Phylogeny of Maleae (Rosaceae) Based on Multiple Chloroplast Regions: Implications to Genera Circumscription

Received Sep 21, 2017; Revised Dec 11, 2017; Accepted Jan 2, 2018

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1. Introduction

Rosaceae or rose family, consisting of approximately 4,828 species in 91 genera [1], is of great economic and ecological importance. Many species are cultivated for their fruits or as ornamentals. The monophyly of the family is implied by the presence of unique floral structures and strongly supported by rbcL phylogeny [2]. However, the rose family displays a considerable diversity in morphology and anatomy, and it had been generally subdivided into four subfamilies, that is, Rosoideae, Spiraeoideae, Amygdaloideae (incorrectly Prunoideae), and Maloideae. Such a subdivision was recently challenged by molecular phylogenies of matK and trnL-F [3], six nuclear and four chloroplast regions [4], and hundreds of nuclear genes [5]. A formal three-subfamily classification was proposed: Dryadoideae, Rosoideae, and Amygdaloideae (incorrectly Spiraeoideae in [4]). Dryadoideae was separated from Rosoideae, and Spiraeoideae and Maloideae were merged with Amygdaloideae (incorrectly Spiraeoideae).

One of the most striking changes in the new classification is that traditional Maloideae became subtribe Malinae (incorrectly Pyrinae). Here we use tribe Maleae instead of supertribe Pyrodae sensu [4] to include the traditional pome-bearing Maloideae plus Gillenia Moench (=Porteranthus Britton), Kageneckia Ruiz & Pav., Lindleya Kunth, and Vauquelinia Corrêa ex Bonpl. in traditional Spiraeoideae [4, 6–9].

Maleae consists of about 1,000 species, occurring mostly in the temperate Northern Hemisphere. The tribe includes many well-known fruit crops such as apple (Malus pumila Mill.), pear (Pyrus spp.), loquat (Eriobotrya japonica (Thunb.) Lindl.), and black chokeberry (Aronia melanocarpa (Michx.) Elliott), as well as many ornamentals. The core Maleae is characterized by a synapomorphic pome, a type of accessory fruit that does not occur in other Rosaceae plants [10], and a basal chromosome number, $x=17$. With the addition of Gillenia, Kageneckia, Lindleya, and Vauquelinia, the tribe has drupaceous or follicle fruits and $x=9$ (or 15) as well [2, 4, 6, 9, 11–13].

The origin of core Maleae $(x=17)$ has long been considered an example of allopolyploidization...

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