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1.
The prevalence and intensity of the parasites from 50 wild doves (Columba livia) from the city of Santa Cruz de Tenerife, in the island of Tenerife (Canary Archipelago), were studied. The following ectoparasites were found in apparently healthy pigeons (prevalences are shown in percentage (%) and mean intensities with their standard deviations): the acari Dermanyssus gallinae (De Geer, 1778) (6, 241.0 +/- 138.9) and Tinaminyssus melloi Fain, 1962 (10%, 218.3 +/- 117.3); the louses, Columbicola columbae Linnaeus, 1758 (100%, 111.4 +/- 76.8) and Campanulotes bidentatus Scopoli, 1763 (94%, 48.4 +/- 26.6); and the pigeon fly, Pseudolynchia canariensis Macquart, 1839 (36%, 6.2 +/- 1.6). The endoparasites we found were: a haemoprotozoan species, Haemoproteus columbae Kruze, 1890 (82%, 14.8 +/- 10.3 per 1000); coccidian oocysts, Eimeria sp. (50%, 0.2 x 10(3) +/- 1.7 x 10(3) per gr); a cestode species Raillietina micracantha (Fuhrmann, 1909) López Neyra, 1947 (44%, 12.3 +/- 9.4); and four nematode species, Tetrameres (Tetrameres) fissispina (Diesing, 1861) Travassos, 1915 (4%, 99.5 +/- 34.1), Synhimantus (Dispharynx) spiralis (Molin, 1858) (8%, 46.8 +/- 11.6), Ascaridia columbae (Gmelin, 1790) Travassos, 1913 (40%, 8.4 +/- 8.8) and Aonchotheca sp. (18%, 6.0 +/- 3.1). Several species detected in our study can be pathogens for C. bollii and C. junoniae, which are endemic pigeons of the Canary Islands, considered endangered species. Parasites (ectoparasites, protozoa and helminths) of C. livia found in Tenerife and others from wild and farm birds in the island were considered as healthy controls.  相似文献   

2.
The laurel-forest of the Canary Islands is a montane cloud-forest. In order to gain some knowledge on the processes that maintain tree species diversity, we conducted an analysis of three different laurel-forest plots of the Anaga massif (Tenerife), varying in canopy composition but growing under similar environmental conditions. For each plot we recorded basal area of the canopy trees (h<1.30 m), the density of suckers and seedlings (h>1.30 m), as well as seed-bank composition. The plots have similar regeneration composition, which appears to be independent of differences in canopy composition. Laurus azorica is the most common seedling species, whereas Prunus lusitanica is the most abundant species among suckers and basal shoots. Neither Erica arborea nor Myrica faya, the two main canopy trees in one of the plots, were found in any of the stands as seedlings or suckers, despite their existence as viable seeds in the seed-bank. The regeneration composition and the canopy composition in one of the plots is remarkable different, revealing differents dynamics processes in the three plots. The results suggest the existence of three well-defined ecological groups: pioneer (regeneration primarily by seedlings), non-pioneer (regeneration by seedlings and suckers) and remnant species (regeneration primarily by suckers).These three groups and the effect of small scale disturbances (natural and human-induced), could help to understand the maintenance of tree species richness.  相似文献   

3.
Spatial patterns are important characteristics of the forest and theycan reveal such things as successional status and ecological characteristics ofthe species. We tested the hypothesis that spatial distribution will bedifferent, depending on whether the species is intolerant or tolerant to shade.We assessed the spatial distribution of trees (> 4 cm dbh) andjuveniles in eight laurel forest plots. A univariate spatial analysis(performed with Ripley's K1) showed that all tree species havesignificantaggregation at short distances (2 m). Nevertheless, two groups ofspecies could be differentiated: Erica scoparia,Myrica faya and Ilex canariensisshowed a tendency for aggregation at large distances (larger than 6m)while L. azorica and Prunuslusitanicashowed aggregation only at shorter distances. Ripley's BivariateK1,2 analyses showed no significant differences in the spatialdistribution ofanalyzed species pairs from a null model. Only Laurusazoricahad a sufficient sample size for analysis of juvenile distribution. Aunivariateanalysis revealed thatL. azorica seedlings (stems < 50 cm high)were clumped in some plots up to 5 m, but this was not consistent.Saplings (stems > 50 cm high and < 4 cm dbh)didnot show strong clumping even at short distances. L.azoricasaplings had no significant aggregation with, nor repulsionfrom, adults of the same or different species. Spatial patterns of the speciesshould be considered in the development of restoration plans of the laurelforest 90%of which has disappeared or been intensively disturbed on Tenerife Island.  相似文献   

