Seven new species of funnel web spiders (Agelenidae, Tegenaria), unique to caves in Israel, have been discovered and are detailed in a new study conducted by researchers from the Hebrew University of Jerusalem and the University of Madison-Wisconsin.
The unique, isolated conditions in cave habitats lead to a process of convergent evolution, causing the development of exceptional adaptations to life in the dark, such as blindness, loss of pigments, and sensory organ enlargement.
These species join a large number of invertebrates recently found in Israeli caves that are new to science. The study was recently published in the Molecular Phylogenetics and Evolution journal and has extensive scientific implications for uncovering the evolution of speciation in caves and the historical, geographic, and climatic processes that occurred in Israel.
Doctoral student Shlomi Aharon led the study under the guidance of Dr. Efrat Gavish-Regev, from the Hebrew University National Natural History Collections and Prof. Dror Hawlena from the Department of Ecology, Evolution, and Behavior.
“In many cases, these adaptations will lead to the creation of new species, whose distribution is geographically limited in areas with unique ecological conditions, such as a single cave or a system of connected caves,” Aharon says. “In this study, we sought to understand the evolutionary relationships between funnel web spiders with normal eyes that are found at the cave entrance, with those that are further in the cave and are pigmentless, eye-reduced, and even completely blind.”
In the study, the researchers collected the spiders by hand and then conducted a series of microscopic examinations, recorded the morphology, and extracted DNA from each to compare them to sequences of known species of the same genus that exist in GenBank.
“Among the spiders we found, five were unique to different caves, and the two other species were found in several caves in the Galilee and in caves situated at the Ofra karst field, which is now under threat from planned construction,” says Dr. Gavish-Regev. “One of the surprising findings in the study shows that the new species are evolutionarily closer to species from caves in Mediterranean areas in southern Europe than to species living in close proximity to them at cave entrances in Israel.”
Five of the new species described had reduced eyes, while the other two were completely blind. The researchers suggest that the new species developed adaptations to life in underground habitats and speciated in caves, after or simultaneously with the extinction of the ancestor species from which they evolved, which lived outside caves and became extinct due to historical regional climate changes.
“We are currently witnessing the effects of climate change on many habitats, which obliges us to consider, maintain, and promote programs that include the preservation of underground habitats – many of which are at immediate risk,” concludes Professor Hawlena. “We must protect Israel’s unique nature, preserve its underground systems for the future, and further explore the processes that created these systems in the country.”