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Protistology 18 (3): 189-211 (2024) | doi:10.21685/1680-0826-2024-18-3-2 PPOtÎStOlOây
Original article
Myxomycete diversity of deciduous dry lowland forests of the Binh Chau-Phuoc Buu Nature Reserve (Vietnam) as revealed by moist chamber cultures
Yuri K. Novozhilov1*, Anna D. Luptakova1 Fedor M. Bortnikov1 and Thi Ha Giang Pham2
1 V.L. Komarov Botanical Institute of the Russian Academy of Sciences, 197376 St. Petersburg, Russia
2 Joint Vietnam-Russia Tropical Science and Technology Research Centre, Nguyen Van Huyen, Nghia Do, Cau Giay, Hanoi 122100, Vietnam
| Submitted May 27, 2024 | Accepted June 26, 2024 |
Summary
A first systematic survey of myxomycetes in the deciduous dry lowland forests of the Binh Chau-Phuoc Buu Nature Reserve in Southern Vietnam was carried out in November 2014. In total, the survey yielded 168 records belonging to 43 taxa from 18 genera and nine families. Due to the dry climatic conditions in the study region between September and April, all specimens of sporocarps were obtained using moist chamber cultures prepared with samples of the bark taken from the surface of living trees (122 cultures), ground litter (123), and the weathered dung of cattle (28) and cultured for 90 days. All taxa were new for the nature reserve and 11 species (including one variety) were recorded for the first time in Vietnam. Only six species of myxomycetes (Arcyria cinerea, A. marginoundulata, Craterium minutum, Echinostelium minutum, Licea pseudoconica, Physarum cinereum, and Metatrichia vesparia) were widespread. One specimen belonging to the genus Trichia could not be clearly assigned to any described species. The coprophilous myxomycetes Perichaena cf. pachyderma and P. liceoides were found in Vietnam for the first time. The highest diversity was observed for corticolous species inhabiting the bark of living trees, especially Dipterocarpus spp. that have deeply furrowed bark. Only L. pseudoconica was found exclusively on bark and this species appeared to prefer the thick bark of older trees of Dipterocarpus sp. with furrowed and slightly acidic bark (pH 5.16 ± 0.51). The poorest corticolous myxomycete biota was recorded for the peeling bark of Melaleuca cajuputi and Eucalyptus sp.
Key words: Amoebozoa, biodiversity, coprophilous myxomycetes, corticolous myxomycetes, ecology, Myxogastria, savanna-like woodlands, Southeast Asia, Southern Vietnam, species inventory
Introduction
Currently, 190 morphospecies of myxomycetes are known from Vietnam (Loi et al., 2023; Luptakova et al., 2024). However, these data are mostly reports
https://doi.org/10.21685/1680-0826-2024-18-3-2
© 2024 The Author(s)
Protistology © 2024 Protozoological Society Affiliated with RAS
from monsoon lowland tropical forests (Novozhilov et al., 2017a) and mountain tropical forests (Fedoro-va et al., 2020; Novozhilov et al., 2020). In contrast, the myxomycete diversity of semi-deciduous and deciduous dry lowland forests and open savanna-like
Corresponding author: Yuri K. Novozhilov. V.L. Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov St. 2k, St. Petersburg 197376, Russia; [email protected]
Fig. 1. Maps of the study area. A — Schematic map of the study area, 14 sampled localities are indicated by numbers and circles. B — Black dot indicates the geographical position of the Binh Chau-Phuoc Buu Nature Reserve (BCPB). Source: Google Earth (modified).
woodlands in Vietnam has not been studied thus far, although these vegetation types characterize one of the main phytogeographic regions and extend across all mainland Southeast Asia (Averyanov et al., 2003). In other tropical regions of the world, myxomycetes of savannas and semi-arid grasslands are also poorly studied. There are only a few studies focusing on the assemblages of myxomycetes associated with the cerrado (tropical savanna) in eastern Brazil (Maimoni-Rodella and Gottsberger, 1980) and the African savannas and tropical dry forests in Ethiopia (Harkonen, 1981; Dagamac et al., 2017).
In these regions, especially during dry season, myxomycete sporocarps in the field are very rare since these organisms need substrates covered with a film of water for their active life. For this reason, most of the data recorded in arid regions of the world (e.g., Novozhilov et al. 2003, 2006; Novozhilov and Schnittler, 2008; Schnittler et al., 2013, 2015; Zemlyanskaya et al., 2020) have been obtained in moist chamber cultures (MCCs).
The primary objective of the present study was to collect and describe taxonomic and distributional data on the myxomycetes of the deciduous dry
lowland forests of the Binh Chau-Phuoc Buu Nature Reserve (BCPB) in southern Vietnam.
Material and methods
Study area
Study area: BCPB is situated in the South Eastern region of Vietnam (Fig. 1), in Ba Ria-Vung Tau Province, and centered at 10°28' to 10°38' N and 107°25' to 107°36' E (Danilov et al., 2020). The southern boundary of the nature reserve is a 12-km long coastline (Fig. 1, A, B). The nature reserve contains three areas of low hills, 100 to 162 m a.s.l. There are very few streams and rivers within the nature reserve, but there are some small bodies of standing water, including swamps and hot springs. Tropical broad-leaved semi-deciduous forests are the dominant vegetation in the nature reserve. The most important families are the Dipterocarpaceae, Lythraceae, Sapindaceae, Myrtaceae, Sterculiaceae, and Anacardiaceae (Nguyen et al., 2019; Dang et al., 2020). The primary dominants in the driest
Fig. 2. A, B — Savanna-like woodland with scattered trees ofDipterocarpaceae on sandy soil, locality 1; C — area of swamp near the border of the forest with Melaleuca cajuputi and Dipterocarpus sp. around a dried lake, locality 2; D — dense swamp forest with M. cajuputi, locality 2; E — dry semi-deciduous tropical opened forest on sandy soil with many stones and rocks, locality 4; F — mixed deciduous coastal forest with trees of Dipterocarpaceae on sand dunes, locality 9; G — plantation of Eucalyptus sp., locality 7; H — xerophilic coniferous coastal forest with Casuarina sp. near a sandy sea shore, locality 6.
open lowland forests are no taller than 15—20 m, and semi-deciduous trees of the Dipterocarpaceae are very typical within the highest tier of the canopy (Averyanov et al., 2003). Ferallitic pale yellow and gray-yellow soils predominate in these areas. However, the largest area is occupied by acidic sulfate soils (pH 4—4.5), which are suitable for trees of Melaleuca cajeputii (Fig. 2, D). Trees of Casuarina sp. (Dang et al., 2020) dominate sandy soils along the coast. The climate in the reserve is a "tropical savanna climate — a dry winter" or "Aw" in terms ofthe Kopen climate classification (https:// en.wikipedia.org/wiki/Tropical_savanna_climate). Annual rainfall is less than 1,500 mm in most of the region and as low as 800 mm in some places. This climate is characterized by relatively even temperatures throughout the year but a pronounced dry season. The driest month has less than 60 mm of precipitation. The dry season usually lasts from November to April (six months), sometimes up to seven months.
