Island Floras Research Articles

Lauraceae fossils from a volcanic Palaeocene oceanic island, Ninetyeast Ridge, Indian Ocean: ancient long‐distance dispersal?

AbstractAim Geological and fossil records are critical for historical biogeography studies. A plant fossil assemblage from a small, well‐dated, transient late Palaeocene island was re‐investigated with regard to regional geology and vicariance versus dispersal hypotheses.Location Deep Sea Drilling Program Leg 22, Site 214 on the Ninetyeast Ridge (NER) in the mid‐Indian Ocean region.Methods Leaf cuticular material was recovered from residues from a previous palynofloral study of Site 214 sediments during the 1970s and identified. The palynoflora was reassessed.Results The only leaf cuticular material recovered with stomata can be placed in crown‐group Lauraceae. It is confirmed that the palynoflora reflects the presence of a low‐diversity island flora in the late Palaeocene, comprising ferns and mostly herbaceous angiosperms with readily dispersible propagules, and perhaps austral podocarps. Other pollen taxa of almost certain local origin were arecoid palms and taxa related to Chloranthaceae. The strong overall similarity of the palynoflora to Australo‐Antarctic and New Zealand assemblages is also confirmed.Main conclusions Foliar fossils of Lauraceae demonstrate the occurrence of one of the world’s largest, most widely distributed woody plant families on a late Palaeocene island. The presence of plants on this island could be explained by vicariance via a vegetated Upper Cretaceous Kerguelen Plateau, in part because crown‐group Lauraceae may be at least this old. However, there are records of other taxa in the Kerguelen region that are anomalous with vicariance, plus evidence for a catastrophic biotic extinction event centred in the area in the latest Cretaceous. Plants were therefore most likely to have reached the island by means of dispersal. This suggests either the presence of presently unknown vegetated land nearby in the Kerguelen region in the late Palaeocene, or long‐distance dispersal, probably from the Australian region. The dispersal of viable seeds could have been facilitated by birds or perhaps by ocean‐surface drift with or without the assistance of ocean‐going animals. The fossils allow that even small, short‐lived islands could have acted as ‘stepping stones’ for biotic interchange between Australia and Africa, and perhaps other regions.

The Transformation of Environment into Landscape: The Historical Ecology of Monumental Earthwork Construction in the Bolivian Amazon

Although the Neotropics are recognized as a region rich in biological diversity, the origin, evolution, and maintenance of this phenomenon continues to be debated. Historical ecologists and landscape archaeologists point out that the Neotropics have a long, complex human history that may have been a key factor in the creation, shaping, and management of present day biodiversity. The construction of monumental earthworks referred to as ring ditches of the Bolivian Amazon and surrounding regions in late prehistory had considerable impact on the fauna, flora, soils, and topography of forest islands. Patterned landscape features, historical documents, energetics, and historical ecology are used to understand the transformation of forest islands into anthropogenic built environments.

Contrasting environmental and regional effects on global pteridophyte and seed plant diversity

Pteridophytes (ferns and fern‐allies) represent the second‐largest group of vascular plants, but their global biogeography remains poorly studied. Given their functional biology, pteridophytes are expected to show a more pronounced relation to water availability and a higher dispersal ability compared to seed plants. We test these assertions and document the global pattern of pteridophyte richness across 195 mainland and 106 island regions. Using non‐spatial and spatial simple and multiple regression models, we analyze geographic trends in pteridophyte and seed plant richness as well as pteridophyte proportions in relation to environmental and regional variables. We find that pteridophyte and seed plant richness are geographically strongly correlated (all floras: r=0.68, mainland: r=0.82, island floras: r=0.77), but that the proportions of pteridophytes in vascular plant floras vary considerably (0–70%). Islands (mean=15.3%) have significantly higher proportions of pteridophytes than mainland regions (mean=3.6%). While the relative proportions of pteridophytes on islands show a positive relationship with geographic isolation, proportions in mainland floras increase most strongly along gradients of water availability. Pteridophyte richness peaks in humid tropical mountainous regions and is lowest in deserts, arctic regions, and on remote oceanic islands. Regions with Mediterranean climate, outstanding extra‐tropical centres of seed plant richness, are comparatively poor in pteridophytes. Overall, water‐energy variables and topographical complexity are core predictors of both mainland pteridophyte and seed plant richness. Significant residual richness across biogeographic regions points to an important role of idiosyncratic regional effects. Although the same variables emerge as core predictors of pteridophyte and seed plant richness, water availability is clearly a much stronger constraint of pteridophyte richness. We discuss the different limitations of gametophytes and sporophytes that might have limited the ability of pteridophytes to extensively diversify under harsh environmental conditions. Our results point to an important role of taxon‐specific functional traits in defining global richness gradients.

