Content uploaded by Juan D. Delgado
Author content
All content in this area was uploaded by Juan D. Delgado
Content may be subject to copyright.
A preview of the PDF is not available
Los bosques termófilos de Canarias
Figures
Figures - uploaded by Juan D. Delgado
Author content
All figure content in this area was uploaded by Juan D. Delgado
Content may be subject to copyright.
... It does not grow on the driest Canary Islands, Lanzarote, and Fuerteventura, which are exposed to dry and warm winds (Bechtel, 2016;Cropper, 2013). The climate of the Canary Islands is oceanic, with low temperature amplitudes and high humidity, but J. canariensis forms homogeneous patches and enters shrub communities in places with relatively low rainfall (Fernández-Palacios et al., 2008Luis González et al., 2017;Otto et al., 2010Otto et al., , 2012Romo 2018;Romo et al., 2014;Romo & Salvà-Catarineu, 2013). It grows at elevations mostly between 400 and 1,000 m, higher on the leeward than the windward sides of the islands (Fernández-Palacios et al., 2008;Otto et al., 2012). ...
... The climate of the Canary Islands is oceanic, with low temperature amplitudes and high humidity, but J. canariensis forms homogeneous patches and enters shrub communities in places with relatively low rainfall (Fernández-Palacios et al., 2008Luis González et al., 2017;Otto et al., 2010Otto et al., , 2012Romo 2018;Romo et al., 2014;Romo & Salvà-Catarineu, 2013). It grows at elevations mostly between 400 and 1,000 m, higher on the leeward than the windward sides of the islands (Fernández-Palacios et al., 2008;Otto et al., 2012). ...
... The species distribution in the Macaronesian province is associated with a thermo-Mediterranean type of bioclimate (Fernández-Palacios et al., 2008;Rivas-Martínez et al., 2004) with BIO12, BIO13, and BIO18 being the most influential climate factors. The climate conditions of the current potential niche are characterized by low annual precipitation, which reaches about 340 mm on average and does not go above 420 mm. ...
Aim
The aim of this study is to model the past, current, and future distribution of J. phoenicea s.s., J. turbinata, and J. canariensis, based on bioclimatic variables using a maximum entropy model (Maxent) in the Mediterranean and Macaronesian regions.
Location
Mediterranean and Macaronesian.
Taxon
Cupressaceae, Juniperus.
Methods
Data on the occurrence of the J. phoenicea complex were obtained from the Global Biodiversity Information Facility (GBIF.org), the literature, herbaria, and the authors’ field notes. Bioclimatic variables were obtained from the WorldClim database and Paleoclim. The climate data related to species localities were used for predictions of niches by implementation of Maxent, and the model was evaluated with ENMeval.
Results
The potential niches of Juniperus phoenicea during the Last Interglacial period (LIG), Last Glacial Maximum climate (LGM), and Mid‐Holocene (MH) covered 30%, 10%, and almost 100%, respectively, of the current potential niche. Climate warming may reduce potential niches by 30% in RCP2.6 and by 90% in RCP8.5. The potential niches of Juniperus turbinata had a broad circum‐Mediterranean and Canarian distribution during the LIG and the MH; its distribution extended during the LGM when it was found in more areas than at present. The predicted warming in scenarios RCP2.6 and RCP8.5 could reduce the current potential niche by 30% and 50%, respectively. The model did not find suitable niches for J. canariensis during the LIG and the LGM, but during the MH its potential niche was 30% larger than at present. The climate warming scenario RCP2.6 indicates a reduction in the potential niche by 30%, while RCP8.5 so indicates a reduction of almost 60%.
Main conclusions
This research can provide information for increasing the protection of the juniper forest and for counteracting the phenomenon of local extinctions caused by anthropic pressure and climate changes.