Study localities and habitat types
Substrate samples for MCCs were obtained from 14 principal collecting localities along the studied landscape profiles in what were considered to be the most typical and representative plant communities (Fig. 1, A). Geographical coordinates and elevation above sea level were measured for each site, using the GPS receiver of the iPhone 8 plus and the program Gaia v2020.3 for iOS.
List of localities: A) Savanna-like woodland with scattered Melaleuca cajuputi trees and trees of Dipterocarpus spp. on sandy soils. Locality 1: 10°32'25" N, 107°28'15" E, 60 m a.s.l.; Locality 14: 10°32'30" N, 107°29'36" E, 35 m a.s.l. (Fig. 2, A, B); B) Dense swamp forest with M. cajuputi and Dipterocarpus spp. trees around a dried-lake bed. Locality 2: 10°32'45" N, 107°29'18" E, 70 m a.s.l. (Fig. 2, C, D); C) Dry semi-deciduous tropical open forest on sandy soils with many stones and rocks. Locality 4: 10°30'28" N, 107°29'50" E, 30 m a.s.l. (Fig. 2, E); Locality 5: 10°30'2" N, 107°29'49" E, 20 m a.s.l.; D) Dry semi-deciduous dense forest on sandy soil at the border with dunes and a sea shore. Locality 5: 10°29'35" N, 107°27'38" E, 5 m a.s.l.; Locality 8: 10°29'50" N, 107°27'50" E, 5 m a.s.l; E) Mixed deciduous dense coastal forest with trees of Dipterocarpaceae. Locality 9: 10°31'44" N, 107°29'45" E, 70 m a.s.l. (Fig. 2, F); Locality 10: 10°31'40" N, 107°29'47" E, 70 m a.s.l.; Locality 11:
10°32'37" N, 107°29'47" E, 60 m a.s.l.; Locality 12: 10°31'40" N, 107°29'15" E, 70 m a.s.l.; Locality 13: 10°31'37" N, 107°29'36" E, 85 m a.s.l.; F) Xerophilic coniferous coastal forest with Casuarina sp. near a sandy sea shore. Locality 6: 10°29'28" N, 107°27'40" E, 10 m a.s.l. (Fig. 2, H); G) Plantation of Eucalyptus sp. near a sanatorium. Locality 7: 10°36'09" N, 107°33'02" E, 25 m a.s.l. (Fig. 2, G).
Specimen collection and substrate sampling
A total of 273 substrate samples of three main types of substrates for MCCs were sampled by the first author during field work carried out in the middle of November, 2014: (b) 122 samples of dead outer part of the bark from living trees, (l) 123 samples of ground litter consisting of decaying leaves, small twigs and dry fruits of trees (Fig. 3, F), forming mats 0.5—2 cm thick at the base oftrees, and (d) 28 samples of partially decomposed weathered droppings of cattle 4—20 cm in diam. A small, sharp-edged knife was used to remove several pieces of bark in a separate paper bag for each sample of 10 trees enough to cover tightly the whole area (app. 60 cm2 of a Petri dish). Bark of living plants was further subdivided in texture groups according to its physical features (Schnittler, 2001). Those were the peeling bark (b3) of Melaleuca cajuputi (Fig. 3, A) and Eucalyptus sp., (Fig. 3, B), the scaly bark (b7) of Dipterocarpus spp. (Fig. 3, C) and Casuarina sp., (Fig. 3, D), and the solid and deeply furrowed bark (b4) of old trees of Dipterocarpus spp. (Fig. 3, E).
The substrate samples were allowed to air-dry for several days and then were stored with silica gel. In the laboratory, the moist chamber cultures were set up in the beginning of January 2015 by the first author according to the classical protocol (Novozhilov et al., 2017a). From each of the 273 substrate samples, one MCC was prepared with distilled water, using three layers of white toilet paper to cover the bottom of Petri dishes (9 cm in diam.). After approximately 24 h, the pH value of excess water in the Petri dish was determined using a Hanna model HI 98128 of pH meter with a touch down probe. Cultures were incubated under ambient light at room temperature (ca. 20—24 °C) for up to 90 days and scanned for myxomycetes seven times (days 6, 10, 15, 30, 45, 60, 90) using a Stemi 508 (Zeiss) dissecting microscope.
Air-dried sporocarps were studied with an Axio imager A1 (Carl Zeiss AG, Germany) light microscope (LM) with differential interference
Fig. 3. A — Peeling bark (b3) of Melaleuca cajuputi; B — peeling bark (b3) of Eucalyptus sp.; C — scaly bark (b7) of Dipterocarpus sp.; D — scaly bark (b7) of Casuarina sp.; E — solid and deeply furrowed bark (b4) of old tree of Dipterocarpus sp.; F — Ground litter.
contrast (DIC), a Stemi 2000 dissecting microscope (DM), a Zeiss motorized stereomicroscope ZEISS Axio Zoom.V16 and a JSM-6390LA (JEOL, Japan) scanning electron microscope (SEM) at the Core Facility Center ofthe Komarov Botanical Institute of the Russian Academy ofSciences. For microscopy, sporocarps were preserved as permanent slides in polyvinyl lactophenol. Microscopic measurements were made using a Zeiss Zen 3.2 software (free license, blue edition). Specimens for SEM were mounted on copper stubs with a double-sided tape and sputter-coated with gold.
Specimens were identified to the lowest possible taxonomic level according to Martin and Alexo-poulos (1969) and various original descriptions from the literature (e.g., Farr, 1976; Poulain et al., 2011) applying a morphospecies concept. Nomenclature followed Mycobank (Robert et al., 2005).
Sporocarps were mounted in herbarium boxes and are currently deposited in the herbarium of the Komarov Botanical Institute ofRussian Academy of Sciences, Laboratory ofSystematics and Geography of Fungi (LE). The myxomycetes that were still in the plasmodial stage were not considered.
Data analysis
In order to estimate the degree to which the survey was exhaustive, individual-based species accumulation curves (SAC) were plotted using the Estimates version 9.0 software (Colwell, 2014). The number of recorded species to the number of expected species according to the Chao1 estimator (S*100/Chao1) ratio was used to evaluate the local species inventory completeness. Species diversity (alpha-diversity) was calculated using Shannon's diversity index H
K
H' = - ^ Pi In Pi
¡=1
where p, is the particular species' relative abundance (the total number of individuals or records represented by the ith species ratio), and inverse Simpson's dominance index D
The mean number of species per genus (S/G) was used as an indicator of the overall taxonomic diversity.
Results
The following checklist consists of all species of myxomycetes recorded during the present study. These are arranged alphabetically by genus and then to species. Every taxon name is supported by the following data: total number of records of this species from moist chamber cultures (given in brackets); occurrence of the species on three types of substrates; all localities where a species was found; all or some (indicated by the string "...") specimen numbers as given in the herbarium (LE).
An exclamation mark in superscript (!) indicates a species recorded as new for Vietnam. For those taxa already reported for Vietnam, the references are given as numbers in superscript preceding the taxon name: 1 — Van Hooff, 2009; 2 — Tran et al., 2014; 3 — Novozhilov et al., 2017a; 4 — Redeca-Santos et al., 2017; 5 — Novozhilov et al., 2020; 6 — Fedorova et al., 2020; 7 — Loi et al., 2023; 8 — Luptakova et al., 2024.
