Sunyer P., Muñoz A., Bonal R., Espelta J.M. (2013) The ecology of seed dispersal by small rodents: A role for predator and conspecific scents. Functional Ecology. 27: 1313-1321.LinkDoi: 10.1111/1365-2435.12143
Seed-caching rodents play a key role in the ecology of seed dispersal by not only consuming but also dispersing seeds. Rodent foraging behaviour is usually framed within optimal models, which predict that their decisions should maximize food intake and minimize foraging costs. Although predation risk and seed pilferage by conspecifics have been envisaged as two potential costs, their relevance for seed-caching behaviour and seed dispersal has barely been addressed. To test the effect of predation and pilferage risk on the patterns of seed predation/dispersal by rodents, we performed a field experiment using a tri-trophic-level model (plant-mice-carnivore; Quercus spp-Apodemus sylvaticus-Genetta genetta) and the scents of the predator and conspecifics as direct cues. The behaviour of mice was analysed with video cameras set for continuous recording on consecutive nights, and we used tagged acorns to assess the patterns of acorn predation and dispersal. Our results revealed that rodents were able to discriminate between the scents of genet and conspecifics and modified their seed dispersal behaviour accordingly. Mice spent more time 'sniffing' in rodent cages than in genet cages, where they displayed more 'vigilance and freezing' behaviours. In sites with mice scents, acorns were dispersed at shorter distances and were less predated. Conversely, in sites with genet scents acorn removal was delayed. These results show that chemosensory information on predators and conspecifics influences the foraging decisions of seed-caching rodents over short spatial and temporal scales. This might entail cascading effects on the regeneration of plants. In sites where rodents perceive the risk of predation, inefficient foraging behaviour may result in less successful seed dispersal. Conversely, the detection of conspecific scents may increase dispersal efficiency and seedling recruitment. Ultimately, the relationships between two distant levels in trophic webs (plants-carnivores) appear intricate, since carnivores may affect seed dispersal by changing the foraging behaviour of their prey (the seed disperser). This indirect relationship should be considered as a new dimension of the ecology of seed dispersal by small rodents. © 2013 British Ecological Society.
Bonal R., Hernández M., Ortego J., Muñoz A., Espelta J.M. (2012) Positive cascade effects of forest fragmentation on acorn weevils mediated by seed size enlargement. Insect Conservation and Diversity. 5: 381-388.LinkDoi: 10.1111/j.1752-4598.2011.00172.x
1.Today, forest fragmentation is one of the major threats to biodiversity worldwide. In this context, fragmented populations of specialised forest organisms face an increasing risk of extinction because of factors such as local food scarcity. Nonetheless, the role of food availability may differ depending on organism size, which is expected to determine the energy requirements and mobility between fragments. 2.A field study was carried out on Curculio elephas, a forest beetle with low dispersal potential, whose larval development takes place in oak Quercus spp. acorns. 3.For a similar seed crop per tree, acorn size was larger in isolated oaks than in trees located in forest patches. Thus, fragmentation increased local food availability for C. elephas. Larger acorns enabled larval size to increase, a key fitness proxy associated with individual survival, adult size, and potential female fecundity. Indeed, the number of both adults and larvae was higher in isolated trees than in forest patches. 4.In the current scenario of increasing forest fragmentation, the survival likelihood of specialist insects may strongly depend on their ability to adapt to altered environmental conditions. To the best of our knowledge, this is the first study to report on how some forest insects may take advantage of fragmentation-mediated changes to survive in isolated trees. 5.From a conservation perspective, management policies should preserve isolated trees as a source of seeds and fauna for the natural regeneration of forest ecosystems after unproductive farmlands have been abandoned. © 2011 The Royal Entomological Society.
