Sky's the limit: Phylogeography of Amblycheila baroni Rivers in the Madrean Archipelago (Coleoptera: Cicindelidae)

The genus Amblycheila includes 8 species found in Mexico and the United States. This charismatic tiger beetle is a favorite in many collections due to its large size (21-36mm) and unique morphology as a blind, flightless, nocturnal predator. Amblycheila baroni, the Montane Giant Tiger Beetle, is endemic to the Madrean Archipelago (MA), a sky island system spanning southern Arizona into northern Mexico. The MA Sky Islands possess a dynamic history with an oscillating paleoclimate that resulted in periods of forest expansion and contraction. These oscillations assisted in creating the sky islands that mirror the concept of oceanic islands, where hospitable “islands” of high-elevation forests are isolated by “seas” of lowland desert. Amblycheila baroni is found at mid to high elevation in pine-oak woodland habitats across the MA, but not in the intervening lowlands between mountain ranges.  Given its dispersal limitations and observed distribution within the MA , we hypothesize that phylogeographical analysis of A. baroni  will demonstrate monophyly between mountain ranges in the MA and correlate with isolated populations following forest contraction. To test this, we used molecular and biogeographical analyses to determine (i) population dynamics for A. baroni, (ii) identify potential cryptic species, and (iii) test if gene flow and speciation coincide with paleoclimate and forest fragmentation in the MA. Models predict that high elevations in the southwest will be disproportionately impacted by anthropogenic climate change compared to the rest of the United States, creating an urgency to explore natural laboratories like the MA Sky Island system.