To obtain data on the distribution of recorded species in Southeast Asia (SE Asia), we used a public database available online at http://www. myx.dk/wrom/ (Gotzsche, 2016—2024, accessed
20.V.24). Where appropriate, we provide references to additional publications.
l'2'3'4'5'6'7Arcyria cinerea (Bull.) Pers. [12] b: 3, l: 7, d: 2; Loc. 1, 5, 7, 8, 9, 10, 12, 14; LE 305681, LE 305682, LE 305684...
In SE Asia also known from Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, and Thailand (Gotzsche, 20162024).
3Arcyria cinerea var. digitata (Schwein.) G. Lister [1] l: 1; Loc. 12; LE 305704.
In SE Asia also known from the Philippines (Gotzsche, 2016-2024) and Malaysia (Sanderson, 1922).
1-2'3'4'5'6'7Arcyria marginoundulata Nann.-Bremek. & Y. Yamam. [10] b: 1, l: 9; Loc. 3, 7; LE 305430, LE 305436, LE 305437... (Fig. 4, A-F).
Our specimens conform to the original description from Japan (Nannenga-Bremekamp and Yamamoto, 1983). They have small sporocarps with white globose sporothecae (Fig. 4, A) and grayish stalks with rusty-brown bases in transmitted light (Fig. 4, C, D). The peridium is preserved as a small calyculus, which is radially wrinkled. Capillitium grayish, pale yellowish in transmitted light and densely ornamented with spines and warts having expanded apices, sometimes connected into crests (Fig. 4, E). Spore mass cream or pale grey, spores hyaline by transmitted light (6-) 6.5-8 (-9) ^m diam., ornamented with small and larger warts combined in small clusters (Fig. 4, F). In addition to Japan, A. marginoundulata has been recorded in Vietnam (Novozhilov et al., 2017a), the Russian Far East (Novozhilov et al., 2017b), Taiwan (Liu et al., 2002), Europe (Ronikier et al., 2013), and the United States (Winsett and Stephenson, 2012), and the species is usually associated with fallen inflorescences and leaf litter. In Binh Chau-Phuoc Buu Nature Reserve, it was found on leaf litter and once on the bark of Dipterocarpus sp. with pH 4.4-5.5.
In SE Asia known from Laos and the Philippines (Gotzsche, 2016-2024).
1-2'3'7Arcyria minuta Buchet [1] l: 1; Loc. 2.
In SE Asia also known from Myanmar and Singapore (Gotzsche, 2016-2024)
8Arcyria pomiformis (Leers) Rostaf. [3] b: 3; Loc. 6, 12; LE 305434; LE 305703.
Fig. 4. Arcyria marginoundulata (LE 305430). A — As seen by a dissecting microscope (DM); B — sporocarp as seen by a scanning electron microscope (SEM); C — opened sporocarp as seen with a light microscope and differential interference contrast (DIC); D — part of the sporocarp stalk (DIC); E — capillitium (SEM); F — spore (SEM). Collaria arcyrionema var. japonica (LE 305432). G — Opened sporocarp (DIC); H — capillitial threads and the collar (marked with arrow) at the top of the stalk (DIC); I — spore ornamentation (DIC, oil immersion, 100*, top and median view). Scale bars: A — 100 ^m; B, C, G — 50 ^m; D, H, I — 10 ^m; E — 2 ^m; F — 1 ^m.
In SE Asia known from the Philippines, Myanmar, and Singapore (Gotzsche, 2016-2024).
2,3,4,5,6,7Clastoderma debaryanum A. Blytt [5] b: 5; Loc. 1, 6, 8, 10; LE 305639, LE 307266, LE 307270...
In SE Asia known from Laos, Myanmar, the Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
8! Collaria arcyrionema var. japonica (Meyl.) Nann.-Bremek. & Y. Yamam. [1] b: 1; Loc. 5; LE 305432 (Fig. 4, G-I).
This variety, originally described from Japan as Lamproderma arcyrionema var. japonicum Meyl. (Meylan, 1935; Kowalski, 1975; Yamamoto and Nannenga-Bremekamp, 1995), differs from the type variety by a more weakly developed capillitium and larger spores, which in our case are even slightly larger (9.4—9.9 ^m) than in specimens from Japan (about 9 ^m; Yamamoto and Nannenga-Bremekamp, 1995).
In SE Asia known only from Vietnam.
3 5 6 7 Comatricha elegans (Racib.) Lister [4] b: 4; Loc. 6, 7, 8; LE 305444, LE 305638 (Fig. 5, A).
In SE Asia also known from Cambodia, Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
8! Comatricha pulchella var. fusca (Lister) Lister [4] l: 4; Loc. 2, 3; LE 305656, LE 305657, LE 305658...(Fig. 5, B-C).
Our specimen has spores ornamented with large scattered spines (Fig. 5, C). It was identified as C. pulchella var. fusca, because the spore mass is rusty brown in color (Fig. 5, B). Moreno et al. (2018) emphasized that these differences are insufficient to separate this variety from C. pulchella var. pulchella, since both varieties have similar spore ornamentation. However, we continue to consider both varieties as separate taxonomic units until comparative molecular genetic studies have been carried out.
In SE Asia known only from Vietnam.
!Craterium aureum (Schumach.) Rostaf. [1] l: 1; Loc. 4; LE 307298.
In SE Asia also known from Indonesia, Philippines, Singapore, and Thailand (Gotzsche, 20162024).
2,4,5,7 Craterium minutum (Leers) Fr. [6] l: 6; Loc. 3, 14; LE 305661, LE 305665, LE 305669...
In SE Asia also known from Indonesia, Malaysia, the Philippines, and Thailand (Gotzsche, 2016 -2024).
3,4,5,6,7Cribraria confusa Nann.-Bremek. & Y. Yamam. [25] b: 25; Loc. 1, 5, 8, 9, 10, 11, 12, 13, 14; LE 305530, LE 305641, LE 305689.
In SE Asia also known from Indonesia and Singapore (Gotzsche, 2016-2024).
2 3 5,6,7Cribraria microcarpa (Schrad.) Pers. [A, 6] b: 6; Loc. 2, 14; LE 305708, LE 305710, LE 307287...
In SE Asia also known from Brunei, Indonesia, Laos, Myanmar, Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
23,4,5,6,7 Cribraria violacea Rex [2] b: 2; Loc. 4, 5; LE 305678.
In SE Asia also known from Cambodia, Laos, Malaysia, Myanmar, Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
61Diderma chondrioderma (de Bary & Rostaf.) Kuntze [1] b: 1; Loc. 4; LE 305679.
In SE Asia also known from Cambodia, Laos, Malaysia, Myanmar, Philippines, and Singapore (Gotzsche, 2016-2024).
5-67 Diderma deplanatum Fr. [3] b: 1, l: 2; Loc. 3,
4; LE 305662, LE 305676, LE 305680.
In SE Asia known only from Vietnam.
23,4,5,7 Diderma effusum (Schwein.) Morgan [3] l: 3; Loc. 4, 11; LE 307256, LE 307349.
