Age, origins and extinctions of the avifauna of Macaronesia: a synthesis of phylogenetic and fossil information

Summary 1 Published molecular phylogenies show that many plant groups in the Canary Islands are monophyletic despite the fact that the short distance between the islands and Africa should have led to many independent colonization events. 2 Low establishment rates of later migrants owing to niche pre-emption by earlier, already established, colonists could explain these patterns. The apparent monophyly is, however, also compatible with multiple colonizations, with later colonizers making only limited contributions to the total gene pool (and therefore being undetected in the molecular phylogeny) or being wiped out by stochastic processes. 3 Experimental evidence for niche pre-emption and species-specific interactions in plants is weak, with survival and establishment of a newly immigrant species depending on the overall composition of the community, rather than on the presence of a particular ‘ecologically similar’ species. 4 Although niche pre-emption might have contributed to the observed patterns of monophyly, we do not think that phylogeographical data from Macaronesia can be taken as evidence for its action in the geological past.

Species richness on oceanic islands has been related to a series of ecological factors including island size and isolation (i.e. the Equilibrium Model of Island Biogeography, EMIB), habitat diversity, climate (i.e., temperature and precipitation) and more recently island ontogeny (i.e. the General Dynamic Model of oceanic island biogeography, GDM). Here we evaluate the relationship of these factors with the diversity of bryophytes in the Macaronesian region (Azores, Madeira, Canary Islands and Cape Verde). The predictive power of EMIB, habitat diversity, climate and the GDM on total bryophyte richness, as well as moss and liverwort richness (the two dominant bryophyte groups), was evaluated through ordinary least squares regressions. After choosing the best subset of variables using inference statistics, we used partial regression analyses to identify the independent and shared effects of each model. The variables included within each model were similar for mosses and liverworts, with orographic mist layer being one of the most important predictors of richness. Models combining climate with either the GDM or habitat diversity explained most of richness variation (up to 91%). There was a high portion of shared variance between all pairwise combinations of factors in mosses, while in liverworts around half of the variability in species richness was accounted for exclusively by climate. Our results suggest that the effects of climate and habitat are strong and prevalent in this region, while geographical factors have limited influence on Macaronesian bryophyte diversity. Although climate is of great importance for liverwort richness, in mosses its effect is similar to or, at least, indiscernible from the effect of habitat diversity and, strikingly, the effect of island ontogeny. These results indicate that for highly vagile taxa on oceanic islands, the dispersal process may be less important for successful colonization than the availability of suitable ecological conditions during the establishment phase.

Molecular phylogenetics of Lotus (Leguminosae) with emphasis in the tempo and patterns of colonization in the Macaronesian region

First steps to develop the Surveillance Net in Macaronesian Detection of Ciguatera in species of fishing interest.

The Canaries: an important biogeographical meeting place

AimWe documented how the similarity of mammal assemblages on continental and oceanic islands has changed since initial human colonization, since European arrival and overall. We investigated how levels of similarity might change in the future.LocationContinental and oceanic islands worldwide.Time periodHuman settlement of islands to the present, as well as projections for the future.Major taxa studiedMammals.MethodsWe used mammal occurrence data on islands to calculate the change in similarity using a pairwise approach based on Jaccard's index and a multisite approach based on Jaccard's and Sørensen's measures. We divided the mammal assemblages into two time periods, before and after island colonization or trade began with Europeans. We unpacked the mechanisms driving changes in similarity, exploring how initial similarity interacts with seven types of species turnover events to determine overall change. Finally, we calculated how future similarity levels will change if past trends in introductions and extinctions continue.ResultsMammals, on both continental and oceanic islands, show one of the most pronounced cases of homogenization ever observed, and on oceanic islands mammals show the largest increase in homogenization ever observed for a terrestrial group. Most of the homogenization observed to date has been driven by recent historical changes, not by changes that occurred before European arrival. If current patterns of species introductions and extinctions continue, then oceanic islands will experience little additional homogenization, whereas continental islands will homogenize greatly beyond current levels.Main conclusionsMammal assemblages on oceanic islands show nearly an order of magnitude greater change in similarity than plant and bird assemblages. Projections of future similarity indicate that continental and oceanic islands are on different trajectories of change. These trajectories could be altered by management actions, but in some cases those actions that would be impactful run counter to current conservation norms.

Oceanic islands are mostly of volcanic origin. Most of them harbour a diverse fauna and flora, which had not been there before. All plants and animals must have reached the islands by sea or wind or through human activities. Thus, all these island taxa are witnesses of migration events in the past and are models for biogeography. In this review, fauna (especially birds) and flora of the Macaronesian islands west of Europe and North Africa in the Atlantic are discussed. The Macaronesian islands comprise 4 archipelagos with 31 main islands, including the Azores, Madeira, Canary Islands and Cape Verde Islands. These islands are of volcanic origin and between 120 and < 1 million years old. Flora and fauna mostly consist of species, that originally originated from Europe or Africa and arrived within the last 4 million years. More than 23% of the terrestrial taxa are endemic to the area. Genetic analyses have confirmed most of the morphologically defined endemic species and subspecies. In some species groups, a strong speciation signal becomes visible in that distinct genetic lineages occur on individual islands or archipelagos. This is especially apparent in Phylloscopus canariensis, Regulus regulus, Cyanistes [caeruleus] teneriffae, Erithacus rubecula, and Fringilla coelebs. The diversity of the Macaronesian islands offers an excellent opportunity to study adaptive radiation and speciation in organisms of differing complexity and mobility.

