Figure 1 from: Espinasa L, D. Bartolo N, E. Newkirk C (2014) DNA sequences of troglobitic nicoletiid insects support Sierra de El Abra and the Sierra de Guatemala as a single biogeographical area: Implications for Astyanax. Subterranean Biology 13: 35-44. https://doi.org/10.3897/subtbiol.13.7256

Figure 1 - The Cañon de la Servilleta of the River Boquillas separates the contiguous Sierra de Guatemala, to the north, from the Sierra de El Abra, in the south. Limestone is restricted to the green forested hills. This study tested if this 100 m high, 100 m wide canyon was an effective biological barrier that prevented underground migration of troglobites between the two karstic areas.