基于形态与微形态分析确认枝毛野牡丹野牡丹科系一独立的种英文

温振英 周育真 翟俊文 吴沙沙 兰思仁 陈进燎 彭东辉

摘 要： 枝毛野牡丹（Melastoma dendrisetosum）属于野牡丹科野牡丹属，首次发表于1983年，而Chen & Renner（2007）则将其归入了毛菍（M. sanguineum）。为弄清二者的区别及枝毛野牡丹的分类地位，该研究采用野生地实地考察、各大标本馆标本比较鉴定、引种地植株形态测定以及微形态扫描电镜观察，现已证实：枝毛野牡丹是明显区别于毛菍的一个独立的植物种，该种自然分布区极其狭窄，正处于极度濒危的生存状态。该文对枝毛野牡丹进行了最新的形态描述，为正确识别、积极保护该物种奠定了基础。

关键词： 枝毛野牡丹， 独立物种， 证據， 最新形态描述， 海南

The genus Melastoma Linn.（Linnaeus， 1753）（Melastomataceae）comprises approximately 100 species distributed from South Asia to the northern part of Oceania and the Pacific Islands（Chen， 1983， 1984; Meyer， 2001）， but only 22 species have been recognized in Flora of China（Chen & Renner， 2007）， and 31 new species in Borneo were published by Wong（2016）; he believed that there were 80-90 species in Melastoma. In fact（Huang et al.， 2018）， thought this genus was not detailed enough to ensure the exact number of species in it， and there might thus be other new species yet to be discovered.

Nine species and one variety in China were reported in the revision of the Chinese Melastoma（Chen， 1983）， wherein the new species M. dendrisetosum was only reported to be distributed in Hainan and was similar to M. penicillatum. This treatment was followed by the same author in Flora Reipublicae Popularis Sinicae（Chen， 1984）. However， in Flora of China， Chen & Renner（2007）followed revision of Meyer（2001）and recognized only five Chinese taxa and incorporated M. dendrisetosum and M. penicillatum into M. sanguineum. However， subsequent studies indicated that M. penicillatum was a distinct species from both morphological characteristics and molecular results（Chao et al.， 2014）; Research of Huang et al.（2018）indicated that M. dendrisetosum was an independent species mainly based on from the difference in the indumentum of the hypanthium and the molecular results; however， there are other morphological differences between the two， and the taxonomic status of M. dendrisetosum also needs to be further assessed from multiple perspectives.

Leaves were one of the important vegetative organs of plants， and were also one of the important bases for plant species identification（Zeng et al.， 2017）. In plant taxonomic studies， leaf characteristics were next only to those of flowers and fruits（Li et al.， 2010; Wang et al.， 2012; Yang et al.， 2016）. The leaf epidermis of plants has certain genetic stability， and thus， the micromorphological characteristics of leaf epidermis were of important research value for interspecies or intergeneric classification（Zeng et al.， 2017）and the microscopic morphological characteristics of leaves had been increasingly used in the study of modern plant taxonomy and in the classification and identification of difficult groups（Peng et al.， 2011; Xu et al.， 2013; Yang et al.， 2016）. Epidermal hair was the most common appendage on plant leaves， and its distribution characteristics and morphological characteristics were important means of plant identification and taxonomic study（Baran & Zdemir， 2009; Wang et al.， 2015）. Epidermal hair was confirmed as a classification feature with applied value for interspecies classification（Yang et al.， 2016）. Stomata were the subsidiary structure of leaf epidermis and were evolved from epidermal cells during long-term development. The densities of stomatal organs were also different among species， and could be used as the basis of species classification（Zeng et al.， 2017）. The results of previous studies proved that sporopollen was an important basis for plant classification（Shao & Fan， 2003）. The morphological characteristics of flower pollens were controlled genetically and had strong stability and genetic conservatism， which are not easily affected by environmental factors. Pollen grain size， shape， and outer wall ornamentation could be used to study plant classification（Erdtman， 1978; Xu， 2007）. When the classical morphological method proved to be difficult to solve the problem of classification， study of pollen morphology and surface ornamentation often played a very valuable role（Zhang & Zhou， 1998; Zhang et al.， 2001; Zhang， 2004; Yan & Li， 2003a， b; Zhang et al.， 2014; Hong et al.， 2015; Li et al.， 2017）.

