Hikobia 18: 231–243. 2022

The relationship between species diversity of myxomycetes on litter
twigs and forest vegetation types in western Japan
Kazunari Takahashi*, Mina Fukushima, Yukimi Arayama, Mio Matsuda, Yuri Kidachi, Fukuto
Tanaka, Kotaro Minami, Akira Tominaga, Kyoko Tateishi, and Yuichi Harakon
Takahashi, K., Fukushima, M., Arayama, Y., Matsuda, M., Kidachi, Y., Tanaka,
F. Minami, K., Tominaga, A., Tateishi, K. & Harakon, Y. 2022. The relationshipbetween species diversity of myxomycetes on litter twigs and forest vegetation types
in western Japan. Hikobia 18: 231–243.
Myxomycetes mostly inhabit detritus environments of forests in terrestrial ecosystem.
However, differences in myxomycete communities among various vegetation types of
local forests have been little known. We examined the myxomycete communities on
litter twigs in six types of forests (three types of natural and three types of countryside forests) due to clarify characteristics of the myxomycete diversity in westernJapan. Fallen twigs were collected from the forest floor under trees dominating the
canopy in all six forests, and moist chamber cultures were established in 640 Petridishes. In total, 42 taxa belonging to 19 genera were recorded, of which only four
species were common to all six forests. The natural broad-leaved evergreen forest (21taxa) and the country-side pine forest (7 taxa), respectively, showed the highest andlowest α-diversities for myxomycete communities. The species diversity in countryside forests was lower than that in natural forests. Non-metric multidimensional
scaling revealed that the myxomycete communities in natural forests distinctively
had characteristic community structures and those in country-side forests resembled
those in the adjacent natural forests, except in the country-side pine forest. To ourknowledge, this is the first comprehensive study on the relationships between forest
types and myxomycete communities living on litter twigs in Japan; these findings
indicate the potential effects of geographical location and forest types, including
biodiversity decreasing influenced by anthropogenic activity.
Kazunari Takahashi*, Kurashiki City College, 160 Hieda-cho, Kojima, Kurashiki
City, Okayama, 711–0937 Japan.
Kazunari Takahashi, Mina Fukushima, Yukimi Arayama, Mio Matsuda, Yuri Kidachi
and Fukuto Tanaka, Notre Dame Seishin Gakuen Seishin Girls’ High School, 120
Futago, Kurashiki-shi, Okayama, 701–0115 Japan.
Kotaro Minami, Graduate School of Integrated Arts and Sciences, Kochi University,
2–5–1 Akebono-cho, Kochi-shi, Kochi, 780–8520 Japan.
Akira Tominaga, Fukui Tushima, Kita-ku, Okayama-shi, Okayama, 700–0080 Japan.
Kyoko Tateishi and Yuichi Harakon, Japanese Society of Myxomycetology.
*kumakusu03@yahoo.co.jp (author for correspondence)

Introduction
Myxomycetes, or slime molds, are amoeboid
protists that inhabit decaying plant materials
in terrestrial ecosystems; they use substrates,

such as coarse woody debris, leaf litter, twigs,
dung, and soil (Stephenson et al. 2008 a , 2011,
Novozhilov et al. 2017). They may play asubstantial role in nutrient cycling during
detritus degradation (Urich et al. 2008) as they

