Introduction

The current catalog of lichenized fungi in Colombia registers 1,732 species (^{Lücking, et al., 2021}), but there are still many species to be discovered or described since almost 2,800 are estimated for the country (^{Soto, et al., 2021}). Arthoniaceae is one of the largest lichen families in the Neotropics with approximately 56 species occurring in Colombia. Currently, several new species of this family are being described but there are still genera with few records. Synarthonia is a recently recognized genus with several new records for the Neotropics. It is characterized by mono- to pluri-carpocentral synascomata immersed in a pseudostroma. The ascospores are similar to those of Arthonia and range from septate (macrocephalic) to muriform (^{Joseph & Sinha, 2015}). Some species show a UV+ yellow reaction due to the presence of lichexanthone as is the case in S. xanthosarcographoides (^{Aptroot & Spielman, 2020}).

In the framework of the INCIVA tropical dry forest project, new Arthoniaceae species have been documented for Colombia (^{Soto, et al., 2021}), among them, Synarthonia robertiana. However, since both the diagnosis and the description were given in Spanish, the name was not validly established and is validated here now. The genus Synarthonia was not previously known in Colombia (^{Lücking, et al., 2021}) but three other species have already been found besides S. robertiana. Here these new Synarthonia records for Colombia with a key to all four known species are documented.

Materials and methods

The material deposited in the herbaria TULV (INCIVA) and CUVC at Universidad del Valle, Colombia, collected in the framework of the project aimed at contributing to the conservation of Valle del Cauca dry tropical forests (OCAD n° 61 del 7/11/2017 bpin_2016000100013 de 7 de noviembre 2017), was examined. The samples were examined to determine the characteristics of the thallus and ascomata, as well as their reaction to UV light and the type and size of the ascospores, using a stereoscope (YAXUN YXAK21) and a microscope (CARL ZEISS Jena) while ascospores were measured with a micrometer ruler. All samples were photographed with a VIVITAR 100 mm macro lens adjusted to a CANON T3 digital camera. ^{Van den Broeck, et al. (2018)} was used to key out the species.

Results and discussion

Synarthonia inconspicua (Stirt.) Van den Broeck & Ertz, S. muriformis Van den Broeck, Frisch & Ertz, and S. xanthosarcographoides Aptroot are recorded here for the first time in Colombia. S. inconspicua has a pantropical distribution but S. muriformis has only been reported in Madagascar thus far (^{Van den Broeck, et al., 2018}), which means this the first record for the Neotropics. S. xanthosarcographoides was recently described in Brazil (Aptroot & Spielman, 2020) so this is the second record for the species in the region. In total, four species of the genus are now known in Colombia including S. robertiana Soto-M. & Aptroot (Soto, et al., 2021), which has been recently described in the country, although it requires validation because the original diagnosis and description were both in Spanish and they are required in Latin or English by the Code (^{Greuter & Rankin-Rodríguez, 2018}). Here the name is validated as follows:

Synarthonia inconspicua (Stirt.) Van den Broeck & Ertz (Figure 1)

Description. Thallus corticolous, crustose, smooth, inconspicuous to whitish. Ascomata solitary, rounded, disc with white pruina. Ascospores septate, macrocephalic, (15-) 16.5- 21.3 (-24.5) x (5.3-) 6.2-7.7 (-8.5) urn, hyaline (^{Van den Broeck, et al., 2018}).

Specimen examined. COLOMBIA: Departamento Valle del Cauca, Municipio de Tuluá, bosque seco tropical, La Valenzuela, 4°01.297'N 76°21.930'W, ca 1159 m. 22-082020. Soto sn (TULV).

Synarthonia muriformis Van den Broeck, Frisch & Ertz (Figure 1)

Description. Thallus corticolous, crustose, smooth, whitish to greyish green. Ascomata solitary, rounded, with a thick white pruine. Ascospores muriform, (22.0-36.5 x 10.0-14.5 um, hyaline (^{Van den Broeck, et al., 2018}).

Specimen examined. COLOMBIA: Departamento Valle del Cauca, Municipio de Roldanillo, bosque seco tropical, Higueroncito, 4°29'52.2''N 76°06'39.1''W, ca 998 m. 16/11/2020. Soto 117H (TULV).

Synarthonia robertiana Soto-M & Aptroot, sp. nov. MB 842197 Synarthonia robertiana Soto-M. & Aptroot in ^{Soto-Medina, et al., Rev. Acad. Colomb. Cienc. Ex. Fis. Nat. 45(175): 418 (2021}); nom. inval. (ICN Art. 39.2).

Diagnosis: A new species presenting ascomata with lichexanthone (UV+ yellow) as in S. xanthosarcographoides but with hyaline spores, 3-4 septate, and 28-32 x 9-14 um in size. For a full description, see ^{Soto, et al. (2021}: 418).

TYPE: COLOMBIA. VALLE DEL CAUCA: Municipio de Riofrío, Hacienda la

Gitana, ca 1150 m, 4,1666 N, 76,336W, sobre corteza en bosque de transición, 27 agosto 2020, E. Soto 158G (holotipo: TULV 19108; isotipo: CUVC).

Synarthonia xanthosarcographoides Aptroot (Figure 2)

Description. Thallus corticolous, crustose, smooth, inconspicuous to whitish. Ascomata solitary, rounded, in branched white stromata. Ascospores 7 x 0-2-septate, 20-22 x 8-9 um, brown grayish (^{Aptroot & Spielman, 2020}). UV+ yellow stromata.

Figure 1 Synarthonia inconspicua (A) y Synarthonia muriformis (B). 

Figure 2 Synarthonia xanthosarcographoides, habit (A) and pseudoestroma with UV (B) 

Specimen examined. COLOMBIA: Departamento Valle del Cauca, Municipio de Roldanillo, bosque seco tropical, Higueroncito, 4°29'52.2''N 76°06'39.1"W, ca 998 m. 16/11/2020. Soto 104H (TULV).

Key to Synarthonia species in Colombia

1. Ascospores muriform...............................................................................................2

1'. Ascospores septate..................................................................................................3

2. Pseudostromata UV+ yellow...........................Synarthonia xanthosarcographoides

2'. Pseudostromata UV-..........................................................Synarthonia muriformis

3. Pseudostromata UV+ yellow...............................................Synarthonia robertiana

3'. Pseudostromata UV-.........................................................Synarthonia inconspicua