The Madeiran plants collected by Sir Hans Sloane in 1687, and his descriptions

AbstractThe Macaronesian Islands comprise the Atlantic archipelagos of Azores, Madeira, Selvagens, Canaries and Cape Verde. These islands were a major focus for plant exploration during the 17th and 18th centuries. Sir Hans Sloane (1660–1753), one of the most important patrons and sponsors of natural sciences and botanical research, visited Madeira on his way to Jamaica in 1687. Although he stayed in Madeira for only three days, he collected plant specimens of 38 taxa (including one brown alga) and made important observations concerning the flora and fauna of Madeira from near Funchal. Sixty–six polynomial names of plants from the island are recorded in Sloane's published work along with 18 copperplate engravings, ostensibly from Madeira, although our study shows that only thirteen of them are of taxa occurring on the island. Fourteen of the sixty–six polynomials reported by Sloane relate to Macaronesian endemic taxa, six of them restricted to Madeira. Our study shows that nine of the fifteen polynomials that he putatively recorded for Madeira and/or the Antilles or for which he was unsure of their origin are from the West Indies and do not occur on this Macaronesian island. Two of the taxa that are listed for Madeira and the Caribbean Islands were likely to be present in both insular systems. Although there is evidence of earlier botanical explorations in Macaronesia, the herbarium collections made by Sloane in Madeira represent the earliest documented plant hunting expedition to Macaronesia, and Sir Hans Sloane can be considered as one of the pioneers of botanical exploration in these Atlantic Islands. Sloane's records provide an early floristic study of a diverse island flora.

Additive partitioning as a tool for investigating the flora diversity in oceanic archipelagos

This paper introduces the integration of additive partitioning with species—area relationships to island biogeography in order to address the question ''How are the pteridophyte and spermatophyte native and endemic flora of different oceanic archipelagos partitioned across islands?''. Species richness data of all endemic species and all native species of pteridophytes and spermatophytes were obtained for the Azores, Canaries and Cape Verde in the Atlantic Ocean and Galapagos, Hawaii and Marquesas in the Pacific Ocean. Additive partitioning of species diversity was used to quantify how much of the total diversity of an oceanic archipelago flora (g-diversity) is due to (i) the mean species richness of the flora of each island (a-diversity), (ii) the variability in species richness of the floras across islands (bNestedness) and (iii) the complementarity in species composition of the floras of different islands (bReplacement). The analysis was separately performed for the native and endemic pteridophyte and spermatophyte floras. The diversity partitioning of the six archipelagos showed large differences in how the flora of each archipelago is partitioned among the a, bNestedness and bReplacement components, for pteridophytes and spermatophytes and for all endemic species and all native species. The a-diversity was more important for all native species than for endemic species and more important for pteridophytes than for spermatophytes, with the Azores showing outstanding high values of a-diversity. The bNestedness was higher for pteridophytes than for spermatophytes and higher for endemic species than for all native species in both pteridophytes and spermatophytes. The values of bReplacement suggested that: (i) the spermatophyte native flora is more differentiated across islands than the pteridophyte native flora and (ii) the pteridophyte endemic flora and, especially, the spermatophyte endemic flora are more differentiated across islands than the corresponding native flora. An outstanding value of bReplacement for endemic and all native spermatophytes was found in Hawaii, confirming the biogeographical island differentiation in this archipelago. & 2010 R ¨ ubel Foundation, ETH Z ¨

Using taxonomic and phylogenetic evenness to compare diversification in two Island Floras

