臺灣產蘋果亞科(薔薇科)之分類研究

Abstract

蘋果亞科(Maloideae)約有28個屬940種，其中有許多重要果樹或具有觀賞和藥用價值，是一龐大且重要類群。本亞科於臺灣紀錄有10至12屬和約30個種或種以下分類群，但因過去缺乏系統性研究，在分類上仍相當混亂，實有必要再進一步進行系統性研究。本研究利用形態比較、花粉電子顯微鏡形態觀察及葉綠體DNA(chloroplast DNA, cpDNA)內的matK序列、核DNA(nuclear ribosomal DNA, nrDNA)內轉錄區(internal transcribed spacers, ITS)序列之分子親緣關係等研究結果，針對臺灣產蘋果亞科進行分類訂正。 花粉電子顯微鏡觀察結果，臺灣產本亞科類群的花粉為3溝孔粒或4溝孔粒，花粉近球形至長橢圓形，極面觀多呈三裂圓形，極軸長為20-31 μm，赤道軸長為21-46 μm，外壁紋飾可分為穴狀、散條紋、散條紋-穴狀、條紋-穴狀、條紋狀等紋飾變化，外壁紋飾在種的鑑定上具有輔助效果。 在葉綠體matK序列之親緣關係樹中蘋果亞科各類群形成一個單系群(monophyletic group)，顯示蘋果亞科是一個相當自然的分類群，亞科下形成了兩個主要分支，第一分支包含赤楊葉梨屬(Aria)、腺肋花楸屬(Aronia)、栒子屬(Cotoneaster)、蘋果屬(Malus)、小石積屬(Osteomeles)、石楠屬(Photinia)、老葉兒樹屬(Pourthiaea)、火刺木屬(Pyracantha)、梨屬(Pyrus)、花楸屬(Sorbus)及紅果樹屬(Stranvaesia)，第二分支包含枇杷屬(Eriobotrya)及石斑木屬(Rhaphiolepis)，兩個分支的bootstrap分析在鄰接法(Neighbor Joining method)、最大簡約法(Maximum Parsimony method)及最大概似法(Maximum likelihood method)的親緣關係樹中均獲得高達97-100%的支持度。第一分支的類群均具小型種子，直徑多在5mm以下，種子多呈瘦長之瓣狀、長卵形或彎月形；第二分支類群則具有大型種子，直徑多在5mm以上，多呈厚實之半球形或球形。此結果說明種子形態在系統分類上具重要意義，可作為族或亞族建立的一項依據。而傳統分法將蘋果亞科分為蘋果族(Maleae)及山楂族(Crataegeae)，但過去置於山楂族中的火刺木屬、栒子屬及小石積屬等，在親緣關係樹中形成了併系群(paraphyletic group)或多系群(polyphyletic group)，並不支持山楂族及蘋果族的分法。過去被置於石楠屬的臺東石楠(Photinia ardisiifolia Hayata)其親緣關係與花楸屬及梨屬等形成單系群，與石楠屬則形成併系群。臺東石楠莖幹具刺、果實上半部外皮與心皮近1/2離生、內果皮硬殼狀，成熟乾燥後開裂成2或3瓣，與石楠屬其他的類群明顯不同，其系統位置仍待進一步增加更多研究資料加以探討。 廣義花楸屬包含單葉的赤楊葉梨屬，本研究支持將其分立。本研究加入腺肋花楸屬模式種紅果腺肋花楸(Aronia arbutifolia)的matK序列進行親緣分析，所得親緣關係樹中，紅果腺肋花楸與紅果樹(Stranvaesia davidiana Decne.)形成單系群，但bootstrap分析的支持度並不高，石楠屬、老葉兒樹屬與腺肋花楸屬形成多系群，並不支持廣義腺肋花楸屬的觀點。 臺灣原生枇杷屬植物原被處理為2種、3變種、3變型或處理為2變種1變型。本研究利用matK序列及ITS序列探討臺灣枇杷(Eriobotrya deflexa (Hemsl.) Nakai form. deflexa)、武威山枇杷(E. deflexa (Hemsl.) Nakai form. buisanensis (Hayata) Nakai)及恆春山枇杷(E. deflexa (Hemsl.) Nakai form. koshunensis (Kanehira & Sasaki) H. L. Li)之親緣關係。分析結果，臺灣枇杷與武威山枇杷、恆春山枇杷的matK序列658個鹼基對中並無任何變異位點，為親緣關係極其相近的族群。在ITS序列的593個鹼基對中，則僅有9個變異位點，親緣關係樹中均無法將此3個分類群完全區隔。外部形態及花粉外壁紋飾上雖可區別出3個分類群，但在分子親緣演化上並無明顯分化，因此建議將武威山枇杷及恆春山枇杷處理為臺灣枇杷的變型。 依據研究結果，將臺灣產蘋果亞科處理為12屬33種4變種2變型。其中清水山栒子(Cotoneaster chingshuiensis Kun C. Chang & Chih C. Wang)、呂氏栒子(C. lui Kun C. Chang, K. S. Lai & Y. H. Tseng)及粉紅花舖地蜈蚣(C. rosiflorus Kun C. Chang & F. Y. Lu)為新種，小泉氏蘋果(Malus koidzumii Kun C. Chang, Y. H. Tseng, C. H. Ou & F. Y. Lu)為新提出之名字，確認泡葉栒子(C. bullatus Bois)、矮生栒子(C. dammeri C. K. Schneid.)及中華石楠(Pourthiaea beauverdiana (C. K. Schneid.) Hatsusima var. beauverdiana)亦產於臺灣，小葉石楠(P. parvifolia E. Pritz.)與毛葉石楠處理為兩個不同種，並將清水石楠(P. chingshuiensis T. Shimizu)處理為小葉石楠之同物異名，刻脈石斑木(Rhaphiolepis indica (L.) Lindl. var. impressivena (Masamune) Kun C. Chang, F. Y. Lu & C. H. Ou)為石斑木之變種，恆春石斑木(R. shilanensis (Y. P. Yang & H. Y. Liu) Kun C. Chang, F. Y. Lu & C. H. Ou)提升為種階。文中並提供各分類群的檢索表、分類處理、線繪圖及彩色照片等。