... palm groves that occur within the thermophilous vegetation zone (De Nascimento et al., 2015). Taking account of the modern pollen rain threshold values (Figure 5), it is evident that the palm groves were important in the area and the number of palm trees at that time around the site may even have exceeded that of palm groves occurring in the islands at present (Fernández-Palacios et al., 2008; Sosa et al., 2007). The prevalence of these communities in the area in this period is unexpected. ...
... Thus, we can confirm the past presence of Olea and Pistacia woodlands in the islands, but we cannot estimate their importance based on the available data. Canarian palm groves in Gran Canaria are among the best represented in the archipelago, together with those of La Gomera (Fernández-Palacios et al., 2008). It has been variously estimated that they cover between 600 and 1200 ha (Del Arco et al., 2010; Sosa et al., 2007). ...
... Since the establishment of the Mediterranean climate regime c. 2.5 Ma, the Canarian laurel forest has been dependent on the constant supply of humidity provided by the NE trade winds. We may assume the laurel forest to have been restricted to the area of influence of the 'sea of clouds' on windward slopes, while the thermophilous woodlands and the Canarian pine forest, which are more tolerant of the summer drought, were spread, respectively, below and above the laurel forest (Fernández-Palacios et al., 2008). Palaeoecological records of several islands within the archipelago have provided evidence of a trend towards a drier climate during the late Holocene (Nogué et al., 2013; Von Suchodoletz et al., 2010; Yanes et al., 2011), which may have favoured the expansion of thermophilous woodlands within the last 5000 years, at least until human arrival. ...
We provide the first fossil pollen and charcoal analysis from the island of Gran Canaria (Canary Islands). The pollen record obtained from Laguna de Valleseco (870 m a.s.l.) spans the late Holocene (c. 4500–1500 cal. yr BP) and thereby captures the impact of human colonization. During the earliest period, pollen composition resembled contemporary thermophilous communities, with palms (Phoenix canariensis) and junipers (Juniperus cf. turbinata) being the dominant trees, suggesting that these elements were more widespread in the past. Vegetation in Valleseco began to change at around 2300 cal. yr BP, 400 years before the earliest archaeological evidence of human presence in the island (c. 1900 cal. yr BP). Our data show an increased frequency of fires at that time, coinciding with the decline of palms and the increase of grasses, indicating that humans were present and were transforming vegetation, thus showing that the demise of Gran Canaria’s forest began at an early point in the prehistoric occupation of the island. In the following centuries, there were no signs of forest recovery. Pollen from cultivated cereals became significant, implying the introduction of agriculture in the site, by 1800 cal. yr BP. The next shift in vegetation (c. 1600 cal. yr BP) involved the decrease of grasses in favour of shrubs and trees like Morella faya, suggesting that agriculture was abandoned at the site.
... Our results therefore imply that, despite the low number of individuals sampled, as well as the documented historical decrease of populations throughout the Canarian archipelago (Fernández- Palacios et al. 2008), J. turbinata has moderate levels of genetic diversity (evidenced by AFLP) with no apparent evidence pointing to genetic bottlenecks. Long-lived woody perennials are expected to be resilient to changes in genetic diversity due to ample gene flow and long generation times. ...
... The ability of J. phoenicea s.l. to disperse both pollen (by wind) and seeds (by birds) to distant locations has already been documented in mainland populations (Jordano 1993). The known dispersers of J. turbinata in Canary Islands are ravens, blackbirds and lizards (Nogales et al. 1999;Fernández-Palacios et al. 2008;Otto et al. 2010). Long distance dispersal (LDD) mechanisms in oceanic islands involves several types of dispersal; anemochory, zoochory, by birds capable to fly over long distances, as well as diplochory or secondary seed dispersal, in which the primary disperser, is hunted by a predator capable to travel between islands, and sea dispersal or hydrochory. ...