This study compares the phylogenetic structure in the Canary Islands and Hawaii by means of the distributions of the species number for plant families (Taxonomic evenness) and lineages (Phylogenetic evenness) across archipelagos and across habitats in both archipelagos using the Gini coefficient. We then investigate phylogenies to identify particular habitats contributing to such differences using Taxonomic distinctness (AvTD) and its variation (VarTD). Our results show that the distribution of species number among Hawaiian lineages is much more uneven than the Canary Islands. In contrast, Hawaii produces a more even distribution of species number by family than the Canary Islands. This may be due to the Hawaiian Flora being derived from considerably fewer colonists than the Canarian Flora as a result of its much greater degree of isolation. At the same time, Hawaii is represented by the same number of families as the Canary Islands. This may stem from Hawaii's flora being derived from a greater range of source areas despite its isolation. Finally, there is much more diversification spread across a larger number of lineages in Hawaii. The higher degree of Hawaiian diversification may be due to a greater range of habitats, more diverse and phylogenetically distinct floristic sources, and low initial species diversity resulting from extreme isolation. Two Canarian habitats (Rock communities and Thermophilous habitats) and one Hawaiian habitat (Wet communities) contribute to the differences in phylogenetic structure between the two archipelagos. These habitats exhibit disproportionate levels of unevenness and may represent centres of diversification. We propose a combination of two habitat properties, high receptivity and low stability, to explain these results.

New and interesting species of the genus Muelleria (Bacillariophyta) from the Antarctic region and South Africa

Van de Vijver B., Mataloni G., Stanish L. and Spaulding S.A. 2010. New and interesting species of the genus Muelleria (Bacillariophyta) from the Antarctic region and South Africa. Phycologia 49: 22–41. DOI: 10.2216/09-27.1During a survey of the terrestrial diatom flora of some sub-Antarctic islands in the southern Indian and Atlantic Oceans and of the Antarctic continent, more than 15 taxa belonging to the genus Muelleria were observed. Nine of these taxa are described as new species using light and scanning electron microscopy. Comments are made on their systematic position and how they are distinguished from other species in the genus. Additionally, two previously unrecognized taxa within the genus were discovered in samples from South Africa. One of these, Muelleria taylorii Van de Vijver & Cocquyt sp. nov., is new to science; the other, Muelleria vandermerwei (Cholnoky) Van de Vijver & Cocquyt nov. comb., had been included in the genus Diploneis. The large number of new Muelleria taxa on the (sub)-Antarctic locations is not surprising. Species in Muelleria occur rarely in collections; in many habitats, it is unusual to find more than 1–2 valves in any slide preparation. As a result, records are scarce. The practice of “force-fitting” (shoehorning) specimens into descriptions from common taxonomic keys (and species drift) results in European species, such as M. gibbula and M. linearis, being applied to Antarctic forms in ecological studies. Finally, the typical terrestrial habitats of soils, mosses and ephemeral water bodies of most of these taxa have been poorly studied in the past.

Challenges and Unique Solutions to Rodent Eradication in Florida

Once established, invasive rodents cause significant impacts to island flora and fauna, including species extinctions. There have been numerous efforts to eradicate invasive rodents from islands worldwide, with many successes. For a number of reasons, many invasive vertebrates have become established in Florida, including several rodent species. We have implemented rodent eradication efforts on two Florida islands. Using the successful eradication strategy developed for Buck Island, U.S. Virgin Islands, we have attempted the eradication of roof rats from Egmont Key off Tampa Bay. We also are attempting to eradicate Gambian giant pouched rats from Grassy Key in the Florida Keys. On Egmont Key, we used a grid of bait stations containing diphacinone rodenticide bait blocks and hand tossing of bait blocks into thickets. On Grassy Key, we used a grid of bait stations containing a zinc phosphide bait along with intensive live-trapping. We discuss the eradication planning, efforts to minimize nontarget animal losses, and follow-up activities. We also discuss some of the difficulties encountered in each of these two different situations.

The Azores diversity enigma: why are there so few Azorean endemic flowering plants and why are they so widespread?

