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Heleno R.H.,University of Coimbra | Vargas P.,Real Jardin Botanico de Madrid CSIC RJB
Global Ecology and Biogeography

Aim: Four long-distance dispersal (LDD) modes have generally been considered to play central roles in the colonization of islands by plants: anemochory (dispersal by wind), thalassochory (dispersal by oceanic currents), endozoochory (internal dispersal by animals) and epizoochory (external dispersal by animals). However, seeds can also be transported by vectors different from those to which they are best suited (non-standard dispersal), meaning that the actual vector of colonization cannot be inferred based on diaspore traits alone. We propose an alternative approach to explore the relative contribution of LDD syndromes to island colonization. Location: Europe and the Azores. Methods: We scored the presence of syndromes relevant for LDD in the native flora of Europe (c. 10,000 species) and the Azores (148 species). We then contrasted the importance of each syndrome in the recipient flora (Azores) and the source floras (Europe and mainland Portugal) to estimate which, if any, syndrome was particularly successful for overseas colonization. We further investigated whether particular LDD syndromes increased plant distribution within the Azores archipelago. Results: Most native species in Europe (63%), mainland Portugal (67%) and the Azores (63%) produce unspecialized diaspores. Only species adapted to sea dispersal were overrepresented in the Azores, while those adapted to wind dispersal were underrepresented. The presence of LDD syndromes did not significantly improve the distribution of plant species across the archipelago, except for the moderate advantage of endozoochorous diaspores. Differences in the importance of LDD syndromes across plant families at least partially explain the floristic disharmony of the Azorean flora. Main conclusions: Only thalassochory appeared to have significantly favoured the colonization of the Azores. The high proportion of unspecialized diaspores, the unexceptional representation of most specialized LDD syndromes and the dissociation between syndromes and inter-island plant distribution in the Azores suggest that non-standard events are more common than previously believed in the colonization of islands by plants. © 2014 John Wiley & Sons Ltd. Source

Vargas P.,Real Jardin Botanico de Madrid CSIC RJB | Rumeu B.,Real Jardin Botanico de Madrid CSIC RJB | Heleno R.H.,University of Coimbra | Traveset A.,Linc Global | Nogales M.,CSIC - Institute of Natural Products and Agrobiology

Colonization across the Galápagos Islands by the carpenter bee (Xylocopa darwini) was reconstructed based on distribution of mitochondrial haplotypes (cytochrome oxidase II (COII) sequences) and haplotype lineages. A total of 12 haplotypes were found in 118 individuals of X. darwini. Distributional, phylogenetic and phylogeographic analyses suggest early colonization of most islands followed by historical isolation in two main groups: eastern and central-western islands. Evidence of recurrent inter-island colonization of haplotypes is largely lacking, despite strong flight capability and ecological amplitude of the species. Recent palaeogeographic data suggest that several of the current islands were connected in the past and thus the isolation pattern may have been even more pronounced. A contrast analysis was also carried out on 10 animal groups of the Galápagos Islands, and on haplotype colonization of seven animal and plant species from several oceanic archipelagos (the Galápagos, Azores, Canary Islands). New colonization metrics on the number of potential vs. inferred colonization events revealed that the Galápagos carpenter bee shows one of the most significant examples of geographic isolation. © 2015 Vargas et al. Source

Esteves C.F.,University of Coimbra | Costa J.M.,University of Coimbra | Vargas P.,Real Jardin Botanico de Madrid CSIC RJB | Freitas H.,University of Coimbra | Heleno R.H.,University of Coimbra

