In a new study, seven species new to science were discovered, distinct cave dwellers (troglobite), described from the depths of caves in the Mediterranean regions of Israel, two of which are completely blind, and another five are eye-degenerative.
One of the surprising findings in the study shows that the new species are evolutionarily closer to the species living in Southern Europe in Mediterranean areas, at the entrance to caves and outside the caves, than to the troglophile species that live in sympatry with them at the entrance to caves in Israel.
Caves are unique habitats because of the conditions prevailing in them, such as: lack of light and energy sources. These conditions lead to the development of adaptations to life in caves such as: blindness, loss of pigments, and enlargement of other sensory organs in a process called convergent evolution (independent development of similar traits in creatures of different origin). These adaptations develop due to selection pressures in caves and are an advantage for living in the dark. These adaptations together with different levels of isolation from the outside, will lead to the creation of new species in an evolutionary process of differentiation (speciation). In many cases, these cave species will be endemic (species that are distributed in a limited geographical area, usually with unique ecological conditions), and can only be found in a single cave, or in one system of connected caves.
As part of the doctoral research of Shlomi Aharon, from the National Nature Collections, and the Department of Ecology, Evolution and Behavior, The Hebrew University of Jerusalem (under the direction of Dr. Efrat Gabish-Regev and Prof. Dror Hawlena), spiders from the Agelenidae family living in caves in Israel were examined. The findings of the research, which Published in Molecular Phylogenetics and Evolution, they point to an extraordinary diversity of spiders from this family in the caves of the country. Seven species new to science, distinct cave dwellers (troglobite), were described from the depths of caves in the Mediterranean regions of Israel, two of which are completely blind, and another five with degenerate eyes. Five of them are endemic, each to a different cave, while one species is found in several caves in the Galilee, and one species is found in several nearby caves in the Ofra karst field - caves whose existence is now under threat, due to construction expansion plans. One of the surprising findings in the study suggests that the new species are closer evolutionary for the species living in Southern Europe in Mediterranean areas, at the entrance to caves and outside caves, than for the troglophile species living in sympatry with them at the entrance to caves in Israel. After analyzing molecular and morphological data, Aharon and his colleagues It is suggested that the species new to science found in the caves are relict species that developed adaptations to life in underground habitats and differentiated in the caves, after or simultaneously with the extinction of the ancestor from which they evolved, who lived outside the caves and became extinct due to historical climate changes in our region. These findings have extensive scientific implications, for understanding the evolution of differentiation in caves and for understanding historical, biogeographic and climatic processes that took place in Israel.
The species were found in a survey of arachnids in caves conducted by Shlami Aharon as part of his master's degree (at Ben Gurion University under the guidance of Prof. Yael Lubin, Prof. Merav Sifen and Dr. Efrat Gabish-Regev), and in subsequent surveys (the researchers have visited over 100 caves to date). The researchers found 26 caves with spiders from the agelenidae family belonging to the same genus (Tegenaria funnel) at the entrance to the cave - species with normal eyes; 14 caves with degenerate or blind spiders in the depth of the cave; 10 of the caves included both species with normal eyes and species with degenerated eyes or blind
The purpose of the research (Shlomi Aharon's doctoral thesis) was to understand the evolutionary connections between the funnels found at the entrance to the caves that have eyes, and those found in the depths of the cave and are atrophied or completely blind. What are the closest species to the degenerate and blind species living in caves?
In order to answer the question, the team used morphological and molecular methods (COI barcode and NGS (genomic methods)). The arachnids were collected manually, examined under a stereo microscope (binocular), their morphology was recorded, DNA was extracted and the COI barcode gene was sequenced - so that it would be possible to compare with sequences from around the world found in the gene bank, and in addition, advanced genomic methods were used that allow examining kinship between very close groups (NGS - RADSEQ ).
In this period, when we are witnessing the effects of climate change on many habitats, consideration must be given to the effect of climate change on underground habitats in Israel, and on the species known only from these caves. The seven new species found join a much larger number of invertebrates new to science found in Israel's caves in recent years. This fact obliges us to preserve these unique habitats, many of which are at immediate risk due to development, and to promote nature conservation programs that also include underground habitats. We must protect Israel's unique natural world and preserve the underground systems for the future, as well as preserve the research potential for understanding the processes that created these unique systems in our region.
For the full scientific article click here.
For the article on YNET, click here.
