ROLE OF CLIMATE AND TOPOGRAPHY IN THE EVOLUTION OF SCAPHINOTUS PETERSI IN THE SKY ISLANDS OF CORONADO NATIONAL FOREST, ARIZONA

Geographically isolated environments such as the forest-topped peaks of the Sky Islands of Coronado National Forest (CNF) in southeastern Arizona provide natural laboratories for studying topographic and climactic factors involved in speciation and origins of biodiversity. Using an interdisciplinary combination of genetic and geospatial analyses, we examine beetle phylogeny, regional climate records, and the Quaternary paleobiogeography of the Sky Islands to evaluate four hypotheses regarding the current geographic and population genetic patterns of Scaphinotus petersi. S. petersi is a large, flightless beetle that resides only in the Sky Island conifer forests above ~1900 m.a.s.l. Our results do not support the prevailing hypothesis, which was that the S. petersi populations found on seven separate peaks became separated as temperatures warmed and became drier after the Last Glacial Maximum (LGM) and are genetically distinct today. Rather, we show that 1) only some of the peaks hold genetically distinct populations, 2) the timing of separation among the populations does not appear to coincide with specific climatic events such as post-LGM warming, and 3) there is no consistency between the timing or degree of separation and the proximity of populations. In addition, we show that S. petersi (and potentially other species endemic to the Sky Island conifer forests) may disappear from some of the lower peaks of CNF as forests essentially run out of room to retract upslope as climate warms and becomes drier.