Medium-term response of breeding Blue Chaffinch Fringilla teydea teydea to experimental thinning in a Pinus canariensis plantation (Tenerife, Canary Islands)

We studied the medium-term response of the endemic Blue Chaffinch Fringilla teydea teydea to experimental thinning in a Pinus canariensis plantation on the island of Tenerife during breeding season. Distance Sampling method was applied to line transects, and habitat preferences were modelled by means of univariate regression trees. The density was 1.70 birds/ha (1.09 to 2.68 95%CI) in thinned areas and 0.56 birds/ha (0.33 to 0.97 95%CI) in unthinned areas. The Blue Chaffinch densities peaked in thinned areas where the density of trees with Diameter at Breast Height of <25 cmwas between 10.5 and 16.5 trees/plot (r = 25 m) and the cover of Adenocarpus shrubs was 82.5%. Thinning had added heterogeneity into the stand structure at least in terms of lowering the basal area of small pine trees and increasing the understorey cover of Adenocarpus shrubs, with average cover being 37.15% in thinned and only 1.40% in unthinned areas.Our results justify the silvicultural thinning of 2844 hectares of pine plantation on the summit of Gran Canaria as a means of increasing the density of the endangered Gran Canaria Blue Chaffinch (Fringilla teydea polatzeki)

Biogeographic ranges do not support niche theory in radiating Canary Island plant clades

Aim: Ecological niche concepts, in combination with biogeographic history, underlie our understanding of biogeographic ranges. Two pillars of this understanding are competitive displacement and niche conservatism. The competitive displacement hypothesis holds that very similar (e.g. closely related) co-occurring species should diverge, forced apart by competition. In contrast, according to the niche conservatism hypothesis, closely related species should have similar niches. If these are fundamental structuring forces, they should be detectable when comparing the climatic niches of endemic species in radiating clades in oceanic archipelagos, where closely related species exist in both sympatry and allopatry and the species' entire ranges are known. We took advantage of this natural experimental system to test whether the climatic niche relationships predicted by the two hypotheses are found. Location: Canary Islands. Methods: For the plant clades Aeonium, Argyranthemum, Descurainia, Echium, Lotus and Sonchus, separately, we tested relationships between phylogenetic distance and climatic niche differentiation (in temperature, precipitation and their combination), using a high-resolution dataset. We also tested for niche conservatism using Blomberg's K and Pagel's λ. We compared climatic niche differentiation between pairs of species existing in sympatry with that for pairs of species in allopatry. For each comparison, we focused on the climatic niche space available to both species. Results: The relationships between phylogenetic distance and climatic niche differentiation were mostly non-significant; some weak but significant positive relationships were found, mainly for Aeonium and Sonchus. Where differences between sympatry and allopatry were found, niche differentiation tended to be greater in allopatry. Main conclusions: The expectations from niche conservatism were frequently not met; instead our results suggest considerable climatic niche lability. All significant differences in climatic niche differentiation were opposite to the predictions from competitive displacement. These forces may be less important in structuring biogeographic ranges than is commonly thought, at least on islands

Assembly of functional diversity in an oceanic island flora

Oceanic island floras are well known for their morphological peculiarities and exhibit striking examples of trait evolution1–3. These morphological shifts are commonly attributed to insularity and are thought to be shaped by the biogeographical processes and evolutionary histories of oceanic islands2,4. However, the mechanisms through which biogeography and evolution have shaped the distribution and diversity of plant functional traits remain unclear5. Here we describe the functional trait space of the native flora of an oceanic island (Tenerife, Canary Islands, Spain) using extensive field and laboratory measurements, and relate it to global trade-offs in ecological strategies. We find that the island trait space exhibits a remarkable functional richness but that most plants are concentrated around a functional hotspot dominated by shrubs with a conservative life-history strategy. By dividing the island flora into species groups associated with distinct biogeographical distributions and diversification histories, our results also suggest that colonization via long-distance dispersal and the interplay between inter-island dispersal and archipelago-level speciation processes drive functional divergence and trait space expansion. Contrary to our expectations, speciation via cladogenesis has led to functional convergence, and therefore only contributes marginally to functional diversity by densely packing trait space around shrubs. By combining biogeography, ecology and evolution, our approach opens new avenues for trait-based insights into how dispersal, speciation and persistence shape the assembly of entire native island floras.Fil: Barajas Barbosa, Martha Paola. Martin-luther-Universität Halle-Wittenberg; Alemania. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig; Alemania. Universität Göttingen; AlemaniaFil: Craven, Dylan. Data Observatory Foundation; Chile. Universidad Mayor; ChileFil: Weigelt, Patrick. Universität Göttingen; AlemaniaFil: Denelle, Pierre. Universität Göttingen; AlemaniaFil: Otto, Rüdiger. Universidad de La Laguna; EspañaFil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Price, Jonathan. University Of Hawaii At Hilo; Estados UnidosFil: Fernández Palacios, José María. Universidad de La Laguna; EspañaFil: Kreft, Holger. Universität Göttingen; Alemani

Estrategias de regeneración en la laurisilva

Estrategias de regeneración del bioma forestal de laurisilva en Canarias analizando los precedentes en otros territorios

Impacts of Forest Fire on Understory Species Diversity in Canary Pine Ecosystems on the Island of La Palma

