Oedohysterium

The genus Oedohysterium E.W.A. Boehm & C.L. Schoch
Studies in Mycology 64: 59 (2009).

by Eric W.A. Boehm

The genus Oedohysterium (Clade D). A-D. Oedohysterium insidens (ANM 1443 [BPI 879799], USA). E-H. Oedohysterium sinensis (ANM 119 [ILLS], USA; not incl.). Scale bar (habitat) = 500 μm; Scale bar (spores and asci) = 20 μm. Fig. 3 from Boehm et al. 2009b.
Oedohysterium E.W.A. Boehm & C.L. Schoch, gen. nov. MycoBank MB515421.

Type: Oedohysterium insidens (Schwein.) E.W.A. Boehm & C.L. Schoch, comb. nov.

Etymology: Greek, Oedo- meaning swollen, referring to the swollen supra-median cell of the ascospores and Hys– from Hysterium.

Hysterothecia solitaria vel gregaria, iuvenia erumpentia, deinde superficialia, navicularia, nonnumquam linearia, plus minusve parallela, neque confluentia, nonnumquam angulo inserta, raro flexuosa vel furcata,  plerumque utrinque obtuse, et fissura longitudinali prominente praedita. Latitudo altitudine minor vel major. Peridium crassum, carbonaceum, maturum fragile, per longitudinem striatum, basim versus incrassatum, sursum attenuatum, bistratosum. Pseudoparaphyses cellulares, 1-2.5 µm latae, hyalinae, septatae, sursum ramosae, vulgo epithecium pigmentatum ascos obtegens formantes. Asci cylindrici vel clavati, bitunicati. Ascosporae irregulariter biseriatae, phragmoseptatae (dictyoseptatae), fusiformes, curvatae, utrinque angustatae, ad septum medium constrictae, (4-)6-8(-11) septis divisae, primum pallide luteae, deinde brunnescentes. Cellula (raro duo cellulae) ascosporarum supramediana conspicue inflata. Anamorphe ad Septonema pertinens.

Hysterothecia isolated to gregarious, erumpent when young, superficial when mature, navicular, sometimes linear in more or less parallel rows, but non confluent laterally, or sometimes situated at angles, rarely flexuous or bifurcating, usually with obtuse ends, and with a prominent longitudinal slit. Sometimes, taller than wide, other times wider than tall. Peridium thick, carbonaceous, brittle with age, longitudinally striated on the margins, thickened towards base, less thick apically, composed of two to three distinct layers, the inner compressed and pallid, the outer thickened and pigmented.Pseudoparaphyses cellular, 1-2.5 μm wide, hyaline, septate, branched above, forming a usually pigmented epithecium above the asci. Asci cylindrical to clavate, usually short stipitate, and bitunicate. Ascospores irregularly biseriate in ascus, typically phragmospores, in one case dictyospores, curved, fusiform, with tapering apices, constricted at the median septum, with (4-)6-8(-11) septa, at first hyaline-yellow, then pigmented sepia to brown at maturity. Genus characterised by a swollen or tumid supra-median cell, rarely with two cells swollen. AnamorphSeptonema Corda.