Therefore， in order to clarify the difference between M. dendrisetosum and M. sanguineum and the taxonomic and survival status of M. dendrisetosum， we made several botanical trips to Hainan. Along with morphological observation and comparative identification， micromorphological scanning electron microscopy was performed to evaluate the species status of M. dendrisetosum to lay the foundation for its further protection and utilization.

1 Materials and Methods

1.1 Materials

The morphological data of the species described here were based on living plants growing in the Diaoluo Mountain Nature Reserve and introduced from there to grow in Fujian Agriculture and Forestry University（FAFU）， and specimens collected in Diaoluo Mountain Nature Reserve， Hainan（Table 1）were deposited at major herbariums such as HITBC， IBK， IBSC， and KUN.

1.2 Methods

1.2.1 Morphological observation and conservation status investigation Morphological observation The morphological traits of M. dendrisetosum and M. sanguineum were based on living plants， growing in the wild or in the campus of FAFU. We selected 30 individuals of M. dendrisetosum and M. sanguineum grown in the wild， and ten from the campus of FAFU and observed them with naked eyes; the whole plants or some organs were photographed with a digital camera（Canon HG10）and the specimens introduced in 1.1 were observed and compared carefully.

Conservation status investigation Several scientific trips were made to the wild native places recorded in previous literature such as Luohui（currently Qionghai）， Baoting， Wanning， and Lingshui to investigate the distribution of M. dendrisetosum in the wild and its survival status.

1.2.2 Micromorphology observations by scanning electron microscope（SEM）

Leaf stomata micro-morphology observation by SEM According to the method of Guo（2006）， fresh mature leaves of M. dendrisetosum and M. sanguineum were cut separately into 5 mm × 5 mm square blocks near the midrib; the blocks were quickly dipped in formal-aceto-alcohol（FAA）fixative solution for 2 h at room temperature， then stepwise dehydrated twice with 30%， 50%， 70%， 85%， 95% and 100% ethanol， each stage was dehydrated for 15 min. The blocks were dried using the critical point drying method， fixed on copper tables， coated with the JFC-1200 ion sputter coater， and observed and photographed under the JSM-5310LV SEM.

Feature description terminologies on stoma in this article are used with reference to Zhang & Zhuang（2004）， Zhang et al.（2013）and Zeng et al.（2017）.

Pollen micromorphology observation by SEM The anthers of long stamens of M. dendrisetosum and M. sanguineum were collected， stored in a dust-free place， and naturally dried for 48-72 h to collect the pollens. The pollens were bonded on copper tables using double-sided tape， coated with the JFC-1200 ion sputter coater， and observed and photographed under the JSM-5310LV SEM. Ten pollen grains of each of the two species were randomly selected to measure the length of the polar axis P and the equatorial axis E， respectively.

Feature descriptions on pollen shape， size， and exine ornamentation in this article were in reference to Li et al.（2017）.

2 Results

2.1 Obviously different morphological traits between M. dendrisetosum and M. sanguineum

The obviously different morphological traits between M. dendrisetosum and M. sanguineum are shown in Fig. 1 and Table 2.

According to our investigation， a few traits such as plant height， oblique branchlet， and seed color are slightly similar between M. dendrisetosum and M. sanguineum， but rather obvious differences are present in many traits including the flower， fruit， stem， and leaf characteristics， especially the flower and fruit traits（Fig. 1， Table 2）. Moreover， the flowering time of the two species is also different， M. dendrisetosum blooms

A-C， G-I. M. dendrisetosum; D-F， J-L. M. sanguineum; A， D. Stem and petiole; B， E. Leaf; C， F. Opening flowers; G， J. Flower anatomy; H. I， K. L. Fruit.