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feed on organisms, such as bacteria and fungi,
as well as organic matter in the forest detritus.
Their life cycle comprises different trophic
stages: amoeboflagellates and plasmodia, which
feed on bacteria and organic material, and thedevelopment of fruiting bodies, which thendisperse over long distances via air (Schnittler
et al. 2017). Myxomycetes can broadly spreadand grow in favorable microhabitats in various
terrestrial ecosystems. The fruiting bodies havemorphological features that are used to classify
myxomycete species based on microscopic
observation. The fruiting bodies differ among
species and provide a basic unit to quantify
species richness and abundance as well as
facilitate research on the occurrence, ecology,
and biogeography of myxomycetes (Novozhilov
et al. 2017).
Litter on the forest floor is generally diverseand preser ves microorganisms i n habiti ng
detritus, including myxomycetes (Walker et al.
2019). Substrate types, such as coarse woody
debris, fallen twigs, and leaf litter in forests,
cause differences in myxomycete communities(Novozhilov et al. 2017, Rollins & Stephenson2012), processes and periods of decomposition,and nutrient availability (Matumoto & Niijima
1993, Yoneda 2000). Fallen twigs have beenrecognized as ecologically distinct habitats(Stephenson 1989, Stephenson et al. 2008 b).
Thus, fallen t wigs in var ious forest t y pes
constitute an important ecological aspect of
myxomycetes and forest ecosystem function.
However, studies investigating fallen twigs ashabitats for myxomycetes remain lacking.
Important factors that may locally influence
myxomycete habitat likely include environmental
differences, such as geographical location(Takahashi & Hada 2010), topography (Takahashi
2017, Takahashi et al. 2020), and anthropogenic
differences (Takahashi & Yano 2021) inJapan. Recent natural disturbances and forest
degradation caused by urbanization may havegreatly influenced the local ecosystems (Davison
et al. 2021, Sejati et al. 2018). However, theeffects of these factors have not been fully
investigated, though anthropogenic activity
does influence myxomycete species diversity as
well as that of every organism on a global scale.
Myxomycete diversity has decreased with theloss of forest area along river courses (Takahashi2021). Current disturbances caused by forest use
have resulted in habitat loss for myxomycetes,
leading to differences in the abundance of fruiting
bodies (Dagamac et al. 2015, Macabago et al.
2017, Rojas & Stephenson 2013). Around Mt.
Fuji in Japan, a world cultural heritage area,
myxomycetes inhabiting the bark of living
Cryptomeria japonica trees have been affectedby declining forest coverage as a result of humanactivity (Takahashi & Yano 2021). The present
study thus examines whether myxomycete
inhabitation is affected by long-term human useof forests compared with that in the neighboring
natural forests.
The Chugoku and Shikoku regions in westernJapan contain three types of natural, broadleaved deciduous, coniferous, and broad-leaved
evergreen forests (Yamanaka 1990). Theirfoothills also have country-side forests, whichwere used by people for their livelihoods andfor the forest industry until approximately 60

Fig. 1. Location of the six su r vey sites in the
Chugoku–Shikoku region, Japan. ● indicates naturalforests and ∆ indicates secondar y forests. ND:
natural broad-leaved deciduous forest dominatedby Fagus crenata in Mt. Daisen, Tottori Prefecture;
Sc: country-side forest of Pinus densif lora in thefoothills of Mt. Daisen; Sm: country-side mixed
forest of evergreen and deciduous trees in Kurashiki,
Okayama Pref.; NE: natural broad-leaved evergreen
forest at Yokogurayama, Kohchi Pref.; Se: countryside forest in broad-leaved evergreen forest; NC:
coniferous natural forest dominated by Abies firma.
The vegetation types are color-coded in the figure,and from the lowlands, broad-leaved evergreens,high conifers in the transition zone, broad-leaved
deciduous trees, and sub-alpine coniferous forests are
distributed.

K. Takahashi, M. Fukushima, Y. Arayama, M. Matsuda, et al.

233

Table 1. Information on vegetation, geographical and climatic variables in surveyed forests. Mt: annual
mean temperature, Pre: annual mean precipitation.

years ago (Yano 1988). In the present study, we
examined myxomycete distribution in different
forest types in the Chugoku‒Shikoku region ofwestern Japan to determine whether forest type(i.e., natural forest and country-side forest) andanthropogenic activity influence myxomycete
communities and species inhabitation. We
selected sites in forest areas located in the
Chugoku–Shikoku region, which wererepresentative of typical forest communities withrespect to both vegetation and site conditions. The
highest mountain in western Japan, Mt. Ishizuchi(1,982 m asl.), located in the Chugoku–Shikoku
region. It includes surveyed sites including thenatural deciduous forests of Fagus crenata, which
are protected in the limited mountain areas above
800 m in elevation at Mt. Daisen (1729 m asl) in
the Tottori prefecture (Miyawaki 1982, 1983); thenatural broad-leaved evergreens in Yokogurayama(above 800 m asl) at the Takaoka-gun, Kohchi
prefecture; and the transition forest locatedbetween these, with coniferous forests dominatedby Abies species in the Kohchi prefecture(Uchiyama 2003). The foothills and lowlands
around these mountains have natural forests
including broad-leaved deciduous, evergreen,
and/or coniferous forests; these are country-side
forests that have been extensively affected byhuman activity.
Fallen twigs on forest floors are recognized as
ecologically distinctive habitats of myxomycetes
and thus, species living on twigs from dominating