Notes: Recent molecular data (Boehm et al. 2009b) based on an analysis of five genes (nuSSU, nuLSU, TEF1, RPB1 & RPB2) indicate that the genus Hysterium is highly polyphyletic. This was seen in an earlier study (Boehm et al. 2009a) using four genes (nuSSU, nuLSU, TEF1 & RPB2). Species of Hysterium fall into two distinct clades, one (Clade C in Fig. 1 Boehm et al. 2009b) containing species related to the type, Hysterium pulicare, and another much more distant within the family (Clade D). These two clades each reside within separate groups within the family are thus phylogenetically unrelated. Since both clades contain phragmospores residing in hysterothecia, the question becomes are there morphological features that can be used to substantiate the molecular data? In this case, spore morphology is concordant with molecular data because we can find a morphological basis that differentiates the two genera. The genus Oedohysterium differs morphologically from the genus Hysterium, with spores that correspond to a different type of phragmospore (Type II mentioned previously under the genus Hysterium), one in which, typically, there are five or more septa, and in which there exists a swollen cell, either just above the median septum (i.e., supramedian) or, rarely, some distance up from the median septum. This feature is not found in species belonging to the genus Hysterium. Type II includes, by increasing spore length, the cosmopolitan H. insidens Schwein., the larger-spored counterpart H. sinense Teng, and the unusual H. magnisporum W.R. Gerard, 7-septate, with three of the septa crowded to each end, the two central cells much larger. Material of the latter species has not been examined, and no molecular data exist for this taxon. Thus H. magnisporum, while possessing swollen median cells (from published accounts), is still retained within Hysterium until such time that it can be recollected and validated. Hysterium insidens and H.. sinense, here both transferred to the genus Oedohysterium (see below), have been collected from China (Teng 1933) and North America (Boehm, unpubl. data). Species of Oedohysterium belonging to Clade D (Boehm et al. 2009b) are characterised by elongate asymmetric spores with more than 3 septa, typically showing a swollen or tumid supra-median cell. In this study, two single-ascospore isolates of Od. sinense, one from South Africa (CBS 123345 / BPI 878730), and one from the United States, New Jersey (EB 0339 / BPI 879800), clustered in the same subclade with two isolates of Od. insidens, both from the United States, Massachusetts (CBS 238.34) and Tennessee (ANM 1443 / BPI 879799). Both species have remarkably similar phragmospores (e.g., see Fig. 3D versus Fig. 3H in Boehm et al. 2009b). As these two taxa belong to Clade D and are far removed from the type species, H. pulicare, in Clade C, we propose that they be accommodated in the new genus Oedohysterium.

The newly described Hg. pulchrum from Costa Rica (Checa et al. 2007) also falls within Clade D (Fig. 1) and is here transferred to Oedohysterium, as Od. pulchrum (DQ 402184 / DAOM 234345). This is because molecular data indicate a close association with the two species of OedohysteriumOd. insidens and Od. sinense. At first surprising, on further consideration, this sub-clade forms a natural assemblage premised on morphological features. The spores of all three taxa show a remarkable degree of similarity in morphology, which includes being similarly pigmented, slightly curved and fusiform, with a common number of transverse septa. The sole difference is the presence of one or two vertical septa in Od. pulchrum, a feature noted by the authors to be absent in some spores (Checa et al. 2007). Most importantly, like Od. insidens and Od. sinenseOd. pulchrum also possesses a swollen supra-median cell. Interestingly, a striking resemblance to the phragmospores of Od. insidens can be seen for those spores of Od. pulchrum that do not possess vertical septa (Checa et al. 2007). This is based on similarities in shape (e.g., curved and fusiform), size [(20-)23-28(-38) x (5-)7-10(-13) μm versus 22-25(-27) x 5-6 μm], and in the number of transverse septa (4-)6-8(-11) versus (5-)6, for Od. insidens and Od. pulchrum, respectively. As molecular data indicate that the presence or absence of vertical septa should be considered a sympleisiomorphic character state within the Hysteriaceae (Boehm et al. 2009), we feel justified in including both phragmospores and dictyospores within the genus Oedohysterium.

We choose to provide the following dichotomous key whereby all hysteriaceous fungi, bearing transversely septate pigmented phragmospores (including both Hysterium Oedohysterium) are identified together, with the caveat that unrelated taxa appear in the same key.

