This key contains some corrections to the one published in the recent monograph by the first author (Bibliotheca Lichenologica vol. 62, 1996) and includes later additions, see literature at the bottom of this page. The first version of this Internet edition was produced by H. Sipman on 20 November 1997. All species are epiphytic, unless otherwise indicated.

a   Thallus isidiate and/or lobulate                                   2
 b   Thallus not isidiate or lobulate                                  18

2a   Isidia globose to cylindrical                                      3
 b   Isidia dorsiventral, becoming lobulate, or lobules only           12

3a   Lower surface pale brown to dark brown                             4
 b   Lower surface black, rarely brown-black at lobe margins            7

4a   Rhizines simple or sparingly branched                              5
 b   Rhizines with secondary rhizines which are densely branched and
     agglutinated                                                       6

5a   Isidia branched and coralloid; hypostictic and menegazziaic acid
     absent or present in traces only (stictic acid major); Japan, 
     Taiwan, India, SE Asia, Australia, epiphytic and on rock
                                             R. sydneyensis (Gyeln.) Hale
 b   Isidia simple; hypostictic and menegazziaic acid present in
     significant amounts (stictic acid major); Queensland
                                           R. ramboldii Elix & J. Johnst.

6a   Cilia dense, to 2 mm long; containing protocetraric acid (major); 
     SE Asia, Australia                       R. circumnodata (Nyl.) Hale
 b   Cilia sparse to moderate, to 0.3 mm long; containing succinprotoce-
     traric acid (major) and fumarprotocetraric acid (minor); Queensland
                                        R. conglutinata Elix & J. Johnst.

7a   Lobes very narrow and tightly adnate, 0.3-1.0 mm wide; containing
     echinocarpic acid; paleotropical                  R. amphithrix Hale
 b   Lobes broader, adnate, 1-3 mm wide                                 8

8a   Medulla K+ intense yellow (or orange) or yellow turning red, 
     containing stictic or norstictic acids                             9
 b   Medulla K-, or K+ pale yellow, containing 4-O-demethylbarbatic,
     echinocarpic or gyrophoric acids                                  10

9a   Rhizines branched; medulla K+ intense yellow (or orange), containing
     stictic acid (major) and norstictic acid (minor); Australia,
     epiphytic and on rock                  R. subnigra Elix & J. Johnst.
 b   Rhizines simple; medulla K+ yellow turning red, containing
     norstictic acid (major) rarely with diffractaic acid, stictic
     acid absent; pantropical                    R. abstrusa (Vain.) Hale

10a  Medulla P+ yellow or orange, containing echinocarpic acid (major);
     SE Asia, Australia                      R. planiuscula (Kurok.) Hale
  b  Medulla P-, containing 4-O-demethylbarbatic or gyrophoric acids   11

11a  Lobes narrow, 0.3-1.5 mm wide; medulla C- or C+ yellow-orange, 
     containing 4-O-demethylbarbatic acid (major); Queensland
                                   R. demethylbarbatica Elix & J. Johnst.
  b  Lobes broader, 1.0-3.5 mm wide; medulla C+ pink or red, containing
     gyrophoric acid (major); New Guinea                  R. vinasii Elix

a (2) Cylindrical isidia present                                     13
  b  Cylindrical isidia absent                                         15

13a  Lobes narrow, tightly adnate, 0.3-1.0 mm wide; containing
     echinocarpic acid; paleotropical                  R. amphithrix Hale
  b  Lobes broader, adnate, 1-3.5 mm wide                              14

14a  Thallus coriaceous; apothecia ecoronate; containing echinocarpic
     acid (major); SE Asia, Australia        R. planiuscula (Kurok.) Hale
  b  Thallus fragile; apothecia subcoronate; containing echinocarpic acid
     (major); SE Asia, Australia            R. schizospatha (Kurok.) Hale

15a  Lobes narrow, tightly adnate, 0.3-1.5 mm wide                     16
  b  Lobes broader, adnate, 1-3.5 mm wide                              17

16a  Medulla P+ yellow or orange, containing echinocarpic acid (major); 
     SE Asia                                              R. palmata Elix
  b  Medulla P-, containing relicinulinic acids A, B (major): SE Asia, 
     Australia                            R. relicinula (Müll. Arg.) Hale