In SE Asia also known from Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
57 Echinostelium colliculosum K.D. Whitney & H. W. Keller [2] b: 2; Loc. 3; LE 305428.
In SE Asia known only from Vietnam.
i-2-3-4-5-6-7'Echinostelium minutum de Bary [19] b: 18, l: 1; Loc. 1, 3, 5, 6, 8, 9, 10, 14; LE 305429, LE 305433, LE 305637...
In SE Asia also known from Cambodia, Myanmar, the Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
51 Enerthenemapapillatum (Pers.) Rostaf. [2] b: 2; Loc. 1; LE 305651, LE 305653 (Fig. 5, D-F).
In SE Asia also known from Indonesia and the Philippines (Gotzsche, 2016-2024).
i,2,3,4,'7 Gulielmina vermicularis (Schwein.) Garcia-Cunch., J.C. Zamora & Lado (= Perichaena vermicularis (Schwein.) Rostaf. [R, 1] b: 1; Loc. 4; LE 305677 (Fig. 6, A-B).
In SE Asia also known from Indonesia, Malaysia, Myanmar, Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
2 3 5 7 Hemitrichia calyculata (Speg.) M.L. Farr [1] b: 1; Loc. 8; LE 307341 (Fig. 5, G-H).
In SE Asia also known from Laos, Myanmar, Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
5-61 Hemitrichia decipiens (Pers.) Garcia-Cunch., J.C. Zamora & Lado (=Trichia decipiens (Pers.) T. Macbr.) [1] b: 1; Loc. 8; LE 305686.
In SE Asia also known from Indonesia and the Philippines (Gotzsche, 2016-2024).
2'3 5'6 7Hemitrichia serpula (Scop.) Rostaf. [5] b: 2, l: 3; Loc. 3, 4, 11; LE 305749, LE 307343, LE 307344...
Fig. 5. Comatricha elegans (LE 305444). A — Opened sporocarp with capillitium (DIC). Comatrichapulchella var. fusca (LE 305657). B — Sporocarp (DM); C — spores and threads of capillitium at the periphery of the sporotheca (DIC). Enerthenema papillatum (LE 305651). D — Opened sporocarp (DM); E — opened sporocarp with capillitium (DIC); F — capillitium (DIC). Hemitrichia calyculata (LE 307341). G — Sporocarp; H — capillitium (DIC). Licea operculata (LE 305640). I - Sporocarp (DM). Scale bars: A, F — 50 jm; B — 100 jm, C, H — 10 jam; D, I — 200 jam; G — 500 jam.
In SE Asia also known from Brunei, Indonesia, Laos, Malaysia, Myanmar, the Philippines, and Thailand (Gotzsche, 2016-2024).
2-4,5,6,7Licea operculata (Wingate) G.W. Martin [1] b: 1; Loc. 6; LE 305640 (Fig. 5, I).
In SE Asia also known from Myanmar, the Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
81 Licea pseudoconica T.E. Brooks & H.W. Keller [8] b:8; Loc. 1, 6, 8; LE 305642, LE 305643, LE 305654. (Fig. 7).
This highly distinctive corticolous species is easily recognized by its small conical sporocarps with a light "cap" of crystalline material. Our specimens have an inner peridium ornamented with warts (Fig. 7, E, H) and spores 10.4-11.7 jm in diam., which conforms to the original description (Keller and Brooks, 1977). We also observed that during the maturation of spores, pigmentation did not develop simultaneously, but appeared first in the upper part of the sporocarp (Fig. 7, A). In addition, the sporocarps were found to sit on a pillow-like base (a feature not previously noted), the nature of which, however, is unclear (Fig. 7, F). It is also
Fig. 6. Gulielmina vermicularis (LE 305677). A — Sporocarp (DM); B — capillitium and spores (DIC). Scale bars: A — 200 jam; B — 10 jam.
unclear whether the unusual coarsely folded spore ornamentation seen by both LM and SEM is the result of an aberration of development or is a stable trait (Fig. 7, E, I). It is also interesting that we previously found L. pseudoconica in the Russian Far East (Bortnikov et al., 2022), but it was recorded on bark with pH 6.40-7.31 (vs. 4.61-5.75 in Vietnam) and had larger spores (12.6-13.8 ^m in diam.). Given the wide distribution (see for details Bortnikov et al., 2022) and the observed variability in characters, it can be assumed that L. pseudoconica represents more than one closely related species or varieties. However, more collections are needed to study the spore variability of L. pseudoconica to confirm this assumption.
In SE Asia also known from Indonesia (Gilert and Neuendorf, 1991).
3'5 6 7Liceapygmaea (Meyl.) Ing [2] l: 2; Loc. 3; LE 305666, LE 307262 (Fig. 8, A-C).
In SE Asia known only from Vietnam.
81 Licea verrucispora D. Wrigley & Lado [1] l: 1; Loc. 5; LE 305442 (Fig. 8, D-H).
Our specimen has the typical characters (Wrigley De Basanta and Lado, 2005) including a longitudinally folded stalk, the outer surface of peridi-um divided by membranous folds up to 10 ^m high (Fig. 8, F), the inner peridium ornamented with numerous pointed warts (Fig. 8, G) and spores ornamented with rounded verrucae of different size (Fig. 8, H). At high magnification, it also can be seen that the warts have secondary ornamentation of numerous very small warts (Fig. 8, I).
In SE Asia known only from Vietnam.
67Macbrideola cornea (G. Lister & Cran) Alexop. [1] b: 1; Loc. 4.
In SE Asia also known from Thailand (Ko Ko et al., 2010a).
23,5,7 Metatrichia vesparia (Batsch) T. Macbr. [6] b: 4, l: 2; Loc. 2, 11; LE 307261, LE 307271, LE 307272 (Fig.9, A-D).
Our specimens are macroscopically similar to the description of M. vesparia (Fig. 9, A) but have a fragile peridium with irregular dehiscence (Fig. 9, B) and seem to differ from those described in the literature (Martin and Alexopoulos, 1969; Farr, 1976) in the morphology of the capillitium. The elaters within the sporotheca are not arranged chaotically as usual, with numerous free ends, but are coiled as a single thread on a spool. Despite these features, we refer our specimens to the species M. vesparia until detailed morphological and molecular analysis are carried out.
In SE Asia also known from Laos, Malaysia, Myanmar, the Philippines, and Thailand (Gotzs-che, 2016-2024).
2,3,4,5,7 Ophiotheca chrysosperma Curr. (= Pericha-ena chrysosperma (Curr.) Lister) [3] b: 1, l: 2; Loc. 3, 11; LE 307257, LE 307259, LE 307263.
In SE Asia also known from Cambodia, Laos, Malaysia, Myanmar, the Philippines, Singapore, and Thailand (Gotzsche, 2016-2024).
81 Paradiacheopsis cf. fimbriata (G. Lister & Cran) R.J.G. Hertel ex Nann.-Bremek. [1] b: 1; Loc. 1; LE 305652 (Fig.9, E-G).
Our specimen is most similar to Paradiacheopsis fimbriata, but the ends of capillitium threads are without pronounced thickenings (Fig. 9, F, G), so we cannot be sure that the specimen is correctly identified, even though the other characters are consistent with this species.
In SE Asia known only from Vietnam.
