Aim
Understanding the historical and contemporaneous drivers of invasion success in island systems can decisively contribute to identifying sources and pathways that are more likely to give rise to ...new invaders. Based on a floristic‐driven approach, we aimed at determining the origins of the invasive alien flora of the Canary Islands and shedding light in the mechanisms shaping their distribution within the archipelago.
Location
Canary Islands.
Taxon
Vascular plants.
Methods
An updated checklist of the invasive alien flora of the Canary Islands was assembled along with complementary information related to the native biogeographical regions, stage of invasiveness and dates of naturalization. Statistical models were employed to describe differences in the number of species over space and time. We also used multivariate techniques to evaluate competing hypotheses related to the mechanisms driving invasive floristic composition within the archipelago.
Results
We provided a list of 149 alien plant species with a certain degree of invasiveness. The greatest number of invasive species originated from the Neotropics followed by the Cape Region, tropical Africa and the Mediterranean Basin. We observed a slow but steady increase in numbers of invasive species until the 1950s, followed by a stronger rise thereafter. In order to explain composition dissimilarity of the invasive flora among islands, a climatic matching hypothesis was fully supported, with geographic isolation and contemporary human‐mediated connectivity hypotheses receiving less and null support respectively.
Main Conclusions
We showed that the Neotropical region is the main source of plant invasions to the Canary Islands, outnumbering those from other regions with a Mediterranean‐type bioclimate. The assembly of the invasive flora within the archipelago appears to be driven primarily by climate, but with geographic distance also playing a role. This study calls for archipelago‐dependent assessments of the underlying mechanisms that contribute to plant invasion success within insular systems.
Geographic isolation substantially contributes to species endemism on oceanic islands when speciation involves the colonisation of a new island. However, less is understood about the drivers of ...speciation within islands. What is lacking is a general understanding of the geographic scale of gene flow limitation within islands, and thus the spatial scale and drivers of geographical speciation within insular contexts. Using a community of beetle species, we show that when dispersal ability and climate tolerance are restricted, microclimatic variation over distances of only a few kilometres can maintain strong geographic isolation extending back several millions of years. Further to this, we demonstrate congruent diversification with gene flow across species, mediated by Quaternary climate oscillations that have facilitated a dynamic of isolation and secondary contact. The unprecedented scale of parallel species responses to a common environmental driver for evolutionary change has profound consequences for understanding past and future species responses to climate variation.
Using a community of beetle species, we show that when dispersal ability and climate tolerance are restricted, microclimatic variation over distances of only a few kilometres can maintain strong geographic isolation extending back several millions of years. Further to this, we demonstrate congruent diversification with gene flow across species, mediated by Quaternary climate oscillations that have facilitated a dynamic of isolation and secondary contact.
The main vegetation units of the Canary Islands are briefly described and their current surface area established. The area of potential natural vegetation remnants is compared with the supposed ...original area, and expressed also as percent persistence, (area now/potential) × 100. We state that although the islands have between 40 and 50% of their surface under protection, several units of the most representative vegetation (e.g. like Euphorbia scrubs, thermo-sclerophyllous woodland and laurel forest) have retreated greatly, sometimes with little possibility of recovery. Willow, palm, tamarisk, and Plocama pendula communities, sandy beach vegetation, and small-area littoral ecosystems are also severely diminished in area. Comments are made about the conservation status of the most representative communities.
•P. halepensis is expanding at short distance and at several kilometres from plantations in La Gomera.•That expansion is especially affecting the potential areas of endemic Juniper ...woodlands.•Legislation and classification system in the Canary Islands must change to start considering this species as invasive.
Aleppo pine (Pinus halepensis Miller) has been one of the most used Pinus species in reforestation in the Mediterranean Basin and in many other regions outside its native range. Its massive use in plantations combined with its low environmental requirements, relatively short juvenile period and adaptability to human disturbance make P. halepensis a great competitor for local species, becoming invasive in many natural and anthropized areas. As little is known about the effects of these plantations on oceanic islands ecosystems, we evaluated in this study the expansion dynamics of a series of P. halepensis plantations carried out on the island of La Gomera (Canary Islands) in the 1960s and 1970s of the past century. At short distance, we counted and measured P. halepensis individuals along transects of 140 m from the inside of the plantation to the outside, assessing also the proportion occupied by other native, endemic and ruderal species in two habitat types: thermo-sclerophyllous woodlands and laurel forests. To examine seed dispersal over longer distances, we selected one of the areas that showed a greater expansion and we analyzed factors influencing regeneration. Our results revealed that expansion is occurring mostly in open or disturbed areas instead of closed-canopy humid forests and we found a clear negative relationship between the presence of the species and the abundance of other trees or the endemic and native flora. Furthermore, we detected potential new foci of regeneration away from the plantations too. Overall, we suggest that the status of P. halepensis as a non-native species and its classification for the purposes of management in the Canary Islands needs to be re-examined.
