Nepenthes micramphora V. B. Heinrich, S. McPherson, Gronem. & V. B. Amoroso

Nepenthes micramphora is a tropical pitcher plant known only from Mount Hamiguitan on the island of Mindanao in the Philippines.^[1] It is a highland plant growing at elevations of 1100–1635 m.^[1]

Nepenthes micramphora is closely allied to N. abgracilis and N. cid, both also from Mindanao, and together these species comprise the informal "N. micramphora group".^[2]

The specific epithet micramphora is derived from the Greek mikros (small) and Latin amphora (amphora, urn), and references the tiny pitchers of this species.^[3]

Botanical history

Nepenthes micramphora was formally described in 2009 by Volker Heinrich, Stewart McPherson, Thomas Gronemeyer, and Victor Amoroso. The description was published in the second volume of McPherson's Pitcher Plants of the Old World.^[1] The herbarium specimen V.Amoroso & R.Aspiras CMUH 00003545 is the designated holotype, and is deposited at the Central Mindanao University Herbarium in Musuan, Bukidnon, the Philippines.^[1] It was collected on 31 January 2005, from Mount Hamiguitan, on the trail from San Isidro, at an altitude of 1300–1600 m.^[1]

Inflorescence measurements for the formal description were taken by Volker Heinrich at the type locality on 22 July 2008, since herbarium material of the floral structures could not be located.^[1]

Description

Nepenthes micramphora is a climbing plant growing to a height of 2.5 m.^[4] The stem is circular in cross section and up to 3.5 mm in diameter, with internodes up to 15 mm long.^[1]

A typical upper pitcher

Leaves

Leaves are sessile and coriaceous in texture. The lamina (leaf blade) is lanceolate-elliptic in shape and reaches 8 cm in length by 1 cm in width,^[1] being widest in its distal half.^[2] The lamina has an acute apex and is shortly attenuate at the base, clasping the stem for approximately one-third of its circumference. It is not decurrent down the stem. Two to three longitudinal veins are present on either side of the midrib, while pinnate veins are numerous. Tendrils are up to 7.5 cm long and 1 mm wide.^[1]

Pitchers

Rosette and lower pitchers are narrowly ovate in the basal portion and cylindrical or sometimes slightly infundibular above.^[3] They are very small, reaching only 4.1 cm in height by 1.6 cm in width. A pair of wings (≤4 mm wide) typically runs down the ventral surface of the pitcher cup, although these may be reduced to ribs.^[3] The wings bear fringe elements measuring around 3 mm and spaced 2.5–3 mm apart. Only the basal third of the interior surface of the pitcher is glandular. The peristome is cylindrical and up to 0.8 mm wide, bearing ribs up to 0.1 mm high and spaced 0.1 mm apart.^[3] Teeth are not visible on the inner margin of the peristome.^[2] The pitcher lid or operculum may be elliptic, ovate, or orbicular, and generally has a cordate base.^[3] The lid lacks appendages^[3] and measures up to 2 cm in length by 1.8 cm in width, being slightly wider than the pitcher mouth.^[1] The nectar glands of the lower lid surface number more than 100.^[2] A branched or divided^[3] spur (≤3 mm long) is inserted near the base of the lid.^[1]

A rosette plant with a bright red stem

Upper pitchers are produced from an early age.^[3] They may be infundibular throughout^[1] or narrowly infundibular in their basal part, becoming narrower and roughly cylindrical above.^[3] They are broadest in the middle or in the upper portion.^[2] Aerial pitchers are larger than their terrestrial counterparts, growing to 6.7 cm in height by 2 cm in width (although more often around 4 cm by 1.7 cm).^[3] The pitcher lid is of the same width as the mouth. Wings are always reduced to ribs.^[3] In other respects, upper pitchers are similar to the lower traps.^[1]

