Introduction
The genus Pyxine is a predominantly tropical group in the Physciaceae, with c. 70 species currently accepted worldwide (Swinscow & Krog Reference Swinscow and Krog1975; Aptroot Reference Aptroot1987; Kalb Reference Kalb1987, Reference Kalb, Nash, Ryan, Diederich, Gries and Bungartz2002, Reference Kalb2004; Awasthi Reference Awasthi1988; Elix Reference Elix2009; Jungbluth & Marcelli Reference Jungbluth and Marcelli2011; Mongkolsuk et al. Reference Mongkolsuk, Meesim, Poengsungnoen and Kalb2012; Nayaka et al. Reference Nayaka, Upreti, Ponmurugan and Ayyappadasan2013). The majority of these species have atranorin as a cortical substance, but 20 species contain lichexanthone in the upper cortex. It therefore comprises the largest number of foliose species with lichexanthone as cortical pigment, a substance that is largely confined to some groups of tropical crustose lichens, chiefly pyrenocarps and Graphidaceae.
The genus Pyxine has been studied in Brazil for more than a century. Both Malme (Reference Malme1897) and Kalb (Reference Kalb1987) started their series of publications on Brazilian lichens with the genus Pyxine. Recently, Jungbluth & Marcelli (Reference Jungbluth and Marcelli2011) and Jungbluth et al. (Reference Jungbluth, Marcelli and Kalb2011) described four additional species from Brazil. It has by far the highest number of known Pyxine species, with 34 species (out of c. 70 worldwide), seven of which, including the species described above, are so far only known from Brazil (Kalb Reference Kalb1987, Reference Kalb2004; Jungbluth et al. Reference Jungbluth, Marcelli and Kalb2011; Jungbluth & Marcelli Reference Jungbluth and Marcelli2011).
Species with lichexanthone are even better represented in Brazil, with 14 out of the 21 species known worldwide being from Brazil. This agrees with the field observation that Pyxine species with lichexanthone are often in the majority in the Neotropics and Macaronesia, and species with atranorin are often in the majority in Africa, Australia and Asia. Brazil is clearly the centre of Pyxine diversity. The campus of the Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP-Botucatu) and the Botanical Garden of Botucatu in São Paulo State are rich in microfoliose Physciaceae that often grow in close contact with each other on trees planted along the roads and in parks, as well as on some remnants of the original forest preserved in the Botanical Garden. Species present there include Dirinaria applanata (Fée) D. D. Awasthi, D. confluens (Fr.) D. D. Awasthi, D. purpurascens (Vain.) B. J. Moore, Heterodermia albicans (Pers.) Swinscow & Krog, H. diademata (Taylor) D. D. Awasthi, H. japonica var. reagens (Kurok.) J. N. Wu & Z. G. Qian, H. obscurata (Nyl.) Trevis., H. pseudospeciosa (Kurok.) W. Culb., H. speciosa (Wulf.) Trevis., Hyperphyscia cochlearis Scutari, H. granulata (Poelt) Moberg, H. isidiata Moberg, H. syncolla (Nyl.) Kalb, Physcia alba (Fée) Müll. Arg., P. atrostriata Moberg, P. crispa Nyl., P. erumpens Moberg, P. krogiae Moberg, P. pachyphylla Müll. Arg., P. poncinsii Hue, P. sorediosa (Vain.) Lynge, P. undulata Moberg, Pyxine astridiana Kalb, P. berteriana (Fée) Imshaug, P. katendei Swinscow & Krog, P. petricola Nyl., P. simulans Kalb and P. subcinerea Stirt. (all collected on 13 September 2012 by M. Cáceres & A. Aptroot; specimens in ABL). As it is, it is one of the richest areas in the world for microfoliose Physciaceae, and provides a unique opportunity to study many, sometimes very similar-looking, species in close contact in the field. While doing so, we came across one undescribed Pyxine species. It is described below and a world key to all currently accepted Pyxine species with lichexanthone is given.
Materials and Methods
Identification and descriptive work was carried out in the Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP-Botucatu) and in Soest using an Olympus SZX7 stereomicroscope and an Olympus BX50 compound microscope with interference contrast, connected to a Nikon Coolpix digital camera. Sections were mounted in tap water, in which all measurements were also taken. The specimens from this study are preserved in SP and ABL. The chemistry of the type specimen was investigated by UV, spot reactions and TLC (solvent A, Orange et al. Reference Orange, James and White2001).
The New Species
Pyxine pustulata Aptroot & Jungbluth sp. nov.
MycoBank No.: MB 808448
Pyxine with lichexanthone in the cortex, a yellow to ochraceous medulla with negative reaction to spot tests, and clusters of laminal polysidiangia.
Type: Brazil, São Paulo, Botucatu, Botanical Garden on campus, alt. 850 m, 22°53′09″S, 48°29′56″W, on bark of tree in park, 13 September 2012, M. Cáceres & A. Aptroot 13638 (SP—holotype; ABL—isotype).