How plants arrived to originally sterile oceanic islands has puzzled naturalists for centuries. Dispersal syndromes (i.e., diaspore traits that promote dispersal by long-distance dispersal vectors), are generally considered to play a determinant role in assisting island colonization. However, the association between diaspore traits and the potential vectors by which diaspores are dispersed is not always obvious. Fleshy fruits, in particular, are considered tohave evolved to promote the internal dispersal of seeds by frugivores (endozoochory), however some fleshy fruits can also float in saltwater, and thus be potentially transported byoceanic current (thalassochory). We performed saltwater floatation and viability experiments with fruits of the 14 European fleshy-fruited species that naturally colonized theAzores archipelago (North Atlantic Ocean). We show that only Corema album (a berry) and Juniperus oxycedrus (a fleshy cone) floated for as long as 60 days, the estimated minimumtime needed to reach the Azores by oceanic currents. Regardless the floatation potential, exposure to saltwater largely reduced the viability of most seeds of the 14 species (46% ofviability decline within 15 days and 77% within 60 days of immersion), including those of Corema album (61%) and Juniperus oxycedrus (83%). Floatability and viability trials suggestthat while some fleshy-fruited species might have arrived to the Azores by oceanic currents, such would have required extreme meteorological events that could largely reducethe duration of the trip. Thus, the alternative hypothesis that fleshy-fruited species were mostly dependent on animal dispersers (endozoochory) to colonize these remote islands isreinforced. Copyright: © 2015 Esteves et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Vargas P.,Real Jardin Botanico de Madrid CSIC RJB | Heleno R.,University of California at Santa Cruz | Heleno R.,CSIC - Mediterranean Institute for Advanced Studies | Traveset A.,CSIC - Mediterranean Institute for Advanced Studies | Nogales M.,CSIC - Institute of Natural Products and Agrobiology

Since nobody has witnessed the arrival of early plant colonists on isolated islands, the actual long-distance dispersal (hereafter LDD) has historically been a matter of speculation. In the present study, we offer a new approach that evaluates whether particular syndromes for LDD (i.e. the set of traits related to diaspore dispersal by animals, wind and sea currents) have been favourable in the natural colonization of the Galápagos Islands by plants. Dispersal syndromes of the 251 native genera (509 angiosperm species) presently acknowledged as native were carefully studied, combining data from floristic lists of the Galápagos Islands, diaspore traits, characteristics of continental relatives and our own observations. We used these genera (and occasionally infrageneric groups) as the working units to infer the number of introductions and colonists. A final number of native plants was inferred and analysed after correcting by pollen records of six species from six genera previously considered exotic (palaeobotanical correction). The number of early colonists was also corrected by incorporating information from the few (n= 12) phylogenetic studies of genera from both the Galápagos Islands and the Americas (phylogenetic correction). A total of 372 colonization events were inferred for the native flora using the latest check-list. The proportions of native colonists grouped into five categories were: endozoochory 16.4%, epizoochory 15.7%, hydrochory 18.6%, anemochory 13.3%, and unassisted diaspores 36.0%. These figures did not vary significantly on analysing only the 99 genera that include endemic species in order to rule out any human-mediated introductions. Irrespective of the roles of the different agents involved in LDD, diaspores with no special syndrome for LDD (unassisted diapores), such as many dry fruits, have been successful in reaching and colonizing the Galápagos archipelago. This finding leads us to suggest that unpredictable and so far unknown LDD mechanisms should be further considered in the theory of island biogeography. © 2011 The Authors. Source

Heleno R.H.,University of Coimbra | Heleno R.H.,Linc Global | Heleno R.H.,University of California at Santa Cruz | Olesen J.M.,University of Aarhus | And 4 more authors.
Proceedings of the Royal Society B: Biological Sciences

Alien plants are a growing threat to the Galápagos unique biota. We evaluated the impact of alien plants on eight seed dispersal networks from two islands of the archipelago. Nearly 10 000 intact seeds from 58 species were recovered from the droppings of 18 bird and reptile dispersers. The most dispersed invaders were Lantana camara, Rubus niveus and Psidium guajava, the latter two likely benefiting from an asynchronous fruit production with most native plants, which facilitate their consumption and spread. Lava lizards dispersed the seeds of 27 species, being the most important dispersers, followed by small ground finch, two mockingbirds, the giant tortoise and two insectivorous birds. Most animals dispersed alien seeds, but these formed a relatively small proportion of the interactions. Nevertheless, the integration of aliens was higher in the island that has been invaded for longest, suggesting a time-lag between alien plant introductions and their impacts on seed dispersal networks. Alien plants become more specialized with advancing invasion, favouring more simplified plant and disperser communities. However, only habitat type significantly affected the overall network structure. Alien plants were dispersed via two pathways: dryfruited plants were preferentially dispersed by finches, while fleshy fruited species were mostly dispersed by other birds and reptiles. © 2012 The Author(s) Published by the Royal Society. All rights reserved. Source

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