Island Floras Research Articles

Notes à la flore de Corse, XXVI

These “notes” deal with 110 noteworthy taxa amongst which 21 are new to the islands flora. One of these taxa is native: Reseda alba subsp. hookeri and 20 are introduced: Abies pinsapo, Acer —coria

A paradox of latitudinal leaf defense strategies in deciduous and evergreen broadleaved trees

The classical “low latitude–high defense” hypothesis is seldom supported by empirical evidence. In this context, we tested latitudinal patterns in the leaf defense traits of deciduous broadleaved (DB) and evergreen broadleaved (EGB) tree species, which are expected to affect herbivore diversity. We examined the co-occurrence of leaf defense traits (tannin and phenol content, leaf mechanical strength, leaf dry matter content, leaf mass per area, and leaf thickness) in 741 broadleaved tree species and their correlations with species geographical range in East Asian island flora. We discovered contrasting latitudinal defense strategy gradients in DB and EGB tree species. DB species employed chemical defenses (increasing tannin and phenol content) at higher latitudes and physical defenses (softer and thinner leaves) at lower latitudes, whereas EGB tree species exhibited opposite latitudinal defense patterns. The “low latitude high defense” hypothesis included a paradoxical aspect in chemical and physical defense traits across broadleaved tree species. To reconcile paradoxical defense strategies along the latitudinal gradient, we conclude that interactive correlations among leaf traits are controlled by leaf longevity, which differs between DB and EGB tree species.

Traditional uses, antimicrobial and acaricidal activities of 20 plants selected among Reunion Island's flora

The aim of this study was to screen the antimicrobial and acaricidal activity of 20 endemic or indigenous plants from Reunion Island (Indian Ocean). Plants were chosen on the basis of their traditional uses and their biocidal activities found in the literature. A survey was conducted in the local population to assess and supplement knowledge about the selected plants. The collected information confirmed and/or supplemented the data obtained for nine plants. Seven plants were described for the first time for their traditional uses in medicine and ethnoveterinary practices. To evaluate their biocidal activities, leaves or bark were treated with ethyl acetate using an accelerated solvent extraction method. Six bacteria and five fungi, frequently implicated in infectious diseases, were used to assess the antimicrobial activity of these extracts. A preliminary screening using the paper disk diffusion assay showed an effective antibacterial activity of 16 extracts. The minimum inhibitory concentration (MIC) of active plant extracts was then determined using a microdilution method. The leaf extract from Peperomia borbonensis displayed the widest spectrum of antibacterial activity and was the only one to act as a fungicide. In parallel, acaricidal bioassays were performed on the larvae of the tick Rhipicephalus microplus (Ixodidae), and plant extracts from Peperomia borbonensis and Zanthoxylum heterophyllum were the most effective. The preliminary studies of these plant extracts exhibited biocidal activities that were not described in the literature and that are congruent with traditional uses for some of them. Investigations are currently being conducted to isolate the active compound(s) and evaluate their potential for future developments and applications.

Inferring spatial patterns and drivers of population divergence of Neolitsea sericea (Lauraceae), based on molecular phylogeography and landscape genomics

The relative roles of geography, climate and ecology in driving population divergence and (incipient) speciation has so far been largely neglected in studies addressing the evolution of East Asia’s island flora. Here, we employed chloroplast and ribosomal DNA sequences and restriction site-associated DNA sequencing (RADseq) loci to investigate the phylogeography and drivers of population divergence of Neolitsea sericea. These data sets support the subdivision of N. sericea populations into the Southern and Northern lineages across the ‘Tokara gap’. Two distinct sublineages were further identified for the Northern lineage of N. sericea from the RADseq data. RADseq was also used along with approximate Bayesian computation to show that the current distribution and differentiation of N. sericea populations resulted from a combination of relatively ancient migration and successive vicariant events that likely occurred during the mid to late Pleistocene. Landscape genomic analyses showed that, apart from geographic barriers, barrier, potentially local adaptation to different climatic conditions appears to be one of the major drivers for lineage diversification of N. sericea.

