[Fungi] Cookeina cremeirosea, a new species of cup fungus from the South Pacific

Abstract. A new species in the Sarcoscyphaceae from the Samoan Islands, Cookeina cremeirosea, is described and illustrated. This species is morphologically and phylogenetically distinct from the other eight species that are currently accepted for the genus. It is closely related to the Asian species Cookeina indica from which it can be separated by color and spore morphology. 

Keywords: Ascomycota, Pezizales, Phylogenetics, Samoa, Sarcoscyphaceae 

Description

Diagnosis: Cookeina cremeirosea differs from C. indica by having unornamented, rather than striated, ascospores and by its pinkish ascomata.

Etymology: cremeirosea refers to the pinkish color of the fresh ascomata.

Apothecia cup-shaped, centrally stipitate. Receptacle lacking hairs but very minutely granular, uniformly pink (5YR8/3) when fresh, becoming reddish yellow (7.5YR6/8) when dry. Stipe central with a narrow attachment, somewhat compressed and fluted, when dried 1e7 mm long and up to 1 mm

wide, concolorous with the receptacle but somewhat lighter towards the base. Disc up to 8 mm wide when dried, deeply concave, smooth, margin entire and with very minute hairs (60-100 μm long) visible on the rim with magnification, concolorous with the stipe and receptacle. Ectal excipulum 35-70 μm wide of textura angularis to textura globulosa, several cells thick, nongelatinized, with some light granular material on the outer surface composed of clusters of cells, also giving rise tominute hairs on the rim of the disc. Medullary excipulum comprising a single layer between the ectal excipulum and hymenium, 120-228 μm deep, of textura porrecta, hyphae 4-8 μm wide, nongelatinized. Hymenium 312-360 μm wide. Asci long, cylindrical, 324-336 x 14-17 μm, with walls 0.5-2 μm thick, often rounded at the base, usually containing 8 ascospores but sometimes having 6 or 7 ascospores, not reacting in Melzer's reagent. Ascospores 8.0-(9.7)-12.0  23.0-(26.85)-33.0 μm in Melzer's reagent, obliquely uniseriate, hyaline, elliptical, in side view often slightly flattened on one side, some with subpapillate ends, surface not ornamented, guttules variable. Paraphyses 2e4 mm wide, hyaline, septate, adhering to one another, interwoven, and anastomosing with some apical branching. Substrate decaying woody matter.

Additional specimen examined: USA, American Samoa: National Park of American Samoa, Tutuila Unit, on woody material along Mount ‘Alava Trail at Siufaga Ridge, 4 Dec 2013, B. R. Kropp 4-Dec-13-1 (UTC00275475).

The islands of the South Pacific are typically small and scattered over an enormous geographical area. Because of this they are difficult targets logistically for biologists doing species surveys. In addition to the logistical challenges of working on these scattered islands, a varied mix of ecosystems occurs across the region ranging from scrub vegetation found on some low lying atolls to cloud forest at the tops of mountain peaks. As a consequence, progress toward understanding the mycobiota of this region has been slow. The recent monographic treatment of Cookeina published by Iturriaga and Pfister (2006) helps enormously in proposing C. cremeirosea as a new species. Cookeina cremeirosea is easily separated from all of the currently accepted Cookeina species (except C. indica) by its lack of easily visible hairs on the surface of the ascomata and by lacking gelatinized material in the excipulum. It is clearly closely related to C. indica but it is distinct from this species both phylogenetically (Fig. 1) and morphologically. The ascomata of C. cremeirosea differ from those of C. indica by being uniformly light pink rather than yellow. In addition, the ascospores of C. cremeirosea differ from those of C. indica by having unornamented, not ridged, surfaces. 

The close relationship between C. indica and C. cremeirosea is analogous to the relationship between C. sinensis and C. tricholoma. The phylogenetic distance between the latter two species is similar to that between C. indica and cremeirosea and both pairs of species are similarly separated by differences in color and spore ornamentation (Fig. 1). Cookeina mundkurii S. C. Kaushal, another similar species, was synonymized with C. indica by Iturriaga and Pfister (2006). The holotype was

apparently not available to be examined by them, however, the original description of C. mundkurii (Kaushal 1986) corresponds well to C. indica and its yellow color would separate it from C. cremeirosea. Iturriaga and Pfister (2006) also reported that two other species of Cookeina, C. colensoi and C. insititia were collected in Samoa by Lloyd. Thus, the new species reported here brings the number of Cookeina species present in these islands to three. 

Even though the close phylogenetic relationship between the Asian taxon C. indica and C. cremeirosea suggests that C. cremeirosea has ties to Asia, it is premature to say much about the geographic origins of this species. There is no strong geographic pattern among the clades shown in Fig. 1 nor were there any geographic patterns evident in the phylogram of Weinstein et al. (2002). Given that the mycobiota of the South Pacific is so poorly known, much more sampling will be needed to determine the geographic origins of C. cremeirosea or whether it is endemic to Samoa or the South Pacific.

Reference: Kropp BR, Cookeina cremeirosea, a new species of cup fungus from the South Pacific, Mycoscience (2016), http://dx.doi.org/10.1016/j.myc.2016.09.003