Inflorescence

Nepenthes micramphora has a racemose inflorescence measuring up to 35 cm in length by 6 mm in width. The peduncle itself may be up to 8 cm long and 1 mm wide. Flowers are borne on one-flowered, non-bracteate pedicels (3–4 mm long), of which there are between 20 and 40 on the inflorescence. The ovate tepals measure up to 2.5 mm in length by 1.2 mm in width. Fruits are up to 20 mm long.^[1]

Indumentum

The stem, lamina, and pitchers are glabrous. An inconspicuous indumentum of simple, rusty brown hairs (0.1 mm long) covers the inflorescence.^[1]

Ecology

Distribution

A stunted tree growing in the "Bonsai Forest" of Mount Hamiguitan

Nepenthes micramphora has only been recorded from the highland slopes of Mount Hamiguitan, Davao Oriental, in the extreme southeast of Mindanao island in the Philippines. Much of the surrounding region has not been explored for Nepenthes, and this species may therefore be present in other parts of southern Mindanao.^[3] Its altitudinal distribution extends from 1100 m above sea level to the summit at 1635 m.^[1]

Habitat

This species grows terrestrially in a wide range of habitats, including upper montane mossy forest, secondary vegetation, ridge tops, cliff sides, and landslides.^[3] It has also been recorded at the margins of montane forest around the so-called Bonsai Forest,^[1] which is named for its stunted trees. The species is restricted to ultramafic substrates. While N. micramphora tolerates shady conditions, it grows best under direct sunlight.^[3] On Mount Hamiguitan, N. micramphora is sympatric with N. alata (sensu lato), N. justinae^[5] (previously identified as N. mindanaoensis), and N. peltata,^[1] and grows in the same altitudinal range as N. hamiguitanensis.^[4] Despite this, no natural hybrids have been observed with certainty.

Conservation status

In his 2009 book, Pitcher Plants of the Old World, Stewart McPherson writes that N. micramphora is "not currently threatened" owing to its extensive populations on Mount Hamiguitan and the fact that visitors are only permitted to climb the mountain with the assistance of a guide.^[3] The future of wild populations of N. micramphora will be further secured if provincial officials of Davao Oriental are successful in their bid to gain recognition of Mount Hamiguitan as a UNESCO World Heritage Site.^[3][6]

Related species

N. micramphora group

Botanical illustrations of N. abgracilis (left) and N. cid from Cheek and Jebb's type descriptions, showing various aspects of vegetative morphology

Nepenthes micramphora gives its name to the informal "N. micramphora group", which also includes N. abgracilis from northeastern Mindanao and N. cid from north-central Mindanao. This group was introduced by Martin Cheek and Matthew Jebb in a 2013 paper that also included the formal descriptions of the latter two species.^[2] Before this, N. micramphora was considered an outlier or species of uncertain placement that did not fall into any of the established groups of Philippine Nepenthes (the three main ones being the N. alata, N. ventricosa, and N. villosa species groups).^[7]

Nepenthes abgracilis, N. cid and N. micramphora are united by aspects of pitcher and stem morphology as well as shared habitat preferences. Cheek and Jebb identified seven diagnostic characters that they used to define the group:^[2]

1. submontane habitat;
2. stems terete;
3. peristome slender, cylindrical, 0.8–2 mm wide;
4. peristome ridges low, about 0.1 mm high, inconspicuous;
5. inner edge of peristome without visible teeth (in natural position);
6. lower surface of lid lacking a basal ridge and appendage;
7. lid nectar glands>100, monomorphic, large (ca. 0.5 mm diam.) with a narrow border, ± evenly spread over the lid

These species show some similarities to those of the N. alata group, but differ in lacking a basal ridge or appendage on the lower surface of the lid.^[2]

Nepenthes cid differs from the other two species of the N. micramphora group in growth habit (it is epiphytic as opposed to terrestrial), indumentum development (vegetative parts hairy as opposed to subglabrous), and in having a distinct petiole (versus sessile in the other two).^[2] Both it and N. abgracilis have entire spurs, as compared to branched in N. micramphora.^[2]

