Island Plant Research Articles

Investigation of floristic similarities between Taiwan and terrestrial ecoregions in Asia using GBIF data

BackgroundFloristic compositions of non-endemic plants of continental islands were related to the neighboring continents because non-endemic plant species had historically migrated to continental islands from source areas. This study attempts to identify source areas of a continental island by means of floristic analysis and to assess possible migration routes on the basis of geographical distribution ranges of plants. Large quantities of angiosperm data records were downloaded from the Global Biodiversity Information Facility (GBIF). Similarity index and cluster analysis were used to identify the floristic similarities among 22 geographical localities of Taiwan (GLTs) and 34 terrestrial ecoregions in Asia. Geographical distribution ranges of non-endemic angiosperm species in Taiwan (NEASTs) were evaluated to mirror the possible migration routes from different source areas to Taiwan.ResultsThere are 3275 angiosperm species in Taiwan derived from the dataset of GBIF. Among them, 847 are endemic and 2428 are NEASTs. Geographical distribution ranges of the 2428 NEASTs were categorized into 7 distribution groups. They were widely distribution from equator to Siberia (27 species), tropical ecoregions (345 species), tropical and subtropical ecoregions (663 species), tropical to temperate ecoregions (591 species), subtropical ecoregions (265 species), subtropical to temperate ecoregions (387 species), and temperate ecoregions (150 species). Results of similarity indices and cluster analysis demonstrated that high floristic similarities were observed among GLTs at lowland and southern Taiwan and tropical and subtropical ecoregions in Asia. GLTs at high mountains were assumed to have floristic similarity with temperate ecoregions in Asia, whereas the assumption was not supported by our analysis. It is partly because of that angiosperms with tropical and subtropical distributions extend their ranges from low to high elevations in Taiwan.ConclusionsSubtropical ecoregions at southern China and tropical ecoregions at Indochina were more important than temperate ecoregions on playing source areas of NEASTs. Geographical distribution ranges of NEASTs implied that most of the NEASTs were probably migrated from topical or subtropical ecoregions of Asian continent to Taiwan.

The Dynamic Response Analysis of Pseudo Three Dimensional of Nuclear Island Plant Structure under Non-lithology Foundation Condition

Building nuclear power plant structure on lithology ground or soft ground has become an inevitable and popular trend in the development of nuclear island plant structure. It leads the seismic analysis of non-lithology foundation to be the key technical issues to choose the nuclear power plant site. In order to solve the engineering practicality issues of seismic analysis of non-lithology foundation and the issues of simplifying the complex nuclear power plant structure, the three- dimensional (3D) finite element model of the AP1000 nuclear power plant structure has been simplified to two-dimensional model in this paper based on ANSYS software. The principle of the simplification is that the mass and stiffness of models should be equivalent. Then establish the pseudo 3D model in SuperFLUSH software to explore the mechanism of the earthquake loads and seismic response characteristics of nuclear power plant structure. Finally, compare the frequency characteristics and compare the true three-dimensional results of SASSI software with the results of SuperFLUSH software to verify the rationality and effectiveness of the simplification.

Island floras as model systems for studies of plant speciation: Prospects and challenges

AbstractOceanic islands have long been called natural laboratories for studying evolution because they are geologically young, isolated, dynamic areas with diverse habitats over small spatial scales. Volcanic substrates of different ages permit the study of different stages of divergence and speciation within plant lineages. In addition to divergence, the dynamic island setting is conducive to hybridization. Discussion will focus on the potential of systematic/ecological studies, in combination with genomic data from high throughput sequencing and an ever‐increasing array of analytical techniques, for studying evolution in island plants. These studies may include: generation of highly resolved phylogenies to clarify the biogeography of speciation and whether divergence has occurred with or without gene flow; identification of the barriers to gene flow (extrinsic vs. intrinsic) of importance during divergence; documentation of historical and current hybridization events within island lineages; and elucidation of the genomic composition and ecology of hybrid populations in order to infer the evolutionary consequences of hybridization, such as the origin of stabilized homoploid hybrid species.