8!Paradiacheopsis fimbriata var. cf. penicillata
(Nann.-Bremek. & Y. Yamam.) Y. Yamam. [1] b: 1; Loc. 1; LE 305655.
Fig. 7. Licea pseudoconica (LE 305643). A — Unmatured sporocarp in moist chamber (DM); B — wet sporocarp in moist chamber, black spores are visible through the transparent peridium (DM); C — Dry sporocarp (DM); D — opened sporocarp and spores (DIC); E — spores (DIC, top and median view); F — opened sporocarp (SEM); G — collapsed spores on the inner surface of peridium (SEM); H — inner surface of peridium (SEM); I — collapsed spore (SEM). Scale bars: A, B, C — 100 jam; D — 50 jam; E — 10 jam; F — 20 jam; G, H — 5 jm; I — 1 jm.
Our specimen fits better macroscopically with the original description of Comatricha penicillata Nann.-Bremek. & Y. Yamam.; however, it differs in spore size 10.2—11.7 ^m vs. 7—8.5 ^m in the type specimen (Nannenga-Bremekamp and Yamamoto, 1983). For this reason, we cannot be certain that this specimen belongs to this species.
In SE Asia known only from Vietnam.
3 5 7Paradiacheopsis rigida (Brandza) Nann.-Bremek. [C, 5] b: 5; Loc. 1, 4, 7, 9; LE 305431, LE 305443, LE 305694 (Fig.9, H-J).
In SE Asia known only from Vietnam.
8Perichaena cf. areolata Rammeloo [1] b: 1; Loc. 4; LE 307285 (Fig. 10, A-C).
Our specimen has sessile sporocarps with a mottled peridial surface with weakly expressed plates, not marked with dark lines (Fig. 10, A, C), a dense regularly papillate ornamentation on the inner peridium surface (Fig. 10, C), capillitium 2-3 ^m in diam. with small spines 0.5-1.5 ^m long, and spores 10.8-12.1 ^m in diam. (Fig. 10, B). These characters are similar to the descriptions of a type specimen (Van der Veken nr. 10581 in GENT) given by Rammeloo (1981) and Lado et al. (2009). However, the sporocarps of our specimen are smal-ler (about
Fig. 8. Liceapygmaea (LE 305666). A — Sporocarps (DM); B — opened sporocarp and spores (DIC); C — spores and peridium (DIC). Licea verrucispora (LE 305442). D —Sporocarp (DM); E — sporocarp (SEM); F — sporotheca (SEM) covered by peridium with folds; G — collapsed spore on the inner surface of peridium (SEM); H — spore (SEM); I — detail of spore ornamentation (SEM). Scale bars: A, D, E — 100 jam; B — 50 jm; C, F — 20 jm; G — 5 jm; H — 2 jm; I — 0.5 jm.
200 jm in diameter, vs. at least 400 jm in the type specimen from Rwanda) and the capillitial spines are shorter (0.5-1.5 jm vs. 2-3 jm). In addition, our specimen was detected on the bark of Dipterocar-pus sp. with pH 7.09, whereas the type specimen was found on leaf litter.
In SE Asia known only in Vietnam. This species is known also from Rwanda (Rammeloo, 1981) and Ethiopia (Dagamac et al., 2017).
2,3,4,5,7Perichaena depressa Lib. [1] d: 1; Loc. 2;
LE 307280.
In SE Asia also known from Brunei, Cambodia,
Indonesia, Laos, Malaysia, Myanmar, the Philippi-
nes, Singapore, and Thailand (Gotzsche, 20162024).
4 7Perichaena liceoides Rostaf. [1] d: 1; Loc. 1; LE 305646 (Fig. 10, D-E).
Coprophilous myxomycetes were not recorded in previous studies in Vietnam (Novozhilov et al., 2017a, 2020) because dung of herbivorous animals rapidly decomposes in nature due to high humidity and abundance of coprophagous arthropods in the study area.
In SE Asia known only from Vietnam.
8!Perichaena cf.pachyderma D.W. Mitchell, G.
Fig. 9. Metatrichia vesparia (LE 307271). A — Sporocarps (DM); B — opened sporocarps (DM); C — spore mass and capillitium (DIC); D — capillitium and spores (DIC). Paradiacheopsis fimbriata (LE 305652). E — Sporocarp (DM); F — opened sporocarp with capillitium (DIC); G, H — spores (DIC, top and median view). Paradiacheopsis rigida (LE 305431). I — Sporocarp (DM); J — opened sporocarp with capillitium (DIC); K — capillitium and spores (DIC). Scale bars: A, B — 500 ^m; C, F — 50 ^m; D, G, H, K — 10 ^m; E, J — 100 ^m; I = 200 ^m.
Moreno & M. Lizärraga [3] d: 3; Loc. 1, 2, 3; LE 305647, LE 305660, LE 307288 (Fig. 10, F-G).
Our specimens were previously assigned to Perichaena luteola (Kowalski) Gilert (Trang et al., 2020; Luptakova et al., 2024), but a more thorough examination of the collection as well as a review of the literature showed that the identification was not correct. Perichaena luteola has heaped sporocarps 0.1-0.5 mm in diam., verrucose spores 12-13 ^m in diam., a well-developed three-dimensional network
of smooth capillitium threads about 2 ^m in diam. and a thin single-layered peridium (Kowalski, 1969). Our specimens are represented by numerous small sporocarps filled with a dense light yellow spore mass (Fig. 10, F). The peridium is brown, rather thick (3-4 ^m), translucent in transmitted light (Fig. 10, H); spores are verrucose, from 9.1-9.5 to 10.2-10.8 ^m in diam. (mean = 9.85, SD = 0.39, n = 30), ornamented with irregularly distributed warts (Fig. 10, G), and a capillitium is completely absent.
Fig. 10. Perichaena cf. areolata (LE 307285). A — Sporocarp (DM); B — spores, capillitium and inner surface of peridium (DIC); C — peridium, arrow marks the boundaries of peridium lobes (DIC). Perichaena liceoides (LE 305646). D — Sporocarps (DM); E — spores (DIC). Perichaena cf.pachyderma (LE 305647). F — Opened sporocarps with spores (DM); G — spores (DIC, top and median view); H — Details of the peridium (DIC). Scale bars: A, D, F — 100 jam; B, C, E, G — 10 jam; H — 50 jam.
According to the abovementioned characters, these specimens are the closest to the description of another coprophilous species, Perichaena pachyderma D.W. Mitchell, G. Moreno & M. Lizarraga, found in the USA and Mexico (Mitchell et al., 2011). However, for the time being, we prefer to keep LE 305647, 305660 and 307288 identified with the "cf." status, since we have not seen the type specimens of P. pachyderma (Mitchell et al., 2011). More collections are needed to study its morphological variability.
In SE Asia known only from Vietnam.
2,3,4,5,6,7Physarwm album (Bull.) Chevall. [1] b: 1; Loc. 1; LE 307269.
In SE Asia also known from Indonesia Myanmar, the Philippines, Singapore and Thailand (Got-zsche, 2016-2024).
12,3,4,57Physarum cinereum (Batsch) Pers. [7] l: 7; Loc. 3, 5, 9, 10, 13; LE 305675.