trees in the forests were considered to represent
the differences between natural and human used
forests; these were assessed using the moist
chamber culture method (Schnittler & Stephenson
2000, Stephenson et al. 2008b).
Materials and Methods
1. Survey sites and twig sampling
Six survey sites were established in different
locations in the Chugoku and Shikoku regions(Fig. 1). There were three natural forests withvarying forest types and three country-side
forests neighboring natural forests or town
areas. Information in surveyed forests waslisted in Table 1. The natural forests were abroad-leaved deciduous type dominated by
Fagus crenata Blume (Fig. 2A) and Quercus
crispula Blume, partially including C. japonica
D. Don. (Miyawaki 1982) (Daisen-cho, Tottori
prefecture, 35.389587° N, 133.52863° E, 803
m asl). The natural coniferous forest consistedof Abies firma Siebold et Zucc. and Tsuga
sieboldii Carriere and located in the transitionarea between the evergreen and deciduous
vegetation zones in Shikoku region; the samplingsites were at Takatoriyama (Yusuhara-cho,33.345251° N, 132.963355° E, 491 m asl) andat Kajigadani, Ohdou Shimanto-cho, Kochi
prefecture (33.289696° N, 132.859877° E, 578
m asl). The natural broad-leaved evergreen
forest was dominated by Q. acuta Thunb. and234

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Fig. 2. Forest landscapes, moist chamber cultures, and myxomycete fruiting bodies. A: natural broad-leaved
deciduous forest dominated by Fagus crenata in Mt. Daisen; B: country-side coniferous forest dominatedby Pinus densiflora; C: moist chamber culture of twigs; D: white plasmodium occurred on twigs in MC;
E: fruiting bodies of Arcyria cinerea formed on the wall of a Petri dish, F: fruiting bodies of Cribraria
microcarpa.

K. Takahashi, M. Fukushima, Y. Arayama, M. Matsuda, et al.

235

Castanopsis sieboldii (Makino) Hatus. ex T.
Yamaz. et Mashiba subsp. sieboldii, as well aslarge naturally inhabiting coniferous C. japonica
trees (Miyawaki 1983). The three country-side
forests were located adjacent to villages or towns
and neighboring the natural forests; these havebeen traditionally used for forest resources. The
country-side coniferous forest dominated by
Pinus densiflora was shown in Fig. 2B.
Temperature and precipitation data for thesurvey sites were obtained from the Japanese
Meteorological Agency. Observations weretaken from neighboring regions (http://www.
data.jma.go.jp/obd/stats/etrn/index.php?sess,accessed on January 5, 2022) and were analyzed
based on a temperature decrease rate of −0.55°C per 100 m increase in elevation. The annual
mean temperature and regional mean annual
precipitation across the survey sites is shown in
Table 1.
We performed sampling under the dominant
trees in the forests and collected twigs ofapproximately 0.5–1.5 cm in diameter fromaround each tree. Although the supply of fallen
twigs in the study region is sporadic in time andspace throughout the year, the twigs remain on theforest floors for several years (Ishii et al. 1976).
The twigs were selected from those in contact
with the litter surface and had remaining bark andwere randomly sampled at different decay states
ranging from slightly to moderately rotten; freshand soft, highly rotted wood was excluded. The
twigs were then placed in paper bags.

and soaked for a week at 23 °C. The pH of theresulting exudate was measured using a compact
pH meter (Horiba, Kyoto, Japan). The twig
pH was determined as the median per tree andaveraged in each forest. Next, the water was
slowly poured from the dishes, and the dishes
were incubated for over two months at 23 °C
to stimulate sporulation. After two months thecultures were maintained with their lid half open
to slowly dry the twig samples. Myxomycetes
have a short life cycle and tend to sporulate
within 10–70 days in moist chamber cultures;
therefore, the fruiting bodies were assessed at
approximately 50–80 days using a dissecting
stereomicroscope (Nikon SMZ1000) (Wrigley deBasanta et al. 2000). The percentage of positive
cultures was calculated by dividing the numberof dishes with successful cultures (i.e., thosewith plasmodia or sporangia) by the total numberof dishes. The number of myxomycete species
identified per tree species and accumulated perforest was recorded, and species abundance wasestimated as the number of positive culture dishes
in which sporangia appeared.
Myxomycete species classification was
performed as described by Yamamoto (1998), andthe nomenclature from the most recent literature
was followed (Lado 2005–2022). Voucher
specimens were prepared using separate paperboxes for each species. The twig containing
myxomycete fruiting bodies was glued to thebottom of each box, and the collection boxes
were stored in the laboratory.