 

Key to the species of Hysterium and Oedohysterium

  1. Phragmospores mainly 3-septate →  2
  2. Phragmospores concolorous, more than 3-septate, in one instance pigmented dictyospores with 1‑2 vertical septa (Od. pulchrum) →  7

 

  1. Phragmospores either versicolorous or delayed concolorous →  3
  2.  Phragmospores truly concolorous (sepia to dark brown in colour) →  4

 

  1. Terminal cell mainly remaining hyaline with inner spore cells pigmented brown (versicolorous); ascospores 20-40 x 6-12 μm; cosmopolitan →  Hysterium pulicare (Lightf. : Fr.) Pers. 
  2. Phragmospores tardily pigmented, often remaining hyaline for quite some time after discharge, but eventually becoming uniformly concolorous; 20-26(-28) x 6-8.5 μm; North America →   Hysterium hyalinum Cooke & Peck

Note: Currently recognised as Pleosporomycetidae sp. incertae sedis (Boehm et al. 2009).

 

  1. Phragmospores 3-septate, 28 μm or less in length →  5
  2. Phragmospores 3-septate, longer than 28 μm →  6

 

  1. Phragmospores (12-)14-21(-28) x (3-)4-8(-10) μm, firmly 3-septate, no septal constrictions; end-cells obtuse; cosmopolitan →  Hysterium angustatum Pers.
  2. Phragmospores (14-)15-18(-20) x 5-7 μm; 3- (rarely 2- or 4)-septate; prominently constricted at first-formed septum; basal cell extended; red hamathecial pigment; neotropical →  Hysterium asymmetricum Checa, Shoemaker & Umaña

 

  1. Phragmospores fusoid, slightly curved, guttulate; (20-)25-40 x (4-)5-14 μm; West and East Africa →  Hysterium vermiforme Massee
  2. Phragmospores fusoid, curved, highly guttulate; 40-57 x 11-15 μm; on Pinus, North America and China →  Hysterium macrosporum Peck

 

  1. Phragmospores or dictyospores (4-) 6- to 8- (11-) celled, fusiform in outline, with +/- swollen supra-median cell(s) →  8
  2.  Phragmospores with more than 11 septa, fusiform, pale brown, (13-)14-15(-21)-septate, (35-)45-50(-60) x (10-)12-13(-14) μm; Africa → Hysterium velloziae Henn.

 

  1. Swollen supra-median cell(s) present, either phragmospores or dictyospores (Oedohysterium) →  9
  2. Phragmospores only, no swollen supra-median cells(s) present → 11

 

  1. Dictyospores lightly pigmented, 22-25(-27) x 5-6 μm, with (5-)6 transverse and 1 vertical septum in either cell or both cells adjacent to the primary septum, absent in some spores, with a swollen supra-median cell; typically with red pigment in the hamathecium; neotropical (Costa Rica) →  Oedohysterium pulchrum (Checa, Shoemaker & Umaña) E.W.A. Boehm & C.L. Schoch
  2. With no red pigment present → 10

 

  1. Phragmospores with (4-)6-8(-11) septa, slightly curved, fusiform, at first hyaline-yellow then reddish brown at maturity, if 5-septate, showing a swollen cell at the second position, if 6-septate, often the third from the top, +/- median septal constriction, (20-)23-28(-38) x (5-)7-10(-13) μm; cosmopolitan →  Oedohysterium insidens (Schwein.) E.W.A. Boehm & C.L. Schoch
  2. Phragmospores larger, fusiform, straight to curved, at first hyaline, then yellow or pale brown, finally deep brown; swollen supra-median cell(s) present, (3-)5-9(-11) septa, with median septal constriction; (34-)38-50 x 11-15 μm; cosmopolitan →  Oedohysterium sinense (Teng) E.W.A. Boehm & C.L. Schoch

 

  1. Phragmospores fusiform, narrow, straight to very slightly curved, pale hyaline at first, then pale-yellow at maturity, with highly refractive guttules, in every cell, with (7-)9(-11) septa, no supra-median swollen cell(s), (35-)40-45(-55) x (7-)9-10(-12) μm; North America →  Hysterium barrianum E.W.A. Boehm, A.N. Miller, G.K. Mugambi, S.M. Huhndorf & C.L. Schoch
  2. Phragmospores oblong, wide, slightly curved, bulging on one side, nearly hyaline and 1-septate  at first, becoming clear brown and 7-septate, septa highly asymmetric, (2-)3 of the septa close to each end, the two central cells much larger; 48-67 x 15-20 μm; North America →  Hysterium magnisporumW.R. Gerard

 

Oedohysterium insidens (Schwein.) E.W.A. Boehm & C.L. Schoch, comb. nov. MycoBank MB515422.

