Anoectangium sikkimense (Pottiaceae, Bryophyta) new to the New World from Alaska, and its macroevolutionary relationships

Richard H. Zander1

Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63116, U.S.A.

ABSTRACT. Anoectangium sikkimense (Pottiaceae, Bryophyta), a rare species known for China, India andNepal, is reported from the U.S.A. in Alaska. This species, distinctive in the marginal crenulation of theshoulders of the shortly sheathing base, is new to the New World. A key is given to New World species ofAnoectangium. Its serial evolutionary relationships are diagramed and discussed.

The genus Anoectangium Schwagr. (Pottiaceae,Bryophyta) is represented in North America(Zander 1994; Zander & Eckel 2007) by threespecies. Anoectangium aestivum (Hedw.) Mitt. iswidespread and known from mountainous areasworldwide. Anoectangium stracheyanum Mitt. is amore robust, uncommon species known from deepravines and protected places in eastern UnitedStates (Zander & Eckel 2007), while Cano &Jimenez (2013) listed its geographic range to alsoinclude Mexico, Central America, the Andes ofSouth America and eastern Asia. There is also aminiscule species, Anoectangium handelii Schiffn.,which is a rarity of western North America,southern Europe and southwestern and centralAsia. A review of collections on loan from NY

turned up an Anoectangium of novel morphology,described from India and Nepal as Anoectangiumsikkimense Aziz & Vohra.

Anoectangium sikkimense is similar to A. aesti-vum but its leaves in dry condition appear to berounded abaxially (probably because the distal leaf isvery narrow), not keeled, the leaves are verynarrowly acute, with a basal area much broadened,and often constricted above the flaring base, whilethe costa is excurrent in a sharp mucro of severalcells, and the margins of the leaf base at theshoulders are crenulate with mostly antrorse bluntprojections, which are unique in the genus. The

characteristic lateral gametoecia were present in theAlaskan collection, but the sexual organs wereundeveloped. Full descriptions have been providedby Aziz & Vohra (1988, 2008: 28). Sollman (2012)identified A. sikkimense as present in northwestIndia, Kashmir, Sikkim and Nepal, some that hefound to be misnamed as A. thomsonii Mitt. He alsocited two specimens from Yunnan Province, China,one of which is in MO.

Anoectangium sikkimense is reminiscent of Mo-lendoa hornschuchiana (Hook.) Lindb. ex Limpr. inthe lateral gametoecia, rounded abaxial leaf surfacewith leaf appearing tubulose when dry, long andsharp leaf apex, broadened leaf base with marginalantrose crenulation, but the latter species consists ofplants differing in being twice the size, yellow in 2%KOH rather than orange or rusty or brownish, theleaf cells are much larger, and there are two stereidbands in the costa. Below is a description from theAlaskan material.

TAXONOMY

Anoectangium sikkimense Aziz & Vohra, Bull. Bot.

Surv. India 30: 187. f. 1–14. 1988 [1990]. TYPE:

INDIA. SIKKIM: Sinchul, Kurz 2095 (holotype:

CAL, not seen). Fig. 1.

Description. Plants growing in turfs or cush-ions, green distally, light brown proximally. Stemsoften branching, ca. 2 cm in length, not papillose,

1 Author’s e-mail: richard.zander@mobot.org

The Bryologist 120: 435-440. Text and pagination the same as in original publication.

Figure 1. Anoectangium sikkimense Aziz & Vohra. A. Habit, moist. B. Habit, dry. C. Perichaetial branch. D–F. Leaves. G. Leaf apex. H. Detail of back of

costa. I. Leaf base shoulders. J. Leaf section near apex. K. Leaf section near base. L. Stem section. Scale bar: 2 mm, figs. A–B; 0.3 mm, fig. C; 0.5 mm, figs.

D–F; 50 lm, figs. G, I–L. Drawn from Lewis 483 (NY).

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transverse section rounded-pentagonal, centralstrand present and strong, sclerodermis presentbut weak, hyalodermis absent; axillary hairs of ca.6–7 cells, the basal 1–2 smaller and slightlythicker-walled; rhizoids red, dense in older partsof stem. Leaves crowded on stem, appressed-incurved and narrowly channeled when dry,somewhat incurved distally and spreading about458 above a short-sheathing base when moist,weakly constricted just above the broadly chan-neled base, long-lanceolate to long-triangular, ca.1–1.2 mm in length, distal lamina narrowlychanneled, margins plane throughout, essentiallyentire (minutely crenulate by shortly projectingcell walls) distally but crenulate with lateral mostlyantrorse blunt hollow denticulations along shoul-ders of broadened base, unistratose; apex narrowlyacute; base flaring 1.5–2 times width of distallamina; costa narrow distally and widened prox-imally, percurrent and ending in a short, sharpapiculus of 5–10 smooth cells, superficial cellslong-rectangular and smooth adaxially, rectangu-lar and smooth to densely low-papillose abaxially,ca. 2–4 rows of cells across costa adaxially atmidleaf, costal transverse section round distallyand strongly flattened proximally, one stereidband present, epidermis usually present adaxially,present abaxially, guide cells 2 distally grading to 4proximally, in 1 layer, hydroid strand absent; distallaminal cells quadrate, very small, 5–8 lm inwidth, 1:1, walls moderately thick-walled, notporose, superficially bulging-convex on both sidesdistally, unistratose throughout, papillae large,simple to bifid, crowded across the lumens; basalcells differentiated across leaf, rectangular torhomboidal, somewhat wider than medial cells,2–4:1, walls much thickened. Specialized asexualreproduction absent, probably reproducing bysomewhat fragile leaf apices. Lateral perichaetiapresent. Sporophytes not seen. Laminal KOHreaction orange or yellow-brown to rust-brown.