17a  Medulla P+ yellow or orange, containing echinocarpic acid, with or
     without gyrophoric acid (trace); New Guinea
                                          R. gemmulosa (Kurok.) Streimann
  b  Medulla P-, C+ rose; containing gyrophoric acid (major), 
     echinocarpic acid absent; SE Asia      R. luteoviridis (Kurok.) Hale

a (1) Lower surface pale brown to dark brown                         19
  b  Lower surface black, rarely black-brown at lobe margins           30

19a  Rhizines densely branched and agglutinated, at least in part      20
  b  Rhizines simple or sparsely branched                              25

20a  Medulla K+ yellow then dark red; containing salazinic acid        21
  b  Medulla K-, salazinic acid absent                                 22

21a  Spores small, 3-4 x 2 mu; containing barbatic acid (major); Malaysia
                                                       R. sabahensis Elix
  b  Spores larger, 7-8 x 4-5 mu; barbatic acid absent; Java
                                              R. acrobotrys (Kurok.) Hale

22a  Medulla P-; containing barbatic acid; New Guinea
                                         R. agglutinata Elix & J. Johnst.
  b  Medulla P+ red-orange; containing protocetraric, fumarprotocetraric
     or succinprotocetraric acids                                      23

23a  Apothecia coronate; containing protocetraric acid (major); 
     Philippines                                  R. precircumnodata Hale
  b  Apothecia ecoronate or lacking                                    24

24a  Spores small, ca. 3 x 2 mu; containing succinprotocetraric acid
     (major), fumarprotocetraric acid (minor); SE Asia, Australia
                                             R. ramosissima (Kurok.) Hale
  b  Spores larger, 7-9 x 4-5 mu; containing protocetraric acid (major);
     SE Asia, Solomon Islands, Australia        R. subleana (Kurok.) Hale

25a  Medulla K- or K+ pale yellow then dirty brown; containing
     protocetraric acid (major); Queensland               R. dentata Elix
  b  Medulla K+ intense yellow or yellow then red                      26

26a  Medulla K+ yellow then red; containing norstictic acid (major);   27
  b  Medulla K+ intense yellow; containing stictic acid (major), 
     norstictic acid (minor/trace)                                     28

27a  Apothecia ecoronate; New South Wales   R. filsonii Elix & J. Johnst.
  b  Apothecia coronate or subcoronate; New South Wales
                                                  R. barringtonensis Elix

28a  Apothecia subcoronate; lobes tightly adnate; Queensland
                                         R. subcoronata Elix & J. Johnst.
  b  Apothecia ecoronate; lobes adnate                                 29

29a  Lobes narrow, 0.5-1.5 mm wide; containing menegazziaic acid (major
     or submajor); Queensland, on rock    R. clarkensis Elix & J. Johnst.
  b  Lobes broader, 1-3 mm wide; menegazziaic acid absent or present in
     traces only; Australia, epiphytic or on rock
                                                 R. limbata (Laurer) Hale

a (18) Apothecia present, coronate or subcoronate                    31
  b  Apothecia ecoronate or absent                                     42

31a  Medulla K+ yellow then red; containing norstictic acid; pantropical
                                             R. subabstrusa (Gyeln.) Hale
  b  Medulla K- or K+ yellow; norstictic acid absent                   32

32a  Lobes narrow, 0.3-1.5 mm wide, tightly adnate; gyrophoric acid
     absent or present in traces only                                  33
  b  Lobes broader, 1-3 mm wide, adnate; containing gyrophoric acid
     (major); New Guinea, Solomon Islands
                             R. retrospinosa (Kurok. & Kashiw.) Streimann

33a  Medulla P-                                                        34
  b  Medulla P+ yellow, orange or red                                  38

34a  Diffractaic acid present (major); neotropical      R. incongrua Hale
  b  Diffractaic acid absent                                           35

35a  Hirtifructic acid present (major); New Guinea, Fiji
                                           R. fijiensis Elix & J. Johnst.
  b  Hirtifructic acid absent                                          36

36a  Butlerins A, B, C and D present (minors); Queensland
                                                      R. kurandensis Elix
  b  Butlerins A, B, C and D absent                                    37

