The fauna of the Serra de Grândola has once again surprised researchers from the Faculty of Sciences of the University of Lisbon (Ciências ULisboa) with the discovery of six species of spiders previously unknown to the scientific world. The identification of the six species emerged during a sampling project that allowed the collection of small animals at the field station of Herdade da Ribeira Abaixo. The final confirmation of the existence of these six unknown species has just been announced following analyses carried out in laboratories that the Centre for Ecology, Evolution and Environmental Changes (CE3C) has operating within the Department of Biology of Ciências ULisboa.

"We are certain that these are species that were not previously known, and we want to continue with the scientific description of each one of them. It is a process that will require time for detailed measurements, scientific drawings, and comparisons with other species or scientific articles. Furthermore, we will still have to choose a specimen for the holotype, which will then act as the main reference for comparison with other specimens or even species.”, explains Pedro Cardoso, researcher at CE3C.

Two of the species belong to the genus Dysdera; the other two belong to the genus Harpactea; there is a species classified within the genus Pelecopsis; and finally, there is also a species that is part of the genus Scytodes. The scientific names of the "new" spider species should be defined during the next phase of more detailed study.

Researchers at CE3C admit that the Serra de Grândola may have functioned, over time, as an isolated island that led certain species to evolve differently from others that share a common origin, including species known in the Algarve and the Monsanto Park area (in Lisbon).

This and other study hypotheses will still need to be confirmed in the near future, admits Pedro Cardoso. “We are studying possible sources of funding. I believe that, with resources, it's a project that can be completed in two years,” he adds.

The Herdade (farm) is a laboratory!

The discovery of the six spider species has only now entered the public disclosure phase, but the capture dates back to 2024 – and has a direct connection to the project of Biodiversity Assessments at Small Scales (BASS), which aims to understand how the local microclimate affects biodiversity, especially small organisms. Today, the BASS project has 16 sampling sites in Herdade da Ribeira Abaixo. These sampling sites are equipped with sensors to measure soil temperature and moisture, and traps that allow the capture of animals of different species for scientific study. And that's how the spiders were collected, allowing scientists to confirm the existence of six species that were previously unknown to them.

“As a field station linked to a faculty, Herdade de Ribeira Abaixo is a unique example in the country. It is a space that has been used to develop research at the master's and doctoral levels, describes Rui Rebelo, professor at Ciências ULisboa, researcher at CE3C, and member of the Herdade de Ribeira Abaixo field station Management Committee. “On this farm we find all the main groups of plants and animals from the Southwest of the country. The discovery of these six species is incredible and also exemplifies the research opportunities this location presents,” he added.

The announcement of the taxonomic description of six spider species is only the most visible facet of BASS's potential. "With these sampling points, we are able to collect long-term data, which allows students and researchers to ask questions by taking advantage of information produced in the past by other people who also did work there", describes Fernando Ascensão, Ciências ULisboa professor and CE3C researcher.

After being captured at the sampling points installed by the BASS project, the animals were transported directly from the Serra de Grândola to the CE3C laboratories, in order to proceed a detailed analysis under a magnifying glass. Bearing in mind that the largest of the specimens studied will be no more than two centimeters long, such a mission required visual acuity – and constant comparisons with known records of other species.

“When I began analyzing each of the six spider species, I couldn't find anything similar in the taxonomic literature. Over time I gained experience and, talking to other researchers, I began to realize that I was dealing with "new" species", reveals Miguel Sousa, Master's student in Conservation Biology at Ciências ULisboa. “There are species similar to the spiders we captured, but these reveal differences that may be related to the arrangement of the eyes, the spinnerets (which produce the webs), or the characteristics of the legs,” adds Miguel Sousa.

Despite the differences observed in other parts of the body, best practices in arachnology indicate that it is through the comparison of reproductive organs that the various species of spiders can be distinguished with a higher degree of reliability. In males, these organs consist of two stalks in the frontal area, colloquially known as palps. In females, the reproductive organs are located in the belly region of the abdomen and are known as the epigynum.

Because the capture only yielded a set of specimens that are, almost entirely, males, Miguel Sousa ended up taking on the curious task of describing and comparing only the left stalk of the palps, as dictated by scientific conventions applied to the description of spiders. "We're talking about details at the level of tenths of a millimeter," emphasises Pedro Cardoso.