Rodrigo A, Martínez-Vilalta J, Piñol J, Lloret F, Ribas A, Retana J, Losarcos J (2008) Disseny i aplicació d’una proposta d’aprenentatge cooperatiu dels continguts de l’àrea d’Ecologia mitjançant l’estudi de casos. En “Cap a l’espai europeu d’educació superior. Experiències docents innovadores de la UAB en ciències experimentals i tecnol ogies i en ciències de la salut”. Servei de Publicacions UAB. Bellaterra
Broncano M.J., Rodrigo A., Retana J. (2008) Post-dispersal seed predation in Pinus halepensis and consequences on seedling establishment after fire. International Journal of Wildland Fire. 17: 407-414.LinkDoi: 10.1071/WF07095
In the present study, we analyse the spatiotemporal patterns of seed predation and the consequences of this predation in the establishment of new Pinus halepensis individuals. Rodents were the main predators of P. halepensis seeds in burned areas, while predation by ants was considerably lower. Concerning spatiotemporal patterns of seed predation, the results obtained indicate that, although there were some small differences among distances or among seasons, removal of P. halepensis seeds was consistently very high in all situations, whether close to or far from the unburned margins, in pine or mixed forests, in different sites and in all sampling periods throughout the year. We analysed the role of seed predation on the modulation of post-fire regeneration of P. halepensis. Just after fire, no differences in seedling density were found between plots with or without rodent exclusion, probably owing to the high density of seeds on the ground and the low density of rodents affected by fire. One year after fire, when rodent populations had recovered in burned areas and seeds were much less abundant, the combination of addition of seeds and rodent exclusion led to an increase in pine seedling establishment. © IAWF 2008.
Dahbi A., Retana J., Lenoir A., Cerdá X. (2008) Nest-moving by the polydomous ant Cataglyphis iberica. Journal of Ethology. 26: 119-126.LinkDoi: 10.1007/s10164-007-0041-4
In this paper we analyze emigration from nests by the polydomous ant Cataglyphis iberica. Social carrying of workers of this species between different nests of the colony is frequent. In Bellaterra (Barcelona, NE Spain), we monitored field emigration of C. iberica by noting for each nest the migratory behavior of C. iberica workers and, when the nests were attacked by another ant species, Camponotus foreli, we noted the number of C. foreli workers involved in the attacks. Emigration of C. iberica from nests was highly variable. We suggest the main factor determining emigration by this species was attack by workers of C. foreli, so emigration from C. iberica nests was much faster when harassment by C. foreli increased. The system of multiple nests of C. iberica enables this species to abandon attacked nests and to reinstall their population in other nests of the same colony. This reduces risk to the colonies because the route between the different nests is well known by transporter workers. © 2007 Japan Ethological Society and Springer.
Espelta J.M., Cortés P., Molowny-Horas R., Sánchez-Humanes B., Retana J. (2008) Masting mediated by summer drought reduces acorn predation in mediterranean oak forests. Ecology. 89: 805-817.LinkDoi: 10.1890/07-0217.1
Temporally variable production of seed crops by perennial plants (masting) has been hypothesized to be a valuable mechanism in the reduction of seed predation by satiating and starving seed consumers. To achieve these benefits, coexisting species subjected to the same predator would benefit from a similar pattern of seeding fluctuation over time that could lead to a reduction in predation at the within-species level. We tested for the existence of an environmental factor enforcing synchrony in acorn production in two sympatric Mediterranean oaks (Quercus ilex and Q. humilis) and the consequences on within-species and between-species acorn predation, by monitoring 15 mixed forests (450 trees) over seven years. Acorn production in Q. ilex and Q. humilis was highly variable among years, with high population variability (CVp) values. The two species exhibited a very different pattern across years in their initial acorn crop size (sum of aborted, depredated, and sound acorns). Nevertheless, interannual differences in summer water stress modified the likelihood of abortion during acorn ripening and enforced within- and, particularly, between-species synchrony and population variability in acorn production. The increase in CVp from initial to mature acorn crop (after summer) accounted for 33% in Q. ilex, 59% in Q. humilis, and 60% in the two species together. Mean yearly acorn pre-dispersal predation by invertebrates was considerably higher in Q. humilis than in Q. ilex. Satiation and starvation of predators was recorded for the two oaks, and this effect was increased by the year-to-year variability in the size of the acorn crop of the two species combined. Moreover, at a longer time scale (over seven years), we observed a significant reduction in the mean proportion of acorns depredated for each oak and the variability in both species' acorn production combined. Therefore, our results demonstrate that similar patterns of seeding fluctuation over time in coexisting species mediated by an environmental cue (summer drought) may contribute to the reduction of the impact of seed predation at a within-species level. Future research should be aimed at addressing whether this process could be a factor assisting in the coexistence of Q. ilex and Q. humilis. © 2008 by the Ecological Society of America.
Picó F.X., Retana J. (2008) Age-specific, density-dependent and environment-based mortality of a short-lived perennial herb. Plant Biology. 10: 374-381.LinkDoi: 10.1111/j.1438-8677.2008.00044.x
Density-independent and density-dependent processes affect plant mortality. Although less well understood, age-specific mortality can also play an important role in plant mortality. The goal of this study was to analyse several factors accounting for mortality in the Mediterranean short-lived perennial herb Lobularia maritima. We followed three cohorts of plants (from emergence to death) during 4 years in field conditions. We collected data on plant mortality of the effect of biotic agents (moth larvae and mycoplasma-like organisms, MLOs) and environmental variables. We also estimated density-dependent relationships affecting the fate of seedlings and adults. Results show that cohorts differed in their survival curves and ageing significantly increased mortality risk. Seedling mortality was density-dependent whereas adult mortality was not affected by density. MLO infection led to higher plant mortality whereas moth larvae attack did not affect plant mortality. In general, seedlings and adult plants experienced the highest mortality events in summer. We found, however, weak relationships between weather records and plant mortality. Age and size structures were not correlated. Overall, this study provides a comprehensive review of age-specific, density-dependent and density-independent factors that account for mortality of L. maritima plants throughout their life cycle in field conditions, highlighting the fact that age is an important factor in determining plant population dynamics. © 2008 German Botanical Society and The Royal Botanical Society of the Netherlands.
Rodrigo A., Sardà-Palomera F., Bosch J., Retana J. (2008) Changes of dominant ground beetles in black pine forests with fire severity and successional age. Ecoscience. 15: 442-452.LinkDoi: 10.2980/15-4-3117
This study analyzes the effect of fire on the composition and abundance of ground beetles in Pinus nigra forests. We used pitfall traps to sample beetles in burned P. nigra forests in Catalonia (Spain). Since fire dramatically alters forest structure and composition and beetles follow vegetation changes, we expected drastic changes in beetle composition and abundance immediately after fire. Because P. nigra forests do not recover after fire, we also expected beetles in burned and unburned areas to differ along a chronosequence. Beetle abundance per plot increased in canopy-fire-burned areas, but per plot species richness, diversity, and dominance were not affected by fire. Species composition varied depending on fire intensity. Some species were associated with canopy fire and low vegetation cover. Other species were associated with shrub cover and time since fire. Finally, some species were not dependent on fire or vegetation cover. Beetle abundance in burned areas was independent of time since fire. This lack of medium-term convergence between burned and unburned P. nigra forests agrees with our second hypothesis. Given the increase in fire frequency and size in submediterranean areas and the observed slow recovery of beetle species, a decline in beetle diversity at a regional scale is expected.
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