Insular woody daisies (Argyranthemum, Asteraceae) are more resistant to drought‐induced hydraulic failure than their herbaceous relatives

Abstract Insular woodiness refers to the evolutionary transition from herbaceousness towards derived woodiness on (sub)tropical islands and leads to island floras that have a higher proportion of woody species compared to floras of nearby continents. Several hypotheses have tried to explain insular woodiness since Darwin's original observations, but experimental evidence why plants became woody on islands is scarce at best. Here, we combine experimental measurements of hydraulic failure in stems (as a proxy for drought stress resistance) with stem anatomical observations in the daisy lineage (Asteraceae), including insular woody Argyranthemum species from the Canary Islands and their herbaceous continental relatives. Our results show that stems of insular woody daisies are more resistant to drought‐induced hydraulic failure than the stems of their herbaceous counterparts. The anatomical character that best predicts variation in embolism resistance is intervessel pit membrane thickness (TPM), which can be functionally linked with air bubble dynamics throughout the 3D vessel network. There is also a strong link between TPM vs. degree of woodiness and thickness of the xylem fibre wall vs. embolism resistance, resulting in an indirect link between lignification and resistance to embolism formation. Thicker intervessel pit membranes in Argyranthemum functionally explain why this insular woody genus is more embolism resistant to drought‐induced failure compared to the herbaceous relatives from which it has evolved, but additional data are needed to confirm that palaeoclimatic drought conditions have triggered wood formation in this daisy lineage. A plain language summary is available for this article.

Strong indication of an extinction-based saturation of the flora on the Pacific Robinson Crusoe Islands.

Oceanic islands are vulnerable ecosystems and their flora has been under pressure since the arrival of the first humans. Human activities and both deliberately and inadvertently introduced biota have had and continue to have a severe impact on island endemic plants. The number of alien plants has increased nearly linearly on many islands, perhaps resulting in extinction‐based saturation of island floras. Here, we provide evidence for such a scenario in Alejandro Selkirk, Robinson Crusoe Islands (Archipelago Juan Fernández, Chile). We compared species richness and species composition of historical vegetation samples from 1917 with recent ones from 2011. Changes in species’ relative occurrence frequency were related to their taxonomic affiliation, dispersal mode, distribution status, and humidity and temperature preferences. While total species richness of vascular plants remained relatively similar, species composition changed significantly. Plants endemic to the Robinson Crusoe Islands declined, exotic species increased substantially within the period of ca. 100 years. Further, the relative occurrence frequency of plants with preferences for very warm and humid climate decreased, while the opposite was found for plants preferring drier and colder environments. Potential drivers responsible for this dramatic shift in the vegetation within only one century might have been the large goat population affecting especially small populations of endemic plants and climatic changes. Taking into account a substantial extinction debt, we expect further shifts in the vegetation of this small oceanic island toward alien plants. This would have significant negative consequences on global biodiversity, considering that island floras contribute substantially to global plant species richness due to their high proportion of endemics.

Morphological and taxonomical analysis of the terrestrial diatom genus Humidophila (Bacillariophyta) on Ile Amsterdam and Ile Saint-Paul (Southern Indian Ocean)

During a survey of the non-marine diatom flora of the volcanic islands, Ile Amsterdam and Ile Saint-Paul (southern Indian Ocean), seven species belonging to the terrestrial diatom genus Humidophila have been recorded. Apart from five previously known taxa (Humidophila contenta, H. crozetikerguelensis, H. gallica, H. brekkaensis, H. vidalii), two taxa could not be identified based on the currently available literature and are described as new to science: Humidophila amsterdamensis sp. nov. and Humidophila rouhaniana sp. nov. Detailed morphological descriptions of these taxa are given based on both light (LM) and scanning electron microscopy (SEM) observations. The morphological features of each taxon have been compared with similar species and notes on their ecology and associated diatom communities have been added.

Flora and species composition similarity of the uninhabited islands in the nearshore Xiamen

Flora and species composition similarity of the uninhabited islands in the nearshore Xiamen

Taraxacum(Asteraceae) in the Azores, Madeira and the Canary Islands

Taraxacum species collected in the Azores, Madeira and the Canary Islands are reported, described and illustrated. Most of them are new records, especially for the Canary Islands flora where T. canariense is the only one reported previously. Taraxacum guanchicum A. Galan & E. Linares & Vicente Orell. is described as a new species from Gran Canaria and Tenerife. A key to and a distribution map of all the species studied are provided.

Plant reproductive ecology and evolution in the Mediterranean islands: state of the art.