Fig. 1 Photographs indicating the obvious difference in some main morphological traits between Melastoma dendrisetosum and M. sanguineum

A， B. Stoma of M. dendrisetosum; C， D. Stoma of M. sanguineum; E， F. Pollen equatorial and polar view of M. dendrisetosum; G， H. Pollen equatorial and polar view of M. sanguineum.

Fig. 2 Photographs demonstrating the micromorphology of stomata and pollen from Melastoma dendrisetosum and M. sanguineum

Qionghai（previously known as Luohui）is the type locality of Melastoma dendrisetosum.

Fig. 3 Location of Diaoluo Mountain National Nature Reserve

from March to April whereas M. sanguineum blooms throughout the year.

2.2 Obviously different micro-morphological traits of stomata and pollens between M. dendrisetosum and M. sanguineum

The obviously different micromorphological traits of stomata and pollen between M. dendrisetosum and M. sanguineum are shown in Fig. 2 and the micro-morphological comparison of the stomata and pollens are shown in Table 3.

Although the micromorphology of the stomata in M. dendrisetosum and M. sanguineum shows similar shape of the stomatal complex and ornamentation of the stomatal outer arch cover， obvious differences were observed in the opening degree， the sunken degree of stomatal complex relative to epidermal cells， stomatal outer arch cover and its inner margin， and the peripheral ornamentation of the stomatal complex（Fig. 2： A-D， Table 3）.

Although the micromorphology of pollen of M. dendrisetosum and M. sanguineum is similar in the six germinating furrows， obvious differences were observed in some aspects such as pollen size（including length of the long axis and P × E）， equator and polar view， and exine ornamentation（Fig. 2： E-H， Table 3）.

2.3 Conservation status of M. dendrisetosum

M. dendrisetosum was only found in a valley of the Diaoluo Mountain National Nature Reserve in April 2012， distributed at an altitude of 350-400 m， and was scattered with a total of less than 300 individuals at nearly 100 km from its type locality Luohui（currently Qionghai）， Hainan， China（Fig. 3）. This entity was a shrub of 2-3 m tall， and grows in slightly shaded places on forest margins， roadsides， or stream sides. The photographs of its habitat and branches are shown in Fig. 4. Other species found growing nearby this species include Sapium discolor， Mallotus japonicas， Passiflora foetida and so on. In addition， although M. dendrisetosum and M. sanguineum were found to grow together in Diaoluo Mountain National Nature Reserve， the authors did not find any intermediate relationship between them in the wild.

3 Discussion and Conclusion

3.1 Discussion

3.1.1 M. dendrisetosum is a distinct species Melastoma dendrisetosum was recognized as a distinct species when it was first published by Chen（1983）， but was incorporated into M. sanguineum by Meyer（2001）and Flora of China by Chen & Renner（2007）， rather than being treated as an independent species. It is well known that the characteristics of flowers and fruits are

important for plant classification. In this study， the authors carefully compared the main differences in some flower and fruit characteristics between M. dendrisetosum and M. sanguineum， and found some morphological traits unaffected by environmental change， such as the petal tip and the accessory hair， the number of petals and stamens， fruit type and color， the mark of calyx tube and so on， which were obviously different. These differences in flower and fruit characteristics indicate that M. dendrisetosum is a species distinct from M. sanguineum.

In this study， the authors found that M. dendrisetosum and M. sanguineum were obviously different in some leaf traits as the midvein， blade epidermal hair， blade margin， and petiole and some stoma traits such as stoma opening degree， stomatal outer arch cover， inner margin of stomatal outer arch cover， and stoma peripheral ornamentation.

The present study indicate that M. dendrisetosum and M. sanguineum are obviously different in some pollen traits such as length of long axis， type， polar and equatorial axis length， and the equatorial and polar view.

These observations strongly confirm that M.dendrisetosum is a species significantly different from  M. sanguineum in the epidermal hairs of leaves， stomata， and pollen micromorphology. In addition， a recent molecular level perspective also indicated that M. dendrisetosum should be considered a distinct species（Huang et al.， 2018）.