AbstractAim Endemism in the flora of the Azores is high (33%) but in other respects, notably the paucity of evolutionary radiations and the widespread distribution of most endemics, the flora differs markedly from the floras of the other Macaronesian archipelagos. We evaluate hypotheses to explain the distinctive patterns observed in the Azorean endemic flora, focusing particularly on comparisons with the Canary Islands.Location Azores archipelago.Methods Data on the distribution and ecology of Azorean endemic flowering plants are reviewed to ascertain the incidence of inter‐island allopatric speciation and adaptive, ecological speciation. These are contrasted with patterns for the Canary Islands. Patterns of endemism in the Azores and Canaries are further investigated in a phylogenetic context in relation to island age. beast was used to analyse a published molecular dataset for Pericallis (Asteraceae) and to investigate the relative ages of Azorean and Canarian lineages.Results There are few examples of inter‐island allopatric speciation in the Azorean flora, despite the considerable distances between islands and sub‐archipelagos. In contrast, inter‐island allopatric speciation has been an important process in the evolution of the Canary Islands flora. Phylogenetic data suggest that Azorean endemic lineages are not necessarily recent in origin. Furthermore, in Pericallis the divergence of the Azorean endemic lineage from its closest relative pre‐dates the radiation of a Canarian herbaceous clade by inter‐island allopatric speciation.Main conclusions The data presented do not support suggestions that hypotheses pertaining to island age, age of endemic lineages and ecological diversity considered individually explain the lack of radiations and the widespread distribution of Azorean endemics. We suggest that palaeoclimatic variation, a factor rarely considered in macroecological studies of island diversity patterns, may be an important factor. Palaeoclimatic data suggest frequent and abrupt transitions between humid and arid conditions in the Canaries during the late Quaternary, and such an unstable climate may have driven the recent diversification of the flora by inter‐island allopatric speciation, a process largely absent from the climatically more stable Azores. Further phylogenetic/phylogeographic analyses are necessary to determine the relative importance of palaeoclimate and other factors in generating the patterns observed.

Darwin on island plants

Islands played a key role in Charles Darwin's observations and experiments on plant dispersal. By means of these experiments, he expunged the old idea that a given species could originate at multiple times and in multiple places. More importantly, by seeing the capabilities for dispersal of plant seeds, fruits and branches, he was able to develop ideas of how plants reach islands and thus he is one of the founders of plant biogeography. For facts regarding floristic distribution of plants, Darwin relied on other workers, most notably Sir Joseph Dalton Hooker. Among his insights were the differences between oceanic and continental islands on a floristic basis, ideas on how age of island and distance from mainland areas influenced composition of island floras, the nature of endemism on islands and the role islands and archipelagos served as stepping stones in dispersal. Ingenious at proposing hypotheses, but always respectful of facts, Darwin sought explanations for plant adaptations on islands at a time when knowledge of island botany was little more than floristic in nature. These explanations are compared with selected recent works in island botany.

Areas and algorithms: evaluating numerical approaches for the delimitation of areas of endemism in the Canary Islands archipelago

AbstractAim Areas of endemism are the fundamental units of cladistic biogeographical analysis but there is no consensus on the most appropriate method for their delimitation. In this paper, the relative performance of a number of algorithmic approaches for the delimitation of areas of endemism is investigated within the context of the Canary Islands flora, and areas of endemism within the Canary Islands archipelago are defined.Location The Canary Islands.Methods A data matrix comprising the distributions of 609 endemic spermatophyte taxa (c. 90% of the endemic flora) scored on a 10 × 10 km UTM grid was analysed using: (1) UPGMA (unweighted pair group method with arithmetic mean) clustering of Jaccard and Kulczynski similarity coefficient matrices, (2) parsimony analysis of endemicity (PAE), and (3) the program ndm (eNDeMism). The performance of each method was then determined by the extent to which the resulting areas of endemism met three criteria: (1) possession of two or more strict endemic taxa, (2) diagnosability, and (3) geographical contiguity.Results Each of the four methods resulted in substantially different sets of areas. ndm analysis resolved 17 areas of endemism consistent with all three criteria, and collectively these accounted for 59% of all cells. In the hierarchical analyses none of the methods recovered more than eight areas of endemism, and the total coverage of cells ranged from 13% to 33% when the results were confined to intra‐island areas of endemism.Main conclusions ndm outperforms hierarchical clustering methods in terms of both the number of intra‐island areas of endemism delimited that meet the three evaluation criteria and the total coverage of those areas. ndm may also be considered preferable because it is non‐hierarchical, incorporates spatial information into the delimitation of areas, and permits overlap between areas of endemism where there is evidence to support it. The results support the use of ndm as the most appropriate method currently available for the delimitation of areas of endemism. The areas of endemism identified by the ndm analysis are discussed.