Carrillo-Gavilán A., Espelta J.M., Vilà M. (2012) Establishment constraints of an alien and a native conifer in different habitats. Biological Invasions. 14: 1279-1289.LinkDoi: 10.1007/s10530-011-0155-z
Alien plants are subjected to different biotic and environmental barriers that limit their establishment success in the introduced range. Pseudotsuga menziesii (Douglas fir), a native conifer from Northwest America, is considered one of the most invasive forestry conifers in Europe. However, little is known about the ecological filters that constrain plant establishment at early life-cycle stages and differences in habitat invasibility to this species. We conducted field experiments to compare the establishment potential (i. e. post-dispersal seed removal, seed germination, seedling survival and growth) of Douglas fir in beech forests, holm-oak forests and heathlands; and compared it with the taxonomically close native conifer Abies alba (Silver fir). Douglas fir seeds were more removed than Silver fir in holm-oak and in heathlands. In all habitats, seed germination was significantly higher for Douglas fir compared to that of Silver fir and, seedling mortality was extremely high in both species due to soil disturbance by wild boars and drought stress. Douglas fir mortality was only lower than Silver fir in beech forests. However, species did not differ in seedling growth. Overall, the probability of invasion success of Douglas fir decreased along the sequential stages of plant establishment in all habitats. Only high seed germination rates of Douglas fir would predict its high invasive capacity but these advantages are counterbalanced by high seedling mortality. Results showed a mismatch between invasibility and current pattern of Douglas fir invasion in the study area. Therefore, future research focused on seed production and on different components of biotic resistance is recommended to elucidate which processes are favoring its establishment success. © 2011 Springer Science+Business Media B.V.
Fernández-Martínez M., Belmonte J., Maria Espelta J. (2012) Masting in oaks: Disentangling the effect of flowering phenology, airborne pollen load and drought. Acta Oecologica. 43: 51-59.LinkDoi: 10.1016/j.actao.2012.05.006
Quercus species exhibit an extreme inter-annual variability in seed production often synchronized over large geographical areas (masting). Since this reproductive behavior is mostly observed in anemophilous plants, pollination efficiency is suggested as one hypothesis to explain it, although resource-based hypotheses are also suggested as alternatives. We analyzed the effect of flowering phenology, airborne pollen presence and meteorological conditions in the pattern of acorn production in mixed evergreen-deciduous oak forests (Quercus ilex and Quercus pubescens) in NE Spain for twelve years (1998-2009). In both oaks, higher temperatures advanced the onset of flowering and increased the amount of airborne pollen. Nevertheless, inter-annual differences in pollen production did not influence acorn crop size. Acorn production was enhanced by a delay in flowering onset in Q. ilex but not in Q. pubescens. This suggests that in perennial oaks a larger number of photosynthates produced before flowering could benefit reproduction while the lack of effects on deciduous oaks could be because these species flush new leaves and flowers at the same time. Notwithstanding this effect, spring water deficit was the most relevant factor in explaining inter-annual variability in acorn production in both species. Considering that future climate scenarios predict progressive warmer and dryer spring seasons in the Mediterranean Basin, this might result in earlier onsets of flowering and higher water deficits that would constrain acorn production. © 2012 Elsevier Masson SAS.
Pérez-Ramos IM, Marañón T, Díaz-Delgado R, Espelta JM, Beudert B, Dirnböck T (2012) Mast seeding of European Fagaceae species in current and future environmental scenarios 10th LTER Europe conference Sofia, Bulgaria 3-7 Desembre (poster)
Pérez-Ramos IM, Marañón T, Díaz-Delgado R, Espelta JM, Dirnböck T (2012) Global Change and mast seeding of European tree species. The EUROMASTING project. IUFRO conference Biological Reaction of Forests to Climate and Air Pollution. Kaunas, Lithuania 18-27 Maig (poster)
Fernández-Martínez M, Belmonte J, Espelta JM (2012). Masting in oaks: Disentangling the effect of flowering phenology, airborne pollen load and drought. Acta Oecologica 43: 51-59.
Peguero G, Lanuza OR, Savé R, Espelta JM (2012) Allelopathic potential of the neotropical dry-forest tree Acacia pennatula Benth.: inhibition of seedling establishment exceeds facilitation under tree canopies. Plant Ecology 213: 1944-1953.
Peñuelas J, Carnicer J (2012) Com finançar la transició a les renovables del sistema energètic mundial?. InfoAproma 39: 6-8.
Espelta JM, Barbati A, Quevedo L, Tárrega R, Navascués P, Bonfil C, Peguero G, Fernández-Martínez M, Rodrigo A (2012) Post-Fire Management of Mediterranean Broadleaved Forests In: Moreira F, Arianoutsou M, Corona P & De las Heras J eds, Post-fire management and restoration of southern European forests. Managing Forest Ecosystems Series, Vol. 24. Springer, ISBN 978-94-007-2207-1. pp. 171-194.
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