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.
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.
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)
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)
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.
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.
Muñoz A., Bonal R., Espelta J.M. (2012) Responses of a scatter-hoarding rodent to seed morphology: Links between seed choices and seed variability. Animal Behaviour. 84: 1435-1442.LinkDoi: 10.1016/j.anbehav.2012.09.011
Seed preferences of scatter-hoarding granivores may influence the evolution of seed traits in plants. However, there is little evidence linking the granivores' responses to specific seed traits to the variability of seeds in a single plant species. This information is essential for understanding how the decisions of granivores can shape plant life histories. We analysed how seed morphology (size and shape) of the Holm oak, Quercus ilex, influences seed choices of the seed-disperser, the Algerian mouse, Mus spretus. We studied the seed variability of the oak and whether the frequency of seed phenotypes matched the seed choices of the disperser. The probabilities of seed removal decreased as the seeds became larger and more bullet-shaped, so that seeds that were simultaneously large and bullet-shaped had the lowest probabilities of being dispersed. These seeds are probably refused by rodents because they impose higher handling and transport costs. The size and shape of the Holm oak seeds were highly variable between trees, but extraordinarily consistent within a single tree over different years. However, the analysis of seed variability revealed a disproportionately low frequency of large bullet-shaped phenotypes, which are those barely removed by rodents. Seed preferences of dispersers of species with high seed variability between trees can lead to differences in the chances of seeds produced by different trees being dispersed. Those seed phenotypes preferred by dispersers could make a higher contribution to the next generation, which could influence the evolution and variability of seeds in a plant species. © 2012 The Association for the Study of Animal Behaviour.
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