Bryophyte flora of the South Kuril Islands (East Asia)

Bryophyte flora of the South Kuril Islands (East Asia)

Notes on the marine algae of the Bermudas. 9. The genus Botryocladia (Rhodophyta, Rhodymeniaceae), including B. bermudana, B. exquisita and B. flookii spp. nov.

C.W. Schneider and C.E. Lane. 2008. Notes on the marine algae of the Bermudas. 9. The genus Botryocladia (Rhodophyta, Rhodymeniaceae), including B. bermudana, B. exquisita and B. flookii spp. nov. Phycologia 47: 614–629. DOI: 10.2216/08-44.1Using morphological and molecular analyses (rbcL gene sequences), three new species, Botryocladia bermudana, B. exquisita and B. flookii, are described from the coastal waters and national aquarium of Bermuda. The new taxa are joined by two others in the island's flora, B. occidentalis and B. wynnei, the last representing a new distributional record. The cryptic species, B. bermudana, is the most common of all Botryocladia species in the islands and was known from Bermuda in the past as B. pyriformis (Børgesen) Kylin. Analysis of rbcL sequences shows that B. bermudana is most closely related to B. caraibica from the Caribbean. These two species share many characteristics in addition to their phylogentic positioning. Botryocladia exquisita is anatomically and molecularly most similar to the much smaller B. monoica from the Caribbean and Gulf of Mexico, and B. flookii bears a striking superficial resemblance to B. macaronesica from the Canary Islands. Several anatomical and reproductive characteristics differentiate the two.

Plant species diversity of Adriatic islands: An introductory survey

The European Mediterranean region is one of the world's major centres of biodiversity. Research on plant species diversity in this region has neglected the area along the eastern part of the Adriatic basin in comparison to the other Mediterranean areas. The main aim of this study was to focus on this neglected area, by supplying data which is at present lacking in order to discuss the species-area relationship (SAR), floristic richness and endemism of the Adriatic islands and coast. Floristic data for 106 Croatian islands collected by different authors were integrated, systematised and presented in a form usable by other researchers worldwide. The Power (Arrhenius) function was used for modelling (by non-linear regression) the SAR. Residuals around the regression curve (as indicators of floristic diversity without the influence of island area) were calculated for each island. The proportion of endemics in the total island flora varies from 0% up to 28.6%, and 17.5% for narrow endemics. Floristic richness of the broader region was estimated (on the basis of SAR extrapolation) on 1807 species for all Croatian islands, and on 2797 species for the entire Mediterranean area in Croatia.

Do non‐native species invasions lead to biotic homogenization at small scales? The similarity and functional diversity of habitats compared for alien and native components of Mediterranean floras

ABSTRACTAlthough a number of recent studies have demonstrated biotic homogenization, these have mainly focused on larger spatial scales. Homogenizing effects are equally important at finer resolutions, e.g. through increasing similarity between habitats, which may result in a simplification of ecosystem structure and function. One major cause of homogenization is the expanding ranges of alien species, although it is not clear whether they are inherently homogenizing at smaller scales. We therefore assessed whether the alien flora is less complex across habitats than the resident native flora of Mediterranean Islands. From a regional data base, we examined floristic lists for between‐habitat taxonomic and functional similarity, and within‐habitat functional diversity, using resampled data sets to control for sample size biases. Aliens and natives showed equivalent complexity in most respects. At the taxonomic level, between‐island and between‐habitat similarities were almost identical, and when ecosystem function was measured by a functional group classification system, this was also true of between‐habitat similarities and within‐habitat diversities. When ecosystem function was measured using Grime's CSR classification, aliens were found to be more functionally homogenous between‐habitats and less functionally diverse within habitats. However, since the CSR profiles of aliens and natives differed, simplification is not inevitable due to ecological segregation of the two floras (aliens tend to be recruited to disturbed habitats rather than displacing natives). One deficiency is a lack of large scale species abundance data. A simple simulation exercise indicated that this is likely to lead to substantial overestimation of true levels of similarity, although would only influence the comparison between aliens and natives if they have different abundance distribution curves. The results indicate that alien floras are not intrinsically more simple than natives, but a higher proportion of competitive strategists among aliens may still cause small‐scale homogenization as these include many strong competitors that are likely to dominate communities.