The ca. 12,000 islands and islets that encompass the Mediterranean Basin represent a biodiversity hotspot. They have been disconnected from each other and from the continent for hundreds of thousands to millions of years and encompass a high incidence of endemic plant species, with values that can exceed 20% of the local flora. Despite this, relatively few studies have been carried out to unravel ecological and evolutionary aspects of plant reproduction. We synthesise here the available information on the breeding systems, pollination and seed dispersal mode of the Mediterranean island flora. The main objective is to identify general patterns as well as to detect the main gaps in information on reproductive ecology in these particular and vulnerable systems in the face of global change. We also briefly review the information on impacts of invasive species on plant reproduction and dispersal, as these are some of the main threats to island biodiversity in general and Mediterranean island plant diversity in particular. The review has revealed that most available information is very geographically biased towards the western Mediterranean islands, especially the Balearic Islands, although a good fraction of studies have also been carried out on the eastern islands in the Aegean archipelago. Moreover, the majority of data come from species-focused studies, mainly endemic species of restricted range, whereas only a small fraction of studies have been performed at a community level. Relatively little work has involved genetic analyses, mainly focused on assessing the genetic differentiation and variability on narrow endemics. Contrary to our expectations, most island species do not rely on autonomous selfing, which might be related to the relatively high diversity of pollinators. The small, uninhabited, islands might be the last refuges of peculiar interactions that evolved in them in ancient times; they thus should be considered as sanctuaries of extraordinary biodiversity. Finally, we point out the main gaps of information and formulate a set of hypotheses that we believe are worth testing in future studies if we are to advance knowledge on the reproductive biology of Mediterranean island plants.

Additions to Flora of Andaman and Nicobar Islands, India

Six Sedges: Cyperus eragrostis, C. pilosus, Pycreus membranaceus, P. polystachyos var. microdontus, Schoenoplectus litoralis and Scleria parvula are being reported as new distributional records for Andaman and Nicobar Islands.

The alien vascular flora of Linosa (Pelagie Islands, Strait of Sicily): update and management proposals

This paper provides an up-to-date overview of the naturalized alien plants of Linosa (Pelagie Archipelago, Sicily), which includes 83 taxa and accounts for 29 % of the total island's flora. Among these plants, 6 are invasive, 49 are naturalized and 28 are casual. With respect to previous available data, our field investigations resulted in the addition of 31 new xenophytes (21 casual and 10 fully naturalized). One of these species is new to the whole European territory (Kleinia anteuphorbia), 6 of them are new to Sicily and 11 are recorded for the first time on circum-Sicilian islets. For each alien plant, we indicate the habitat where the naturalization has been observed by using the codes proposed by Natura 2000 and Corine Biotopes habitat classification. We also provide a list of 159 alien plants that are cultivated in Linosa, but currently not naturalized, in order to underline the key role played by horticulture and gardening in the introduction of exotic species. In order to address this phenomenon and its huge impact on the integrity of both the natural and the traditional rural landscape, several actions are proposed that aim at preventing, controlling and monitoring both the ongoing and the potential invasion processes.Citation: Pasta S., Ardenghi N. M. G., Badalamenti E., La Mantia T., Livreri Console S. & Parolo G. 2017: The alien vascular flora of Linosa (Pelagie Islands, Strait of Sicily): update and management proposals. — Willdenowia 47: 135–144. doi: https//doi.org/10.3372/wi.47.47205Version of record first published online on 13 July 2017 ahead of inclusion in August 2017 issue.

Convergent evolution of gigantism in the flora of an isolated archipelago

Animals often evolve conspicuous differences in body size after colonising isolated islands. However, far less is known about repeated patterns in the evolution of plant size on islands. We tested for convergent evolution of leaf area, seed size and plant stature in the flora of the Chatham Islands (i.e. Rēkohu), which are located 700 km off the east coast of New Zealand. First, we measured leaf area, seed size and plant stature from populations of 22 plant taxa on the Chatham Islands. These data were then compared to analogous measurements from their sister taxa on the mainland to test for evidence of island gigantism, and whether size changes differ between leaves, seeds and stature. Second, we collated data from the literature to test whether size changes in endemic taxa differed among plant growth forms or were correlated with divergence times. Results showed that all three plant traits tended to increase in size on the Chatham Islands. However, field data showed that size increases tended to be more consistent in seeds and leaves than in stature. Data from the literature indicated that size increases also differed among growth forms. Herbaceous species showed the strongest evidence of gigantism, followed by woody plants, while graminoids showed a weak trend towards dwarfism. Insular size increases in seeds and leaves were also positively related to divergence times, indicating that taxa which have resided on the Chatham Islands for longer periods show stronger evidence of gigantism than taxa which arrived more recently. Overall results illustrate that gigantism is a hallmark of the Chatham Island flora, providing a remarkable example of convergent evolution.