The original bird fauna of most oceanic islands has been affected by recent extinction processes associated with human arrival and its subsequent impacts. In the volcanic Macaronesian archipelagos (Azores, Madeira, Selvagens, Canary Islands and Cape Verde), in the North Atlantic, the Late Quaternary fossil record indicates that there was formerly a higher avian diversity, including a high number of now extinct endemic species. This assemblage of extinct birds includes endemic insular quails (Galliformes: Phasianidae). In this study, we describe three newly discovered extinct species of quails, two of which inhabited the archipelago of Madeira (Coturnix lignorum sp. nov. from Madeira Island and Coturnix alabrevis sp. nov. from Porto Santo Island) and one from Cape Verde (Coturnix centensis sp. nov.). The fossil record also indicates the presence of additional species of extinct endemic quails on other Macaronesian islands. These birds plus the extinct Canary Island quail (Coturnix gomerae) indicate a high former endemic diversity of this genus in Macaronesia, a feature unique among oceanic archipelagos. Anatomical traits show that the new taxa were flightless ground dwellers, making them vulnerable to human interference, with their extinction being linked to human arrival and subsequent habitat alterations and the introduction of invasive species.

Numerous phylogenetic studies look for speciation without ecological radiation (PNC = phylogenetic niche conservatism). However, they ask only rarely for the role of the habitats for niche constancy. Starting from the hypothesis of DAVIS (1951) and SNOGERUP (1971) that the rock environment is 1) an evolutionary trap, conserving many old lineages (phylogenetic relicts) and that 2) it serves as a refugium under climate change, the rock vegetation is analysed for relic-tic species and niche conservatism. Three case studies, based upon phytosociological data sets from subtropical Africa, the Mediterranean area and the Eastern Alps are analysed. Molecular phylogenetic trees from selected taxa indicate the time of the splitting of lineages and the dura-tion of niche constancy. The comparison of succulent communities on rocks in SW-Arabia (class Kleinio-Carallumetea) and on the Canary Islands (Kleinio-Euphorbietea) shows numerous vicarious taxa (synvicariism). The phylogenetic tree of Campylanthus allows assuming the origin of this vicariance pattern in a geo-graphical separation of the ancestors in Mid Tertiary. The aridisation of Northern Africa about 6 Mya ago resulted in this high distance disjunction between Macaronesia and the Eritreo-Arabian region. The separated taxa underwent allopatric speciation, without ecological radiation. They remained in their niches. The vegetation of halve-caves with soaking water (class Adiantetea capilli-veneris) in the Mediterra-nean area and adjacent subtropics shelters local endemics, forming a mosaic of vicarious species. They belong to the genus Pinguicula in the NW-Mediterranean, to Hypericum (section Adenosepalum) in the SW-Mediterranean, and to Primula subgenus Sphondylia on the Arabian Peninsula and its surroundings. These vicariance patterns date back to the Late Tertiary and the climatic conditions in the Quaternary. The constant water supply - quite independent from the macroclimatic condi-tions - and the stenothermic rock surface favour in-situ resilience and make the Adiantetea to outstanding refugia for phylogenetic and geographical relicts. The example of the Caricetum firmae demonstrates relict phenomena, dating back to the last ice age. The rock fissures and calciphilous, alpine rock turfs of the massifs fringing the Eastern Alps shelter endemic cushion plants from genera such as Potentilla, Primula, Androsace, and Gentiana. These taxa of low dispersal capacity are still located in their glacial refugia. The actual species combination of rock communities mirrors historical events. The floristic and spatial patterns are influenced by former climatic conditions, by evolutionary processes and by dispersal limitations. Because of the high variety of micro-habitats, rocks offer refugia and shelter relicts. It is a habitat of outstanding niche conservatism, resulting in patterns of vicarious species and parallel evolution.

A molecular phylogenetic study based on chloroplast DNA restriction site and ITS sequence data shows that the two Macaronesian endemics, Lavatera phoenicea and Lavatera acerifolia, represent two independent introductions into the Canary Islands. The molecular phylogenies, combined with morphological, ecological, and biogeographical data, indicate that Lavatera phoenicea may be a bird-pollinated relict of an ancient laurel forest. Lavatera acerifolia, however, is nested in a derived clade of the Lavatera-Malva taxa from the Mediterranean region, suggesting a more recent introduction into the Canary Islands. Incongruence between chloroplast and nuclear phylogenies suggests that hybridization may have played a role in the evolution of L. acerifolia. Several features of L. phoenicea, such as corolla color and high nectar production, appear to be plesiomorphic and are still present because of historical constraints. In contrast, woodiness is a derived feature that originated as an adaptation to insular conditions.