Patterns and processes in insular floras affected by hurricanes

AbstractAim To investigate species compositions, rates of species turnover, species–area and species–distance relationships and patterns of nestedness in the floras of small Bahamian islands, by comparing two groups of islands that had been differentially affected by two hurricanes.Location Small islands occurring on either side of Great Exuma near Georgetown, Bahamas.Methods We surveyed the plant species of 44 small islands over a 5‐year period from 1998 to 2002. Hurricanes Lili and Michelle occurred in 1996 and 2001, respectively; both storms affected small islands on the more exposed south‐west side of Great Exuma to a greater degree than small islands on the more protected north‐east side. A set of 27 islands was surveyed in 1998 and 2002 to evaluate species turnover. Stepwise multiple linear regression analyses and an information‐theoretic approach (the Akaike information criterion) were used to elucidate the importance of area and distance as predictors of plant species number. We compared a piecewise linear regression model with a simple linear regression of species number against area to determine whether a small island effect existed. Nestedness patterns were evaluated by Wilcoxon two‐sample tests to analyse occurrence sequences.Results Species turnover was low in an absolute sense (overall = 0.74% year−1), yet was over three times higher than that documented in a nearby archipelago in the absence of hurricanes. Both vegetated area and distance were important predictor variables for exposed islands but not for protected islands. Some support was found for a small island effect for the exposed islands based on a piecewise linear regression model. Both island groups revealed significant nestedness at the level of the assemblage (both P < 0.001). On exposed islands, 65–79% (depending upon the method of calculation) of all species were significantly nested, but only 47% of all species were significantly nested on protected islands.Main conclusions Overall, these insular floras seem highly resistant to hurricane‐force disturbances. Species turnover was low (< 1% year−1) in an absolute sense, particularly in comparison with rates for other taxa. Higher degrees of nestedness and significant species–area and species–distance relationships for exposed islands indicated stronger patterns of community assembly. It is likely that disturbance is a major structuring force for the exposed islands, although the type of disturbances that mediate these patterns may not be primarily hurricane‐force storms.

Reconstruction of an extraordinary extinct primate from Madagascar

The minicontinent of Madagascar has been separated by 350 miles of ocean from its neighbor Africa for at least the past 120 million years, i.e., since long before the beginning of the Age of Mammals (1). As a result, the island's flora and fauna show extremely elevated levels of endemicity overall (2), and its native mammals show a curious combination of low diversity at the ordinal level with extraordinarily high diversity at lower taxonomic levels (3). Today, for example, Madagascar harbors an astonishing 30% of all primate families and some 21% of all primate genera (3), all of them represented nowhere else. Yet, high as these figures are, they would have been substantially higher a mere 2,000 years ago, before the arrival of Madagascar's first human inhabitants and the probably not coincidental extinction of a substantial proportion of the island's primate (lemur) fauna. In this issue of PNAS, Ryan et al. (4) report how new fossil discoveries and the use of computer-aided visualization techniques have significantly advanced our knowledge of cranial construction and body proportions in Hadropithecus, one of the most unusual of the recently extinct lemur genera.

Plant speciation in continental island floras as exemplified byNigellain the Aegean Archipelago

Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of geographical isolation on non-adaptive radiation and allopatric speciation brought about by genetic drift. The Aegean Archipelago forms a highly fragmented complex of mostly continental shelf islands that have become disconnected from each other and the mainland in relatively recent geological times (ca <5.2 Ma). These ecologically fairly homogenous islands thus provide a suitable biogeographic context for assessing the relative influences of past range fragmentation, colonization, gene flow and drift on taxon diversification. Indeed, recent molecular biogeographic studies on the Aegean Nigella arvensis complex, combining phylogenetic, phylogeographic and population level approaches, exemplify the importance of allopatry and genetic drift coupled with restricted gene flow in driving plant speciation in this continental archipelago at different temporal and spatial scales. While the recent (Late Pleistocene) radiation of Aegean Nigella, as well as possible instances of incipient speciation (in the Cyclades), is shown to be strongly conditioned by (palaeo)geographic factors (including changes in sea level), shifts in breeding system (selfing) and associated isolating mechanisms have also contributed to this radiation. By contrast, founder event speciation has probably played only a minor role, perhaps reflecting a migratory situation typical for continental archipelagos characterized by niche pre-emption because of a long established resident flora. Overall, surveys of neutral molecular markers in Aegean Nigella have so far revealed population genetic processes that conform remarkably well to predictions raised by genetic drift theory. The challenge is now to gain more direct insights into the relative importance of the role of genetic drift, as opposed to natural selection, in the phenotypic and reproductive divergence among these Aegean plant species.