Network biogeography of a complex island system: the Aegean Archipelago revisited

AbstractAimThe Aegean Archipelago has been the focal research area for identifying and testing several ecological and evolutionary patterns, yet its biogeographical subdivision has been somewhat overlooked, with the processes driving the assembly of the Aegean island plant communities still remaining largely unclear. To bridge this gap, we identify the biogeographical modules (highly linked subgroups of islands and plant taxa) within the Aegean Archipelago.LocationThe Aegean Archipelago, Greece.MethodsWe used a network approach to detect island biogeographical roles and modules, based on a large and detailed database including 1498 Aegean endemic and subendemic plant taxa distributed on 59 Aegean Islands and five adjacent mainland areas.ResultsThe Aegean was divided into six biogeographical modules; the network was significantly modular. None of the modules displayed all four possible biogeographical roles (connectors, module hubs, network hubs, peripherals). Six new biogeographical regions in the Aegean were identified.Main conclusionsThe borders of the six biogeographical regions in the Aegean correspond well to the region's palaeogeographical evolution from the middle Miocene to the end of the Pleistocene. The Central Aegean acts as an ecogeographical filter for the distribution of several plant lineages across the Aegean Sea, while there seems to be a N–S‐oriented biogeographical barrier in the Aegean corresponding to the palaeogeographical situation during the middle Ionian. These biogeographical barriers have been fundamental for both plants and animals.

Native-exotic richness relationships: a biogeographic approach using turnover in island plant populations.

Spatial variation in exotic species richness is often correlated with native species richness, for reasons that are poorly understood. To better understand the mechanisms underpinning native-exotic richness relationships, I quantified the colonization and extinction of 18 exotic and 16 native plant species on 39 small islands located off the coast of New Zealand for 8 consecutive yr. Results revealed a positive native-exotic richness relationship, which could be explained by similar demographic responses of native and exotic species to island area. However, native and exotic species showed subtle differences in their response to other island attributes. Turnover in native species declined with island isolation, whereas turnover in exotic species increased with the exposure of islands to ocean-borne disturbances. Overall results illustrate how long-term observations of species turnover can be used to better understand the mechanisms underpinning native-exotic richness relationships, and demonstrate that large, exposed islands can be especially susceptible to invasions by exotic species.

A new framework for investigating biotic homogenization and exploring future trajectories: oceanic island plant and bird assemblages as a case study

Studies of biotic homogenization have focused primarily on characterizing changes that have occurred between some past baseline and the present day. In order to understand how homogenization may change in the future, it is important to contextualize the processes driving these changes. Here, we examine empirical patterns of change in taxonomic similarity among oceanic island plant and bird assemblages. We use these empirical cases to unpack dynamic properties of biotic homogenization, thereby elucidating two important factors that have received little attention: 1) initial similarity and 2) the influence of six classes of introduction and extinction events. We use Jaccard's Index to explore the interplay among these factors in determining the changes in similarity that have occurred between human settlement and the present. Specifically, we develop general formulas for changes in similarity resulting from each of the six types of introductions and extinctions, so that the effect of each event type is formulated in terms of initial similarity and species richness. We then apply these insights to project how similarity levels would change in the future if the present patterns of introductions and extinctions continue. We show that the six event types, along with initial similarity, can show dramatically different behavior in different systems, leading to widely variable influences on similarity. Plant and bird biotas have homogenized only slightly to date, but their trajectories of change are highly divergent. Although existing patterns of colonization and extinction might not continue unchanged, if they were to do so then plant assemblages would show little additional change, whereas bird assemblages would become much more strongly homogenized. Our results suggest that moderate changes in similarity observed to date mask the potential for more dramatic changes in the future, and that the interaction among initial similarity and differential introduction and extinction regimes drives these dynamics.

Phylogeny and Evolution of Endemic Species on Ulleungdo Island, Korea: The Case of <I>Fagus multinervis</I> (Fagaceae)

Abstract The genus Fagus (beech, Fagaceae) consists of about 10 species discontinuously distributed in East Asia, eastern North America, and Europe. Fagus multinervis occurs only on Ulleungdo Island, Korea, and is an important component of the island's plant community. The species was described primarily based on one of its stem characteristics: it branches at the base, producing several primary trunks. In part because no extant Fagus species are found in mainland Korea, and because the closest populations of Fagus are found in Japan, F. multinervis has been considered to be derived from the Japanese species, F. japonica. However, a recent study synonymized F. multinervis under F. engleriana and proposed that the beech population of Ulleungdo Island was derived instead from China via long-distance dispersal. Fagus multinervis is morphologically very similar to F. engleriana, but it can be distinguished by having rhombic lenticels that are vertically elongated. We determined the nucleotide sequences of the...