Oceanic archipelagos provide an important platform from which to evaluate the effects of isolation
and fragmentation on the genetic structure of species. As a result of oceanic isolation, such
species usually show lower levels of genetic diversity and higher genetic differentiation than
their mainland congeners. However, this is not necessarily the case for long distance dispersal
species, whose genetic structure is not strictly defined by population isolation. We assessed the
level and distribution of genetic diversity among Canarian populations of Juniperus turbinata in
order to evaluate the influence of population isolation on its genetic structure. Using Amplified
Fragment Length Polymorphism markers, we analyzed molecular diversity among 175 individuals
from five populations occurring across the Canary Island and three Moroccan populations.
Principal Coordinate Analysis, neighbor joining clustering, AMOVA and Bayesian-based analysis
were applied to examine population structure. Despite the documented habitat loss and decline
in Canarian populations, Amplified Fragment Length Polymorphism markers revealed levels of
intra-population genetic diversity that were similar to those from mainland populations, and low
levels of genetic differentiation. Bayesian analysis of population structure showed three main
clusters, one comprising El Hierro population and a few individuals from several islands, a second
cluster that grouped the remaining Canarian populations together, and a third cluster grouping
Moroccan populations. Our results suggest that the main force driving the genetic structure of
Canarian populations of J. turbinata is its capacity for long distance dispersal.
... It comprises seven main volcanic islands across 400 km and is located in the North Atlantic Ocean, about 100 km off the coast of the Sahara Desert, at ca. 28°N. The archipelago is characterized by significant microclimatic heterogeneity, and the islands are generally subdivided into six major habitats: sub-tropical laurel forest, pine forest, Macaronesian heathland (fayal-brezal), thermophile shrubland, xerophytic scrubland (cardonal-tabaibal), and alpine (Fernández-Palacios et al., 2008;Bañares-Baudet, 2015). ...
Although species radiations on island archipelagos are broadly studied, the geographic and ecological modes of speciation that underlie diversification are often not fully understood. Both allopatry and sympatry play a role during radiations, particularly on islands with profound habitat diversity. Here, we use the most diverse Canary Island plant radiation, Aeonium (Crassulaceae), to phylogenetically test two hypotheses: (i) allopatric speciation, which predicts that closely related taxa are ecologically similar but do not co-occur, and (ii) sympatric speciation, whereby closely related taxa co-occur geographically but are ecologically distinct. We fitted niche and spatial distribution models based on extensive field surveys to quantify geographic and ecological divergence among taxa integrated in a phylogenetic context. Contrary to our expectation, phylogenetically closely related species tend to occupy similar ecological niches, revealing that ecological niche divergence among species accumulates slowly, even in sympatry. This suggests that evolutionary young taxa may be partially reproductively isolated due to subtle phenotypic differences, such as reproductive morphology and phenology, rather than by ecological niche and may putatively exacerbate divergence among populations. Thus, allopatry and sympatry are complementary speciation mechanisms on oceanic islands, jointly spurring this enigmatic radiation.
... It comprises seven main volcanic islands across 400 km and is located in the North Atlantic Ocean, about 100 km off the coast of the Sahara Desert, at ca. 28°N. The archipelago is characterized by significant microclimatic heterogeneity, and the islands are generally subdivided into six major habitats: sub-tropical laurel forest, pine forest, Macaronesian heathland (fayal-brezal), thermophile shrubland, xerophytic scrubland (cardonal-tabaibal), and alpine (Fernández-Palacios et al., 2008;Bañares-Baudet, 2015). ...
Although species radiations on island archipelagos are broadly studied, the geographic and ecological modes of speciation that underlie diversification are often not fully understood. Both allopatry and sympatry play a role during radiations, particularly on islands with profound habitat diversity. Here, we use the most diverse Canary Island plant radiation, Aeonium (Crassulaceae), to phylogenetically test two hypotheses: (1) allopatric speciation, which predicts that closely related taxa are ecologically similar but do not co-occur, and (2) sympatric speciation, whereby closely related taxa co-occur geographically but are ecologically distinct. We fitted niche and spatial distribution models based on extensive field surveys to quantify geographic and ecological divergence among taxa integrated in a phylogenetic context. Contrary to our expectation, phylogenetically closely related species tend to occupy similar ecological niches, revealing that ecological niche divergence among species accumulates slowly, even in sympatry. This suggests that evolutionary young taxa may be partially reproductively isolated due to subtle phenotypic differences, such as reproductive morphology and phenology, rather than by ecological niche and may putatively exacerbate divergence among populations. Thus, allopatry and sympatry are complementary speciation mechanisms on oceanic islands, jointly spurring this enigmatic radiation.