Different spatial interpolation techniques have been applied to construct objective bioclimatic maps of La Palma, Canary Islands. Interpolation of climatic data on this topographically complex island ...with strong elevation and climatic gradients represents a challenge. Furthermore, meteorological stations are not evenly distributed over the island, with few stations at high elevations. We carried out spatial interpolations of the compensated thermicity index (Itc) and the annual ombrothermic Index (Io), in order to obtain appropriate bioclimatic maps by using automatic interpolation procedures, and to establish their relation to potential vegetation units for constructing a climatophilous potential natural vegetation map (CPNV). For this purpose, we used five interpolation techniques implemented in a GIS: inverse distance weighting (IDW), ordinary kriging (OK), ordinary cokriging (OCK), multiple linear regression (MLR) and MLR followed by ordinary kriging of the regression residuals. Two topographic variables (elevation and aspect), derived from a high-resolution digital elevation model (DEM), were included in OCK and MLR. The accuracy of the interpolation techniques was examined by the results of the error statistics of test data derived from comparison of the predicted and measured values. Best results for both bioclimatic indices were obtained with the MLR method with interpolation of the residuals showing the highest R ² of the regression between observed and predicted values and lowest values of root mean square errors. MLR with correction of interpolated residuals is an attractive interpolation method for bioclimatic mapping on this oceanic island since it permits one to fully account for easily available geographic information but also takes into account local variation of climatic data.
The Canary Islands belong to Mediterranean basin hotspot, especially because their rich endemic flora. Nearly 40% of the total archipelago area is protected through protected natural area network. ...However, some plant communities show high degree of disturbance or they develop in unprotected zones. So, multivariate analysis combined with vegetation mapping can be useful for identify, describe and protect the main plant communities. These tools have been applied in Caldera de Taburiente national park (La Palma. Canary Islands). An actual vegetation map of this park is showed and its major natural vegetation units are described. These tools could be applied to other protected and unprotected areas, especially for planning, management and conservation purposes.
The monitoring of ecosystems and forests is an urgent requirement in the current framework of global change. It is particularly necessary on oceanic islands where their rich biodiversity is highly ...vulnerable, with many narrow-ranged endemic species. Quantifying and mapping forest health through key ecological variables are essential steps for management, but it will also be challenging and may require a lot of resources. Remote sensing has the potential to be a very useful tool to assess the development and conservation status of forests. We assessed the applicability of the light detection and ranging (LiDAR) on the laurel forests of La Gomera, making allometric equations for various measurements of the forest structure, linking field inventory from 2019 and 2017 LiDAR data through standard linear regressions. Decision trees and logistic regressions were also used to assess the performance of LiDAR in the recognition of young-growth and old-growth laurel forests. The obtained allometric models were a good fit in general and their predictions were in line with already known data. Likewise, decision tree and logistic regression to distinguish young-growth and old-growth forests had a similar performance in both cases, with a high to medium-high degree of accuracy. Therefore, LiDAR was revealed to be a useful tool for the monitoring of the laurel forest by the managers.
Post-fire salvage logging (SL) is a common management action that involves the harvesting of burnt trees. As a consequence, a large amount of biological legacies in the form of logs and other coarse ...woody debris are removed from the post-fire habitat, creating a more simplified landscape. Therefore, SL could act as an additional disturbance over that produced by fire. In this study, we seek to determine the effect of SL on the regeneration of the bryophyte community of a laurel forest from the Canary Islands (Spain). We hypothesized that SL will act as an additional disturbance and, consequently, salvaged areas will have a higher difference in community composition with respect to a reference ecosystem (RE). Mosses and liverworts were sampled 22 months after the salvage operations in salvaged plots, non-salvaged, and in an RE represented by areas of the original forest. Species richness did not differ between salvage and non-salvaged treatments. However, multivariate analysis and species-indicator analysis showed that non-salvaged plots had a composition closer to that of the RE, with a higher proportion of closed-canopy, perennial, and long-lived species, as well as some epiphytes. By contrast, salvaged plots were dominated by early-successional terrestrial species and species preferring open habitats. We conclude that post-fire SL represents an additional disturbance that further delays succession, a result that is consistent with previous studies using other taxonomic groups. SL should therefore be avoided or, if implemented, the possibility of leaving part of the post-fire biological legacies in situ should be considered.
The endemic flora of the Canary Islands is remarkable but highly vulnerable to environmental changes. Several factors, such as fire, could be threatening. The purpose of this study was to analyze ...various treatments in endemic threatened species which could have been growing in the understory of the Canary pine forest. We attempted to improve germination through dormancy breaking, and analyze the influence of fire on these plants. Seven physical and chemical treatments were tested: control, mechanical scarification, boiling water, dry heat (50 and 120 °C), smoke and smoked water. Mechanical scarification showed a positive response in germination percentage in two species characterized by hard seed coat, but out of all of the species tested, only one demonstrated a positive response to any of the treatments related to fire. At the temperatures registered on wildfires, neither the seeds situated on the aerial structure nor seeds in seed bank seem to be able to survive and germinate. The increasing incidence of fires through anthropogenic causes could contribute to the current threat status of these species and poorness of the Canary pine forest understory.
PDF
