Linking Man and Nature: Relictual Forest Coenosis with Laurus nobilis L. and Celtis australis L. in Antica Lavinium, Italy

The Mediterranean basin has been a refugium for relict plant taxa and native laurophyllic forests. The Latium coasts and, especially, the Antica Lavinium site, host relict forest communities, whose natural importance is enriched by their cultural value. Here, we aim at investigating the ecological framework, cultural and historical values, and management over time, of relict communities that have Laurus nobilis and Celtis australis as their priority habitats. To achieve this, we performed vegetation surveys and we conducted statistical analyses (PCA, NMDS). Among the 45 vegetation surveys, 25 were characterized by the two target species. The PCA analysis highlighted how the L. nobilis formations and the mixed formations with C. australis present some differences but are not sufficient to describe different coenosis. The comparison among similar forests in central and southern Italy confirmed the wide coenological amplitude of L. nobilis with respect to other laurophyllic species. Antica Lavinium has an overall good preservation of laurel forest formations, but also of mixed formation with C. australis. In the area, historical, cultural, and natural characteristics mutually contributed to the development of human civilizations and plant communities, highlighting their deep linkage.

The Madeiran laurel forest endemic Goodyera macrophylla (Orchidaceae) is related to American orchids

Macaronesian laurel forests harbour many herbs and laurophyllous trees with Mediterranean/European or Macaronesian affinities. Traditionally, the origin of these taxa has been explained by the relict hypothesis interpreting these taxa as relics of formerly widespread laurel forests in the European continent and the Mediterranean. We analysed the phylogenetic relationships of the Madeiran laurel forest endemic Goodyera macrophylla (Orchidaceae) using sequences from the nuclear ribosomal DNA Internal Transcribed Spacers (ITS) and plastid DNA regions. The results were incongruent, either the two Central American G. brachyceras and G. striata (ITS) or the North American G. oblongifolia (plastid DNA) were sister group to G. macrophylla. Nonetheless, biogeographic analyses indicated an American origin of this nemoral laurel forest plant in the two data sets. Molecular clock analyses suggest a colonisation of Madeira in the span of the upper Miocene/lower Pliocene to the Pleistocene. Although the relict hypothesis cannot be ruled out by our data when assuming extinction events on the European and northern African mainland, dispersal from Central or North America to the archipelago of Madeira is a much more likely explanation of the data.

Flightlessness in insects enhances diversification and determines assemblage structure across whole communities

Dispersal limitation has been recurrently suggested to shape both macroecological patterns and microevolutionary processes within invertebrates. However, because of potential interactions among biological, environmental, temporal, and spatial variables, causal links among flight-related traits, diversification and spatial patterns of community assembly remain elusive. Integrating genetic variation within species across whole insect assemblages, within a simplified spatial and environmental framework, can be used to reduce the impact of these potentially confounding variables. Here, we used standardized sampling and mitochondrial DNA sequencing for a whole-community characterization of the beetle fauna inhabiting a singular forested habitat (laurel forest) within an oceanic archipelago setting (Canary Islands). The spatial structure of species assemblages together with species-level genetic diversity was compared at the archipelago and island scales for 104 winged and 110 wingless beetle lineages. We found that wingless beetle lineages have: (i) smaller range sizes at the archipelago scale, (ii) lower representation in younger island communities, (iii) stronger population genetic structure, and (iv) greater spatial structuring of species assemblages between and within islands. Our results reveal that dispersal limitation is a fundamental trait driving diversity patterns at multiple hierarchical levels by promoting spatial diversification and affecting the spatial configuration of entire assemblages at both island and archipelago scales.

Assessing the Potential Replacement of Laurel Forest by a Novel Ecosystem in the Steep Terrain of an Oceanic Island

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 islands in the trade wind zone. We detect chestnut presence by taking advantage of the distinctive phenology of this alien tree, which retains its deciduousness while the native vegetation is evergreen. Using both Landsat 8 and Sentinel-2 (parallel analyses), we obtained images in two seasons (chestnuts leafless and in-leaf, respectively) and performed image regression to detect pixels changing from leafless to in-leaf chestnuts. We then applied supervised classification using Random Forest to map the present-day occurrence of the chestnut. Finally, we performed species distribution modelling to map the habitat suitability for chestnut on La Palma, to estimate which areas are prone to further invasion. Our results indicate that chestnuts occupy 1.2% of the total area of natural ecosystems on La Palma, with a further 12–17% representing suitable habitat that is not yet occupied. This enables targeted control measures with potential to successfully manage the invasion, given the relatively long generation time of the chestnut. Our method also enables research on the spread of the species since the earliest Landsat images.

Asexual Regeneration Response of Ilex canariensis Poir. to Management of the Canopy of Pinus radiata D.Don

Exotic afforestation can provide suitable conditions for native shade-tolerant species restoration without threatening native forests. This study analyzes the impact of different thinning intensities of the canopy of an exotic Pinus radiata stand on the asexual regeneration response of Ilex canariensis, a native laurel forest species in the Canary Islands, Spain. The results provide useful indications for how to manage P. radiata stands to promote recovery of native plant communities. For different stand treatments were selected: stand clear cut, low intensity thinning (10–15%), high intensity thinning (25%), and a control. The stand clear cut management revealed Ilex canariensis individuals with a higher number of sprouts and more leaf cover; however, the height of these sprouts two years after the cut did not reach the values of individuals prior to this management. Consequently, the vitality index following clear cut management is significantly lower with respect to the other treatments. Thinning management is shown not to be so useful to promote the growth and vitality of Ilex canariensis individuals. The results suggest that thinning over 50% could be more appropriate in the case of Pinus radiata, allowing resprouting of Ilex canariensis in the understory and improvement in the vitality index.

Oromia orahan (Curculionidae, Molytinae), a new subterranean species for the Canarian underground biodiversity

A new blind weevil belonging to the genus Oromia Alonso-Zarazaga, 1987 is described, being found in the underground of the laurel forest of La Gomera (Canary Islands). Individuals were mainly collected in a colluvial mesocavernous shallow substratum, besides one specimen collected in the deep humic layer of soil. This new species has clear diagnostic differences from the other Oromia species. The number of taxa in this endemic Canarian genus increases to four species, easily identified using the key provided in this article. New data on other Canarian subterranean weevils are also provided.