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Ecological niche modelling and phylogeography reveal range shifts of pawpaw, a North American understorey tree
Author(s) -
Wyatt Graham E.,
Hamrick J.L.,
Trapnell Dorset W.
Publication year - 2021
Publication title -
journal of biogeography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 158
eISSN - 1365-2699
pISSN - 0305-0270
DOI - 10.1111/jbi.14054
Subject(s) - ecology , phylogeography , range (aeronautics) , environmental niche modelling , ecological niche , context (archaeology) , niche , habitat , geography , population , biological dispersal , last glacial maximum , biology , holocene , archaeology , demography , phylogenetics , biochemistry , materials science , sociology , composite material , gene
Aim Predictions of species' responses to accelerating global climate change require an understanding of historical range shifts. However, large‐scale phylogeographical studies of Eastern North American understorey plant taxa are relatively scarce. Here we employ ecological niche modelling and genetic analyses for inference of optimal pawpaw habitat in the past and future. Location In all, 26 states in the eastern United States. Taxon Asimina triloba (L.) Dunal (Annonaceae). Methods The present‐day niche of Asimina triloba was modelled in Maxent using seven bioclimatic variables, elevation and location data from field samples and herbarium specimens. To model historically optimal habitats, the present‐day model was projected onto rasters of seven bioclimatic variables and elevation representing the last glacial maximum (~22,000 years before present [YBP]) and the mid‐Holocene (~6,000 YBP). Predicted habitat suitability for 2070 was also modelled. Additionally, 62 populations were genotyped with nine nuclear microsatellite loci and statistically analysed. Levels and partitioning of genetic variation within and among populations were estimated within a geographical context. Results Models indicate that optimal habitat 22,000 YBP was severely restricted to mostly now‐submerged Gulf of Mexico and southeastern US coastlines. By 2070, models suggest that optimal habitat will expand substantially northward relative to the present. Species‐level genetic diversity (H E = 0.765) is high and genetic structure among populations is moderate (G ST = 0.202). S tructure indicates that there are two population clusters straddling the Appalachian Mountains. Main conclusions Models suggest that 22,000 YBP A. triloba was restricted to two major refugia in narrow bands of mostly now‐submerged habitat and possibly several small inland refugia. Molecular data are consistent suggesting that the eastern refugia expanded to give rise to the eastern cluster which is characterized by higher genetic diversity. The Gulf of Mexico refugium likely gave rise to populations in the western cluster, which is characterized by lower genetic diversity.