20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
Oral presentation
The dark side of climate change
Marco Isaia, Stefano Mammola
Department of Life Sciences and Systems Biology,
University of Torino, Via Accademia Albertina,
13-10123 Torino, Italy
The fact that caves are semi-closed systems with an almost
constant temperature makes them almost ideal sites where
to study where to study the effects of the ongoing global
warming on biological communities. In spite of that, the
underlying mechanisms behind the response of specialized
subterranean species to global warming are still largely
undiscussed. By means of two years observations data,
we characterize the thermic conditions of 33 caves in the
Western Alps, and relate the hypogean microclimate to
the occurrence of subterranean-adapted Troglohyphantes
spiders. Regression analysis points out a specific response to
temperature as well as a significant effect of the past Pleis-
tocene glaciations on their present distribution. In a second
step, we investigate the relationship between temperatures
recorded in monitored caves and the corresponding external
temperature. We emphasize the mechanisms for which the
constant temperature recorded inside corresponds in good
approximation to the mean value of the annual temperature
outside and use this direct relation to extend the results to
a wider dataset, including records from over 350 caves in
the Western Italian Alps. Specifically, we employ Ecological
Niche Modeling techniques to predict habitat suitability both
in the Last Glacial Maximum and in future global warming
scenarios. In light of IPCC’s projections of global average
temperature increases, we assess the general sensitiveness of
our model species to future increase of temperature, point-
ing out a future decline for hypogean adapted species.
Keywords: Global change, subterranean spiders, alpine
spiders, ecological niche modelling
Poster presentation
Threatening the giant: the response of
Vesubia jugorum to climate change
Marco Isaia, Filippo Milano, Stefano Mammola
Department of Life Sciences and Systems Biology
University of Torino Via Accademia Albertina, 13,
10123 Torino Italy
Human-driven climate deterioration is expected to
cause altitudinal shifts in biomes. There is a concern
for high alpine species that suitable habitats will be
reduced, and populations of cold-tolerant species
living on mountain summits will be increasingly
fragmented. Vesubia jugorum, the giant Alpine wolf
spiders, represents a typical example of such cold-
adapted species, as it occurs exclusively on rocky
lands above 2,300 m asl. The species is paleoendemic,
reported exclusively from the Maritime Alps (NW-
Italy), with a very reduced number of populations
reported in literature. On the base of literature and
new original data, we generated a dataset compris-
ing 37 occurrence of the species that we employed to
model potential present distribution of the species via
Ecological Niche Modeling (ENM). On the base of the
model results, we estimated the bioclimatic suitability
of V. jugorum in the past (Last Glacial Maximum,
Pleistocene) and in the future, by projecting the
present-day model into different global warming
scenarios predicted by the International Panel on
Climate Change (IPCC). As expected, given the colder
climatic condition in the Pleistocene, the potential past
distribution of V. jugorum was found to be wider than
today. Future forecasts based on different temperature
scenarios showed a general declining trend of suitable
areas all over the investigated area. We interpreted
our results in light of the expansion–contraction
model, which describes the response of species to the
fluctuations in temperature during glacial-interglacial
cycles. According to our results the giant Alpine spider
expanded its distribution during cooler periods and
contracted it during interglacials. Therefore, we
hypothesize that the species is currently in a refugial
phase, and we suggest that future warmer conditions
might determine a further contraction of the range.
Keywords: giant alpine spiders, global warming sce-
narios, ecological niche modelling, endemic fauna
20th International Congress of Arachnology