Nepenthes micramphora is most easily distinguished from N. abgracilis by its upper pitchers, which are more-or-less infundibular (versus subcylindric in N. abgracilis), narrowest at the base and widest in the middle or upper half (versus widest near the base), and much smaller in all respects (≤6.7 cm versus c. 16 cm high).^[2]

Other similar species

A basal rosette of N. bellii, with lower pitchers and a climbing stem trailing off to the right

Nepenthes micramphora is very similar to N. bellii of northern Mindanao in terms of the morphology of its stem, lamina, and inflorescence. Indeed, prior to the description of N. micramphora in 2009, the species was misidentified as N. bellii on its native Mount Hamiguitan.^[8][9] Nepenthes micramphora is smaller in all respects and can be distinguished on the basis of its pitchers, which differ markedly in shape, size, peristome width, and tendril length. It also produces a greater abundance of pitchers on its rosettes — up to 7 live traps have been recorded at any one time.^[1]

Nepenthes gracilis also bears a superficial resemblance to N. micramphora in the size and shape of its leaves, but this species is absent from the Philippines.^[3]

Natural hybrids

Nepenthes micramphora has no confirmed natural hybrids, although certain plants from Mount Hamiguitan may represent crosses involving it and N. hamiguitanensis, N. justinae^[5] (previously identified as N. mindanaoensis), and N. peltata.^[10] Plants that were originally thought to represent a natural hybrid between N. micramphora and N. peltata^[3] are now recognised as belonging to a distinct species of possible hybridogenic origin, N. hamiguitanensis.^[4]

References

• Co, L. & W. Suarez 2012. Nepenthaceae. Co's Digital Flora of the Philippines.

Nepenthes micramphora V.B.Heinrich, S.McPherson, Gronem. & V.B.Amoroso, 2009 è una pianta carnivora della famiglia Nepenthaceae^[1], endemica del Monte Hamiguitan, nelle Filippine, dove cresce a 1100–1635 m.

Note

Bibliografia

• Cheek, M. & M. Jebb 2013. The Nepenthes micramphora (Nepenthaceae) group, with two new species from Mindanao, Philippines. Phytotaxa 151(1): 25–34. doi:10.11646/phytotaxa.151.1.2
• Heinrich, V., S.R. McPherson, T. Gronemeyer & V.B. Amoroso 2009. Nepenthes micramphora (Nepenthaceae), a new species of Nepenthes L. from southern Mindanao, Philippines. In: S.R. McPherson Pitcher Plants of the Old World. Volume 2. Redfern Natural History Productions, Poole. pp. 1314–1319.

小瓮猪笼草（学名：Nepenthes micramphora）是菲律宾棉兰老岛汉密吉伊坦山特有的热带食虫植物。^[1]其为高地猪笼草，生长于海拔1100米至1635米的地区。^[1]

小瓮猪笼草与产于棉兰老岛的源小猪笼草（N. abgracilis）与熙德猪笼草（N. cid）之间存在着密切的近缘关系。这三个物种共同组成了非正式的“小瓮猪笼草组”。^[2]

其种加词“micramphora”来源于希腊文和拉丁文，“mikros”在希腊文意为“小的”，“amphora”在拉丁文意为“瓮”，指其体型的矮小。^[3]

植物学史

2009年，沃尔克·海因里希、斯图尔特·麦克弗森、托马斯·格罗内迈尔（Thomas Gronemeyer）和维克托·阿莫路索（Victor Amoroso）对小瓮猪笼草进行了正式描述。该描述发表于斯图尔特·麦克弗森的专著《旧大陆的猪笼草》第2册中。^[1]编号为“V.Amoroso & R.Aspiras CMUH 00003545”的标本被指定为模式标本，其存放于菲律宾布基农省慕斯万山的棉兰老中央大学植物标本馆（CMUH）中。^[1]该标本于2005年1月31日采集于汉密吉伊坦山通往圣伊西德罗的路径上海拔1300米至1600米的地区。^[1]

因标本馆中的标本无花序结构，所以关于花序的正式描述来源于沃尔克·海因里希于2008年7月22日在模式产地记录的数据。^[1]