Specimens of Anoectangium sikkimense exam-ined. U.S.A. ALASKA: Shungnak Region, Mauneluk R.region, just NE of base of Mt. 2820, WorthwhileCliff, 668570N, 1568100W, Lewis 483 (NY). CHINA.YUNNAN PROV.: Gongshan Co., Bingshongluo Xiang,E slope of Gaoligong Shan, Nu Jiang (Salween)catchment, valley of SW slope of GawagapuMountain, rocky alpine valley, large cushions oncliff, Long 35917 (MO).

KEY TO SPECIES OF ANOECTANGIUM IN NORTH AMERICA

1. Gemmae abundant in leaf axils; leaves ligulate to short-elliptic or

ovate, 0.4–0.5(–0.6) mm............................. Anoectangium handelii

1. Gemmae absent; leaves lanceolate, usually 1–2 mm ...................... 2

2. Leaves usually distant on the stem, exposing it, short-

lanceolate to nearly ligulate, evenly tapering at leaf middle;

leaf base not broadened; leaf apex ending in a short-triangular

apiculus; costa percurrent in distal leaves into an apiculus of

1–5 cells ................................................ Anoectangium aestivum

2. Leaves dense and hiding the stem, long-lanceolate to linear-

elliptic, often slightly constricted at leaf middle just above the

leaf base; leaf base broadened; leaf apex narrowly acute to

acuminate, apiculus narrowly triangular; costa percurrent or

excurrent, apiculus or mucro of 8–10 cells ..................................... 3

3. Leaves narrowly long-lanceolate, orange or yellow-brown to

rust-brown in 2% KOH; leaves when dry appearing rounded

abaxially or tubulose; leaf apex very narrowly acute, percurrent

but grading evenly into the large apiculus; leaf base broadened

1.5–2 times distal leaf width; basal leaf margins crenulate with

mostly antrorse, blunt denticulations.... Anoectangium sikkimense

3. Leaves lanceolate, yellow in 2% KOH; leaves when dry clearly

keeled; leaf apex acute and mucro distinct; leaf base somewhat

broadened; basal leaf margins smooth or weakly papillose.........

............................................................. Anoectangium stracheyanum

EVOLUTIONARY ANALYSIS

The evolutionary position of Anoectangiumsikkimense is fairly clear. Hymenostylium xanthocar-pum (Hook.) Brid. is morphologically similar inmany respects. Because the rare H. xanthocarpumhas been separated from Hymenostylium recurviros-trum (Hedw.) Dixon (the latter removed to ArdeumaR.H.Zander & Hedd.; Zander & Hedderson 2016),no molecular guidance is at hand. Given thereduction of peristomes among the taxa of bothAnoectangium and Hymenostylium Brid., the group isancient and peristomate generalist progenitor taxaare presumed extinct. With an expectation of ancientheteroplasy (multiple branching of molecular racesand generation of descendant species from various ofthose branches), molecular resolution of the speciesis doubtless poor.

An analytic key (Table 1) is here presented. Thisis an indented prose diagram for species arranged inorder of maximum elimination of redundancyagainst an outgroup (Hymenostylium xanthocarpum)by identification of homology, much as is done inmaximum parsimony, but serially with one speciesgiven rise to another. In other words, two relatedspecies each have many traits; identifying those thatare the same eliminates redundancy of informationand identifies conservative traits that may be used totrack evolution. Noise is also eliminated, noiseconsisting of those traits that pop up in a scattered

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manner among related species. All traits left over arenew adaptive or significant nearly neutral traits. Theanalytic key details trait transformations frommodeled progenitor to descendant, assigning oneinformational bit to each trait transformation. Thebits are summed (they are logarithmic) and directlytranslated to Bayesian posterior probabilities. This isexplained in detail by Zander (2014a,b,c, 2016, 2017:37), with the bit-BPP equivalencies in a table.

In the analytic key presented in Table 1,indentations indicate descendants as taxon-levelsteps, and show trait changes. Bits are informationalunits equal to one trait transformation. BPP areequivalent Bayesian posterior probabilities. EachBPP is support for the order of evolution of aspecies from its progenitor. Summed bits for theAnoectangium lineage are 13, or a BPP of more than0.999, supporting the order of evolution andcoherence of the lineage. Hymenostylium xanthocar-pum, as outgroup, is not included in the Anoectan-gium lineage. The suggested extant progenitor withinthe genus Anoectangium is A. stracheyanum. From itdescended A. sikkimense and A. aestivum. Anoectan-gium aestivum was ancestral to A. handelii. Theevolutionary formula, identifying the species (in-cluding the outgroup) by their numbers, is 1 . 2 .

