Triangulating from the cairns…
The ongoing biodiversity crisis necessitates assessment of rare and endemic taxa so that we can recognize how global climate change influences species distributions and understand when local extirpations may amount to global extinctions. Vertical cliffs provide a unique ecosystem for highly adapted species to avoid competition. Cliff-dwelling species incur strong selective pressures that lead to regional restrictions and narrow distributions. Aliciella penstemonoides (M.E. Jones) J.M. Porter (Black Canyon Gilia) is a cliff habitat specialist in the Polemoniaceae (Phlox) family and is restricted to vertical cliff habitats above stream and river drainages of the Upper Gunnison River Basin and Headwaters of the Rio Grande in southwest-central Colorado, USA. Field research in 2016 located 14 populations of A. penstemonoides and identified over 2,000 individuals, indicating that this species is locally abundant yet regionally rare. I employed distance sampling line transect methods in combination with rock climbing techniques to document population density and threats across five populations. MaxEnt software modeled the current extent of suitable habitat and predicted suitable habitat under projected climate scenarios for 2050. Models had excellent accuracy according to evaluation statistics and indicate a loss of 70 - 99% of suitable habitat by 2050. I screened microsatellite markers developed for a distant relative (Ipomopsis aggregata) for cross-species applicability in A. penstemonoides. Four microsatellites showed amplification of targeted loci and indicate genetic conservatism within the Loeselieae tribe and Polemoniaceae family. Further research is needed to complete an assessment of intraspecific genetic diversity. A. penstemonoides is confined to narrowly distributed habitats across a relatively large range, yet retains the ability to occupy a wide array of microhabitats and morphologies within an occupied cliff face. Morphological diversity may be accompanied by genetic or thermotolerance diversity, and may provide a means for adaptation and survival in future climates. Populations are often separated by expanses of unsuitable habitat and appear to have adapted to local rock surface variability. Future research may use A. penstemonoides as a model species to test how fragmented populations of a narrowly restricted species respond to a rapidly changing climate.
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