形态特征

小瓮猪笼草的莲座状植株，及其下位笼或中位笼

小瓮猪笼草为藤本植物，其可攀爬至2.5米的高度。^[4]茎为圆柱形，直径可达3.5毫米，节间距可达15毫米。^[1]

叶

小瓮猪笼草的叶片无柄，革质，呈披针形至椭圆形，可长达8厘米，宽至1厘米^[1]，最宽处位于叶片末端的二分之一处^[2]。叶尖为急尖，叶基渐狭，包住茎周长的三分之一，不下延。中脉的两侧各有2至3条纵脉，羽状脉众多。笼蔓可长达7.5厘米，直径约1毫米。^[1]

小瓮猪笼草的莲座状植株，及其攀援茎

捕虫笼

小瓮猪笼草下位笼的下部为窄卵形，上部为圆柱形，偶尔略呈漏斗形。^[3]其体型非常小，高仅可达4.1厘米，宽仅可达1.6厘米。腹面的笼翼宽约4毫米，也可能缩小为一对隆起。^[3]翼须长约3毫米，间距约2.5至3毫米。下位笼下表面的基部三分之一具腺体。唇为圆柱形，宽约0.8毫米，唇肋高约0.1毫米，间距约0.1毫米。唇齿在唇内缘不明显。^[2]笼盖为椭圆形、卵形或圆形，基部一般呈心形。^[3]笼盖无附属物，宽可达2厘米，长可达1.8厘米，略宽于笼口。^[1]笼盖下表面的蜜腺数量可超过100个。^[2]在笼盖基部的后方存在分叉或多根笼蔓尾，可长达3毫米。^[1][3]

小瓮猪笼草从幼年就开始出现上位笼。^[3]其可能通体呈漏斗形，^[1]或向基部逐渐缩小呈窄漏斗形，上部为圆柱形。^[3]上位笼最宽处位于中部或上部。^[2]上位笼的体型一般比下位笼大，可高达6.7厘米，宽至2厘米；通常高约4厘米，宽约1.7厘米。^[3]笼盖与笼口等大。笼翼通常缩小为一对隆起。^[3]其他形态特征于下位笼类似。^[1]

花序

小瓮猪笼草的花序为总状花序。其花序可长达35厘米，直径约为6毫米。总花梗可长达8厘米，直径约1毫米。每个花梗带1朵花，无苞片，其长3至4毫米。每个花序共约30至40朵花。花被片呈卵形，长约2.5毫米，宽约1.2毫米。果荚可长达20毫米。^[1]

毛被

小瓮猪笼草的茎、叶片及捕虫笼都无毛被。花序上具有锈棕色的简单毛被，长约0.1毫米。^[1]

生态关系

汉密吉伊坦山上的矮小植被

分布范围

小瓮猪笼草仅被出现于菲律宾棉兰老岛东达沃省东南部的汉密吉伊坦山的高地山坡上。周围的大部分地区都未仅考察过是否存在猪笼草，所以其很可能也出现于棉兰老岛南部的其他地区。^[3]其分布范围从海拔1100米的地区至山顶海拔1635米的地区。^[1]

原生地

其陆生于非常广泛的区域内，包括高地山地苔藓森林、次生植被、山脊顶部、悬崖边缘和塌方处。^[3]其也存在于称之为矮小森林的地区。^[1]小瓮猪笼草生长于超基性岩上。虽然其可以在非常阴暗的环境下生存，但在有直射光的环境下生长得更好。^[3]在汉密吉伊坦山上，小瓮猪笼草与翼状猪笼草（N. alata）、棉兰老岛猪笼草（N. mindanaoensis）和盾叶猪笼草（N. peltata）同域分布，海拔分布范围与汉密吉伊坦山猪笼草（N. hamiguitanensis）相同。^[4]