... Our map highlights that suitable temperature conditions for germination are widespread at low altitudes, and that the Canary Islands dragon tree germination is limited by low temperatures in higher altitudes. The Canary Islands dragon tree is absent and has probably never occurred in the low altitude islands Lanzarote and Fuerteventura, where thermophilous woodlands, i.e., the main habitat of the dragon tree, are very scarce (with the exception of restricted areas, e.g., Famara and Jandia mountains, in Lanzarote and Fuerteventura respectively, Fernández--Palacios et al., 2008b). However, our suitability map for D. draco subsp. ...
... However, our analysis showed a generalized ED for single island endemics across taxonomic groups indicating the need to conserve and restore heavily destroyed habitats on all islands not only on one specific island in order to avoid possible future extinctions. Consequently, we highlight the need to restore the Canary thermophilous woodland, the worst preserved ecosystem with the highest level of threatened endemic plants but the richest in SIEs (Fernández-Palacios et al., 2008). ...
Aim
The majority of documented extinctions world‐wide in the last four centuries are of species endemic to islands. However, the phenomenon of delayed extinctions as a result of habitat loss has rarely been assessed on oceanic islands. In this study, we tested whether extinction debt ( ED ), in general, occurs on islands and for which taxonomical groups this phenomenon is most pronounced by assessing ED for multiple endemic taxa and for each of the main altitudinal ecosystems in a well‐studied oceanic archipelago.
Location
Canary Islands.
Methods
We characterized habitat preferences for all endemic species of several taxonomic groups (vascular plants, ground and darkling beetles, flies and land snails). Using generalized linear mixed models and available data about habitat distributions, we tested for all taxa and habitat types to determine whether past habitat area better explained current richness of habitat specialists than current habitat area. If so, an extinction debt can be assumed.
Results
For all five major habitat types and five taxonomic groups studied, present‐day richness of habitat specialists fitted better with past than current habitat area, evidencing habitat‐ and taxon‐specific extinction debts. This pattern was consistent for both long‐lived vascular plants and short‐lived invertebrates. Single island endemics in each taxonomic group showed steeper slopes of the species–area relationship ( SAR ) compared to archipelago endemics indicating higher sensitivity to habitat loss which might increase sizes of ED .
Conclusion
Despite differences in species’ generation times, plants and invertebrates showed delayed extinctions after habitat destruction in the Canary Islands. Our SAR approach suggests that a considerable number of Canary Island endemics will eventually become extinct in the future without further habitat loss. The case of the Canary archipelago is probably not unique. Hence, we interpret our results as a warning for island conservationists that the worst of the extinction crisis on oceanic islands might be yet to come. Conservation actions should focus on habitat restoration to attenuate or reverse current extinction processes.
Adaptive radiation is a significant driver of biodiversity. Primarily studied in animal systems, mechanisms that trigger adaptive radiations remain poorly understood in plants. A frequently claimed indicator of adaptive radiation in plants is growth form diversity when tied to the occupation of different habitats. However, it remains obscure whether morphological adaptations manifest as growth form diversity per se or as its constituent traits. We use the classic Aeonium radiation from the Canary Islands to ask whether adaptation across climatic space is structured by growth form evolution. Using morphological sampling with site-associated climate in a phylogenetic context, we find that growth forms dictate adaptations to the local environment. Furthermore, we demonstrate that the response of specific traits to analogous environments is antagonistic when growth forms are different. This finding suggests for the first time that growth forms represent particular ecological functions, allowing the co-occurrence of closely related species, being a product of divergent selection during evolution in sympatry.
