Diversity Patterns and Community Structure of the Ground-Associated Macrofauna along the Beach-Inland Transition Zone of Small Tropical Islands

Biodiversity follows distinct and observable patterns. Where two systems meet, biodiversity is often increased, due to overlapping occurrence ranges and the presence of specialized species that can tolerate the dynamic conditions of the transition zone. One of the most pronounced transition zones occurs at shores, where oceans and terrestrial habitat collide, forming the shore–inland transition zone. The relevance of this transition zone in shaping a system’s community structure is particularly pronounced on small islands due to their high shore-to-inland-area ratio. However, the community structure of insular faunas along this transition zone is unknown. Here, we investigated the diversity patterns along the beach–inland transition zone of small islands and tested the hypothesis that species diversity increases toward the transition zone where beach and interior habitat meet. By measuring environmental parameters, resource availability, and ground-associated macrofauna diversity along transects running across the beach–inland transition zone, we show that a gradual change in species composition from beach to the inland exists, but neither taxa richness, diversity, nor overall abundance changed significantly. These findings offer important insights into insular community structure at the transition zone from sea to land that are relevant to better understand the dynamic and unique characteristics of insular ecosystems.

Giants Among Dwarfs: The Arrival Of A New Clade Of Southern Dinosaurs In The Latest Cretaceous Of Europe

The origin of the last sauropod dinosaur communities in Europe and their evolution in the last 15 million years of the Cretaceous has become a complex phylogenetic and paleobiogeographic puzzle portrayed by the controversy on the alleged coexistence of immigrant Gondwana-related taxa alongside relictual and insular clades. In this context, here we describe a new titanosaurian sauropod dinosaur, Abditosaurus kuhnei gen. et sp. nov., from the Upper Cretaceous (Maastrichtian) Tremp Group of Catalonia (Spain). Phylogenetic analyses recover Abditosaurus separately from the rest of European titanosaurs, within a clade of South American and African saltasaurines. The affinity of the new taxon with southern landmasses is reinforced by the spatiotemporal co-occurrence with Gondwanan titanosaur oospecies in southern Europe. The large size and the lack of osteohistological features related to insular dwarfism support the idea that Abditosaurus belongs to an immigrant lineage, unequivocally distinct from the island dwarfs of the European archipelago. The arrival of Abditosaurus lineage to the Ibero-Armorican island is hypothesized to have occurred at the earliest Maastrichtian (72 Ma), probably as a result of a global and regional sea-level drop that reactivated the ancient dispersal routes between NW Africa and SW Europe. The arrival of large-bodied titanosaurs to the European archipelago produced dramatic changes in the insular ecosystems and important evolutionary changes in the dinosaur faunas, especially with respect to the ‘island rule’ effect.

Tail breakage and predatory pressure upon two invasive snakes (Serpentes: Colubridae) at two islands in the Western Mediterranean

Tail breakage is an important anti-predator mechanism in snake populations, which can be used as a proxy for predation intensity as natural observations of predator-prey interactions are scarce. Frequency of tail breakage was calculated for two Iberian colubrids recently introduced in the Balearic Islands (Western Mediterranean, Spain): Hemorrhois hippocrepis (Linnaeus, 1758) in Eivissa and Zamenis scalaris (Schinz, 1812) in Formentera. The effect of sex, life-stage, dorsal coloration pattern, body length and body condition on frequency of tail breakage and on remaining subcaudal scale pairs (SBC) were analyzed and compared between the native range and the invaded islands. An increase of the frequency of tail breakage with body size was found, supporting a size-related effect, which also occurs in the native range. Frequency of tail breakage of H. hippocrepis was lower in Eivissa when compared with the original area, while in Formentera Z. scalaris showed a higher frequency, which could be related to the different predator community on each island compared with the mainland. The study of the main ecological aspects of these recent introduced species may allow to assess their potential impact on insular ecosystems and their native biodiversity as well as to promote future control actions in these areas previously free of snakes.

Cissus quadrangularis (treebine).

Cissus quadrangularis is an aggressive fast-growing vine that has been cultivated primarily as a garden ornamental and medicinal plant. This species escaped from cultivation and can now be found naturalized in dry forests, coastal thickets, forest edges, savannas and scrublands across dry, arid and semiarid habitats in tropical and warm temperate regions of the world. It has become an invasive species with detrimental impacts mostly on insular ecosystems. C. quadrangularis is a vigorous vine that spreads both vertically and horizontally forming dense monospecific stands that outcompete native vegetation. It climbs over trees and shrubs, covering them entirely, blocking light and thus restricting the growth and regeneration of native plants. It may kill or break down trees and shrubs that support it due to its weight. This species is able to inhabit areas subject to water stress and has the potential to spread sexually by seeds and vegetatively by stem fragments.

Pentas lanceolata (Egyptian starcluster).

Pentas lanceolata is a fast growing, small to medium-sized herbaceous shrub that has become very popular as an ornamental and potted plant due to its colourful flowers. It is adapted to grow in a wide range of environmental conditions and tolerates a fair amount of drought. P. lanceolata has been intentionally introduced into many tropical and subtropical regions from where it has escaped to colonize predominantly disturbed sites, open grounds and roadsides near cultivation areas. Once established this species may become dominant in some open areas and can form monospecific stands with the potential to outcompete and exclude native plant species and other early successional vegetation. To date, P. lanceolata has been listed as invasive only in insular ecosystems in Hawaii, Anguilla, Norfolk Island, Mayotte Island and French Polynesia. In Hawaii, it has recently been noted spreading across the Big Island; on Maui, it volunteers in scrub areas and steep banks.

Future climate change vulnerability of endemic island mammals

Despite their high vulnerability, insular ecosystems have been largely ignored in climate change assessments, and when they are investigated, studies tend to focus on exposure to threats instead of vulnerability. The present study examines climate change vulnerability of islands, focusing on endemic mammals and by 2050 (RCPs 6.0 and 8.5), using trait-based and quantitative-vulnerability frameworks that take into account exposure, sensitivity, and adaptive capacity. Our results suggest that all islands and archipelagos show a certain level of vulnerability to future climate change, that is typically more important in Pacific Ocean ones. Among the drivers of vulnerability to climate change, exposure was rarely the main one and did not explain the pattern of vulnerability. In addition, endemic mammals with long generation lengths and high dietary specializations are predicted to be the most vulnerable to climate change. Our findings highlight the importance of exploring islands vulnerability to identify the highest climate change impacts and to avoid the extinction of unique biodiversity.