Forest fires are drivers of spatial patterns and temporal dynamics of vegetation and biodiversity. On the Canary Islands, large areas of pine forest exist, dominated by the endemic Canary Island pine, Pinus canariensis C. Sm. These mostly natural forests experience wildfires frequently. P. canariensis is well-adapted to such impacts and has the ability to re-sprout from both stems and branches. In recent decades, however, anthropogenically caused fires have increased, and climate change further enhances the likelihood of large forest fires. Through its dense, long needles, P. canariensis promotes cloud precipitation, which is an important ecosystem service for the freshwater supply of islands such as La Palma. Thus, it is important to understand the regeneration and vegetation dynamics of these ecosystems after fire. Here, we investigated species diversity patterns in the understory vegetation of P. canariensis forests after the large 2016 fire on the southern slopes of La Palma. We analyzed the effect of fire intensity, derived from Sentinel-2 NDVI differences, and of environmental variables, on species richness (alpha diversity) and compositional dissimilarity (beta diversity). We used redundancy analysis (dbRDA), Bray–Curtis dissimilarity, and variance partitioning for this analysis. Fire intensity accounted for a relatively small proportion of variation in alpha and beta diversity, while elevation was the most important predictor. Our results also reveal the important role of the endemic Lotus campylocladus ssp. hillebrandii (Christ) Sandral & D.D.Sokoloff for understory diversity after fire. Its dominance likely reduces the ability of other species to establish by taking up nutrients and water and by shading the ground. The mid-to long-term effects are unclear since Lotus is an important nitrogen fixer in P. canariensis forests and can reduce post-fire soil erosion on steep slopes

Honeybees and pollen as indicators of alien plant species in two native forest ecosystems of an oceanic island (La Palma, Canary Islands)

Apis mellifera L. is a generalist pollinator present in most of the Canary Islands. When foraging, honeybees transfer pollen grains to honey, and presence and abundance of pollen from different species can be interpreted as a sign of local flora, and a cue to spread of aliens. The relative use of alien vs native species by honeybees could influence island pollination mutualisms and/or favour alien species. Analyzing pollen content data from honey samples an approach can be made to the relative foraging intensity on different plant communities and identify the importance of alien plant species in nearby areas. Based on published information on pollen contents of honeys from beehives in La Palma, we made an indirect evaluation of the use of endemic, native and alien species by honeybees in two native forests of the island (evergreen laurel forest and Canarian pine forest). Some of the most pervasive alien plants in the Canary Islands were represented in these pollen samples. The most frequent species in pollen counts was Castanea sativa. Proportion of alien species’ pollen was significantly higher in the laurel forest, while the most visited group in the pine forest was that of endemics (p < 0.05). Specific composition of pollen samples analysed with Detrended Correspondence Analysis revealed (61.3 % variance explained) a pattern related to species distribution in each forest type. Pollen content has revealed the presence of alien species in forests of La Palma, some of them considered invasive. The laurel forest is the most threatened of both ecosystems, mainly affected by the proximity to urban areas and the presence of intersperse arboreal plantations. The overall prevalence of aliens in the evaluated pollen data suggests that honeybees are prone to exploit exotics, and that the selection of plant species by honeybees in this oceanic island is not random. This may have serious consequences for island pollination systems and favour the spread of some exotic species

Honeybees and Pollen as Indicators of Alien Plant Species in Two Native Forest Ecosystems of an Oceanic Island (La Palma, Canary Islands)

Número especial: Exotic Species in Forest Stands of the Canary IslandsApis mellifera L. is a generalist pollinator present in most of the Canary Islands. When foraging, honeybees transfer pollen grains to honey, and presence and abundance of pollen from different species can be interpreted as a sign of local flora, and a cue to spread of aliens. The relative use of alien vs native species by honeybees could influence island pollination mutualisms and/or favour alien species. Analyzing pollen content data from honey samples an approach can be made to the relative foraging intensity on different plant communities and identify the importance of alien plant species in nearby areas. Based on published information on pollen contents of honeys from beehives in La Palma, we made an indirect evaluation of the use of endemic, native and alien species by honeybees in two native forests of the island (evergreen laurel forest and Canarian pine forest). Some of the most pervasive alien plants in the Canary Islands were represented in these pollen samples. The most frequent species in pollen counts was Castanea sativa. Proportion of alien species’ pollen was significantly higher in the laurel forest, while the most visited group in the pine forest was that of endemics (p < 0.05). Specific composition of pollen samples analysed with Detrended Correspondence Analysis revealed (61.3 % variance explained) a pattern related to species distribution in each forest type. Pollen content has revealed the presence of alien species in forests of La Palma, some of them considered invasive. The laurel forest is the most threatened of both ecosystems, mainly affected by the proximity to urban areas and the presence of intersperse arboreal plantations. The overall prevalence of aliens in the evaluated pollen data suggests that honeybees are prone to exploit exotics, and that the selection of plant species by honeybees in this oceanic island is not random. This may have serious consequences for island pollination systems and favour the spread of some exotic species

New insights on the understanding of forest fires impact in the Canary Islands pine forest

Pine forest in the Canary Islands is mainly dominated by Pinus canariensis, the only species in this genus endemic in oceanic islands. This forest is the most affected by fires in the Archipelago, however adults of P. canariensis are highly adapted to fire. Keyprocesses in ecosystem maintenance such as long term post-fire regeneration dynamic and ecosystem recovery have not been deeply studied. The IEBG had developed in recent years several researches about dynamic of Canarian pine forest under fire regimens in Tenerife, La Palma and Gran Canaria. Despite adaptations to fire, sexual regeneration of P. canariensis not dependent on fire and appears to be adapted rather to phenomena involving the disappearance of adults, such as high winds or colonization of new habitats. Fires also change understory conditions allowing a progressive inflow of herbaceous species that were not part of the ecosystem before the fire. In less than 10 years, these species are displaced by ecosystem mature vegetation. The invertebrate fauna dependent on the Canarian pine mulch is also affected by fires, wich reduces it richness, abundance and composition. However, and because to the overall ecosystem is adapted to this type of disturbance, these effects are mitigated also in less than 10 years