2. Myxomycete cultures
We used the moist chamber culture techniqueto identify myxomycetes; this method has beenpreviously described as useful for observing thesmall fruiting bodies of myxomycetes on twigs(Stephenson et al. 2008b). The twig samples ofdominant trees were air-dried for 1–2 weeks atroom temperature (20–25 °C). The moist chamber
cultures (Fig. 2C) were then established in 20–50
plastic Petri dishes (9 cm in diameter) per tree
at a time and incubated in humid conditions.
Twig samples were cut into 3–8 cm long pieces.
Approximately 10 g of twigs (dry weight) was
placed on a clean filter paper in each Petri dish.
Each dish was then filled with approximately
30 mL of distilled water (pH 6.9), covered,

3. Data analyses
Species richness and abundance were recorded
for each sample tree and summed according to thesurvey forest. Sampling adequacy (percentage ofexactitude) was assessed by dividing the numberof taxa observed (Sobs) within a tree species by
the estimated number of taxa (Sest) (Chao 1, Chao
1984) using PAST software (Hammer et al. 2001,
http://folk.uio.no/ohammer/past/), using theformula, Sobs / Sest × 100.
To quantify the myxomycete α diversity
in each forest, the Shannon–Wiener diversity
index H’ (Shannon and Weaver 1963) andthe equitability index Jʹ (Pielou, 1966) were
determined as described in previous studies(Stephenson, 1989). β diversity, which was used236

Hikobia Vol. 18, No. 4, 2022

to estimate the similarity between communities(Akesaka et al. 2021), was calculated as theBray–Curtis dissimilarity (Doi & Okamura2011). Species relative abundance was calculatedby dividing a given species abundance by the
cumulative abundance of the community forthat forest and was similarly calculated for the
total of all communities. We defined dominant
species as those with ≥ 10 % relative abundanceat the total community level and frequent species
as those with ≥ 1.8 % relative abundance (fiveabundances).
The similarity of six myxomycete communities
was analyzed by non-metric multidimensional
scaling (NMDS; Kenkel & Orlóci 1986) using
PAST software. This software has been usedeffectively in a similar previous study (Takahashi
et al. 2018). NMDS is based on Bray–Curtis
dissimilarities (Bray & Curtis 1957), where higher
values (to a maximum of 1.0) indicate greater
dissimilarity between communities with respect
to species composition and abundance. The scoresof the first two NMDS axes were then checked forcorrelations with twig pH and biogeographicalvariables, including latitude, longitude, elevation,mean temperature, and annual precipitation to
identify important environmental factors for
subsequent analyses. The association among
environmental factors (Table 1) was assessedusing correlation analysis performed with Excel
Statistics version 7.0 (Esumi Co., Ltd, Tokyo),to estimate the association between myxomycete
communities and biogeographical trends. Cluster
analysis (Ward’s method) was performed to groupthe myxomycete communities based on NMDS
scores for the first two axes.
Results
Myxomycete communities on twigs
Fallen twigs from canopy trees were sampledfrom one or more tree species, according to thedominating tree species in the surveyed forests.
Sixty or more moist chamber cultures were
performed per forest. Myxomycetes sporangia
developed following plasmodium appearance(Fig. 2D), and fruiting was observed in 35 % ofculture dishes in all 640 cultures (Table 2). In
total, 42 myxomycete taxa were identified at thesix survey forests (Table 3). The species diversityof the myxomycete community on twigs wasH՛ = 2.73 (J՛ = 0.73) under 76 % exactitude fora total of 55 taxa predicted using Chao-1 (Table2). The following four species were common
to all forests, in descending order: Arcyria
cinerea (Bull.) Pers. (relative abundance, 28.6%) (Fig. 2E), Diderma chondrioderma (de Bary
& Rostaf.) G. Lister (representing 14.9 % of allrecords), Cribraria microcarpa (Schrad.) Pers.
(representing 9.8 % of all records) (Fig. 2F), andClastoderma debaryanum Blytt (representing
4.3 % of all records). Other abundant species
included Stemonaria gracilis Nann-Bremek.
& Y. Yamam. (relative abundance, 7.6 %) andPhysarum pusillum (Berk. & Curt.) G. Lister(relative abundance, 3.3 %), which were thenfollowed by the remaining 36 taxa.
Myxomycete communities associated with
forest types
The α-diversities of myxomycete communities
in natural forests (Table 2) were as follows:
evergreen forest (21 taxa, diversity index H ՛ =2.70, and equitability index J՛ = 0.89), deciduous
forest (13 taxa, H՛ = 1.73, and J՛ = 0.67), andconiferous forest (12 taxa, H ՛ = 2.00, and J՛ =0.80). Further, the α-diversities of myxomycete
communities in country-side forests were as
follows: evergreen forest was 18 taxa (H՛ = 2.46,
J՛ = 0.85), mixed forest with deciduous andevergreen trees (Sm) was 18 taxa (H՛ = 2.33, J՛ =0.80), and coniferous forest was the lowest of 7
taxa (H՛ = 1.67, J՛ = 0.86). The six communities
of different forests were compared in order withthe species diversity and equitability (Fig. 3).
The country-side evergreen forest (Se) and mixed
forest (Sm) located between both natural forest
types of NE and ND demonstrated a medium
level of diversity, but country-side coniferous
forest (Sc) separated from the rest of the forests(Fig. 3). The natural forests had higher diversity
than that in the neighboring country-side forests.
Species diversity in the six communities tended
to decrease from natural forests to country-side
forests.
The different six communities were ordinatedusing NMDS and plot ted (Fig. 4). Cluster
analysis indicated two groups of the communities
bounded by wavy ellipses. The natural broadleaved evergreen forest (NE) differed from theK. Takahashi, M. Fukushima, Y. Arayama, M. Matsuda, et al.