37a  Caperatic acid present (major); Malaysia        R. subconnivens Hale
  b  Relicinulinic acids A, B (major) present; SE Asia, Australia
                                          R. relicinula (Müll. Arg.) Hale

38a  Spores 8 per ascus; malonprotocetraric acid absent                39
  b  Spores 16-32 per ascus; containing malonprotocetraric acid (major); 
     neotropical                               R. relicinella (Nyl.) Hale

39a  Medulla P+ brick red; succinprotocetraric acid present, echinocarpic
     acid absent; Florida, Caribbean         R. eximbricata (Gyeln.) Hale
  b  Medulla P+ pale yellow or yellow-orange; echinocarpic acid present; 
     succinprotocetraric acid absent                                   40

40a  Apothecia stipitate; medulla P+ pale yellow; containing diffractaic
     acid (major), echinocarpic acid (minor/trace); Guyana
                                                        R. stipitata Elix
  b  Apothecia sessile; medulla P+ yellow-orange; containing echinocarpic
     acid (major), diffractaic acid absent                             41

41a  Lobes separate, axils broad; lacking hirtifructic acid; SE Asia, 
     Pacific, Australia                       R. samoensis (Zahlbr.) Hale
  b  Lobes contiguous, axils acute; containing hirtifructic acid; New
     Guinea, Australia                R. terricrocodila Elix & J. Johnst.

a (30) Medulla P-                                                    43
  b  Medulla P+ yellow, orange or red                                  44

43a  Medulla UV+ blue-white; containing alectoronic acid; SE Asia
                                               R. fluorescens (Hale) Hale
  b  Medulla UV-; containing protolichesterinic acid (major), butlerins
     A, B, C, D; SE Asia, Australia            R. connivens (Kurok.) Hale

44a  Medulla K+ yellow then dark red; containing salazinic or norstictic  
     acid (major)                                                      45
  b  Medulla K- or K+ pale yellow-brown; salazinic and norstictic acid 
     absent                                                            47

45a  Thallus saxicolous; cilia 1-2 mm long, weakly inflated; lacking
     echinocarpic acid; Brazil         R. xanthoparmeliformis Elix & Nash
45b  Thallus corticolous; cilia 0.1-0.5 mm long, conspicuously inflated; 
     containing echinocarpic acid (minor)                              46

46a  Containing salazinic acid (maior); Japan           R. segregata Elix
  b  Containing norstictic acid (maior); Thailand
                                              R. polycarpa Elix & Polyiam

47a  Medulla P+ brick red; containing fumarprotocetraric acid          48
  b  Medulla P+ yellow or orange; containing echinocarpic acid         49

48a  Rhizines squarrosely branched; succinprotocetraric acid absent; SE
     Asia                                        R. malesiana (Hale) Hale
  b  Rhizines simple or sparingly furcate branched; succinprotocetraric
     acid present (major); Burma, Thailand      R. sublimbata (Nyl.) Hale

49a  Medulla C+ rose or red; gyrophoric (major) and hirtifructic acids
     present, echinocarpic minor; New Guinea
                                        R. hirtifructa (Kurok.) Streimann
  b  Medulla C-; gyrophoric and hirtifructic acids absent, echinocarpic
     major                                                             50

50a  Lobes narrow, 0.5-2 mm wide; upper cortex not columnar            51
  b  Lobes broader, 1.5-3 mm wide; upper cortex columnar; SE Asia
                                          R. columnaria Elix & J. Johnst.

51a  Lobes narrow, 0.5-1 mm wide, linear-elongate; New Guinea
                                                         R. sipmanii Elix
  b  Lobes broader, 1-2 mm wide, sublinear; Japan
                                             R. echinocarpa (Kurok.) Hale

Literature:
Elix, J. A. 1998. A new species and revised key to the genus Relicina (Ascomycotina, Parmeliaceae). Mycotaxon 69: 129-136.
Noicharoen, K, Polyiam, W, Boonpragob, K, Elix, J. A. & Wolseley, P. A. 2003. New species of Parmotrema and Relicina (Ascomycota, Parmeliaceae) from Thailand. Mycotaxon 85: 325-330.