In SE Asia also known from Brunei, Cambodia, Indonesia, Laos, Myanmar, the Philippines, Thailand, and Timor-Leste (Gotzsche, 2016-2024).
Fig. 11. Trichia sp. (LE 305685). A, B — Opened sporocarp (DM); C, D — capillitium and spores (DIC); E, F — capillitium (SEM); G — end of the capillitial thread (SEM); H — inner surface of peridium (DIC); I — spore ornamentation (SEM). Scale bars: A, B — 200 ^m; C, D, H — 10 ^m; E — 5 ^m; F— 2 ^m; G, I — 1 ^m.
237Physarum echinosporum Lister [3] l: 3; Loc. 3; LE 305663, LE 305664, LE 305668.
In SE Asia also known from Cambodia, Laos, the Philippines, and Thailand (Gotzsche, 2016— 2024).
2 3,4 5,7Stemonitis fusca Roth [2] l: 1, d: 1; Loc. 3, 8; LE 305659, LE 305691.
In SE Asia also known from Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Timor-Leste (Gotzsche, 2016-2024).
Trichia sp. [1] b:1; Loc. 8; LE 305688, (Fig. 11).
The single scarce specimen was found on the bark of Dipterocarpus sp. with a pH 4.97. Due to the
presence of sporocarps on the stalk and dehiscence of the peridium into plates following the shape of the areolae, this taxon can be attributed to the Trichia botrytis complex (Bortnikov et al., 2023). However, we could not assign it to any described species because it combines characters of different taxa. First, it has a straight and long (about 60—70% of the total height) stalk (Fig. 11, A, B) and then resembles T. munda (Lister) Meyl. Second, it has elater tips of8-9 ^m long (Fig. 11, C, G), i.e. shorter than in all other species of the complex except for T. erecta Rex. However, the latter species has baculate spore ornamentation, whereas LE 305688 has clearly pilate ornamentation of the spores (Fig. 11, I). Third, the inner peridium is ornamented with straight dashes and lines, intersecting at different
angles and uniting in a mosaic pattern (Fig. 11, H), similar to T. armillata Bortnikov. Trichia sp. is also similar to the latter species by its habitat: the bark of a living tree with pH about 5. Finally, the capillitium of Trichia sp. is most similar to Hemitrichiapardina (Minakata) Ing, as it has weakly branched elaters 2.6—3.5 ^m wide with numerous spines up to 3 ^m long (Fig. 11, C, E) and short free ends (Fig. 11, G). The ornamentation consists of weakly pronounced spiral thickenings and ridges (Fig. 10, E, F), and under SEM, it looks identical to that given by Neubert et al. (1993, p. 293, fig. c) for H. pardina. However, the peridium of Trichia sp. lacks dark wart-like projections on the peridium surface (Fig. 11, A, B), being the key characters of H. pardina. Moreover, we cannot attribute LE 305688 to any species ofthe genus Hemitrichia because, according to recent studies by Garcia-Cunchillos et al. (2022), this genus includes only species with cyst-like cells in the stalk, which were not found in our specimen. Thus, this specimen requires a more detailed study in the future, and herein we designate it as Trichia sp.
Species diversity
This study is based on a total of 168 records representing 44 taxa (40 morphospecies and four varieties) from 18 genera and 10 families. All observations were obtained from 273 moist chamber cultures (an additional 95 records of non-fruiting plasmodia were not counted). In 19 cases, where only scanty or damaged colonies were observed or collected, determination was possible only to the generic level. Among the 44 taxa, there was one putatively new species of Trichia that could not be clearly assigned to any described morphospecies. Eighteen taxa were classified as singletons for the whole study area and five taxa were represented by only two records. Only six species ofmyxomycetes — Arcyriacinerea (12 records), al. marginoundulata (10), Craterium minutum (6), Echinostelium minutum (19), Liceapseudoconica (8), Physarum cinereum (7), and Metatrichia vesparia (6) — were common. All taxa were new for the nature reserve and 11 species (including one variety) were recorded for the first time in Vietnam. When all of the taxa known from the literature are included, 190 myxomycete morpho-species and five varieties are currently known from Vietnam.
Completeness and productivity of moist chamber cultures
The completeness of the survey of myxomycete assemblages associated with the different substrates varied greatly (Table 1) and increased from bark (29 taxa of104 records, 58% completeness according to the Chaol estimator) over dung (5 taxa of 8 records, 79%) to ground litter (18 taxa, 56 records, 86%).
The productivity of moist chamber cultures calculated as a proportion of moist chamber cultures yielding myxomycete sporocarps to the total number of cultures varied somewhat among substrate types, ranging from 46.7% for the bark of living trees to 32.5% for ground litter and 21.4% for dung of cattle. A different pattern was maintained with respect to the number of chambers in which plasmodia considered, productivity decreased from ground litter (34.1%) through bark (26.21%) and dung (7.1%). The difference is mainly due to the high proportion of plasmodia that formed sporocarps on litter more rarely than on other substrates during substrate incubation in moist chamber cultures (2—3 months).
Substrate-species relationships
Species richness and Shannon's diversity decreased from bark (29 species, H'= 2.7, D = 9.0, Sp/G = 1.6) over ground litter (18 species, H'=2.6, D = 11, Sp/G = 1.6) to dung (5 species, H'= 1.5, D = 4, Sp/G = 1.6). This pattern remained when comparing the Chao1 indices (rarefied values for species richness Chao1 ± SD: bark 49.8 ± 14.6, ground litter 21 ± 3.4, and dung 6.3 ± 2.3 species, Table 1). Interestingly, we found the same trend in the mountain forests of Bidoup-Nui Ba (BDB) and Chu Yang Sin (CYS) national parks (Novozhilov et al., 2020) and in lowland monsoon forests of Cat Tien National park (CT) in southern Vietnam (Novozhilov et al., 2017a). However, this trend was less pronounced than in dry deciduous forests of BCBP. Species richness revealed for bark by moist chamber cultures was higher than numbers for ground litter in BDB and CT (BDB: bark 25 species, Chao1 ± SD: 38.8 ± 11.2, ground litter 23 species, 34.0 ± 8.9; CT: bark 49 species 64.1 ± 9.7, ground litter 47 species, 52.0 ± 4.1 correspondingly). Dung ofherbivorous animals was never encountered
Table 1. Summary data for myxomycetes obtained in moist chamber cultures on bark of living trees, ground litter, and the dung of cattle in the BCPB.