BasionymHysterium insidens Schwein., Trans. Amer. Philos. Soc., New Series 4(2): 244 (1832).
≡ Hysterographium insidens (Schwein.) Sacc., Syll. Fung. 2: 778 (1883).
Hysterium complanatum Duby, Mém. Soc. Phys. Hist. nat. Genève 16(1): 38 (1862).
Hysterium depressum Berk. & M.A. Curtis, Grevillea 4(29): 10 (1875).
Hysterium fusigerum Berk. & M.A. Curtis, Grevillea 4(29): 11(1875) (as ‘fusiger’).
Hysterium berengeri Sacc., Syll. Fung. 2: 751 (1883).
Hysterium janusiae Rehm, Hedwigia 37: 299 (1898).
Hysterium apiculatum Starbäck, Bih. K. Svensk. Vet.-Akad. Handl. 25(1): 19 (1899).
Hysterium batucense Speg., Revista Fac. Agron. Univ. Nac. La Plata 6(1): 116 (1910).
Hysterium andicola Speg., Anal. Mus. Nac. Hist. Nat. B. Aires 23: 85 (1912).
Hysterium atlantis Maire,  Mém. Soc. Sci. Nat. Maroc. 45: 35 (1937).
Hysterium lavandulae Urries, Anal. Jard. Bot. Madrof 1: 64 (1941).

Boehm et al. 2009b: “Hysterothecia isolated to gregarious, variably erumpent to sessile, 0.5-2.5 mm long, 0.2-0.5 mm high, lying parallel, but not confluent laterally, generally in line with the grain of the wood, and striated laterally with age.  Pseudoparaphyses hyaline, cellular, 1-2.0 μm wide, walls thickened at apices, forming an epithecium, borne in mucilage, above the ascal layer, often encrusted with dark, pigmented crystals. Asci bitunicate, cylindrical, 8-spored, irregularly biseriate, 130-150 x 15-24 μm, short stipitate, and with a prominent apical nasse, especially when young. Ascospores phragmospores transversely (4-)6-8(-11)-septate, constricted at the median septum, inequilateral, slightly curved, at first hyaline-yellow, then brown at maturity, with a prominent swollen supra-median cell. If 5-septate, then swollen cell located at the second position; if 6-septate, then often the third from the top, measuring (20-)23-28(-38) x (5-)7-10(-13) μm. Principally North- and South-America, and Europe (Italy), from bark and old wood of Pinus, Larix, Castanea, Quercus, Eucalyptus, Fraxinus, Aspidosperma, and Lavandula (Zogg 1962). Also reported from South Africa (van der Linde, 1992). Anamorph: Septonema spilomeum Berk”.

Rare. Principally North- & South-America, Europe (Italy). Bark & old wood of Pinus, Larix, Castanea, Quercus, Eucalyptus, Fraxinus,Aspidosperma, & Lavandula. Also reported from South Africa (van der Linde, 1992).

Ellis & Everhart (1892): “Schweinitz originally stated: “Seated on a widely effused, black crust. Hysterothecia short, scattered, thick, oblong-ovate, sub-truncate, generally contracted into a pseudo-stipitate base, obtuse at the ends, black; lips gaping, inflexed”. The specimen in Herb. Schw. does not show any black crust, nor can the hysterothecia be called even pseudo-stipitate; the are only erumpent superficial, 0.75-1.25 mm long, obtuse, mostly lying parallel. Asci about 75 x 15 μm. Ascospores overlapping, sub-biseriate, fusoid, slightly curved, 6 – 8 septate, with one joint (about the third from the top) slightly swollen, reddish-brown, ends narrowed but sub-obtuse, 25-30 x 6-8 μm. Found by Schweinitz in Carolina on hard decaying wood. Specimens collected at Poughkeepsie, NY, on old chestnut wood have ascospores 30-40 x 7-9 μm, which is about the size of those in a specimen from Pine shingle found at Newfield, NJ. Hysterothecia variable, as are the number of septa in the ascospores”.