(Fig. 1)
Fig. 1. Pyxine pustulata, isotype, habitus. Scale=0·5 mm.
Thallus appressed foliose, corticate, shiny, pale grey. Lobes irregularly linear, much dissected and not confluent or overlapping, quite regularly c. 0·7–1·2 mm wide throughout. Lobe tips mostly rounded, with few, irregular, linear, white maculae, without pruina. Lobes convex, in older parts with laminal, thallus-coloured pustules c. 0·1–0·3 mm wide and c. 0·2–0·6 mm high. Polysidiangia clustered in generally large groups c. 0·3–1·5 mm wide, corticate when young and at the sides, becoming ecorticate above, when old inside with few granular soredia, occasionally exposing the yellow medulla. Medulla bright yellow to ochraceous above, white below. Lower surface black, shiny, with regularly dispersed, simple, black rhizines.
Ascomata and pycnidia not observed.
Chemistry
Thallus cortex UV+ yellow, K−. Thallus medulla (both layers) UV−, P−, K−. TLC: lichexanthone, terpenoids and pigment.
Ecology and distribution
On smooth bark of trees. Known only from Botucatu, Brazil.
Discussion
This species is close to P. caesiopruinosa (Nyl.) Imshaug and P. physciiformis (Malme) Imshaug. However, the upper medulla of Pyxine physciiformis is K+ faint reddish orange, while P. caesiopruinosa has a K+ purple upper medulla.
World key to the species of Pyxine with lichexanthone
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1 Thallus with isidia, dactyls, pustules or soredia ... 2
Thallus without isidia, dactyls, pustules or soredia, usually with apothecia ... 12
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2(1) Thallus with corticate isidia ... 3
Thallus with at least partly ecorticate dactyls, polysidiangia or soredia ... 4
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3(2) Medulla white; Africa ... P. lyei Swinscow & Krog
Medulla yellow; India ... P. punensis Nayaka & Upreti
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4(2) Thallus with soredia ... 5
Thallus with dactyls or polysidiangia ... 9
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5(4) Medulla white ... 6
Medulla yellow, ochraceous or salmon ... 7
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6(5) Soredia mainly marginal, granular, irregular; pantropical. ... P. cocoes (Sw.) Nyl.
Soredia laminal, farinose originating as dots on flat lobes; Africa ... P. katendei Swinscow & Krog
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7(5) Soredia mainly marginal, medulla K−; pantropical ... P. subcinerea Stirt.
Soredia laminal, medulla at least partly K+ purplish or K+ yellow>red ... 8
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8(7) Medulla partly K−, partly K+ purplish ... P. albovirens (G. Meyer) Aptroot
Medulla partly K+ purplish, partly K+ yellow>red ... P. jolyana Jungbluth et al.
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9(4) Medulla K+ purplish; neotropical ... P. caesiopruinosa (Nyl.) Imshaug
Medulla K− ... 10
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10(9) Thallus with dactyls that do not become sorediate; Africa ... P. lilacina Swinscow & Krog
Thallus with dactyls or pustules that become sorediate ... 11
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11(10) Thallus with discrete lobes with numerous minute pustules; Brazil ... P. pustulata Aptroot & Jungbluth
Thallus with overlapping lobes with irregular, large and often sparse dactyls; pan-tropical ... P. physciiformis (Malme) Imshaug
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12(1) Medulla white ... 13
Medulla yellow, ochraceous or salmon ... 15
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13(12) Apothecium margin grey, thalline; neotropical ... P. astridiana Kalb
Apothecium margin black, not thalline ... 14
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14(13) Thallus lobes at the margin >1 mm wide; pantropical ... P. petricola Nyl.
Thallus lobes at the margin <1 mm wide; pantropical ... P. microspora Vain.
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15(12) Apothecium margin grey, thalline ... 16
Apothecium margin black, not thalline ... 17
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16(15) Thallus lobes at the margin >1 mm wide; pantropical ... P. simulans Kalb
Thallus lobes at the margin <1 mm wide; neotropical ... P. nana Kalb
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17(15) Apothecia without clear stipe. Neotropical ... P. pyxinoides (Müll. Arg.) Kalb
Apothecia with stipe ... 18
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18(17) Apothecium stipe orange, K+ purplish, medulla orange ... 19
Apothecium stipe white, ochraceous or salmon; medulla (partly) yellow ... 20
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19(18) Medulla K+ purplish; Africa ... P. endocrocea Kalb
Medulla K−; pantropical ... P. cognata Stirt.
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20(18) Medulla uniformly yellow; Asia and Australia ... P. australiensis Kalb
Medulla only yellow in upper layers; pantropical ... P. berteriana (Fée) Imshaug
The CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) is thanked for a research grant to MESC (Processo 311706/2012-6). We are grateful to CAPES (Processo CAPES 5324/2012-54 AUX PE-PAEP 1669/2012) for providing funding to PJ, enabling AA and MESC to attend the EGBL6 meeting in Botucatu where the material was collected. AA thanks the Stichting Hugo de Vries-Fonds for a travel fund.
