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Most of our understanding of island diversity comes from the study of aboveground systems, while the patterns and processes of diversification and community assembly for belowground biotas remain poorly understood. Here, we take advantage of a relatively young and dynamic oceanic island to advance our understanding of ecoevolutionary processes driving community assembly within soil mesofauna. Using whole organism community DNA (wocDNA) metabarcoding and the recently developed metaMATE pipeline, we have generated spatially explicit and reliable haplotype‐level DNA sequence data for soil mesofaunal assemblages sampled across the four main habitats within the island of Tenerife. Community ecological and metaphylogeographic analyses have been performed at multiple levels of genetic similarity, from haplotypes to species and supraspecific groupings. Broadly consistent patterns of local‐scale species richness across different insular habitats have been found, whereas local insular richness is lower than in continental settings. Our results reveal an important role for niche conservatism as a driver of insular community assembly of soil mesofauna, with only limited evidence for habitat shifts promoting diversification. Furthermore, support is found for a fundamental role of habitat in the assembly of soil mesofauna, where habitat specialism is mainly due to colonization and the establishment of preadapted species. Hierarchical patterns of distance decay at the community level and metaphylogeographical analyses support a pattern of geographic structuring over limited spatial scales, from the level of haplotypes through to species and lineages, as expected for taxa with strong dispersal limitations. Our results demonstrate the potential for wocDNA metabarcoding to advance our understanding of biodiversity. [ABSTRACT FROM AUTHOR]

Aim: Habitat diversity has been linked to the diversity and structure of island communities, however, little is known about patterns and processes within habitats. Here we aim to determine the contributions of habitat type and inferred dispersal frequency to the differences in taxonomic structure between assemblages in the same island habitat. Location: The Macaronesian archipelagos (Azores, Madeira, the Canary Islands and Cabo Verde). Taxon: Spiders (Araneae). Methods: We established forest and dry habitat sites (each with five plots) on two islands per archipelago. We collected spiders using standardised sampling protocols. We tested the differences in beta diversity separately for each habitat and for each inferred category of ballooning (an aerial dispersal strategy) frequency across geographic scales through nested non-parametric permutational multivariate analyses of variance. We then tested whether ballooning and habitat influenced heterogeneity in species composition (dispersion in beta diversity) in the two habitat types. We analysed the effects of habitat and ballooning on species abundance distribution (SAD) and rarity by fitting Gambin models and evaluating the contribution of ballooning categories to SAD. Results: Communities of the same archipelago and habitat were taxonomically more similar, and beta diversity increased with geographic scale, being greater in dry habitats. There was greater species replacement among assemblages in dry habitats than in forests, with greater differences for rare ballooners. There were no differences in SAD between habitats although dry habitat sites seemed to harbour more species with low abundances (rare species) than forests. Main conclusions: Habitat type does not only condition the differences between spider assemblages of the same habitat but also the scale at which they occur. These differences may be determined by the heterogeneity in the physical structure of each habitat as well as how much this structure facilitates aerial dispersal (ballooning), and should be considered in theories/hypotheses on island community assembly as well as in conservation strategies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aim The majority of documented extinctions world-wide in the last four centuries are of species endemic to islands. However, the phenomenon of delayed extinctions as a result of habitat loss has rarely been assessed on oceanic islands. In this study, we tested whether extinction debt ( ED), in general, occurs on islands and for which taxonomical groups this phenomenon is most pronounced by assessing ED for multiple endemic taxa and for each of the main altitudinal ecosystems in a well-studied oceanic archipelago. Location Canary Islands. Methods We characterized habitat preferences for all endemic species of several taxonomic groups (vascular plants, ground and darkling beetles, flies and land snails). Using generalized linear mixed models and available data about habitat distributions, we tested for all taxa and habitat types to determine whether past habitat area better explained current richness of habitat specialists than current habitat area. If so, an extinction debt can be assumed. Results For all five major habitat types and five taxonomic groups studied, present-day richness of habitat specialists fitted better with past than current habitat area, evidencing habitat- and taxon-specific extinction debts. This pattern was consistent for both long-lived vascular plants and short-lived invertebrates. Single island endemics in each taxonomic group showed steeper slopes of the species-area relationship ( SAR) compared to archipelago endemics indicating higher sensitivity to habitat loss which might increase sizes of ED. Conclusion Despite differences in species' generation times, plants and invertebrates showed delayed extinctions after habitat destruction in the Canary Islands. Our SAR approach suggests that a considerable number of Canary Island endemics will eventually become extinct in the future without further habitat loss. The case of the Canary archipelago is probably not unique. Hence, we interpret our results as a warning for island conservationists that the worst of the extinction crisis on oceanic islands might be yet to come. Conservation actions should focus on habitat restoration to attenuate or reverse current extinction processes. [ABSTRACT FROM AUTHOR]