 

Lohman (1933): “On Quercus palings (Sept. – Oct.) MI. The common habitat is exposed medullary rays on radial surfaces of rails & palings. Conidial stage: Septonema spilomeum Berk., 1845.”

 

van der Linde (1992): “Fruitbodies single or in groups, embedded or erumpent, elongated, linear, tapering towards the ends, straight, not branched , up to 2.4 x 0.26mm. Pseudoparaphyses hyaline, septate, branched, with thickened tips, forming an epithecium above the asci. Asci broad-cylindrical, 8-spored, irregularly biseriate, 140 – 150 x 18 – 23um. Ascospores golden to dark brown, fusiform to oblong, phragmosporous, most commonly with 7 or 8 transverse septa, often constricted at median septum, middle cell usually swollen, 28 – 35 x 10 – 12um. The dimensions of both the asci & ascospores are larger than those given by Zogg (1962), according to whom ascospore length is (20) 23 – 28 (38)um.”

 

Oedohysterium insidens (Schwein.) E.W.A. Boehm & C.L. Schoch (from Zogg 1962, pgs. 22, 29, 131; as Hysterium insidens Schw.)

 

Oedohysterium sinense (Teng) E.W.A. Boehm & C.L. Schoch, comb. nov. MycoBank MB515423.

BasionymHysterium sinense Teng, Sinensia 4: 134 (1933).

Hysterium macrosporum Teng, Sinensia 4: 134 (1933), non Peck, Rep. N.Y. St. Mus. nat. Hist. 26: 83 (1874) (1873).

Boehm et al. 2009b: “Hysterothecia scattered to subgregarious, linear, sometimes parallel but non-confluent laterally, more often lying at irregular angles, depending on the grain of the substrate, striated in age, usually of a similar size (2-3.5 mm in length), that is, maturing synchronously in a given colony. Pseudoparaphyses hyaline to pale-yellow, cellular, 2-2.5 μm wide, apically branched, walls of even thickness along length, forming a darkened gelatinous epithecium above the ascal layer, +/- encrusted with pigmented crystals. Asci bitunicate, cylindrical, 8-spored, irregularly biseriate, 140-170 x 26-30 μm, short-stipitate, ascospores biseriate to subseriate in ascus, with a prominent apical nasse, especially when young, but sometimes persisting through maturity. Ascospores large, fusiform, asymmetric, curved phragmospores, at first hyaline, then pale-yellow to -brown, finally deep brown at maturity, with (3-)5-9(-11) septa, with a medial septal constriction, measuring (34-)38-50 x 11-15 μm, and, like Od. insidens, with a prominent swollen or tumid supra-median cell, usually located just above the median septum. From North America (Boehm, unpubl. data), Europe (Zogg 1962), China (Teng 1933), and South Africa (van der Linde 1992), on decorticated hardwood trees and structures (e.g., aged fence posts)”.

Teng (1933): “Hysterothecia scattered to subgregarious, 0.5-2.5 x 0.35-0.6mm, straight or flexuous, nearly smooth, but distinctly striate in age; asci clavate, short-stipitate, 140-170 x 26-30um; spores biseriate to sub-biseriate, oblong, straight or slightly curved, at first hyaline and continuous, then yellow or pale brown and uni-septate, finally deep brown to almost opaque, 3 – 7 septate, scarcely constricted at the middle, 38-50 x 11-15um. On bark of deciduous trees. Kiangsu: Nanking, Teng 1546. Chekiang: Kinhua, Deng 311, type, and 312. Lanchi Deng 333-335”.