Oceanic islands have long been considered engines of differentiation and speciation for terrestrial organisms. Here we investigated colonisation and radiation processes in the Madeira Archipelago and the Canary Islands of the Andrena wollastoni group of bees (subgenus Micrandrena), which comprises six endemic species and five endemic subspecies on the islands. Mitochondrial COI sequences support the monophyly of the four species of the Canary Islands and the two species of the Madeira Archipelago and suggest a relatively young age for all taxa. The data do not support a simple stepping-stone model (eastern-western colonisation from the mainland, with splitting into new taxa), but suggest Andrena gomerensis (extant on La Gomera and La Palma) or its ancestor as the basal lineage from which all other taxa evolved. Andrena lineolata (Tene-rife) or its putative ancestor (A. gomerensis) is sister to A. dourada (Porto Santo), A. catula (Gran Canaria), and A. acuta (also Tenerife). Andrena dourada (Porto Santo) and A. wollastoni (Madeira Island) are sister species. Morphologically and morphometrically defined subspecies were not distinguishable with COI DNA sequences. Colonisation likely led from the Canary Islands to the Madeira Archipelago and not from the mainland directly to the latter.

AimsThe present study is the first attempt to grasp the scale and richness of marine biological invasions in Macaronesia. We pioneered a comprehensive non‐native species (NNS), inventory in the region to determine their diversity patterns and native distribution origins. NNS were defined here as the result of both introductions and range expansions. We also used statistical modelling to examine relationships among NNS richness, anthropogenic activities, demographic and geographical variables across Macaronesia.LocationMacaronesia.MethodsA comprehensive literature search was conducted for marine NNS records in Macaronesia, registering the first record's location and year from 1884 to 2020. We used univariate and multivariate analyses to evaluate differences and similarities in community composition. By applying a Generalized Linear Model (GLM), we tested hypotheses regarding NNS richness as a function of anthropogenic activities, demographic and geographical variables.ResultsA total of 144 marine non‐native species (NNS) were recorded for the whole of Macaronesia. The highest NNS richness was registered in the Canary Islands (76 NNS), followed by the Azores (66 NNS), Madeira (59 NNS) and finally Cabo Verde (18 NNS). Some differences amongst archipelagos were observed, such as the high number of non‐native macroalgae in the Azores, fishes in the Canary Islands and tunicates in Cabo Verde. Overall, macroalgae, tunicates and bryozoans were the predominant taxonomic groups in the Macaronesian archipelagos. Madeira and Canary Islands were the archipelagos with more similarity in marine NNS, and Cabo Verde the most divergent. Finally, GLM suggested that non‐native richness patterns across Macaronesia were dependent on the considered archipelago and strongly affected by (1) minimum distance to the mainland, (2) the total number of ports and marinas and (3) total marinas area (km2).ConclusionsThe model results and NNS listing in the present study will likely raise the awareness and response regarding marine NNS in the whole Macaronesia region, serving as a baseline for future research as well as implementing and enforcing regulations related to the introduction of marine NNS in oceanic islands.

The causes of Sahul's megafauna extinctions remain uncertain, although several interacting factors were likely responsible. To examine the relative support for hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups, as well as 8 extant species within these groups for comparison. Perturbing specific demographic rates individually, we tested which species were more demographically susceptible to extinction, and then compared these relative sensitivities to the fossil-derived extinction chronology. Our models show that the macropodiformes were the least demographically susceptible to extinction, followed by carnivores, monotremes, vombatiform herbivores, and large birds. Five of the eight extant species were as or more susceptible than the extinct species. There was no clear relationship between extinction susceptibility and the extinction chronology for any perturbation scenario, while body mass and generation length explained much of the variation in relative risk. Our results reveal that the actual mechanisms leading to the observed extinction chronology were unlikely related to variation in demographic susceptibility per se, but were possibly driven instead by finer-scale variation in climate change and/or human prey choice and relative hunting success.

The causes of Sahul’s megafauna extinctions remain uncertain, although several interacting factors were likely responsible. To examine the relative support for hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups, as well as 8 extant species within these groups for comparison. Perturbing specific demographic rates individually, we tested which species were more demographically susceptible to extinction, and then compared these relative sensitivities to the fossil-derived extinction chronology. Our models show that the macropodiformes were the least demographically susceptible to extinction, followed by carnivores, monotremes, vombatiform herbivores, and large birds. Five of the eight extant species were as or more susceptible than the extinct species. There was no clear relationship between extinction susceptibility and the extinction chronology for any perturbation scenario, while body mass and generation length explained much of the variation in relative risk. Our results reveal that the actual mechanisms leading to the observed extinction chronology were unlikely related to variation in demographic susceptibility per se, but were possibly driven instead by finer-scale variation in climate change and/or human prey choice and relative hunting success.

Evolutionary diversification of the genus Theba (Gastropoda: Helicidae) in space and time: A land snail conquering islands and continents