Crossing Tehuantepec

If you look at a topographic map of Mexico, you’ll see a series of mountain ranges extending from Oaxaca in the south through the volcano-studded centre to the northern ranges that extend into the U.S. Their cooler altitudes hold a fauna and flora with many relationships to those of the United States and Canada. Indeed, these Mexican highlands are the heart of North America for many groups of organisms, the place where their diversity is highest.

This broad network of mountains ends at one of Nature’s important boundaries: the Isthmus of Tehuantepec, a swath of low elevation cutting across Mexico at its narrowest point. The isthmus isolates the bulk of Mexico’s highlands from a smaller set to the east, those of Chiapas. The Chiapas highlands are rather different, biologically more related to those of Central American countries to the east and south.

Isthmus of Tehuantepec, shown with arrow (map from Google Maps)

We crossed the Isthmus of Tehuantepec last week, signalling the midway point in our #Mexigonus2017 jumping spider expedition, as well as a transition in our team members. We left Arturo Casasola behind in Ixtlán, and bade farewell to Ricardo Paredes on arrival in Chiapas. Both boosted the success of our expedition enormously. Arturo gave us a home base and guidance to perfect habitats, where we discovered the amazing green ghosts, purple tomatoes, and others. Ricardo not only did the driving, heroically, but he also added to our search effort. To my eternal gratitude, his sharp eyes allowed me to see the blue legged Mexigonus species again.

We spent the last week in Chiapas with two new team members. Jorgé León, a faculty member at ECOSUR, guided us to interesting habitats and facilitated our logistics, providing local knowledge that was vital for our work. Gerardo Contreras, a doctoral student at UNAM, not only has been another hero in driving us to far-flung places, but also a role model for us in going out fearlessly at all hours of the day (and we suspect night) to search the forests for the scorpions he studies. We have now finished with the Chiapas portion of the trip, and in the next few posts I’ll report on the discoveries that Jorgé and Gerardo have enabled.



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