Minimal loss of genetic diversity and no inbreeding depression in blueflag iris (Iris versicolor) on islands in the Bay of Fundy

Isolated island plant populations founded by few individuals are often characterized by decreased genetic variation and increased inbreeding. Our aim was to measure population genetic diversity and inbreeding depression in blueflag iris (Iris versicolor L., Iridaceae), a native allotetraploid, on islands in the Bay of Fundy, Canada. Hand-pollination experiments (inbreeding, within-site outbreeding, between-island outbreeding) on Kent Island, New Brunswick, revealed no evidence for inbreeding depression across a broad array of morphological, physiological, and life-history traits. Leaf tissue samples collected from three mainland sites and 10 islands in the Bay of Fundy and genotyped using three microsatellite primer pairs showed that island populations were less genetically diverse than mainland populations. Island populations were genetically distinct from each other, indicating a bottleneck effect associated with colonization and continued isolation. Nonetheless, substantial genetic variation was maintained at the population level. Polyploidy and a history of self-fertilization may allow Iris versicolor to avoid inbreeding depression in isolated populations. Our study supports Anderson’s (1936) original hypothesis that substantial genetic diversity can be preserved within polyploid species, even with extensive inbreeding.

Island-Biogeographical Characteristics of Insular Flora in Southern Sea of Jeollanamdo, Korea

Present work aims to establish the countermeasure for the better maintenance and preservation of insular floristic diversity at the South Sea of Jeollanamdo Province, ROK, where unique ecosystems are under threat due to climate change, anthropogenic disturbance and habitat destruction. Numerous flora reports from 15 inhabited islands and 60 uninhabited islands as well as field survey data are collated for the compilation of floristic data base and island biogeographical analysis. Out of the 1,940 vascular plant species from 180 families occurring in studies areas, 30.1 percentage or 584 plant species are physiognomically belonging to arboreal plants. Average number of species at individual island is numbered about 222 species, but it varies from about 591 species at the inhabited islands to 129 species at the uninhabited islands. Only 0.15 percentage of species with high proportion above 0.9 in its relative occurrence rate occurs at 68 islands and it includes three species, such as Pinus thunbergii, Eurya japonica and Pteridium aquilinum var. latiusculum. However, about 68 percentage of plant species occurring in study area is confined their distribution to less than seven islands. Presence of high proportion of notable plants in small islands, i.e., 10 critically endangered species compared with 5.5 species in average, 9 endangered species (average 4.2 spp.) at Sonjookdo, and 7 critically endangered species, 8 endangered species at Sokomundo may due to existence of diverse geological and topographical environmental diversity as well as lower human population density and remoteness from the mainland. Since island is small in size and geographically isolated, minor environmental and ecological burdens can cause the critical damages to the diversity of flora and vegetation, urgent island biogeographical research is needed for the scientific conservation and management of island biodiversity.

Low tolerance to simulated herbivory in Hawaiian seedlings despite induced changes in photosynthesis and biomass allocation.

Seedling herbivory is an important factor underlying plant community diversity and structure. While considerable research has characterized seedling defence in terms of resistance, very little is known about seedling tolerance of herbivory. Moreover, few studies have attempted to identify mechanisms of tolerance across a range of plant species. Seedling tolerance of simulated herbivory was tested in a diverse pool of ten Hawaiian plant species, including several lobeliad species (family Campanulaceae), a grass, a herb and common woody trees and shrubs. Tolerance was measured as the relative survival and growth of damaged plants receiving 50% defoliation with simultaneous jasmonic acid application compared with undamaged control plants, assessed 1·5 and 5weeks after damage. Putative mechanisms of tolerance were measured, including photosynthetic parameters, light use efficiency, and biomass allocation reflecting growth priorities, and analysed using species-level regression analyses on tolerance indices. No species fully tolerated 50% defoliation at either harvest date, and simulated herbivory significantly reduced shoot as well as root biomass. Lobeliad species had particularly low tolerance. Species varied considerably in size, biomass allocation parameters and their constitutive (pre-damage) and induced (post-damage) photosynthetic parameters. However, only constitutive levels of non-photochemical quenching were significantly related to tolerance, indicating that species with more efficient light use (and less heat dissipation) are better at tolerating damage than species with high levels of heat dissipation. Native Hawaiian plants expressed low tolerance to a conservative level of simulated herbivory. Root growth decreased in response to damage, but this was not associated with greater tolerance, suggesting this response may be due to allocation constraints following defoliation and not due to adaptive plasticity. Conservation of native island plants threatened by invasive herbivores should prioritize protection for seedlings for improved regeneration and the persistence of native plants in disturbed habitats.