3.1.2 M. dendrisetosum is an endangered species In April 2012， the authors investigated the living condition of M. dendrisetosum and found that it was only sporadically distributed in a valley of the Diaoluo Mountain National Nature Reserve， at an altitude of 350-400 m， with a total of less than 300 individuals at nearly 100 km from its type locality， Luohui（currently

A， B. Wild habitat; C. Branches with many fruits and flowers; D. Branch only with leaves.

Fig. 4 Photographs indicating the habitats or branches of Melastoma dendrisetosum

Qionghai）， Hainan， China. According to the IUCN Red Categories and Criteria（IUCN， 2001）， M. dendrisetosum satisfies the criteria B1（i.e.， extent of occurrence， 100 km2）and B2（i.e.， present only in one location and declining quality of habitat）. Moreover， the authors previous research（Peng et al.， 2014）found that there was no self-compatible self-pollination and agamospermy in this species， and that the breeding system of M. dendrisetosum was a typical facultative inbred type with a relative reproductive success（RRS）of 0.035， which is perhaps one of the main reasons for its endangered status.

Table 2 Comparison of main morphological traits of Melastoma dendrisetosum and M. sanguineum

Moreover， Huang et al.（2018）found that the habitat of M. dendrisetosum in the area was degraded further and that the number of mature individuals was declining， and strongly believed that M. dendrisetosum would be categorized as ‘Critically Endangered. Therefore， the habitat of the species should be first fully protected， and any destruction to it must be strictly prohibited; secondly， measures of habitat protection combined with introduction of propagation protection should be taken to expand the population.

3.1.3 New morphological description of M. dendrisetosum should be prepared So far， the morphological description

of M. dendrisetosum that can be found is still only from Chen（1984）. In the past three decades， the morphological and micromorphological characteristics of this species have been revealed in a stepwise manner， with continuous investigation and studies. Thus， it is necessary to supplement the original description and prepare a new description in order to facilitate the correct understanding and identification this species.

3.2 Conclusion

3.2.1 M. dendrisetosum is a distinct species in an endangered living status Morphological trait observation results showed that M. dendrisetosum was obviously different from M. sanguineum in some traits of the flower， fruit， branch， and leaf as well as in the

Table 3 Comparison of stomata and pollen micromorphology between Melastoma dendrisetosum and M. sanguineum

Item

M. dendrisetosum

M. sanguineum

Stoma

Shape of stomatal complex

L/W=1.52， elliptic

L/W=1.67， oblong elliptic

★Opening degree

Larger

Lower

Sunken degree of stomatal complex relative toepidermal cells

Sunken but not obvious

Sunken obviously

★Stomatal outer arch cover

Narrow， obvious uplift

Wide， slight uplift

Ornamentation of stomatal outer arch cover

Nearly smooth

Nearly smooth

★Inner margin of stomatal outer arch cover

Obvious thickening and sinuate

Slight thickening and sinuous

★Peripheral ornamentation

More slender and uplift wave stripes

Less wider and smooth stripes

Pollen

★Length of long axis

22.60 μm

33.01 μm

★Type

Middle pollen

Large pollen

★Polar axis length（P）× Equatorial axis length（E）

22.60 × 21.23 μm

33.01 × 10.96 μm

★Equator view

Long sphere with furrows

Ultra long sphere with furrows

★Polar view

Six-lobed circular with 6 slight furrows

Six-lobed circular with 3 larger furrows and 3 smaller ones alternately

★Exine ornamentation

Densely covered with wormlike projections

Densely and evenly covered with shallow holes

Note： According the ratio of Length/Width. Elliptic. 1.35 < L/W < 1.55; Oblong elliptic. L/W > 1.55; Widely elliptic. L/W < 1.35（Zeng et al.， 2017）.

flowering date. Micromorphological trait observation by SEM indicated some obvious differences between M. dendrisetosum and M. sanguineum in the traits of stoma as well as pollen. Thus， M. dendrisetosum is a distinct species. Based on the resource investigations of the genus Melastoma， only one clump of M. dendrisetosum was found in Diaoluo National Nature Reserve， with less than 300 individuals left， indicating that this species is in a critically endangered living status and should be protected actively and carefully. Botanical trips to Hainan and our observations of this species at that location will facilitate a better understanding of this species， and help us to determine why it is restricted to such a small area.