237

Table 2. Results of moist chamber cultures (MCs) indicating twig pH, species diversity, and exactitude of
myxomycete communities in natural and country-side forests.

natural broad-leaved deciduous forest (ND) but
was near the natural coniferous forest (NC). The
county-side evergreen forest in Kochi prefecture(Se) was closely situated to the natural evergreen
forest ( NE). The county-side mixed forest(Sm) in Kurashiki City, in the southern part of
Okayama prefecture, was close to the natural
broad-leaved deciduous forest (ND) in Mt.
Daisen, Tottori prefecture. However, the county-

Fig. 3. Species diversity (H՛) and equitability (J՛) of
six myxomycete communities, ● indicates naturalforests, ∆ indicates secondary forest. NE: natural
broad-leaved evergreen forest; ND: natural broadleaved deciduous forest; NC: natural coniferous forest;
Sc: country-side coniferous forest; Sm: country-side
mixed forest with deciduous and evergreen trees; Se:country-side broad-leaved evergreen forest. Numbersin brackets indicate the number of taxa.

side coniferous forest (Sc) dominated by P.
densiflora and Q. crispula in the foothills of Mt.
Daisen was distant from ND or NE, even though
its location was adjacent to that of ND. Thus,
spatially close locations likely contained similar
myxomycete community structures comparedwith those in geographically distant locations,but the tree types constituting the forests affected
myxomycete diversity and similarity between
communities.
The arrangement of the six communities
was determined based on correlations withenvironmental parameters (Table 4). Scores ofthe first two axes in NMDS and the geographicall o c a t i o n e x h i b i t e d n e g a t i ve c o r r e l a t i o ncoefficients with the first axis (latitude r = −0.764,
longitude r = −0.643, and altitude r = −0.096).
However, this correlation was not statisticallysignificant, and climatic factors (annual mean
temperature and annual precipitation) also
indicated low coefficients. Thus, no remarkableassociation was obtained between myxomycete
communities and any of the environment factors
including twig pH.
Discussion
The highest myxomycete diversity on litter
twigs occurred in natural broad-leaf evergreen
forests in wester n Japan. The myxomycete
communities among three different naturalforests were presumed to be of original similarity

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Hikobia Vol. 18, No. 4, 2022

Table 3. Myxomycete taxa and number of fruiting colonies in cultures according to natural forests andcountry-side forests. Italics indicate the relative abundance of total records of individual taxa. Taxa werearranged in order of relative abundance.ests.

