Amanda T. Becker
Adrian Munguia-Vega
Melanie Culver
Benjamin T. Wilder
2022
<p><span>In addition to the Sky Islands of the southwestern U.S. and northwestern Mexico, a series of 900–1200 m desert peaks surrounded by arid lowlands support temperate affiliated species at their summits. The presence of disjunct long-lived plant taxa on under-explored desert mountains, especially Isla Tiburón at 29° latitude in the Gulf of California, suggests a more southerly extent of Ice Age woodlands than previously understood. The phylogeography of the desert edge species </span><i>Canotia holacantha</i><span> (Celastraceae) was investigated to test the hypothesis that insular desert peak populations represent remnants of Pleistocene woodlands rather than recent dispersal events. Sequences of four chloroplast DNA regions totaling 2032 bp were amplified from 74 individuals of 14 populations across the entire range of </span><i>C. holacantha</i><span> as well as nine individuals that represented the other two species in its clade (</span><i>C. wendtii</i><span> and </span><i>Acanthothamnus aphyllus</i><span>) and two outgroups. Results suggest that a </span><i>Canotia</i><span> common ancestor occurred on the landscape, which underwent a population contraction ca. 15 kya. The Isla Tiburón </span><i>C. holacantha</i><span> population and the Chihuahuan Desert microendemic </span><i>C. wendtii</i><span> have the greatest genetic differentiation, are sister to one another, and basal to all other </span><i>Canotia</i><span> populations. Three haplotypes within </span><i>C. holacantha</i><span> were recovered, which correspond to regional geography and thus identified as the Arizona, Sonora, and Tiburón haplotypes, within which </span><i>Acanthothamnus aphyllus</i><span> is nested rather than as a sister genus. These results indicate a once broad distribution of </span><i>Canotia</i><span>/</span><i>Acanthothamnus</i><span> when the current peripheral desert ecotone habitat was more widespread during the Pleistocene, now present in relict populations on the fringes of the southern desert, in the Chihuahuan Desert, with scattered populations on desert peaks, and a common or abundant distribution at the northern boundary of the Sonoran Desert. These results suggest </span><i>Canotia</i><span> has tracked the shift of the desert's edge both in latitude and elevation since the end of the last Ice Age.</span></p>
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10.1016/j.jaridenv.2021.104653
en
Elsevier
Tracking the desert's edge with a Pleistocene relict
article