Félix Manuel Medina

In autumn 2021, the largest volcanic eruption on the island of La Palma in historic records took place. The Canary Islands are of volcanic origin and eruptions have always constituted part of their natural disturbance regime. Until recently, their impacts could not be directly observed and studied. Influence of the emission of phytotoxic gases on biodiversity and ecosystem dynamics was hitherto unknown. The recent eruption is still being intensely monitored. We used Sentinel-2 remote sensing data to analyze the spatial extent and intensity of the impact related to sulfuric emissions, aiming to understand the damage patterns in Canary pine forest. The emissions damaged 10% of that forest and affected 5.3% of the Natura 2000 protected areas. We concluded that this is largely due to the toxic effects of the enormous emissions of SO2. We found a clear correlation between the change in the normalized difference vegetation index (NDVI) and distance from the eruption. This pattern was weak...

La introduccion de especies exoticas es la mayor amenaza para la biota y los ecosistemas en islas, por delante incluso de la destruccion y alteracion del habitat, considerado el principal factor de perdida de biodiversidad a nivel mundial. Una de las especies introducidas que mas impacto ha causado en la conservacion de la fauna nativa en islas de todo el mundo es el gato cimarron. Son unos depredadores generalistas y oportunistas y se alimentan de una amplia variedad de presas, incluyendo especies insulares endemicas y amenazadas. El archipielago canario es uno de las areas insulares del mundo donde la dieta de este depredador ha sido estudiada en mayor profundidad. Sin embargo, existen algunos vacios de informacion relativos a la ecologia trofica en islas oceanicas de ambientes heterogeneos y semiaridos presentes en Canarias, asi como sobre la amenaza sobre las poblaciones de invertebrados endemicos. Ademas, y una vez completados esos vacios de informacion sobre la dieta, era nece...

Biological invasions are a major global threat to biodiversity and often affect ecosystem services negatively. They are particularly problematic on oceanic islands where there are many narrow-ranged endemic species, and the biota may be very susceptible to invasion. Quantifying and mapping invasion processes are important steps for management and control but are challenging with the limited resources typically available and particularly difficult to implement on oceanic islands with very steep terrain. Remote sensing may provide an excellent solution in circumstances where the invading species can be reliably detected from imagery. We here develop a method to map the distribution of the alien chestnut (Castanea sativa Mill.) on the island of La Palma (Canary Islands, Spain), using freely available satellite images. On La Palma, the chestnut invasion threatens the iconic laurel forest, which has survived since the Tertiary period in the favourable climatic conditions of mountainous i...

Rabbits are invasive to the Canary Islands, where they were introduced 500 years ago, during the conquest, from mainland Spain. Nowadays, they occupy all islands, almost all islets, and all the habitats of the archipelago. Rabbit negative impacts are manifested at different ecological levels, from affecting species population, to disrupt native networks of interactions, or to even cause the complete alteration of the structure of the ecosystem. Current ongoing researches in various ecosystems are very concluding: we are far from knowing how would be the natural looking of the ecosystems of the islands, and today we only see what is left after 500 years of herbivorous pressure. It is urgent to raise awareness of this serious problem to subsequently implement appropriate conservation measures to control and minimize the effects that rabbits are provoking to the incomparable and unique ecosystems of the Canary Islands.

Se estudia la distribución del gato cimarrón (Felis catus) en la isla de Alegranza y la evolución de su dieta en los últimos diez años (1987/1997). Los gatos se distribuyeron en todos los hábitats de la isla, siendo La Caldera donde se detectó el mayor número de excrementos (40,9%). ...