K. Takahashi, M. Fukushima, Y. Arayama, M. Matsuda, et al.

239

Table 3. (continued)

Table 4. Correlation coefficients among NMDS scoresof myxomycete communities in six forest types andenvironment variables.

based on biogeog raph ical locat ion i n t hepresent survey region (Fig. 4). Spatially close
myxomycete communities exhibited similar
structures as shown between natural broad-leaved
evergreen forest (NE) and natural coniferous
forests ( NC). The difference of vegetation
types also inf luenced dissimilarity between
the communities. The three communities ofcountry-side forests were considerably affectedby geographical distances and difference ofvegetation types. The original forests impacted
by anthropogenic activity were presumed tocause diversity loss of myxomycete communities
as likely degraded as in the country-side forests
in geographically neighboring natural forest(Figs. 3 & 4). The country-side forests surveyed
in present study were left unused since the 1960s

Fig. 4. Ordination plots of six forest types in naturaland second a r y forests analyzed usi ng N M DS;
the st ress value was 0.080. T he coeff icient ofdetermination for the first axis was r2 = 0.814, and thatfor the second axis was r2 = 0.010. As in Table 1 andFig. 3, ● and Δ indicate natural forest and secondary
forest, respectively. Ovals with a dashed line indicate
similar groups with 70 % reliability in the cluster
analysis (Ward’s method). ND: natural broad-leaved
deciduous forest dominated by Fagus crenata in Mt.
Daisen, Tottori Pref.; Sc: country-side forest of Pinus
densiflora in the foothills of Mt. Daisen; Sm: countryside mixed forest of evergreen and deciduous trees inKurashiki, Okayama Pref.; NE: natural broad-leaved
evergreen forest at Yokogurayama, Kohchi Pref.; Se:country-side forest in the broad-leaved evergreen
forest; NC: coniferous natural forest dominated byAbies firma.

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because of fuel use revolution, whereas species
diversity of myxomycetes cannot be considered
restored likely natural forests.
A change in vegetation from natural broadleaved deciduous forest to country-side pine
forest induced a strong impact on myxomycete
com mu nit y and diversit y decreasing. The
country-side mixed forest comprised deciduousand evergreen trees maintaining intermediate
diversity, suggesting that forest vegetation was
an important factor for species inhabitationand suitability of myxomycetes. Although thesix different forests surveyed did not indicate a
direct correlation with geographical location andclimates (Table 4), the differences in myxomycete
communities were suggested to be because ofdifferences in biogeographical location, forest
vegetation types, and anthropogenic impact.
Complex environmental variables derived
from the geohistorical geography and climate
i n f luence t he or ig i n of forest veget at ion(Momohara 2017). The spatial distribution
patterns of myxomycetes also associated withgeohistorical host tree diversification can bestudied using C. japonica on the myxomycetes
living on the bark (Takahashi 2020). Myxomycete
distribution is successfully related to differencesin climate and/or vegetation on a global scale,and to the ecological differences that exist amongindividual habitats on a local scale (Stephenson
et al. 2008a). The vegetation differences among
natural forests on a local scale provide specifichabitats for myxomycetes (Takahashi & Harakon
2010). The a ltitudinal differences affected the
myxomycete communities on the bark of C. japonica
trees in western Japan (Takahashi 2017), and the