Ecological systems as computer networks: Long distance sea dispersal as a communication medium between island plant populations

Ecological systems are known to exchange genetic material through animal species migration and seed dispersal for plants. Isolated plant populations have developed long distance dispersal as a means of propagation which rely on meteorological such as anemochory and hydrochory for coast, island and river bank dwelling species. Long distance dispersal by water, in particular, in the case of water current bound islands, calls for the analogy with computer networks, where each island and nearby mainland site plays the role of a network node, the water currents play the role of a transmission channel, and water borne seeds as data packets.In this paper we explore this analogy to model long distance dispersal of seeds among island and mainland populations, when traversed with water currents, in order to model and predict their future genetic diversity. The case of Pancratium maritimum L. populations in Tunisia is used as a proof of concept, where their genetic diversity is extrapolated.

Island biogeography: Shaped by sea-level shifts.

An analysis of changes in island topography and climate that have occurred since the last glacial maximum 21,000 years ago shows how sea-level change has influenced the current biodiversity of oceanic islands. See Letter p.99 Our understanding of biodiversity on islands assumes that either they are the geologically static backgrounds for immigration and emigration, or that they are more dynamic, influenced by geological and tectonic change over millions of years. Neither model, however, accommodates the rapid change over the past 20,000 years or so, during which time the melting of ice caps has driven up sea levels by more than 100 metres, dividing up landmasses, making small islands smaller and more remote. Patrick Weigelt et al. find that such inundations have had a measurable effect on island plant biodiversity. In particular, islands that were larger during the Last Glacial Maximum have more endemic species today than one would expect from their current size and remoteness, whereas the number of native species is essentially the same.

Loss of a single tree species will lead to an overall decline in plant diversity: Effect of Dracaena cinnabari Balf. f. on the vegetation of Socotra Island

Dracaena cinnabari, the dominant endemic tree of Socotra Island (Yemen), is in serious decline. The effect this will have on the island's plant diversity remains unknown. We aimed to identify plants associated with Dracaena understorey and assess the importance of Dracaena for maintaining plant diversity. A total of 272 relevés were sampled in Dracaena understorey and in open sites to record the number of individuals of vascular plants. Species richness and composition were compared between understorey and open sites, and species associated with each of these habitats were identified. Additionally, the effect of canopy closure on species richness and abundance was analysed. We also recorded woody species composition of Dracaena stands and investigated spatial relations between Dracaena and other mature woody plants. Understorey plant species composition differed from open site composition. The former habitat showed higher β-diversity and species richness. Among recorded plants, 15 species were classified as understorey specialists, 6 as open-site specialists, and 23 as generalists. Rare species, especially endemics, were more common in the understorey. Canopy closure had differential effect on species abundances among the species classes. Species richness and total abundance were found to be highest in the understorey, particularly in the case of low-to-intermediate canopy closure where understorey and open-site specialists may co-occur. For mature woody plant species, Dracaena was spatially independent from other woody species at most distances. Our results suggest that the decline of Dracaena may negatively affect plant diversity, reduce abundance of rare endemic plants and lead to homogenization of vegetation. As no other tree species exists in the study area which could replace the Dracaena, our findings underline the importance of conservation efforts to preserve Dracaena stands on Socotra.

Geographical distance and barriers explain population genetic patterns in an endangered island perennial.

Island plants are frequently used as model systems in evolutionary biology to understand factors that might explain genetic diversity and population differentiation levels. Theory suggests that island plants should have lower levels of genetic diversity than their continental relatives, but this hypothesis has been rejected in several recent studies. In the Azores, the population level genetic diversity is generally low. However, like in most island systems, there are high levels of genetic differentiation between different islands. The Azores lettuce, Lactuca watsoniana, is an endangered Asteraceae with small population sizes. Therefore, we expect to find a lower level of genetic diversity than in the other more common endemic Asteraceae. The intra- and interpopulation genetic structure and diversity of L. watsoniana was assessed using eight newly developed microsatellite markers. We included 135 individuals, from all 13 known populations in the study. Because our microsatellite results suggested that the species is tetraploid, we analysed the microsatellite data (i) in codominant format using PolySat (Principal Coordinate Analysis, PCoA) and SPAgedi (genetic diversity indexes) and (ii) in dominant format using Arlequin (AMOVA) and STRUCTURE (Bayesian genetic cluster analysis). A total of 129 alleles were found for all L. watsoniana populations. In contrast to our expectations, we found a high level of intrapopulation genetic diversity (total heterozigosity = 0.85; total multilocus average proportion of private alleles per population = 26.5%, Fis = -0.19). Our results show the existence of five well-defined genetic groups, one for each of the three islands São Miguel, Terceira and Faial, plus two groups for the East and West side of Pico Island (Fst = 0.45). The study revealed the existence of high levels of genetic diversity, which should be interpreted taking into consideration the ploidy level of this rare taxon.