4.
We examined bryophyte species growing on Laurus azorica, in three localities of the laurel forest in Tenerife (Canary Islands), in order to determine differences in species composition, richness and cover, that depend on variations in mist frequency and density. Among the 35 bryophyte species found (26 liverworts and nine mosses), 16 occurred in all three locations while nine species occurred in only one location. Detrended correspondence analysis and canonical correspondence analysis revealed that the epiphyte–phorophyte relationship varied in terms of cover, richness and bryophyte composition, depending on the humidity conditions (related to mist frequency and plot height) and tree age. In spite of differences in the dominant species found at each locality, the community types have many species in common and may be seen as a natural unit of the communities involved. Variation in the dominant species at each locality is mainly related to a trade off between humidity conditions and tree diameter, and the speed of the successional processes. Plot aspect was the only variable among those considered with no significant influence, which might be related to the closed canopy conditions. Variation in cover, richness and bryophyte composition related to plot height and tree diameter increased in the drier location. Cover was positively related to species richness in all analyses. This is related to low diversity during initial colonization and the fact that the highest biomass species, related to later successional stages, also occur on younger trees, especially in the more humid areas.  相似文献   

5.
This study is based on a phytosociological table and a matrix of species and morphological characters. The relevés were taken along a transect in a Myrica faya-Erica arborea formation on Tenerife (Canary Islands). The analysis of the phytosociological table reveals a vegetational succession and a corresponding ecological gradient. The study of correlations between morphological and ecological data leads to the creation of groups of species with different combinations of characters, and to a discussion of the adaptive values of each character combination. The species of each group occupy similar niches.Abbreviations AOC= Analysis of Concentration - P/C= index ratio between the perimeter of a leaf and the circumference of a circle having the same area as the leaf  相似文献   

6.
The spatial and temporal structure of Carabus (Nesaeocarabus) interruptus Dejean, 1831 populations and the independent effects of climate along altitudinal gradients in the island of Tenerife, especially whether environmental preferences constrains the species breeding patterns at local and regional scales were evaluated. Ground-beetles were sampled with twenty-one pitfall traps in each of the forty-one plots during one year study. Some sampled specimens were dissected and dried to determine sex, weight and ovarian maturation. The populations were restricted to the middle climatic zone (600–1700 m). There was a long adult activity period from October to June and the changes in the weekly capture success were strongly correlated with the rainfall and temperature. Overall the males during winter were more active than the females. The emergence of new adults occurred only in spring and the body dry weight peaked in April–May. From start of autumn the weight was recovered to the initial values of the cycle, increased and peaked in January. The females prolonged its oviposition period from mid-autumn to the starting of spring. The species showed a winter breeding pattern and the seasonal variations in multiple life history traits could correspond with the changing conditions of the microclimatic variables. An evolutionary ecological model could help explain the life history pattern variability among the Carabus species in South-western Europe. The species could tackle the geographic dispersion of their populations for the single purpose of seeking a suitable hydrothermal environment (high rainfall and mild temperatures) if the food was insured.  相似文献   

7.
8.
《Ostrich》2013,84(3):583-589
We describe the density, breeding and foraging ecology of the Berthelot's Pipit (Anthus berthelotii), an endemic passerine to the Atlantic islands, in the semi-arid coastal scrub of Tenerife. Furthermore, we analyse the effects of temperature and rainfall in the onset of reproduction and the behaviour (nest site and foraging site selection). The average density of the Pipit (using DISTANCE methodology) in the semi-arid coastal scrub was 7.1 birds 10ha?1, and the overall density estimate in grassland was 3.3 birds 10ha?1. The Pipit bred early (mean average first-egg laying date 12 February) and in response to rainfall (but not temperature). By the Mayfield method, the probability of the nests surviving the egg stage was 0.77 and of and the nests surviving the chick stage 0.67 — assuming an incubation period of 13 days and a chick stage of 12.5 days — based on the European average for the similar-sized Meadow Pipit Anthus pratensis. Overall nest survival pooling stages were 0.51. The Pipits had a low clutch size (3.3 eggs, range of 2–4). Nest damage by heavy rainstorms was the major cause of nest failures (three out of five failures). The Pipits nested preferentially in grass with relatively low densities of Euphorbia balsamifera bushes. Birds selected grassy areas as their main foraging site but also preferred to forage on large rocks during nesting: caterpillars were the main food items (14 out of 17 prey captures).  相似文献   