topographical differences in the present region
inf luenced the communities on the bark ofliving C. japonica (Takahashi et al. 2020). I n
Philippines, the highest taxonomic diversity wasrecorded for study sites at the highest elevations(i.e., 700–800 m asl) in a secondary deciduous
sub-tropical forest at Mt. Arayat National Park,
using moist chamber cultures of leaf litter andtwigs, of which substrates yielded a total of
30 species of myxomycetes (Dagamac et al.
2014). The results of the present study extended
understanding, that is, the community structureof myxomycetes responds to local environmental
variables, including human impact such ascountry-side or natural forests.
We found that myxomycete species richness
a n d s p e c ie s d ive r sit y (H ՛ ) d e c r e a s e d i ncountry-side forests compared with that in theneighboring natural forest, for example, thebroad-leaved deciduous forests in Mt. Daisen
exhibited a decline from 13 to seven taxa (H՛from 1.73 to 1.68); the broad-leaved evergreen
forest areas in Yokogurayama showed a decrease
from 21 to 18 taxa (H՛ from 2.70 to 2.46), andthe mixed forest in the urban area recorded
18 taxa (H՛ = 2.33). It was suggested that the
impact of anthropogenic activities inf luences
microorganisms as well as animals and plants(Davison et al. 2021). The change identified in
myxomycete communities between mountain
forests and banana plantations in Vietnam(Novozhilov et al. 2019) may indicate the effectof ecological distance on detritus decomposition
and the influence of human activity.
Deforestation derived from human activity
was found to reduce the species diversity ofcor ticolous myxomycetes along the downstream section of a river (Takahashi 2021)
or in the developed region around Mt. Fuji
(Takahashi & Yano 2021). Forest fragmentation
in southeastern Peru has also caused habitat
loss and demonstrated that differences in forest
structure contributed the most to the differencesin myxomycete fruiting body abundance among
forest types (Rojas & Stephenson 2013). Overall,these studies indicate that forest ecosystems
individually establish inherent functions within
decomposing detritus and in the microbialcommunities, including myxomycetes, in aforest.
I n forest ecosystems, my xomycetes are
assumed to play important nutrient cycling roles
in complex food webs (Gessner 2010). Changes
in the species diversity of detritivores within
and across trophic levels can significantly alterdecomposition (Gessner 2010); further, low
diversity slows the rate of litter decomposition(McLaren 2014). This suggests that differencesin the species diversity of myxomycetes between
different forest types, such as natural or countryside, and broad-leaved evergreen or deciduous,
are related to divergent habitat conditions andaffect certain ecological functions. The diversityof the myxomycete community may associate

K. Takahashi, M. Fukushima, Y. Arayama, M. Matsuda, et al.
with functional interactions with other microbes
and is important to preserve balance in theforest ecosystem and sustainable carbon cycle.
Overall, this is the first comprehensive study
on the distribution pattern of myxomycetes
living on litter twigs in different forest types;
these findings suggest the potential inf luenceof anthropogenic activity on myxomycetes andforest ecosystem.
Acknowledgments
We thank students in Notre Dame Seishin
G a k u e n S e i s i n G i r l’s H i g h S c h o ol w h ocollaborated and worked on this study as a biology
club activity. We are grateful to Seihin Girls’High School for supporting our investigation andallowing us to use the laboratory.
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Accepted 4 XII. 2022

K. Takahashi, M. Fukushima, Y. Arayama, M. Matsuda, et al.

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高橋和成・福島実奈・荒山幸美・松田実桜・木立侑里・林と里山林との比較をした．森林ごとに採取した優占田中福人・南耕太郎・冨永 晃・立石京子・原紺勇一 :

樹種の落枝を全体で 640 枚のペトリ皿で湿室培養し，西日本における落枝生変形菌の種多様性と森林タイプ

発生した変形菌子実体コロニーの数と出現種を記録しとの関係た．出現種は全体で 19 属 42 種であったが，6 つの森
林タイプに共通して出現したのは 4 種のみであった．天変形菌の多くは森林の枯死木や落葉・落枝などの腐然林の常緑広葉樹林で 21 種が出現し，種多様性が最植で生活するが，森林タイプの違いがどのように変形菌も高くなった．一方，里山のアカマツ林では 7 種しか出群集に影響を与えているのかは十分に分かっていない．

現しないなど，里山林では種多様性が低下した．非計

落枝は変形菌にとって生態的なニッチになっているた

量多次元尺度構成法で変形菌群集を序列化すると，地め，森林の優占種の落枝で生育する変形菌（落枝生変

理的に近接する森林間では類似性が高いが，森林タイ形菌）の分布を異なる森林タイプ間で比較した．調査

プにより個別の群集構造を形成した．本研究では，西地は，西日本の中国・四国地方に立地する 6 つの異な日本の森林タイプの違いによる落枝生変形菌の分布パる森林タイプ（3 つの天然林と 3 つの里山林）を選定し，ターンが明らかになり，人間活動の影響を受けた里山

それぞれの落枝生変形菌群集の類似性，および天然林で変形菌の多様性が低下していることが分かった．