Grasshopper outbreak challenges conservation status of a small Hawaiian Island

A tiny (63.1 ha) and uninhabited Nihoa Island within the Hawaiian Archipelago is situated 250 km NW of Kauai. It is a part of Papahānaumokuākea National Marine Monument established in 2006 and jointly administered by NOAA, USFWS, and the State of Hawaii (Department of Land and Natural Resources). The island’s known terrestrial biota include 26 vascular plant species, 27 bird species, and 243 arthropod species. Approximately half of the species are endemic to Nihoa or indigenous to Hawaii. Four plant species and two resident bird species are federally listed as threatened or endangered species. Gray bird grasshopper Schistocerca nitens has occurred on the main Hawaiian Islands since 1964 and was first reported from Nihoa in 1977. In 2002–2004, there was an outbreak of this grasshopper that aggravated the drought and denuded most of the island’s vegetation. Since then, grasshopper numbers crashed, most probably due to insufficient soil moisture for embryonic development. With subsequent rains, the island’s vegetation recovered. During the USFWS expedition to Nihoa in October 2006, grasshopper population assessments were undertaken. Based on 18, 300 × 2 m transect counts, the Nihoa grasshopper population was estimated at 19,430 ± 10,360 individuals. Laboratory rearing of S. nitens revealed that its development occurs without diapause. Potentially, the grasshopper can produce as many as four annual generations on Nihoa, although it is likely that only two generations occur. This article reviews the implications of fluctuations in S. nitens population dynamics for island flora and entomo- and avifauna, in particular, for the endangered endemics, the insectivorous Millerbirds. Potential threats to the island’s biota and challenges for conservation are discussed.

ORIGINAL ARTICLE: Why is habitat breadth correlated strongly with range size? Trends amongst the alien and native floras of Mediterranean islands

AbstractAim To identify the factors determining the relationship between habitat breadth and range size in the Mediterranean alien flora. Strong relationships have previously been uncovered between the two variables, which raises the possibility that habitat breadth could be used as a powerful predictor of invasiveness. However, previous investigations have yet to explain the phenomenon adequately, and greater understanding is required to establish its importance.Location Ninety‐one islands in the Mediterranean basin.Methods I examined a data base of Mediterranean naturalized plant species created for the EU project EPIDEMIE, and containing information on island distributions, habitat occupancy and other descriptive parameters compiled from published floras. As a null hypothesis, I assumed that the relationship between habitat breadth and range size was a spatial scale artefact: if species colonize habitats at random, with the likelihood determined by a weighted probability in each habitat, then perceived habitat breadth will increase with the number of populations examined. I modelled this effect, and also considered circumstantial evidence (via indirect indicator variables) for six hypotheses to determine whether both habitat breadth and range size may be jointly driven by a major third factor (introduction frequency, residence time, dispersal ability, generation time, dependence on mutualisms, release from herbivory). The explanatory power of the hypotheses was compared using correlative statistics.Results When habitat breadth was modelled according to the null hypothesis, the form of its relationship with range size was very similar to that from the observed data, and the predicted range size estimates explained almost half the observed variance. The unexplained component may have been due to the same mechanism operating at finer spatial scales. From the direction of the residual effect, increases in habitat breadth were probably driven by range size rather than vice versa. None of the alternative hypotheses were found to be significant predictors of habitat breadth and range size in invasive species.Main conclusions Although a number of minor explanations cannot be ruled out (e.g. that widespread species have greater regional genetic diversity enabling them to adapt to local conditions), it seems likely that the habitat breadth effect is largely artefactual and does not have particularly great value as a predictor of invasiveness.