Contrasting decadal-scale changes in elevation and vegetation in two Long Island Sound salt marshes.

Northeastern US salt marshes face multiple co-stressors, including accelerating rates of relative sea level rise (RSLR), elevated nutrient inputs, and low sediment supplies. In order to evaluate how marsh surface elevations respond to such factors, we used surface elevation tables (SETs) and surface elevation pins to measure changes in marsh surface elevation in two eastern Long Island Sound salt marshes, Barn Island and Mamacoke Marsh. We compare marsh elevation change at these two systems with recent rates of RSLR and find evidence of differences between the two sites; Barn Island is maintaining its historic rate of elevation gain (2.3± 0.24 mm yr-1 from 2003 to 2013) and is no longer keeping pace with RSLR, while Mamacoke shows evidence of a recent increase in rates (4.2 ± 0.52 mm yr-1 from 1994 to 2014) to maintain its elevation relative to sea level. In addition to data on short-term elevation responses at these marshes, both sites have unusually long and detailed data on historic vegetation species composition extending back more than half a century. Over this study period, vegetation patterns track elevation change relative to sea levels, with the Barn Island plant community shifting towards those plants that are found at lower elevations and the Mamacoke vegetation patterns showing little change in plant composition. We hypothesize that the apparent contrasting trend in marsh elevation at the sites is due to differences in sediment availability, salinity, and elevation capital. Together these two systems provide critical insight into the relationships between marsh elevation, high marsh plant community, and changing hydroperiods. Our results highlight that not all marshes in southern New England may be responding to accelerated rates of RSLR in the same manner.

Inbreeding, low genetic diversity, and spatial genetic structure in the endemic Hawaiian lobeliads Clermontia fauriei and Cyanea pilosa ssp. longipedunculata

The endemic lobeliad genera Cyanea and Clermontia (Campanulaceae) are among the largest in the native Hawaiian flora, and contain large numbers of endangered and threatened taxa. As a baseline for future studies of rare species in this group, we used RAD markers to estimate genetic variation and spatial genetic structure in single populations of two common species, Cyanea pilosa ssp. longipedunculata on Hawai`i and Clermontia fauriei on Kaua`i. We found low to moderate levels of genetic diversity (He ≈ 0.13 and πall ≈ 0.0013 for both species), consistent with studies of several other island plant species, and substantial inbreeding (Fis ≈ 0.17). There was no evidence for spatial genetic structure in Cyanea, and in Clermontia SGS was weak and restricted to small spatial scales (<10 m). The relative dearth of genetic diversity and high levels of inbreeding in these common lobeliads may reflect pre-existing conditions in this group or selfing in response to a decline in native avian pollinators, raising concerns that inbreeding and loss of genetic variation may be even more severe in rare species of this highly diverse but endangered group.

Introduction to the Special Issue: Advances in island plant biology since Sherwin Carlquist's Island Biology.

Sherwin Carlquist's seminal publications-in particular his classic Island Biology, published in 1974-formulated hypotheses specific to island biology that remain valuable today. This special issue brings together some of the most interesting contributions presented at the First Island Biology Symposium hosted in Honolulu on 7-11 July 2014. We compiled a total of 18 contributions that present data from multiple archipelagos across the world and from different disciplines within the plant sciences. In this introductory paper, we first provide a short overview of Carlquist's life and work and then summarize the main findings of the collated papers. A first group of papers deals with issues to which Carlquist notably contributed: long-distance dispersal, adaptive radiation and plant reproductive biology. The findings of such studies demonstrate the extent to which the field has advanced thanks to (i) the increasing availability and richness of island data, covering many taxonomic groups and islands; (ii) new information from the geosciences, phylogenetics and palaeoecology, which allows us a more realistic understanding of the geological and biological development of islands and their biotas; and (iii) the new theoretical and methodological advances that allow us to assess patterns of abundance, diversity and distribution of island biota over large spatial scales. Most other papers in the issue cover a range of topics related to plant conservation on islands, such as causes and consequences of mutualistic disruptions (due to pollinator or disperser losses, introduction of alien predators, etc.). Island biologists are increasingly considering reintroducing ecologically important species to suitable habitats within their historic range and to neighbouring islands with depauperate communities of vertebrate seed dispersers, and an instructive example is given here. Finally, contributions on ecological networks demonstrate the usefulness of this methodological tool to advancing conservation management and better predicting the consequences of disturbances on species and interactions in the fragile insular ecosystems.