Obtaining fundamental biodiversity metrics such as alpha, beta and gamma diversity for arthropods is often complicated by a lack of prior taxonomic information and/or taxonomic expertise, which can result in unreliable morphologically based estimates. We provide a set of standardized ecological and molecular sampling protocols that can be employed by researchers whose taxonomic skills may be limited, and where there may be a lack of robust a priori information regarding the regional pool of species. These protocols combine mass sampling of arthropods, classification of samples into parataxonomic units ( PUs) and selective sampling of individuals for mt DNA sequencing to infer biological species. We sampled ten lowland rainforest plots located on the volcanic oceanic island of Réunion (Mascarene archipelago) for spiders, a group with limited taxonomic and distributional data for this region. We classified adults and juveniles into PUs and then demonstrated the reconciliation of these units with presumed biological species using mt DNA sequence data, ecological data and distributional data. Because our species assignment protocol is not reliant upon prior taxonomic information, or taxonomic expertise, it minimizes the problem of the Linnean shortfall to yield diversity estimates that can be directly compared across independent studies. Field sampling can be extended to other arthropod groups and habitats by adapting our field sampling protocol accordingly. [ABSTRACT FROM AUTHOR]

Using a series of standardized sampling plots within forest ecosystems in remote oceanic islands, we reveal fundamental differences between the structuring of aboveground and belowground arthropod biodiversity that are likely due to large-scale species introductions by humans. Species of beetle and spider were sampled almost exclusively from single islands, while soil-dwelling Collembola exhibited more than tenfold higher species sharing among islands. Comparison of Collembola mitochondrial metagenomic data to a database of more than 80 000 Collembola barcode sequences revealed almost 30% of sampled island species are genetically identical, or near identical, to individuals sampled from often very distant geographic regions of the world. Patterns of mt DNA relatedness among Collembola implicate human-mediated species introductions, with minimum estimates for the proportion of introduced species on the sampled islands ranging from 45% to 88%. Our results call for more attention to soil mesofauna to understand the global extent and ecological consequences of species introductions. [ABSTRACT FROM AUTHOR]

Aim To obtain nuclear and mitochondrial phylogenies of Macaronesian Rhopalomesites weevils and test the monophyly and time of origin of two species groups feeding on Euphorbiaceae and other plants. Additionally, to investigate the population structure within species, and its associations with geographical isolation versus trophic selection. Location Macaronesian Islands and the British Isles. Methods Maximum likelihood and Bayesian phylogenetic analyses were undertaken using mitochondrial ( cox1 and cytb) and nuclear ( ITS-2 and 28S RNA) genomic sequences. Ancestral Rhopalomesites host plant associations and divergence times were inferred from Bayesian analyses and population data. Results Evidence was found for two Rhopalomesites clades. One was associated with Euphorbia host plants, having vicariant species in the Madeira and Canary archipelagos. In this lineage, an ancestral association with Euphorbia mellifera in the two island groups was deduced, which has subsequently undergone shifts to related host plant species in marginal areas. The second clade was found to be an ecological generalist, exploiting decaying wood from the Lauraceae or other forest trees - is also present on such islands along with the Azores and parts of Atlantic Western Europe. Main conclusions The results point to a quasi-parallel colonization by the two ecologically distinct lineages in Macaronesia, dating to the early Pliocene, followed by allopatric isolation according to the presence of suitable habitats on particular islands in more recent times. [ABSTRACT FROM AUTHOR]