9.
We confirmed functional dioecy of Withania aristata via field and greenhouse studies. Male flowers are significantly larger. Female flowers bear stamens with no pollen; males bear 220?000 grains. Stigmata of male flowers senesce in buds. Anatomical observations confirm more ovules in females and an ovarian nectary in both sexes. We detected nectar in female flowers in the greenhouse but found no nectar in males. Thus, males offer pollen and females nectar. Females bear large numbers of fruits and, infrequently, male plants bear few significantly smaller fruits with few seeds. Outcrosses of females (self crosses impossible without pollen) yielded fruits in young buds, older buds, and open flowers. Self crosses of male flowers succeeded only with very young buds. Although functionally dioecious, this species manifests self-compatibility; however, no fruits are produced autonomously. Bee species (Lassioglossum, Amegilla, Apis) visit flowers and mature buds. Bud visits in which bees force petal tips apart, coupled with self-compatibility, may explain infrequent fruit on males. Thus, dioecy in W. aristata seems to have evolved from self-compatible ancestors, that leaky dioecy may have been favored during colonization, and, that despite autogamy and a low floral visition rate, this endemic enjoys a high rate of reproductive success.  相似文献   

10.
DNA nucleotide sequences from two mitochondrial genes (cytochrome b and NADH dehydrogenase subunit 2) and the nuclear intron 7 of β-fibrinogen were obtained to infer the phylogenetic origin of the two endemic Canarian pigeons: Bolle’s Pigeon (Columba bollii) and Laurel Pigeon (C. junoniae). Phylogenetic analyses of mitochondrial and nuclear genes based on maximum parsimony, maximum likelihood and Bayesian inference all converged into a congruent topology: C. bollii clusters together with the Wood Pigeon (C. palumbus) which is common in Europe and Asia, while C. junoniae was found near the base of the clade that includes other species of the genus Columba from the Old World. Laurel Pigeon probably represents an old lineage that might have colonized the Canary Islands a long time ago (20 My) while Bolle’s Pigeon might have arrived on the archipelago much later during the Upper Miocene (5 My). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

11.
12.
The biodiversity of honeybee (Apis mellifera) populations from Tenerife (Canary Islands, Spain) has been assessed by restriction analysis of a mitochondrial non-coding intergenic region. Seventy-nine colonies were analysed from thirteen apiaries in six populations that have been kept from recent queen introduction. The length and restriction pattern of the PCR amplified products of the intergenic region identified four mitochondrial haplotypes. One of these haplotypes shows the same restriction pattern and composition of the intergenic region carried by honeybees belonging to the African lineage. Two haplotypes are characterised by a particular intergenic region found with high frequency in the Canarian populations. The haplotype representative of the East European honeybee lineage shows a frequency of 35%, thus indicating introduction of queen honeybees. The finding of this haplotype in Canarian honeybees suggests that hybridisation between the endemic Apis mellifera populations and imported bees is occurring in Tenerife.  相似文献   

13.
How climate-change induced environmental stress may alter the effects of inbreeding in patchy populations of rare species is poorly understood. We investigated the fitness of progeny from experimental self- and cross-pollinations in eight populations of different size of Echium wildpretii, a rare endemic plant of the arid subalpine zone of the Canarian island of Tenerife. As control treatments we used open pollination and autonomous selfing. The seed set of open-pollinated flowers was 55% higher than that of autonomously selfed flowers, showing the importance of animal pollination for reproductive success. The seed set, seed mass and germination rate of seedlings of hand-selfed flowers was similar to that of hand-crossed flowers, indicating weak inbreeding depression (seed set –4.4%, seed mass –4.1%, germination –7.3%). Similarly, under normal watering there were no significant effects of inbreeding on seedling survival (–3.0%). However, under low watering of seedlings inbreeding depression was high (survival –50.2%). Seed set of open- and hand-outcrossed-pollinated flowers was higher in large than in small populations, possibly due to more frequent biparental inbreeding in the latter. However, later measures of progeny fitness were not significantly influenced by population size. We predict that increasing drought duration and frequency due to climate change and reductions of population sizes may increase inbreeding depression in this charismatic plant species and thus threaten its future survival in the longer term.  相似文献   

14.
We analyzed the variation in island bird communities of urban environments related to habitat characteristics, using regression/classification tree analyses. Data from field censuses in cities/towns representing the urban heterogeneity of the whole island were obtained in Tenerife (Canary Islands, Spain). Urban bird abundance in Tenerife was negatively affected by altitude and the cover of dry Euphorbia shrubs and positively influenced by the height and cover of the tree layer. Species richness was negatively associated with building cover and positively related to tree height and altitude. Data from field censuses in Tenerife were compared with that of similar urban environments in the mainland (Madrid Province, central Spain). Species diversity was higher in the urban sample of Tenerife than in that of Madrid and the proportion of bird species from the regional pool captured by urban environments was higher in the island than in the mainland. Nine native species and three alien species were more abundant in island urban environments than in the continent (densities, at least, 100% higher), the converse occurring for only five species. At a biogeographic scale, we conclude that the avifauna of Tenerife Island is more prone to occupy a new artificial environment than the mainland bird fauna of central Spain.  相似文献   