Non‐random patterns of invasion and extinction reduce phylogenetic diversity in island bird assemblages

Anthropogenically driven changes in bird communities on oceanic islands exemplify the biotic upheaval experienced by island floras and faunas. While the influence of invasions and extinctions on species richness and beta‐diversity of island bird assemblages has been explored, little is known about the impact of these invasions and extinctions on phylogenetic diversity. Here we quantify phylogenetic diversity of island bird assemblages resulting from extinctions alone, invasions alone, and the combination of extinctions and invasions in the historic time period (1500 CE to the current), and compare it to the expected phylogenetic diversity that would result if these processes involved randomly selected island bird species. We assessed phylogenetic diversity and structure at the scale of the island (n = 152), the archipelago containing the islands (n = 22), and the four oceans containing the archipelagos using three measures. We found that extinction, invasion, and the combination of invasion and extinction generally resulted in lower phylogenetic diversity than expected, regardless of the spatial scale examined. We conclude that extinction and invasion of birds on islands are non‐random with respect to phylogeny and that these processes generally leave bird assemblages with lower phylogenetic diversity than we would expect under random invasion or extinction.

Self-compatibility is over-represented on islands.

Because establishing a new population often depends critically on finding mates, individuals capable of uniparental reproduction may have a colonization advantage. Accordingly, there should be an over-representation of colonizing species in which individuals can reproduce without a mate, particularly in isolated locales such as oceanic islands. Despite the intuitive appeal of this colonization filter hypothesis (known as Baker's law), more than six decades of analyses have yielded mixed findings. We assembled a dataset of island and mainland plant breeding systems, focusing on the presence or absence of self-incompatibility. Because this trait enforces outcrossing and is unlikely to re-evolve on short timescales if it is lost, breeding system is especially likely to reflect the colonization filter. We found significantly more self-compatible species on islands than mainlands across a sample of >1500 species from three widely distributed flowering plant families (Asteraceae, Brassicaceae and Solanaceae). Overall, 66% of island species were self-compatible, compared with 41% of mainland species. Our results demonstrate that the presence or absence of self-incompatibility has strong explanatory power for plant geographical patterns. Island floras around the world thus reflect the role of a key reproductive trait in filtering potential colonizing species in these three plant families.

A Landmark Publication for The South Pacific, Flora of The Cook Islands, Was Sponsored By The IAPT Book Publication Fund

TAXONVolume 66, Issue 2 p. 532-532 Plant Systematics WorldsFree Access A Landmark Publication for The South Pacific, Flora of The Cook Islands, Was Sponsored By The IAPT Book Publication Fund First published: 01 April 2017 https://doi.org/10.12705/662.31AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Literature Cited Funk, V.A., Susanna, A., Stuessy, T. & Bayer, R. 2009. Systematics, evolution, and biogeography of the Compositae. Vienna: IAPT. Sykes, W.R. 1970. Contributions to the flora of Niue. Bulletin, New Zealand Department of Scientific and Industrial Research 200. Wellington: DSIR. [Out of Print.] Sykes, W.R. 1977. Kermadec Islands flora: An annotated check list. New Zealand Department of Scientific and Industrial Research 219. Wellington: DSIR. [Out of Print.] Sykes, W.R. 2016. Flora of Cook Islands. Hawaii: National Tropical Botanical Garden. Volume66, Issue2April 2017Pages 532-532 ReferencesRelatedInformation

Life cycle matters: DNA barcoding reveals contrasting community structure between fern sporophytes and gametophytes