Assessing the environmental status of Protected Areas (PAs) is a challenging issue. To indicate that status, the identification of a common set of variables that are scientifically sound, and easy to assess and monitor by the PA practitioners, is particularly important. In this study, a set of 27 Essential Variables (EVs) for PA management was selected in a bottom-up process from 67 harmonised variables that describe the status of Ecosystem Functions and Structures, Ecosystem Services, and Threats in PAs. This bottom-up process involved 27 internationally recognised PAs, mostly European, with different level of protection, different extent, and a wide range of human-nature interactions. The EVs were selected by more than 120 practitioners, i.e. PA managers and rangers, as well as scientists, working in terrestrial and aquatic PAs. Across both terrestrial and aquatic PAs, scientists and practitioners largely identified the same variables as important. Data availability for these 27 EVs varied between PAs and averaged 67% across all studied PAs. As this set of EVs for PAs is defined through a bottom-up approach considering variables already in use both in management and research, it is more than for previous EVs likely to be adopted, applied and developed to record the status and changes in the ecological and socio-economic conditions of PAs and to forecast future changes. Thereby, the EVs for PAs present a common vocabulary and tool to enhance in a uniform way the (inter)national communication, exchange and comparison of information on the status of PAs between policy makers, scientists and PA managers. The perceived status of the EVs, on an average 3.6 on a scale to a maximum of 5, indicates the surveyed PAs are in a moderate to good environmental condition. Moreover, the EVs for PAs form a cost- and time-efficient tool for PA managers to monitor developments in essential elements of their PAs, including the potential for Societal Goods and Benefits (SG&B), and to (pro-)actively tackle the potential threats that may arise in their area. Likewise, for policy makers EVs for PAs may support decision making on ecosystem management, spatial planning, and predictive modelling on the future status and requirements of PAs in their country or region.

In this paper we present an unusual incidence of an introduced Camivora Felis catus as indirect seed disperser of plants that produce fleshy fruits in different ecosystems in the Canary Islands. Four hundred and twenty six seeds from at least 8 fleshy fruit plant species have been identified in the analysis of 1047 scat groups, the majority of them being found in the lower habitats (<600 m a.s.l.) of the Canary archipelago. Seeds from two plant species were significantly matched with the presence of lizard prey, and fruits of Juniperus phoenicea, Neochamaelea pulverulenta and Withania aristata were directly consumed by the cats. Passing through the gut of the Gallotia galloti (Lacertidae) and Felis catus apparently does not damage the seeds. At the moment, the phenomenon studied in this paper does not seem to have a great quantitative importance in the natural regeneration of the plants if we compare the direct vs indirect seed dispersal.

Predation of insects by feral cats (Felis silvestris catus) on a heterogeneous oceanic island (La Palma, Canary Islands) was studied. A total of 127 invertebrates were identified in the analysis of 500 scats (100 from each habitat of the Island). Invertebrates appear in 18.00% of the scats, representing an insignificant percentage of the total consumed biomass by feral cats on La Palma Island (0.05%). Insects were the most common invertebrate prey both in percentage of occurrence (90.6%) and invertebrate biomass (93.53%), with a total of 115 prey items. Orthoptera, Lepidoptera and Coleoptera were the main prey groups. Among the five main habitats present in La Palma Island, the temperate forest shows the lowest consumption of invertebrates, although insect consumption did not show statistical differences. However Orthoptera and Lepidoptera were more frequently preyed on in the pine forest and in the xerophytic shrub, respectively. Moreover, applying the Simplified Morisita index, a different insect composition of the diet was observed among habitats. Although, none of insects predated by feral cats are threatened, the identification of invertebrate component of the feral cats’ diet is an important tool for the correct understanding of predation significance and to prevent damage to endangered insect species.