Data bark b3 b4 b7 DIP MEL CAS EUC litter dung Total for reserve
Rec 104 9 62 33 84 4 11 5 56 8 168
Sp 29 6 24 10 27 4 6 3 18 5 43
G 18 7 17 7 17 4 5 3 11 3 21
Sp/G 1.6 0.9 1.4 1.4 1.6 1.0 1.2 1.0 1.6 1.6 2.0
Chao1 49.8 7 39 17 61 NO 7 NO 21 6.3 68
SD (Chao1) 14.6 1.3 11 8.0 23 NO 1.7 NO 3.4 2.3 16.3
% (Sp/Chao1) 58 90 62 58 45 NO 87 NO 86 79 43
H' 2.7 1.7 2.7 1.8 2.6 NO 1.6 NO 2.6 1.54 3.3
D 9 5.4 10 4.3 7.4 NO 4.5 NO 11 4 17
MC 123 30 62 30 83 20 9 10 123 28 273
% MC for sporocarps 46.7 26.7 50 60 55.4 25.0 33.3 30.0 32.5 21.4 37.7
% MC for plasmodia 26.2 0 45 13 28.9 0 88.9 0 34.1 7.1 27.8
Mean (Sp per MC) 0.7 1.0 1.2 1.4 0.86 0.2 0.8 0.3 0.40 0.28 0.53
SD (Sp per MC) 1.0 0.3 1.0 0.8 1.0 0.4 1.7 0.7 0.73 1.06 0.87
Notes. Rec = Number of specimens of myxomycetes identified to species level; Sp = number of morphospecies; G = number of genera; Sp/G = species / genus ratio; Chao1 = individual-based richness estimator; SD (Chao1) = standard deviation of Chao1; % (Sp/Chao1) = degree of completeness that was achieved for the data set (the percentage of recorded species on the figures for the Chao1 richness estimator); H' = Shannon's diversity index; D = Simpson's (inverse) diversity index; MC = number of the prepared moist chamber cultures; % MC for sporocarps = number of positive moist chamber cultures in which sporocarps of myxomycetes were developed; % MC for plasmodia = number of positive moist chamber cultures in which plasmodia were registered; Mean (Sp per MC) = the mean value for the number of species per one moist chamber culture; SD (Sp per MC) = standard deviation of the mean value for the number of species per one moist chamber culture; abbreviations of the tree names: DIP - Dipterocarpus spp., MEL - Melaleuca cajuputi, CAS - Casuarina sp., EUC - Eucalyptus sp.
in CT, BDB and CYS due to its fast degradation during the rainy wet season in these regions during our surveys, and for this reason, we cannot include coprophilous species in this comparison.
Corticolous myxomycetes were represented by the highest number of species and records (104 records of 181 total records, Table 2), more than a half (21 of 29 taxa) was found exclusively on this substrate. However, many taxa were recorded only once (15) or twice (4). The most common corticolous species found on bark were Cribraria confusa (25), Echinostelium minutum (18), Licea pseudoconi-ca (8), Cribraria microcarpa (6), Clastoderma deba-ryanum (5), Paradiacheopsis rigida (5), Arcyria pomiformis (3), and Comatricha elegans (4). Echi-nostelium minutum, one of the most common cor-ticolous species in Vietnam (Novozhilov et al., 2020), may switch to ground litter (1 of18 records). All these species are acidotolerant, which explains their preference for slightly acidic bark of the studied trees. In this group of species, C. confusa, C. microcarpa, and Enerthenema papillatum prefer bark with the lowest pH values below 5.0 (Table 2). These species are widely distributed in the world, the exception being L. pseudoconica, which had not
been recorded in Vietnam prior to this study.
In addition, species diversity of corticolous myxomycetes varied on bark with different textures and roughness. Species richness and Shannon's diversity increased from peeling bark (b3) of Melaleuca cajuputi and Eucalyptus sp. (6 species, H = 1.7, D = 5.4, Sp/G = 0.9) over large scaly bark (b7) of Dipterocarpus spp. and Casuarina sp. (10 species, H = 1.8, D = 4.3, Sp/G = 1.4) to fissured bark (b4) of old trees of Dipterocarpus spp. (24 species, H'= 2.7, D = 10, Sp/G = 1.4). The average number of species recorded in each moist chamber culture also increased in this succession (Tables 1, 2).
The species composition of litter-inhabiting myxomycetes is quite specific and includes common species of this ecological group recorded in other regions of Vietnam (Loi et al., 2023). This guild includes Arcyria cinerea (7 records out of 12), A. marginoundulata (9 out of 10), Craterium minutum (6 out of 6), Physarum cinereum (7 out of 7), and P. echinosporum (3 out of 3). The exception is Comatricha pulchella var. fusca (4 out of 4), common in BCBP, but not previously recorded in Vietnam.
Coprophilous species seem to be more specialized than other myxomycetes. Of the five species
Table 2. Corticolous myxomycetes (29 taxa) recorded on the bark of trees of Dipterocarpus spp. (DIP), Casuarina sp. (CAS), Melaleuca cajuputi (MEL) and Eucalyptus sp. (EUC) and bark with different texture (b3, b4, b7). For all species found on bark of trees, average ± SD for pH, bark with different texture of surface (b3, b4, b7) and the day of the first appearance in a moist chamber culture are given.
Taxa Trees Type of bark day Total in reserve
DIP CAS MEL EUC pH b3 b4 b7
Arcyria cinerea 1 1 0 1 5.07±0.78 2 1 - 25 12
Arcyria marginoundulata 1 0 0 0 5.17 - 1 - 25 10
Arcyria pomiformis 1 0 2 0 5.28±0.43 - 2 1 6 3
Clastoderma debaryanum 3 0 2 0 5.10±0.38 - 4 1 6 5
Collaria arcyrionema var. japonica 1 0 0 0 5.98 - 1 - 15 1
Comatricha elegans 1 0 1 2 5.71±0.39 2 2 - 15 4
Cribraria confusa 25 0 0 0 4.96±0.56 - 12 13 6 25
Cribraria microcarpa 5 1 0 0 4.51±0.55 1 - 5 15 6
Cribraria violacea 2 0 0 0 5.74 - 2 - 6 2
Diderma chondrioderma 1 0 0 0 7.09 - 1 - 45 1
Diderma deplanatum 1 0 0 0 6.91 - 1 - 35 3
Echinostelium colliculosum 2 0 0 0 6.1 - 2 - 6 2
Echinostelium minutum 14 0 4 0 5.37±0.68 - 11 7 6 19
Enerthenema papillatum 1 1 0 0 4.78±0.14 1 - 1 25 2
Gulielmina vermicularis 1 0 0 0 6.91 - 1 - 45 1
Hemitrichia calyculata 1 0 0 0 4.5 - 1 - 90 1
Hemitrichia decipiens 1 0 0 0 4.36 - 1 - 45 1
Hemitrichia serpula 2 0 0 0 5.57±0.97 - 2 - 90 4
Licea operculata 0 0 1 0 5.15 - 1 - 25 1
Licea pseudoconica 7 0 1 0 5.16±0.52 - 7 1 6 8
Macbrideola cornea 1 0 0 0 7.09 - 1 - 6 1
Metatrichia vesparia 4 0 0 0 5.64±0.67 - 4 - 15 6
Ophiotheca chrysosperma 1 0 0 0 5.8 - 1 - 25 3
Paradiacheopsis cf. fimbriata 1 0 0 0 4.47 - - 1 35 1
Paradiacheopsis fimbriata var. cf. penicillata 1 0 0 0 4.68 - - 1 35 1
Paradiacheopsis rigida 3 0 0 2 5.72±1.04 2 1 2 15 5
Perichaena cf. areolata 1 0 0 0 7.09 - 1 - 45 1
Physarum album 0 1 0 0 4.64 1 - - 25 1
Trichia sp. 1 0 0 0 4.97 - 1 - 60 1
found on cattle dung, Perichaena liceoides, P. cf. pachyderma, and P. depressa were recorded only on this substrate. However, these species were recorded only once (P. depressa and P. liceoides) or three times (P. cf. pachyderma).