Maloideae (Rosaceae) included about 28 genera and 940 species, with many fruit trees species, and some as ornamental or medicinal plants, were a large and important taxon. There were 10 to 12 genera and approximately 30 species of the subfamily recorded in Taiwan. But their systematic classification was still in disarray and really necessary to study and revise. This revision of Maloideae in Taiwan was made based on morphological, pollen morphology by scanning electron microscope (SEM), and phylogenetic study based matK sequences from chloroplast DNA, and internal transcribed spacers sequences from nuclear ribosomal DNA. Pollen grains of 38 taxa of Formosan Maloideae were 3-colporate or 4-colporate, sub-globose to elliptic, Amb often 3-lobed circular, polar axis length 20-31 μm, equatorial axis length 21-46 μm. The sculptural types were distinguished into foveolate, foveolate-rugulate, striate-foveolate, and striate. Patterns of sculpture were helpful to identification. All taxa of Maloideae formed a monophyletic group in phylogenetic trees according to chloroplast matK. It meant that Maloideae was a natural group. Two main clades showed in the subfamily: Clade-I contained Aria, Aronia, Cotoneaster, Malus, Osteomeles, Photinia, Pourthiaea, Pyracantha, Pyrus, Sorbus, and Stranvaesia, and Clade-II contained Eriobotrya and Rhaphiolepis. The bootstraps of both clades attained to 97-100 % by Neighbor Joining method, Maximum Parsimony method, and Maximum likelihood method. Taxa in Clade-I have lankily, long-ovate, or crescent smaller seed (diameter under 5 mm). Taxa in Clade-II they have hemispherical or globose bigger seeds (diameter over than 5 mm). So the seed morphology is significant in the systematic arrangement and classification of tribe or subtribe in Maloideae. Maloideae were used to be divided into two tribes Maleae and Crataegeae. But Pyracantha, Cotoneaster and Osteomeles, which were used to be put in Crataegeae were formed paraphyletic groups or polyphyletic groups. This result not supported the former circumscription of tribe Crataegeae. Besides, Photinia ardisiifolia Hayata formed a monophyletic group with Sorbus and Pyrus, and formed a paraphyletic group with Photinia. As to morphology, P. ardisiifolia has thorny stem, the upper portion of exocarp about half free to the carpel, the endocarp becaming a hard shell, dehisced into 2 or 3 segments in matured and dried period. That was conspicuously different from other species of Photinia, wherefore its phylogenetic position would need for more research and discussion. The broad sense genus Sorbus included single-leaved genus Aria. In this study it was suggested to divided into two distinct genera. Broadly defined Aronia as a included Photinia, Pourthiaea and Stranvaesia. Aronia arbutifolia (L.) Pers., the type species of Aronia was put into phylogenetic analysis. The result showed that A. arbutifolia and S. davidiana Decne. formed a monophyletic group, but the bootstrap was not sufficient. On the other side, Photinia, Pourthiaea and Aronia formed a polyphyletic group. The result did not stand a broad sense Aronia. Eriobotrya of Taiwan was usually comprised in 2 species, 3 varieties, 3 forms, or 2 varieties with 1 form. ITS sequences and matK sequences to showed that Eriobotrya deflexa (Hemsl.) Nakai form. deflexa, E. deflexa form. buisanensis (Hayata) Nakai and E. deflexa form. koshunensis (Kanehira & Sasaki) H. L. Li no variable site can be found in 658 base pair (bp) of matK. It meant they were a very close population. There is only 9 variable sites on ITS with 593 bp. These 3 taxa were not hard to separate completely in the phylogenetic tree, although they can be distinguished by some morphological characteristics. Therefore, E. deflexa form. buisanensis and E. deflexa form. koshunensis were suggested to treat as two forms of E. deflexa. As a result of above studies, 12 genera, 33 species, 4 varieties, and 2 forms were recognized in Taiwan. Cotoneaster chingshuiensis Kun C. Chang & Chih C. Wang, C. lui Kun C. Chang, K. S. Lai & Y. H. Tseng, and C. rosiflorus Kun C. Chang & F. Y. Lu were new species. Malus koidzumii Kun C. Chang, Y. H. Tseng, C. H. Ou & F. Y. Lu was a new name. Cotoneaster bullatus Bois, C. dammeri C. K. Schneid., and Pourthiaea beauverdiana (C. K. Schneid.) Hatsusima var. beauverdiana were confirmed in the flora of Taiwan. Pourthiaea parvifolia E. Pritz. and P. villosa (Thunb.) Decne. were treated as different species, and P. chingshuiensis T. Shimizu was treated as a synonym of P. parvifolia. Rhaphiolepis impressivena Masamune was treated as a variety of R. indica (L.) Lindl., and R. shilanensis (Y. P. Yang & H. Y. Liu) Kun C. Chang, F. Y. Lu & C. H. Ou was upgraded to species rank. The paper provided keys, color photographs, line drawings and taxonomic treatment to aid in identification of these taxa.