Phylogenomic, morphological, and niche differentiation analyses unveil species delimitation and evolutionary history of endangered maples inAcerseriesCampestria(Sapindaceae)

Abstract

AbstractAccurate species delimitation is crucial for biodiversity conservation. TheAcerseriesCampestriacomprises four species,A. campestreL.,A. miyabeiMaxim.,A. miaotaienseP. C. Tsoong, andA. yangjuechiFang & P. L. Chiu. To clarify controversies over the taxonomic status of the latter three endangered species, we undertook phylogenomic, morphological, and niche differentiation analyses in seriesCampestria. Our coalescent species tree of 544 and 77 single‐copy nuclear genes supported seriesCampestriaas monophyletic, withA. yangjuechihaving the closest relationship withA. miaotaiense. However, in the plastome‐derived tree based on 64 protein coding sequences, the four species did not cluster together, and each of them grouped with some other sympatricAcerspecies. Given this nuclear‐cytoplasmic conflict, we hypothesize thatA. yangjuechihave been subject to nuclear gene introgression and plastid (pt) capture involving another sympatric maple, that is,A. amplum Rehder. Principal component analysis and machine learning based on morphological data could not separateA. yangjuechiandA. miaotaiense, but they both could be clearly distinguished fromA. miyabei. Moreover, the niche overlap tests of the two more widespread species,A. miyabeiandA. miaotaiense, showed they clearly occupy distinct niches. Overall, we conclude thatA. miyabeiandA. miaotaienseare distinct species, whileA. yangjuechi(endemic to Mt. Tianmu/East China) should be treated as a subspecies ofA. miaotaiense. Our study points out that multiple lines of phylogenomic, morphological, and ecological evidence prove highly useful in species delimitation. Additionally, our results should help to inform conservation measures for endangered species of the genusAcer/seriesCampestriain East Asia.