1. The large flightless grasshopper Acrostira bellamyi Uvarov, endemic to the island of La Gomera ( Canary Islands), inhabits two different environments: the xeric euphorb shrubland, as is typical for congeneric Canarian species, and the humid laurel forest, a novel habitat for the genus. 2. We investigate genetic, morphological, and ecological variation among individuals of A. bellamyi from the two habitats. DNA sequence data were used to evaluate whether grasshoppers from the two environments represent distinct lineages. Morphological and trophic analyses were performed to assess phenotypic differentiation between the two different habitats. 3. Population genetic analyses support the hypothesis that the euphorb shrubland is the ancestral habitat for this species. Female laurel forest specimens are larger than those inhabiting the euphorb shrubland, and some external body parts exhibit significant morphometric differences between the two populations. Diet of shrubland individuals is completely different from that of laurel forest individuals. Although in each habitat they consume the most abundant plants, individuals are able to select food plants, which appear to be explained by their nutrient content. 4. Our results suggest that A. bellamyi has colonised laurel forest from shrubland, and that this habitat shift has resulted in genetic, morphological, and ecological changes, perhaps as an adaptation to this new habitat. [ABSTRACT FROM AUTHOR]

Aim The seminal theory of island biogeography, based on changing rates of immigration and extinction, should be seen in a geological context, as an island's maturity influences the richness of its biota. Here, we develop an island biogeography of biotic interactions, recognizing that, besides species richness, biodiversity also encompasses the multitude of interactions among species. By sampling interactions between plants and pollinators across the Canarian archipelago, we illustrate how the local richness, specialization and endemism of biotic interactions vary with island age and area. Location Canary Islands (27.62° N-29.42° N and 13.33° W-18.17° W). Methods On five islands, covering the full age range of the archipelago, plant-pollinator interactions were catalogued and their strength estimated. Network parameters (e.g. interaction richness and specialization) and the number of single-island interactions (equivalent to single-island endemics) were estimated from interaction matrices and related to island area and age. Results Plant species richness, interaction richness and average degree of specialization of pollinator species showed hump-shaped relationships with island age. Pollinator richness varied with island area and plant richness. Plant specialization increased with island age, and the proportion of single-island interactions ( pSII) exhibited a U-shaped relationship with age. Main conclusions The previously reported hump-shaped relationship between species richness and island age, both on the scale of islands and of habitats, was confirmed for plant species in local networks. Both plants and pollinators were more generalized on the youngest island, which may be due to a predominance of generalist colonists. Pollinator specialization peaked on mid-aged islands, whereas plants showed the highest specialization on old islands, potentially reflecting their different life histories. The U-shaped relationship between the proportion of single-island interactions and island age might be explained by (1) young islands having a high proportion of unique interactions, due to interactions between generalists, and (2) old islands having unique interactions due to an accumulation of unique pairwise interactions that have evolved through time. Thus, island age - which not only captures time per se, but also the geomorphological changes of islands - may act as a regional driver of local network structure, and so the contemporary networks we observed across the Canarian archipelago illustrate the development of a network through geological time. [ABSTRACT FROM AUTHOR]

We investigated the phylogenetic patterns, evolutionary processes, and their taxonomic implications, of two closely related shield-backed katydid genera endemic to the Macaronesian archipelagos: the monotypic Psalmatophanes Chopard, 1938 endemic to Madeira and Calliphona Krauss, 1892, which includes three species restricted to the Canary Islands. Two main hypotheses have been proposed to explain the origin and colonization pathways of these two genera: a single origin with subsequent sequential colonization of the islands, or three independent colonization waves from continental Africa. We used DNA sequence information from the mitochondrial genes cox1, tRNAleucine, rrnL and nad1 to infer phylogenetic relationships among Psalmatophanes and Calliphona species. Our results provide support for the independent colonization of Madeira and the Canary Islands, and suggest that Psalmatophanes is actually more closely related to the continental genus Tettigonia than to the Canarian representatives. Deep genetic divergence among Canarian species provides further support for the assignment of the Canarian species into two subgenera. Tree topology along with Bayesian-based estimates of lineage age suggest a pattern of colonization from Tenerife to La Palma, and from Tenerife to Gran Canaria with subsequent dispersal to La Gomera. We report the first collection of a Calliphona specimen in the island of El Hierro, which molecular data suggest is a recent immigrant from La Gomera. We hypothesize that the patterns of distribution and genetic divergence exhibited by Calliphona in the Canary Islands are compatible with a taxon cycle process. Our results have further implications for the higher level phylogeny of the subfamily Tettigoniinae and suggest that some of the tribes as currently delimited may not correspond to natural groups. [ABSTRACT FROM AUTHOR]