AbstractFerns are the only major lineage of vascular plants that have nutritionally independent sporophyte (diploid) and gametophyte (haploid) life stages. However, the implications of this unique life cycle for fern community ecology have rarely been considered. To compare patterns of community structure between fern sporophytes and gametophytes, we conducted a survey of the ferns of the islands of Moorea and Tahiti (French Polynesia). We first constructed a DNA barcode library (plastid rbcL and trnH‐psbA) for the two island floras including 145 fern species. We then used these DNA barcodes to identify more than 1300 field‐collected gametophytes from 25 plots spanning an elevational gradient from 200 to 2000 m. We found that species richness of fern sporophytes conforms to the well‐known unimodal (i.e., mid‐elevation peak) pattern, reaching a maximum at ~1000–1200 m. Moreover, we found that fern sporophyte communities become increasingly phylogenetically clustered at high elevations. In contrast, species richness of fern gametophytes was consistent across sites, and gametophytes showed no correlation of phylogenetic community structure with elevation. Turnover of sporophyte and gametophyte communities was closely linked with elevation at shallow phylogenetic levels, but not at deeper nodes in the tree. Finally, we found several species for which gametophytes had broader ranges than sporophytes, including a vittarioid fern with abundant gametophytes but extremely rare sporophytes. Our study highlights the importance of including diverse life history stages in surveys of community structure, and has implications for the possible impacts of climate change on the distribution of fern diversity.

Pollination Syndromes of Chinese Gesneriaceae: a Comparative Study between Hainan Island and Neighboring Regions

The species-rich Gesneriaceae are typically a tropical family in Asia, showing a monophyletic radiation and high endemism in Southwest China and Hainan Island. The Chinese species have diverse floral traits and pollination systems, but the detailed patterns of diversity and possible differentiations between Hainan Island and the Chinese mainland remain unclear. Here, we enumerate the species diversity and proportion of endemics of Gesneriaceae for Hainan Island and the nearby Chinese provinces of Yunnan, Guangxi, Guizhou, and Guangdong. We then investigate the species evolutionary histories and main floral traits to evaluate speciation and pollination syndromes for the island and mainland flora. We recognize 24 (eight endemic) species on Hainan Island, 236 (106 endemic) in Yunnan, 211 (120 endemic) in Guangxi, 97 (28 endemic) in Guizhou, and 60 (20 endemic) in Guangdong. Although Hainan Island harbors fewer species than nearby regions, probably due to its smaller area, its endemic ratio is high, only slightly lower than Guangxi. A phylogenetic tree based on nuclear ITS 1/2 and chloroplast Trn L-F indicated most Hainan-endemic species were genetically close to species from Southeast Asia, rather than mainland China. For most floral traits, e.g., growth form, corolla type and color, Hainan Island species show no differences from other regions. Hainan Island and Yunnan Province have equal proportions of species with four or two stamens, whereas most species in other regions have two stamens. Hainan Island has a much higher percentage (21%) of actinomorphic species than other regions (< 10%). Most species in Hainan Island have exserted stamens, while stamens are included in most species in other regions. We did not find any increased tendency in floral traits that promote selfing for the island flora. Generalist pollination mechanisms, supported by characters such as actinomorphic corolla, appear to provide sufficient reproductive assurance in pollinator-depauperate Hainan Island.

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.

Vegetation ecology and diversity of six Kuwait Islands: factors influence on species composition and richness

Kuwait lies at the Northwest corner of the Arabian Gulf, and its eastern coast comprises parallel arcs of nine islands. The present study dealt with vegetation ecology and species diversity analysis of six uninhabited islands, except Failaka, Warba, and Bubiyan islands, with varied sizes of area ranging from 0.5 to 863 km2. A total of 70 species of flowering plants (60% annuals and 40% perennials), belonging to 32 families, were collected from the islands and their list is given. The main phytogeographical category was represented by Saharo-Arabian elements followed by the Irano-Turanian and Mediterranean elements. The vegetation type is essentially halophytic with widespread annuals. Six associations were identified with the application of TWINSPAN, DCA, and CCA programs. They were named after the characteristic species as follows: VG I: Polycarpon tetraphyllum, VG II: Zygophyllum qatarense, VG III: Emex spinosa, VG IV: Seidlitzia rosmarinus, VG V: Malva parviflora-Salsola imbricata, and VG VI: Suaeda aegyptiaca. These associations were compared with the plant communities of Kuwait and neighboring countries of Gulf region. The soil characteristic factors alkalinity, moisture, soil texture, and minerals showed the best correlation with the distribution of the associations. Significant differences between island area, species diversity indices, organic matter, and minerals contents of the islands were observed. Flora of these uninhabited islands with un-grazed plants constituted about 37% of the flora of the mainland of Kuwait and their valuable elements warrant prioritized conservation measures.