Taxonomic history Museum
Herbarium. Dried specimens like this serve to preserve plants, including the
type of a species, that is, the original
specimen that the description of a new species is based on. The taxonomic history of
Malus trilobata is complex, reflecting its unique morphology. The species was
formally described by
Jean Louis Marie Poiret based on a
specimen, the
type, that
Jacques Labillardière had collected in
Lebanon, in 1810. Poiret, however, considered the species to be a
hawthorn, and consequently placed it in the genus
Crataegus, as
Crataegus trilobata. Since then, the species has also been placed within the genera
Pyrus, as
Pyrus trilobata,
Sorbus, as
Sorbus trilobata,
Cormus, as
Cormus trilobata, and
Malus, as well as in
Eriolobus, whereby the latter was variably considered to include either only
M. trilobata or also
M. florentina. Many authorities have sought to emphasise the species' distinctiveness by assigning it to unique
genera,
sections or
subsections. Traditionally, many researchers have further classified the species within its own section,
Eriolobus, but the validity of these subgroupings on morphological grounds in
Malus has been questioned more recently. Both classifications, in
Malus and in
Eriolobus, appear to be supported by research findings.
M. trilobata resembles other
Malus species in
floral morphology, and it is similar to some
Malus species in leaf shape. For these reasons, the Polish
dendrologist Kazimierz Browicz (1969) considered it to be most closely related to
Malus doumeri and, to a lesser extent, to
Macromeles tschonoskii (which is also often placed in
Malus), both of which are native to East Asia. Furthermore,
phytochemical studies have shown that, uniquely in
Malus, trilobatin replaces
phloridzin as the main
phenolic compound in the leaves in
M. trilobata, which may similarly be taken to indicate a need for separation. Current consensus, however, recognises no subdivisions. In a study by Liu and colleagues (2022), this branch, called
Clade II (a clade being a group of all organisms that descend from a common ancestor), is shown to either be
basal to the rest of
Malus, in
nuclear phylogenies, or to be sister to
Pourthiaea and thus closer to other
Maleae such as
Sorbus and
Aronia than to
Malus proper, in
plastid phylogenies. This discordance between nuclear and plastid phylogenies, the authors proposed, could be due to several factors during the speciation process:
incomplete lineage sorting, that is, the inheritance of an incomplete set of
alleles from the
most recent common ancestor;
allopolyploidy, that is, the inheritance of more than two copies of alleles; or
hybridisation, the crossing of species. All of these were important mechanisms underlying the evolution of the
Maleae, the apple
tribe, rendering the reconstruction of its evolutionary history difficult.
Etymology The genus name
Malus is derived from
Latin malus, meaning "apple tree". The
epiphet trilobata means "three-lobed", and refers to the leaves of the species. ==Description==