15.
Endemic species swarms constitute large fractions of the millipede faunas of Madeira (29 species of the Cylindroiulus madeirae group, plus six species of Acipes , out of a total of 60 species) and the Canary Islands (46 species of Dolichoiulus , plus four species of the Glomeris alluaudi-group , out of a total of about 79 species). The poorer faunas of the Azores (22 species) and the Cape Verde Islands (15 species) in contrast only include a few endemics. The Cylindroiulus madeirae group and Dolichoiulus show a high degree of diversity of structure (size, colour, leg length etc.) and habitat (laurisilva, xeric habitats, caves). The C. madeirae group, unlike Dolichoiulus , is strongly concentrated in the laurisilva. In this habitat, microhabitat differentiation is pronounced in both swarms.  相似文献   

16.
《Ostrich》2013,84(1):93-96
Nest predation is the leading cause of reproductive failure in birds and thus it shapes their life history strategies. Intensities of nest predation appear to differ among nest locations and types in both temperate and tropical regions. However, there is limited knowledge of factors influencing susceptibility of avian nests to predation in Africa. The aim of our study was to investigate artificial nest predation rates of different ground and shrub nests located at different heights in the rainforest undergrowth. We placed artificial avian nests within a homogeneous lowland forest interior with sparse forest undergrowth in the Mount Cameroon National Park, Cameroon. We exposed three sets of nests: 50 bare-ground, 50 cup-ground and 50 cup-shrub nests, for 10 d. Predation was higher for cup-ground nests compared to cup-shrub nests, and bare-ground nests were more depredated than cup-ground nests. We concluded that the presence of a cup as well as higher nest position significantly increased probability of artificial nest survival. The results of this study suggest a potential selection pressure on nest type and placement in lowland forest birds for a poorly known tropical region.  相似文献   

17.
In our six-year study, we investigated the dynamics of the meiofaunal community directly under the influence of a fish farm, in adjacent areas and in control areas outside the fish farm influence. Our data showed spatial, seasonal and annual variation in the meiofaunal community under the influence of the fish farm; however, no clear trend is discernible. Copepods are positively associated with mud and very fine sands, which seem to increase with time under the fish farm and adjacent areas, particularly in summer. As shown throughout the study period, copepods could soon take over other components of the community, resulting in a community shift. Our approach to investigate the dynamics of a community with a quick response to environmental changes proves useful to detect early-stage deviations from non-affected areas, which could be critical to distinguish environmental impacts before they cause major shifts in the environment.  相似文献   

18.
1. Empirical testing of optimal foraging models for breath-hold divers has been difficult. Here we report data from sound and movement recording DTags placed on 23 short-finned pilot whales off Tenerife to study the foraging strategies used to catch deep-water prey. 2. Day and night foraging dives had a maximum depth and duration of 1018 m and 21 min. Vocal behaviour during dives was consistent with biosonar-based foraging, with long series of echolocation clicks interspersed with buzzes. Similar buzzes have been associated with prey capture attempts in other echolocating species. 3. Foraging dives seemed to adapt to circadian rhythms. Deep dives during the day were deeper, but contained fewer buzzes (median 1), than night-time deep dives (median 5 buzzes). 4. In most deep (540-1019 m) daytime dives with buzzes, a downward directed sprint reaching up to 9 m s(-1) occurred just prior to a buzz and coincided with the deepest point in the dive, suggestive of a chase after escaping prey. 5. A large percentage (10-36%) of the drag-related locomotion cost of these dives (15 min long) is spent in sprinting (19-79 s). This energetic foraging tactic focused on a single or few prey items has not been observed previously in deep-diving mammals but resembles the high-risk/high-gain strategy of some terrestrial hunters such as cheetahs. 6. Deep sprints contrast with the expectation that deep-diving mammals will swim at moderate speeds optimized to reduce oxygen consumption and maximize foraging time at depth. Pilot whales may have developed this tactic to target a deep-water niche formed by large/calorific/fast moving prey such as giant squid.  相似文献   

19.
Plant Ecology - Invasive alien species and climate change are two of the main current threats to conservation of biodiversity worldwide. Their effects have been extensively studied individually,...  相似文献   

20.
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