3.2.2 Redescription of M. dendrisetosum Melastoma dendrisetosum C. Chen in J. S China， Agric. Coll. 4（1）： 35， Fig.10-12， 1983; C. Chen in Fl. Reip. Pop. Sin. 53（1）168， 1984.

Type： China， Hainan， Lohwei（Luohui）， orient. Hainan Exp. 89（ANT）. Specimens cited： Hainan， Wenning， I Chung 4016（IBSC）; Hainan， Lingshui， C. Wang 36782（IBSC）; Hainan， Wannin， Z. X. Li 628676（IBSC）; Hainan， Wannin， F. W. Xin 634549（IBSC）; Hainan， Wannin， F. W. Xin 634103（IBSC）; Hainan， Diaoluo Z. X. Li 522642（IBSC）; Hainan， Wannin， F. W. Xin 634549（IBSC）; Hainan， Wannin， Y. Zhong 316567（IBSC）; Hainan， Xinlong， 317381（IBSC）; Hainan， Jiaziling， 299256（IBSC）; Hainan， Baoting， S. Q. Chen 199964（IBSC）; Hainan， Linshui， Z. Huang 70921（IBSC）; Hainan， Diaoluo National Nature Reserve， D. H. Peng et al. 201203（FAFU）; Hainan， Diaoluo National Nature Reserve， D. H. Peng et al. 201204（FAFU）Hainan， Diaoluo National Nature Reserve， D. H. Peng et al. 201206（FAFU）.

Shrub， 2-3 m. Stems terete， densely long sericeous and puberulous with branches; leaf blade stiffly papery， lanceolate to oblong-lanceolate， apex acuminate， cuneate or obtuse at base， 4.5-8.5 × 1.7-3 cm， secondary veins 2 on each side of midvein， margin entire or densely shallow-denticulate， bristly ciliate， adaxially strigose， abaxially densely villous and puberulent. Inflorescence terminal， umbellate， very short， subcapitate， 3-4 flowered， base with 2 foliaceous bracts， smaller than leaves; peduncle densely long sericeous and puberulous， ca. 0.2 cm. Hypanthium densely white branching setae， ca. 1 cm. Calyx lobes linear-triangular， ca. 0.6 cm long， covered with branching setae， with a small lobe， ca. 0.2 cm long between them. Petals rose red， rhombic-obovate， oblique above middle， ca. 2.5 × 2 cm， with a bundle of bristles at apex， with shortly ciliate. Stamens heteromorphic， longer stamens ca. 3.6 cm， anthers ca. 2.4 cm， purplish red， connectives extended at base， curved， bases with 2 tubercles， filaments slightly longer than extended connection; shorter stamens ca. 1.7 cm， anthers ca. 0.8 cm， with connection not extended， bases with 2 tubercles. Ovary half-inferior， densely setose. Fruit urceolate when young， truncate， apex covered with bristles. Persistent hypanthium covered with branching bristles. Capsule diameter ca. 1.5-1.9 cm. Flowering from March to April， and fruiting from May to August.

Distribution and Habitat： M. dendrisetosum is only found in Diaoluo Mountain National Nature Reserve， Hainan， China. It grows in slightly shaded places on forest margins， roadsides， or stream sides between 350-400 m， and tends to grow in areas that receive 5-6 h of sunlight a day. Other species found growing nearby this species include Sapium discolor， Mallotus japonicas， Passiflora foetida， etc.

Acknowledgments We appreciate Prof. RENNER Susanne Sabine， Ludwig Maximilians University Munich， Nymphenburg Botanical Garden， for her helpful suggestions. We also thank Prof. SONG Xiqiang and Mr. LIN Weiguo for joining and supporting our field work， and Prof. ZHOU Xiumei for her helpful comments and suggestions.

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（责任编辑 李 莉）