Development time of sporocarps in the moist
CHAMBER CULTURES
The time of appearance of the first sporocarps in moist chamber culture varies among species of myxomycete. The first small sporocarps appear between 6—10 days for species of the genus Echino-
stelium and Cribraria confusa, but most species of myxomycetes form sporocarps between 15—45 days, and only the sporocarps of Hemitrichia serpula and H. decipiens appear after 90 days (Table 2).
Discussion
This first preliminary checklist of myxomycetes recorded from dry lowland deciduous forests of Vietnam includes species of three ecological guilds ofmyxomycetes: corticolous, litter-inhabiting, and dung-inhabiting (coprophilous) species. The first
ecological guild contains ca. 120 species known in the entire world, the members ofwhich are associated with the bark surface ofliving trees, shrubs and lianas (Schnittler, 2016; Novozhilov et al., 2021). It is well known that low substrate pH appears to be a limiting factor for the growth and development of many corticolous species of myxomycetes. In general, deciduous trees are characterized by moderately acidic bark displaying a more diverse assemblage of corticolous myxomycetes than coniferous trees with highly acidic bark (Snell and Keller, 2003; Wrigley de Basanta, 2004; Ndiritu et al., 2009). In BCBP, the dominant trees are species of the genus Dipterocarpus with slightly acidic pH (5.22 ± 0.83). This is one of the reasons of relatively high species diversity of corticolous species on this bark. In contrast, the bark of Melaleuca cajuputi is quite acidic (4.68 ± 0.31) and moist chamber cultures with this substrate produced only a limited species assemblage compared to that found on the bark of deciduous trees of Dipterocarpus spp. Other important environmental factor limiting the species diversity of corticolous myxomycetes is bark texture. It has been reported in several studies that the thick, furrowed, rough bark oftrees could be more effective at trapping myxomycete spores from the air and yield more species than trees with the thin, smooth bark surface (Stephenson, 1988; Ko Ko et al., 2010b; Clayton et al., 2014; Schnittler et al., 2016). Our results also confirm this pattern. Species richness and Shannon's diversity increased from peeling bark (b3) of M. cajuputi and Eucalyptus sp. (6 species, H = 1.7, D = 5.4, Sp/G = 0.9) over large scaly bark (b7) of Dipterocarpus spp. and Causarina sp. (10 species, H'= 1.8, D = 4.3, Sp/G = 1.4) to fissured bark (b4) of old trees of Dipterocarpus spp. (24 species, H'= 2.7, D = 10, Sp/G = 1.4). The average number of species recorded in each moist chamber culture also increased in this succession (Tables 1, 2).
The most common litter-inhabiting species in BCBP were Arcyria cinerea (7 records out of 12), A. marginoundulata (9 out of 10), Craterium minutum (6 out of 6), Physarum cinereum (7 out of 7) and P. echinosporum (3 out of 3). These are quite common in other regions of Vietnam (Loi et al., 2023) as well as in other regions of the world. The exception is Comatricha pulchella var. fusca (4 out of4), common in BCBP, but not previously recorded in Vietnam.
Coprophilous species seem to be more specialized than other myxomycetes. Members of this ecological guild are widely distributed in different regions and comprise ca. 126 species (Calaça et
al., 2020). However, they were never recorded in previous studies in lowland and mountain tropical forests ofVietnam (Novozhilov et al., 2017a, 2020; Fedorova et al., 2020) due to fast degradation of the weathered dung of herbivorous animals in these regions. In our survey, this ecological guild was represented by five taxa, three ofthem are found only on this substrate type. We expect that some of the coprophilous species may be found also in other arid regions ofVietnam where climatic conditions allow weathered dung to persist in nature for long periods of time for myxomycetes to colonize it.
The moist chamber culture technique is often used for the detection of minute myxomycetes in many surveys in different regions of the world including tropical regions (Stephenson et al., 2004). However, some authors show that the percentage of positive moist chambers as well as the number of taxa recovered decreases sharply in areas with high annual precipitation as is the case in Costa Rica (Schnittler and Stephenson, 2000). In contrast, our studies in Vietnam did not reveal this pattern. As shown in Table 3, for both substrate groups, diversity indices as well as the mean number ofspecies per one MCC were higher for lowland moist forests of CT than for mountain forests of BDP and dry deciduous forests of BCBP. The result was probably influenced by the wider range of trees and lianas studied in Cat Tien compared to the other two reserves, as well as the significantly higher number of moist chamber cultures used in the former study.
In general, the results we obtained in this study represent just a small part of the species diversity of this region, revealed by moist chamber cultures in the dry season. Only 43% of the expected number of species based on the Chao1 index (43 taxa of 68 expected) were identified in our study in the reserve (Table 1). Specific additional field studies are needed, especially during the rainy wet season of the year when myxomycetes can form sporocarps on coarse woody debris, soil and aerial litter in the field, as well as additional experiments with moist chamber cultures, to better identify the species and ecological diversity of myxomycetes in the reserve.
Acknowledgements
We acknowledge the use of equipment of the Core Facility Center "Cell and Molecular Technologies in Plant Science" at the Komarov Botanical Institute of the Russian Academy of Sciences (BIN
Table 3. Summary data for myxomycetes obtained in moist chamber cultures on the bark of living trees and ground litter in three surveys in Vietnam (CT = Cat Tien National Park, BDP = Bidoup Nui Ba National Park, BCBP = Binh
Chau-Phuoc Buu Nature Reserve).
Data bark litter
CT BDP BCBP CT BDP BCBP
Rec 296 158 104 272 67 56
Sp 49 25 29 47 23 18
G 18 15 18 20 14 11
Sp/G 2.7 1.7 1.6 2.4 1.6 1.6
Chao1 64.1 38.8 50 52.0 34.0 21.0
SD (Chao1) 9.74 11.2 14.6 4.1 .9 8. 3.4
% (Sp/Chao1) 76.6 64.5 58 90.4 67.6 86
H' 3.3 2.3 2.7 3.3 2.8 2.6
D 18.7 5.5 9 20.0 11.4 11
MC 296 261 123 382 338 123
% MC for sporocarps 56 43 47 44 18 33
% MC for plasmodia 15 13 26 47 43 34
Mean (Sp per MC) 1.0 0.61 0.7 0.7 0.20 0.40
SD (Sp per MC) 1.15 0.42 1.0 1.0 0.42 0.73
Notes. Abbreviations as given in the Table 1.
RAS, St. Petersburg). The field work was funded by Joint Vietnam-Russia Tropical Science and Technology Research Center (project "Ecolan 1.5" No 1.2). We thank Nadezhda Bortnikova and Prof. Steven L. Stephenson for linguistic corrections, and an anonymous reviewer for comments to the manuscript. The laboratory work was supported by the state task "Taxonomic, ecological and structural-functional diversity of fungi and fungus-like protists", 12401310-0829-3 (Komarov Botanical Institute RAS) and by the Ministry of Science and Higher Education of the Russian Federation (agreement No 075-15-2021-1056).
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