X Close Direct and indirect effects of climate and seed production on the reproduction of the edible dormouse (Glis glis) at the edge of its distribution
The work conducted by the BiBio Research Group of the Natural Sciences Museum of Granollers in collaboration with CEAB-CSIC has been published in the journal Ecology and Evolution. It explains how changes in climate and landscape affect the reproductive performance of edible dormouse (Glis glis) populations at the edge of their distribution in the Mediterranean region, where these populations are more exposed to the impacts of global change.
Populations at the edge of their distribution typically have low densities and are considered particularly vulnerable to environmental stress and global change. This study analyzed the reproductive performance of the edible dormouse, a hibernating rodent that mainly feeds on seeds in deciduous forests, in two populations located at the southern edge of its distribution area. These populations were specifically in two different natural areas within the XPN of Diputació de Barcelona: the Parc Natural i Reserva de la Biosfera del Montseny and the Parc del Montnegre i el Corredor (Barcelona).
Data on the edible dormouse were collected by the Dormouse Project (www.lirons.org) during the period 2012–2021. Information on the number of reproductive females and juveniles was obtained using the capture-mark-recapture (CMR) method with nest boxes in 6 study plots, three in each natural area. Each plot, approximately 1 hectare in size, contained 20 nest boxes attached to trees in a 5 x 4 grid, with each box located 25-30 meters apart. The nest boxes were checked during the day every two weeks from mid-July to mid-November.
The study also included data from the weather stations closest to the study plots, Viladrau in Montseny (953 m a.s.l.) and Pla de la Tanyada in Montnegre (690 m a.s.l.), provided by the Catalan Meteorological Service. Pollen data were provided by the Aerobiological Network of Catalonia, and official land cover maps from the 2007-2017 period were used, both around the plots and within the elevation belt where the plots were located (600–800 m a.s.l. in Montnegre and 1000–1200 m a.s.l. in Montseny). Additionally, seed availability data for each study plot were collected during the 2012-2021 period by counting seeds in 20 sampling plots on the ground (50 x 50 cm), each placed beneath a nest box. Seed counts were conducted biweekly from late August to late November.
Figure 1. (a) Location of the two study sites, Montseny and Montnegre Natural Parks. (b) The six plots in red. (c) Distribution of the 20 nest boxes in each plot, which includes seed data grids. The picture shows a nest box (black circle) and the seed sampling grid in yellow.
Although the two populations studied were at the edge of their distribution and close to each other (approximately 20 km apart), the results confirmed significant differences between them. On one hand, environmental conditions in Montnegre were more adverse than in Montseny, with a notable increase (+0.6°C) in annual mean temperature during the study period, which was not observed in Montseny. Additionally, landscape alterations showed a decline in deciduous and sclerophyllous forests with an increase in pine forests in Montnegre, unlike Montseny, where sclerophyllous forests increased.
Regarding the availability of acorns and beechnuts, it was influenced by local weather conditions, with a significant relationship between seed production and summer conditions (temperature and precipitation). A strong correlation was also observed between annual pollen levels and beech seed availability, confirming that beech seed production, almost nonexistent in Montnegre and relatively abundant in Montseny, could be anticipated by dormice through pollen production. However, this relationship was not significant for acorns, indicating that their availability is independent of pollen production.
The influence of climate on the number and reproductive success of breeding females also differed between the two areas. In Montseny, reproductive performance was not affected by spring and summer weather conditions, whereas in Montnegre, it decreased during dry and hot summers. Interestingly, and unlike what was observed in Montseny, the reproduction of the edible dormouse in Montnegre was not associated with seed availability.
Figure 2. Structural equation models (SEM) showing significant pathways between climatic factors (blue box: dark blue circle–Spring, and light blue circle–Summer), pollen (green box), seed count (orange box: orange circle–acorns, and brown circle–beechnuts), and reproductive females and juveniles of the edible dormouse in Montseny (a) and Montnegre (b). All significant regression coefficients are shown within the ellipses, and the r² values explained by all predictors are displayed within the squares. The thickness of the lines indicates stronger associations.
Regarding occupancy and colonization parameters, they were lower in Montnegre, with higher extinction probabilities compared to Montseny. The analyses also highlight the crucial role of deciduous tree cover in predicting the presence of reproductive females, with a positive association between deciduous tree cover and the occupancy of reproductive females.
Figure 3. Change in forest cover of deciduous (left) and sclerophyllous (right) forests at both the plot and altitudinal range levels where the plots of Montnegre and Montseny are located during the 2007–2017 period.
The study highlights the importance of deciduous forests in shaping habitat suitability for the edible dormouse and how this influences the species' reproduction depending on local weather conditions and seed availability.
The monitoring of the edible dormouse is part of the collaboration agreement between the Diputació de Barcelona and the Patronat del Museu de Granollers for the implementation of monitoring and research programs related to wildlife of conservation interest in the Natural Parks Network (wildlife: butterflies, small mammals, bats, amphibians, and reptiles).
Read the original publication in the journal Ecology and Evolution: Direct and indirect effects of climate and seed dynamics on the breeding performance of a seed predator at the distribution edge. Daniel Oro, Lídia Freixas, Carme Bartrina, Silvia Míguez, and Ignasi Torre.
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