The Eastern Canary Islands are the emerged tips of a continuous volcanic ridge running parallel to the northeastern African coast, originated by episodic volcanic eruptions that can be traced back to the Miocene and that, following a major period of quiescence and erosion, continued from the Pliocene to the present day. The islands have been periodically connected by eustatic sea-level changes resulting from Pleistocene glacial cycles. The ground-dwelling spider Dysdera lancerotensis Simon, 1907 occurs along the entire ridge, except on recent barren lavas and sand dunes, and is therefore an ideal model for studying the effect of episodic geological processes on terrestrial organisms. Nested clade and population genetic analyses using 39 haplotypes from 605 base pairs of mitochondrial DNA cytochrome c oxidase I sequence data, along with phylogenetic analyses including two additional mitochondrial genes, uncover complex phylogeographical and demographic patterns. Our results indicate that D. lancerotensis colonized the ridge from north to south, in contrast to what had been expected given the SSW-NNE trend of volcanism and to what had been reported for other terrestrial arthropods. The occurrence of several episodes of extinction, recolonization and expansion are hypothesized for this species, and areas that act as refugia during volcanic cycles are identified. Relaxed molecular clock methods reveal divergence times between main haplotype lineages that suggest an older origin of the northern islets than anticipated based on geological evidence. This study supports the key role of volcanism in shaping the distribution of terrestrial organisms on oceanic islands and generates phylogeographical predictions that warrant further research into other terrestrial endemisms of this fascinating region. [ABSTRACT FROM AUTHOR]

The volcanic island of Tenerife (Canary archipelago) was formerly covered at 600–1200 m above sea level on most of its northern side by a cloud forest holding much of the endemic insect fauna. In the most significant surviving patches of this laurel forest at the eastern and western tips of the island occur two forest-specialist, closely related species of Eutrichopus (Coleoptera, Carabidae); here we present data on mitochondrial DNA variation among populations of these species. In total, 116 individuals from 16 localities were sampled and a 638 bp fragment of the cytochrome oxidase subunit 11 gene was sequenced, obtaining evidence for two distinct evolutionary lineages, in accordance with morphological and biogeographical data. Volcanic events at ∼0.7 Ma might be responsible for vicariance and the fragmentation of the geographical range of an ancestral species, causing the establishment of two matrilineal lineages. Using nested clade and historical demography analyses we infer past cycles of demographic bottlenecks followed by population expansion, mostly in agreement with the geological timescale of volcanic events. Recent trends, however, refer to fragmentation of the cloud forest due to human intervention. [ABSTRACT FROM AUTHOR]

Six polymorphic microsatellite markers have been developed for the Canary endemic ground beetle Trechus flavocinctus, and the performance of primer pairs amplifying these loci in closely related taxa (including two cave-obliged species) has been tested. The number of alleles in T. flavocinctus samples taken from three distant localities in two islands ranged from four to 14 per locus. Observed heterozygosities were from 0.333 to 0.933. These markers could be useful tools to study the population structure and the genetic consequences of island and cave colonization by ground beetles. [ABSTRACT FROM AUTHOR]

The cover image, by Rüdiger Otto et al., is based on the Biodiversity Research Unpaid extinction debts for endemic plants and invertebrates as a legacy of habitat loss on oceanic islands, DOI: 10.1111/ddi.12590. Photo Credit: Miguel Ibanez. [ABSTRACT FROM AUTHOR]