菅島の蛇紋岩土壌に生育する植物の元素組成と、ツゲの特異的なニッケル・鉄集積

菅島の蛇紋岩土壌に生育する植物の元素組成と、ツゲの特異的なニッケル・鉄集積

Herbicide application as a habitat restoration tool: impact on native island plant communities

AbstractQuestionsWhich physical or chemical removal method is most effective in controlling woody invasive alien plant (IAP) species in sensitive conservation areas, while minimizing the impact on different life stages of native plant communities? Is there a distinct influence of removal method on successional trajectories of post‐treatment seedling communities?LocationMid‐altitude inselbergs, Mahé, Seychelles, Indian Ocean.MethodsWe conducted two field experiments. First, to test the effects of four IAP control methods (cut, 5%, 10%, 15% Tordon 101 herbicide concentration) on ten woody IAP species, we treated a total of 320 adults and monitored mortality for 18 wk. Second, we set up five blocks each with four plots (4 m × 4 m) at three inselberg sites (N = 60 plots) and recorded the response of seedlings, saplings and adults of all native and IAP species to four Tordon 101 (a.i. picloram and 2,4‐D) herbicide and manual control treatments (cut, cut‐stump, foliar spray, control) over 22 mo. Treatment effects were analysed with GLMM models, and community responses were investigated with NMDS and multivariate ANOVA.ResultsThe first experiment showed that IAP mortality (98.3%) was similar across all three herbicide concentrations, but markedly higher than mortality of cut plants (42.5%). In the second experiment, abundance, but not diversity, of native seedlings declined with herbicide application in the first 6 mo after treatment. Ordination analysis showed that seedling communities experienced high turnover driven by early successional IAP species and abundance, and that between‐plot variation was determined by site‐specific differences, with only a weak treatment effect. Foliar spray resulted in high mortality of native saplings (52.7%) and adults (18.3%), and both herbicide applications reduced adult growth over a post‐treatment period of 12 mo.ConclusionIAP removal controlled plant invasion processes and altered community composition in the short term, regardless of removal method. Post‐treatment trajectories of seedling communities are determined by site‐specific differences. Chemicals can strongly increase the efficacy of IAP control, but short‐term detrimental effects on native saplings and adults may be expected. As re‐invasion by IAPs is likely, a long‐term restoration plan is required. Management strategies that aim to conserve β‐diversity should employ a landscape approach to habitat restoration to buffer against site idiosyncrasies.

Phytogeographical affinities at the crossroads of two continents: Distribution patterns of Lamiaceae in Chios Island (East Aegean Islands, Greece) and Çeşme–Karaburun Peninsula (West Anatolia, Turkey)

The East Aegean (East Aegean Islands, Greece and West Anatolia, Turkey) is a biogeographically transitional region, where biodiversity elements from Europe and Asia join. However, affinities in the region were until recently scarcely explored. We assess biogeographical affinities in the East Aegean focusing on distribution patterns of Lamiaceae plants in Chios Island and its adjacent Çeşme–Karaburun Peninsula. Detailed in-situ record was acquired for 48 native species. These were grouped based on their habitat and geological substrate preference, their distribution was mapped in grid cells and distribution patterns were analysed in relation to species groupings. In both Chios and Çeşme–Karaburun, species follow five distribution patterns: widespread, locally widespread, locally restricted, sporadic and rare. Fifty to 62% of the species exhibit similar distribution patterns, trends in habitat and geological substrate preference in Chios and Çeşme–Karaburun, results complying with previous evidence of close biogeographical affinities of the East Aegean Islands and neighbouring Anatolia. Differences observed between the two regions may be attributed to insularity effects, human impact and the melange, an old rock matrix known for its key role in elucidating regional geodynamic evolution. Distributions of widespread and locally widespread species in Chios give evidence of density compensation and niche shifts responses, however, the actual occurrence of these phenomena in island plant populations is still to be elucidated. Overall, the species distribution patterns, particularly those of rare ones, reflect the complex geological history, palaeogeography and human influence in the Aegean region.