AimFew data sets exist on the role of gulls as seed dispersal agents. Our purpose is to quantify the number of seeds dispersed, to assess damage to the seeds regurgitated and those expelled via cloaca, to check for possible differences in seed viability and germination rates, to study the seed retention time, and to evaluate gulls as adequate dispersal agents throughout the Canary Islands and for the colonization of this archipelago by this plant species (or its ancestor), from Africa.Few data sets exist on the role of gulls as seed dispersal agents. Our purpose is to quantify the number of seeds dispersed, to assess damage to the seeds regurgitated and those expelled via cloaca, to check for possible differences in seed viability and germination rates, to study the seed retention time, and to evaluate gulls as adequate dispersal agents throughout the Canary Islands and for the colonization of this archipelago by this plant species (or its ancestor), from Africa.LocationThis study was developed in ‘Los Islotes’, a small archipelago located off the northern part of Lanzarote Island (Canaries).This study was developed in ‘Los Islotes’, a small archipelago located off the northern part of Lanzarote Island (Canaries).MethodsWe counted the number of seeds in each pellet and dropping collected and we measured and weighed them. Seed viability and germination from the three treatments (plants, pellets and droppings) were studied. Gut pass time (GPT) was assessed in two gulls by using glass beads (similar in size with Rubia fruticosa Ait. seeds). We employed a combination of univariate and bivariate statistical tests to analyse the data.We counted the number of seeds in each pellet and dropping collected and we measured and weighed them. Seed viability and germination from the three treatments (plants, pellets and droppings) were studied. Gut pass time (GPT) was assessed in two gulls by using glass beads (similar in size with Rubia fruticosa Ait. seeds). We employed a combination of univariate and bivariate statistical tests to analyse the data.ResultsFrom 81 pellets and 84 droppings, we extracted a total of 60,679 seeds (48,460 and 12,219, respectively). Data obtained in the GPT experiments show that a similar number of seeds are defecated and regurgitated. No externally damaged seed was observed and the majority were viable, giving more than 95% in all treatments (seeds from plants, droppings and pellets). Most seeds on these treatments showed germination rates of over 80%, verifying the importance of the gulls as legitimate dispersers of this Macaronesian endemic plant species. Taking into account that the gulls’ flight cruise speed is about 31–40 km h–1 and mean GPT of these birds is between 9.51 and 16.92 h, they could cover a distance between 295 and 677 km before expelling the seeds. This distance is well within the range of colonization of the different islands of the Canaries and the neighbouring archipelagos of Salvages and Madeira from the north-west of Africa, where the ancestor of this plant may have originated.From 81 pellets and 84 droppings, we extracted a total of 60,679 seeds (48,460 and 12,219, respectively). Data obtained in the GPT experiments show that a similar number of seeds are defecated and regurgitated. No externally damaged seed was observed and the majority were viable, giving more than 95% in all treatments (seeds from plants, droppings and pellets). Most seeds on these treatments showed germination rates of over 80%, verifying the importance of the gulls as legitimate dispersers of this Macaronesian endemic plant species. Taking into account that the gulls’ flight cruise speed is about 31–40 km h–1 and mean GPT of these birds is between 9.51 and 16.92 h, they could cover a distance between 295 and 677 km before expelling the seeds. This distance is well within the range of colonization of the different islands of the Canaries and the neighbouring archipelagos of Salvages and Madeira from the north-west of Africa, where the ancestor of this plant may have originated.Main conclusionsThe results support the idea that gulls could have been one of the main agents responsible for the movement of R. fruticosa seeds among the islands of the Canaries and for the colonization of the Macaronesian archipelagos from Africa. Furthermore, this study suggests that gulls are generalist feeding seabirds with high capacity for seed transport and high long-distance power displacements, could have played a more important role than that currently recognized by most authors, in the colonization of oceanic islands by some plants whose genetic origins were located at long-distances.The results support the idea that gulls could have been one of the main agents responsible for the movement of R. fruticosa seeds among the islands of the Canaries and for the colonization of the Macaronesian archipelagos from Africa. Furthermore, this study suggests that gulls are generalist feeding seabirds with high capacity for seed transport and high long-distance power displacements, could have played a more important role than that currently recognized by most authors, in the colonization of oceanic islands by some plants whose genetic origins were located at long-distances.

... new food resource that has been utilized by several groups of birds, notably of the family Otididae, eg Great Bustard Otis tarda and ... and their use for feeding encouraged the Canary Island government to include them in the species&amp;#x27;s recovery plan (F. Dominguez-Casanova and ...

Feral cats have been directly responsible for the extinction of numerous species on islands worldwide, including endemic species of mammals, birds and reptiles. The diet of feral cats in the main habitats of the Canary Islands, as generally occurred on oceanic islands, is mainly composed of introduced mammals, and native species of birds, reptiles and insects. The impact of feral cat upon the endangered species was assessed by evaluating their relative abundance in the cats’ diet and by considering their current conservation status. A total of 68 different preys were identified at species level in all studies carried out in the Canary Islands (5 mammals, 16 birds, 15 reptiles and 32 invertebrates). From all the species preyed by feral cats in the Canary Islands, only four of them are considered threatened by the IUCN Red List of Threatened Species: one endemic bird Saxicola dacotiae and three endemic giant lizards, Gallotia simonyi, Gallotia intermedia, and Gallotia gomerana. Although some efforts on management control have been carried out, it is necessary to enforce these conservation activities on those areas of Tenerife, La Gomera and El Hierro where giant lizards are still present. Furthermore some local areas where endangered bird species are highly predated should be protected. Nevertheless, it is important to take into account the presence of other introduced species such as rats, mice or rabbits in order to avoid problems derived from the hyperpredation process and mesopredator release effect.