保护状况

由于小瓮猪笼草广泛的分布于汉密吉伊坦山中，且只允许来访者在向导的协助下攀登汉密吉伊坦山。所以斯图尔特·麦克弗森在2009年的专著《旧大陆的猪笼草》中，认为小瓮猪笼草“尚未受到威胁”。^[3]如果东达沃省政府成功将汉密吉伊坦山申请为联合国教科文组织世界自然遗产，那么小瓮猪笼草的野生种群在未来将会得到进一步的保护。^[3][5]

相关物种

来源于马丁·奇克及马修·杰布模式描述中源小猪笼草（左）及熙德猪笼草（右）的植物学插图，示其营养组织的差异

小瓮猪笼草组

小瓮猪笼草组因小瓮猪笼草而得名，其内还包括产自棉兰老岛东北部的源小猪笼草及产自棉兰老岛中北部的熙德猪笼草。该分类群出现于马丁·奇克及马修·杰布2013年的一篇论文中，论文中还包含了源小猪笼草及熙德猪笼草的正式描述。^[2]在此之前，小瓮猪笼草被视为一个偏离正常特征范围的物种，所以其未被归入任何一个既定的菲律宾猪笼草类群中（其中主要为翼状猪笼草组、葫芦猪笼草组及长毛猪笼草组）。^[6]

源小猪笼草、熙德猪笼草及小瓮猪笼草在捕虫笼及茎形态及原生地方面都存在着许多共同点。马丁·奇克和马修·杰布确定了七个用于定义该组的鉴定特征：^[2]

1. 亚山地环境；
2. 茎为圆柱形；
3. 唇窄，圆柱形，宽0.8至2毫米；
4. 唇楞不明显，高约0.1毫米；
5. 唇内缘无明显的唇齿；
6. 笼盖细胞膜缺少基部的盖龙骨及附属物；
7. 笼盖蜜腺数量大于100个，单型，大（直径约0.5毫米）具窄边缘，± 均匀分布于笼盖

这些物种也表现出与翼状猪笼草组存在一定的相似性，但不同之处在于这些物种的笼盖下表面缺少基部的盖龙骨及附属物。^[2]

熙德猪笼草与小瓮猪笼草组的另两个物种之间在原生地（其为附生，其余为陆生）、毛被的发达程度（其营养组织具毛，其余几乎无毛被）及叶柄（相对无柄）方面也存在差异。^[2]熙德猪笼草与源小猪笼草的笼蔓尾单一，但小瓮猪笼草的笼蔓尾分叉。^[2]

小瓮猪笼草与源小猪笼草最大的差异在于上位笼。小瓮猪笼草的上位笼多少为漏斗形，而源小猪笼草为亚圆柱形；其最窄处位于上位笼基部，最宽处位于中部或上部，而源小猪笼草最宽处近基部；其上位笼高约6.7厘米，而源小猪笼草可高达16厘米。^[2]

其他相似物种

贝里猪笼草的莲座状植株，示其下位笼及攀援茎

小瓮猪笼草的茎、叶片和花序等形态特征与棉兰老岛北部的贝里猪笼草（N. bellii）非常相似。在小瓮猪笼草2009年被描述前，在汉密吉伊坦山的小瓮猪笼草即被标记为贝里猪笼草。^[7][8]小瓮猪笼草的体型较小，且捕虫笼的形状、大小、唇的宽度和笼蔓的长度都不同。小瓮猪笼草的莲座状植株可生长出更多的捕虫笼，几乎每个植株都可达到7个以上。^[1]

小猪笼草（N. gracilis）的叶片大小和形状也表现出与小瓮猪笼草的相似性，但该物种并不存在于菲律宾。^[3]

自然杂交种

小瓮猪笼草的自然杂交种尚未被确认，但汉密吉伊坦山存在部分可能为其与汉密吉伊坦山猪笼草、棉兰老岛猪笼草和盾叶猪笼草的杂交植株。^[9]

原被认为是小瓮猪笼草与盾叶猪笼草^[3]的自然杂交种的类群已被认定为一个杂交起源的独立物种——汉密吉伊坦山猪笼草。^[4]

参考文献

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