 704.86. In single-locus phylogenetic analyses of rpb 1, MK 882623 nests firmly within the S. lanosoniveum clade, whereas all other loci of MFLUCC 18–1379 consistently place the strain within S. formicae (Suppl. material 1: figs S 1 – S 5). Given that both strains were processed in the same study, this incongruence most probably arose from sequence misassignment during data processing, annotation, or GenBank submission. The newly generated rpb 1 sequences from GMBC 3237 –3239 are fully congruent with the multilocus phylogenetic framework and provide a reliable reference barcode for S. formicae. This erroneous rpb 1 sequence has likely artificially inflated the perceived genetic distance between S. formicae and S. puwenense, contributing to the latter’s original description as a separate species (Lu et al. 2025). With corrected rpb 1 data, S. puwenense falls entirely within the S. formicae clade with no significant molecular divergence, and its morphological characters fall within the circumscription of S. formicae. Furthermore, the proposed diagnostic distinction based on host association (spider vs. ant) is no longer valid, as S. formicae isolates from Malaysia have also been recovered from spider hosts (Shahbaz et al. 2026). Since no stable morphological, molecular or ecological diagnostic traits separate the two taxa, S. puwenense is here synonymized with S. formicae.
Institutions: Guiyang Medical University, National University of Laos
Language: English
Subfield: Insect Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7225835077
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