(3 (4 . 5)), where numbers of modeled theoretic

progenitors are bold-faced, and light-faced taxa arehighly specialized end members.

Given the analytic key, a caulogram (a diagramof putative serial relationships) may be constructed.Here the caulogram (Fig. 2) is embedded in a muchsimplified diagram of the theoretical general trend ofmacroevolutionary relationships in any large group,but crudely applicable to the Pottiaceae. Theevolutionary lineages may be modeled as a centrallineage forming a front of evolutionary change, withgeneralist progenitor species creating usually shortside lineages of more specialized descendants (the‘‘dissilient genus’’ concept, see Zander (2013: 85,152). As progenitor species age, side lineages becomemore common and get longer, thus the apex ofmacroevolutionary change in the family lookssomewhat like a cone advancing through time. Withincreasing geologic time, species begin to go extinct.Generalist progenitor species in one (or more)lineages central to the larger group probabilisticallygo extinct more quickly than their specialistdescendants because (1) there are fewer progenitorsthan descendants, and (2) descendants may survivegeneral climate changes in specialized microenvi-ronments. Thus, another cone is formed travelingthrough time behind the macroevolutionary front,but this is a following cone of extinction. If mostprogenitor species in Pottiaceae have the character-istic twisted peristome, then descendant species fromancient pottiaceous genera specialized throughpleurocarpy, strongly keeled leaves, loss of peri-stome, and loss of costal adaxial stereid band andhydroid strand would well describe and explainAnoectangium. The genus Anoectangium is heretheoretically placed near the cone of extinction thatfollows the macroevolutionary front of the Pottia-ceae. Progenitor species of Anoectangium havethemselves generated descendants. Of course, fillingin the Pottiaceae caulogram requires significantadditional study.

DISCUSSION

The occurrence of Anoectangium sikkimense innorthwestern North America is another example ofan eastwardly scattering of uncommon species moreprevalent in eastern Asia. Given that winds arewesterly, it is possible that long-distance dispersal isto some extent operative. This might explain therarity of this species and of other species in westernNorth America that are more common in eastern

Table 1. Analytic key to Anoectangium in North America with

Hymenostylium xanthocarpum as outgroup. Order minimizes redundan-

cy of traits. Letters indicate degrees of indentation, modeling serial

evolutionary descent. Informational bits (as number of traits) supporting

order of evolution of two species are directly translated to Bayesian

posterior probability.

Trait transformations Bits BPP Species

A. Perichaetia terminal; leaves long-

ligulate, broadened at the base,

slightly constricted above the base

just below midleaf; stem central

strand present; costa percurrent, two

stereid bands; papillae massive

Outgroup 1. Hymenostylium

xanthocarpum

B. Gametoecia lateral on the

stem; leaves with a strong mucro;

costa with one stereid band,

lacking adaxial epidermis

4 0.94 2. Anoectangium

stracheyanum

C. Leaves narrowed above,

flared basally, shoulders

crenulate

3 0.89 3. A. sikkimense

C. Leaves shortened, short-

apiculate, base not widened

3 0.89 4. A. aestivum

D. Leaves very short, blunt;

gemmae present

3 0.89 5. A. handelii

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Asia. These include, in the Pottiaceae, species with

asexual reproduction by fragile leaf apices or

gemmae: Didymodon anserinocapitatus (X.J.Li)

R.H.Zander, Fuscobryum perobtusum (Broth.)

R.H.Zander, Vinealobryum murrayae (Otnyukova)

R.H.Zander, and V. tectorum (Mull. Hal.)

R.H.Zander. Anoectangium sikkimense may be a

member of this asexually reproducing group in that

its leaf tips are often broken off and may act as

diaspores.

ACKNOWLEDGMENTS

Patricia M. Eckel kindly contributed the excellent illustration.

Thanks are extended to the Missouri Botanical Garden for its

continued support and encouragement. I appreciate the loan of

material from NY.

LITERATURE CITED

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Figure 2. Diagram of theoretic macroevolution of a large taxonomic group with one central lineage of progenitor species and lateral descendant lineages

of increasing specialization. To the right is a traveling front of macroevolutionary evolution, with descendant lineages increasing in length (numbers of

species) with time, trailed by a cone of extinction leaving a set of highly dissected lineages of mostly specialized descendants. Were this Pottiaceae,

Anoectangium would be a lineage with its generalist, probably peristomate progenitors extinct. Its caulogram is here situated near the traveling cone of

extinction with part of the lineage extinct. Diagram is an explanatory cartoon, not software generated.

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Zander, R. H. 2014b. Classical determination of monophyly,

exemplified with Didymodon s. lat. (Bryophyta). Part 2 of 3,concepts. Phytoneuron 2014–79: 1–23.

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