Using as a basis the UTM projection (Universal Transverse Mecator), the distribution and abundance of Dracaena tamaranae A. Marrero, R. S. Almeida & M. Gonzalez Martín is plotted using 1 km2 grid squares. Likewise, precise information about the population size, the age structure, the extent of occur-rence, the area of occupancy, the altitudinal distribution, the habitat characteristics and the conservation status of this new dragon tree endemic species from Gran Canaria are reported for the first time.
RESUMEN. Utilizando como base la proyección UTM (Universal Transversa Mercator), se representa sobre cuadrículas de 1 km2 la distribución y abundancia de Dracaena tamaranae A. Marrero, R. S. Almeida & M. González-Martín. Asimismo se aportan por primera vez datos muy precisos sobre el tamaño de la población, la estructura por edades, la extensión de presencia, el área de ocupación, la distribución altitudinal, las características del hábitat y el estado de conservación de esta nueva especie de drago endémica de Gran Canaria.
During 1996 and 2006 we studied the population size and breeding success of Common Raven in Teno massif, where the majority of Tenerife reproductive pairs reside. Breeding population size remained more or less stable during the study period, varying between four (2001) and nine (2005–2006) pairs. Fledging rate (fledged chicks/successful nests) in 2006 was 2.63 and eight of the nine pairs bred successfully (89% of the nests producing surviving offspring). During 1996–2005, the mean fledging rate of 36 broods randomly selected was 2.72. Implementation of a food supply program to increase the survival rate of non reproductive birds is needed urgently along with other conservation measures.
The role of the common raven (Corvus corax; Corvidae) as a seed dispersal agent for plants in the Canary Islands was studied by analysing 2672 pellets collected from all islands of the archipelago. Seeds of 16 species of phanerogams were found (four endemic to the Canaries, three endemic to the Macaronesian islands, six not endemic, and three introduced by man). Vegetation in this archipelago is highly structured according to altitude creating different types of macrohabitats. The quality of the transport of seeds between habitats was evaluated in a preliminary way by making use of the very high fidelity of the plant species to particular macrohabitats. Of the 102 580 potentially fertile seeds (excepting the other 51 061 infertile Ficus carica seeds) transported by common ravens, 76.5% were regurgitated in theoretically suitable habitat while the remaining 23.5% were taken to habitats that were not appropriate for the establishment. Common ravens improved germination of six species, whereas an opposite effect was observed for three others. The percentage of viable seeds did not differ for any species between pellet seeds and seeds collected directly from the plants. Considering results from germination and viability experiments and macrohabitat patterns of dispersal, the common raven seems to be an important disperser for nine plant species: Lycium intricatum (Solanaceae), Opuntia ficus-indica (Cactaceae), Rubia fruticosa and Plocama pendula (Rubiaceae), Juniperus turbinata and J. cedrus (Cupressaceae), Phoenix canariensis (Arecaceae), Asparagus pastorianus (Liliaceae), and Myrica faya (Myricaceae).
Data are provided on the density and distribution of an oceanic island population of Ravens (El Hierro, Canary Islands). The density of both the breeding population (ca. 35 pairs/100 km2) and that censused from a vehicle (35 birds/100 km) is the highest recorded in island environments and the second highest in the species' entire distribution area. The high density is probably due to an abundant food supply and numerous suitable nesting sites. Relief and altitude influenced the distribution of breeding territories which showed a high level of constancy from one year to the next.
The first data on bird hunting by the ancient people from El Hierro island are given here. Ninety-three bones have been examined from a cave situated in the archaeological site of Guinea. The majority of the bones are broken, burned and some of them have cuts showing human exploitation. There are species that have been eaten from the lower levels to the present day (Calonectris diomedea, Columba sp. and Corvus corax), one species that does not now live on El Hierro (cf. Pyrrhocorax pyrrhocorax), and an extinct species (Coturnix gomerae). © 1997 John Wiley & Sons, Ltd.