Alberto L. Teixido

Impacts of changes in land use and fragmentation patterns on Atlantic coastal forests in northern Spain

Changes in forested landscapes may have important consequences for ecosystem services and biodiversity conservation. In northern Spain, major changes in land use occurred during the second half of the 20th century, but their impacts on forests have not been quantified. We evaluated the dynamics of landscape and forest distribution patterns between 1957 and 2003 in Fragas do Eume Natural Park (northwestern Spain). We used orthoimages and a set of standard landscape metrics to determine transitions between land cover classes and to examine forest distribution patterns. Eucalypt plantations showed the greatest increase in area (197%) over time. Furthermore, transitions to eucalypt plantations were found in all major land cover classes. Forest showed a net decline of 20% in total area and represented 30% of the landscape area in 2003. Forest losses were mainly due to eucalypt plantations and the building of a water reservoir, while forest gains were due to increases in shrubland, meadows and cultivated fields which had been recolonised. Forest patch size and core area decreased, and edge length increased over time. In turn, increases were obtained in mean distance between forest patches, and in adjacency to eucalypt plantations and to a water reservoir. These results suggest an increase in forest fragmentation from 1957 to 2003, as well as a change in the nature of the habitat surrounding forest patches. This study shows that land use changes, mostly from eucalypt plantation intensification, negatively affected forested habitats, although some regeneration was ongoing through ecological succession from land abandonment.

Large and abundant flowers increase indirect costs of corollas: a study of coflowering sympatric Mediterranean species of contrasting flower size

Large floral displays receive more pollinator visits but involve higher production and maintenance costs. This can result in indirect costs which may negatively affect functions like reproductive output. In this study, we explored the relationship between floral display and indirect costs in two pairs of coflowering sympatric Mediterranean Cistus of contrasting flower size. We hypothesized that: (1) corolla production entails direct costs in dry mass, N and P, (2) corollas entail significant indirect costs in terms of fruit set and seed production, (3) indirect costs increase with floral display, (4) indirect costs are greater in larger-flowered sympatric species, and (5) local climatic conditions influence indirect costs. We compared fruit set and seed production of petal-removed flowers and unmanipulated control flowers and evaluated the influence of mean flower number and mean flower size on relative fruit and seed gain of petal-removed and control flowers. Fruit set and seed production were significantly higher in petal-removed flowers in all the studied species. A positive relationship was found between relative fruit gain and mean individual flower size within species. In one pair of species, fruit gain was higher in the large-flowered species, as was the correlation between fruit gain and mean number of open flowers. In the other pair, the correlation between fruit gain and mean flower size was also higher in the large-flowered species. These results reveal that Mediterranean environments impose significant constraints on floral display, counteracting advantages of large flowers from the pollination point of view with increased indirect costs of such flowers.

Sex-dependent selection on flower size in a large-flowered Mediterranean species: an experimental approach with Cistus ladanifer

Larger flowers increase pollinator visit rates and reproductive success, so selection on flower size is usually mediated by pollinators. However, larger flowers involve costs imposed by resource limitation so environmental conditions may also modulate flower size. “Male function” hypothesis entails that the intensity of selection is sex-dependent, being greater through male fitness, whereas female fitness is more limited by resources. In this study we analyse pollinator-mediated phenotypic selection on flower size through both sexes in a large-flowered Mediterranean species, Cistus ladanifer. We experimentally manipulated flower size in two populations, measured its effect on male and female fitness and estimated the strength and direction of phenotypic selection through both sexes and populations. Unmanipulated control flowers received higher pollinator visit rates and dispersed a higher pollen amount than reduced flowers. This translated into selection towards larger flowers through male fitness in both populations. Nevertheless, flower size had little effect on female fitness. Fruit set was high but selection through this component of female function was not significant. Seed number increased in control flowers, especially in one population, where we detected positive selection on flower size. Our results suggest that pollinator-mediated phenotypic selection on flower size in this large-flowered Mediterranean species is especially modulated by male fitness, but flower size adjustment may also be a result of a simultaneous selection through both sexes that, in turn, is dependent of ecological context.

Temperature-Limited Floral Longevity in the Large-Flowered Mediterranean Shrub Cistus Ladanifer (Cistaceae)

Premise of research. Larger and longer-lived flowers are more frequently pollinated, but they are associated with high maintenance costs due to greater water usage. The Mediterranean climate limits plant reproduction and maximizes resource use efficiency, so smaller and short-lived flowers are potentially advantageous under hot and dry conditions. Methodology. We experimentally evaluated the relationship between the floral longevity of Cistus ladanifer, a large-flowered Mediterranean shrub, and pollination, flower size, and temperature at two different altitudes with contrasting climatic conditions. We hypothesized that flower size and longevity would be reduced in the drier and hotter conditions of the lower-altitude site. In addition, we expected that floral longevity would decrease with experimental pollen deposition, flower size, and temperature. We pollinated and capped flowers to evaluate the variation in floral longevity by comparing actual and potential floral longevity at low and high altitudes. Pivotal results. In agreement with our hypothesis, flower size was observed to increase with altitude, but, contrary to expectations, floral longevity decreased at the high altitude since temperature increased during the flowering time. Floral longevity tended to be short but depended on pollination, such that potential floral longevity was greater than actual floral longevity. Capped flowers lasted longer (1.31 ± 0.65 d) than control (0.95 ± 0.39 d) or hand-pollinated (0.60 ± 0.08 d) flowers. At the high altitude, larger flowers and higher temperatures resulted in a reduction in both the observed and potential floral longevity, but temperature had a differential effect in limiting potential floral longevity. Conclusions. Our experimental survey reported short-lived flowers and limitations in floral longevity when flowers were larger and temperatures were higher. Overall, the results reveal an important effect of temperature on increasing floral maintenance costs, imposing selective pressures on flower size, and longevity in large-flowered Mediterranean plants.