van der Linde (1992): “This species was originally described from China & is retained by Zogg (1962) on the basis of ascospore septation & length. Fruitbodies much the same as those of Hysterium insidens, single or closely associated in groups, embedded or erumpent, long, linear, tapering towards the ends, straight, not branched, up to 2.0 x 0.5m. Pseudoparaphyses hyaline, septate, slightly thickened & branched at the tips to form an epithecium. Asci broad-cylindrical (with a broader upper half), 8-spored, irregulary viseriate, 155 – 165 x 25 – 30um. Ascospores dark brown, fusiform to oblong, phragmosporous, usually constricted at median septum, middle cell swollen, most commonly 8- or 9-septate, 40 – 45 x 12 – 14um.”

Oedohysterium sinense (Teng) E.W.A. Boehm & C.L. Schoch. Fig. 3 from Boehm et al. 2009b.

Oedohysterium pulchrum (Checa, Shoemaker & Umaña) E.W.A. Boehm & C.L. Schoch, comb. nov. MycoBank MB515424.

BasionymHysterographium pulchrum Checa, Shoemaker & Umaña, Mycologia 99: 289 (2007).

Boehm et al. 2009b: “The newly described Hg. pulchrum from Costa Rica (Checa et al. 2007) also falls within Clade D (Fig. 1) and is here transferred to Oedohysterium, asOd. pulchrum (DQ 402184 / DAOM 234345). This is because molecular data indicate a close association with the two species of OedohysteriumOd. insidens and Od. sinense. At first surprising, on further consideration, this sub-clade forms a natural assemblage premised on morphological features. The spores of all three taxa show a remarkable degree of similarity in morphology, which includes being similarly pigmented, slightly curved and fusiform, with a common number of transverse septa. The sole difference is the presence of one or two vertical septa in Od. pulchrum, a feature noted by the authors to be absent in some spores (Checa et al. 2007). Most importantly, like Od. insidens and Od. sinenseOd. pulchrum also possesses a swollen supra-median cell. Interestingly, a striking resemblance to the phragmospores of Od. insidens can be seen for those spores of Od. pulchrum that do not possess vertical septa (Checa et al. 2007). This is based on similarities in shape (e.g., curved and fusiform), size [(20-)23-28(-38) x (5-)7-10(-13) μm versus 22-25(-27) x 5-6 μm], and in the number of transverse septa (4-)6-8(-11) versus (5-)6, for Od. insidens and Od. pulchrum, respectively. As molecular data indicate that the presence or absence of vertical septa should be considered a sympleisiomorphic character state within the Hysteriaceae (Boehm et al. 2009), we feel justified in including both phragmospores and dictyospores within the genus Oedohysterium”.

Checa, Shoemaker & Umaña (2007): “Ascomata in bark, semi-immersed, hystereiform, 0.5 – 2mm long, 250um wide, 250um high, smooth, glabrous. Sulcus central. Ascocarp wall in section mostrly 20-30um thick, of about seven layers of rectangular, brick-like thin-walled cell 8-20 x 2-4um, with occasional lateral excrescences of 20-25 layers of similar cells and 50um wide. Paraphyses numerous, 1um wide, aseptate, without guttules, without slime coating, outermost centrum tissue red. Asci bitunicate, numberous, in a basal cluster, somewhat clavate, 80-90 x 13-15um (par sporif.), long-stalked (ca. 50um) with eight, over-lapping linearly tetraseriate ascospores above to uniseriate below. Ascospores terete, ellipsoid, L/W 3.7, straight to inequilateral, 22-25 (-27) x 5-6um, transversely (5) 6-septate, in centrifugal sequence (4):3:2:1:2:3:(4), mostly with one vertical septum in both cells next primary septum (absent in some spores), first-formed septum supramedian (0.40), constricted at first-formed septum and slightly so at others, without dots at ends of septa, septa thin, sidest at third cells from apex, pale reddish brown, without guttules, smooth, without sheath.”

Oedohysterium pulchrum (Checa, Shoemaker & Umaña)
E.W.A. Boehm & C.L. Schoch. From Checa et al. (2007).