Determinants of native and non‐native plant community structure on an oceanic island (original) (raw)
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Functional and phylogenetic consequences of plant invasion for coastal native communities
Journal of Vegetation Science, 2019
QuestionDo invasions by alien plant species with contrasting trait profiles (Arctotheca calendula, Carpobrotus spp., Conyza bonariensis and Opuntia dillenii) change the functional and phylogenetic structure of coastal plant communities?LocationAtlantic coastal habitats in Huelva (Spain).MethodsWe identified species diversity and composition in 220 paired (invaded and non‐invaded) plots along the coast (440 plots in total). We measured nine functional traits for every native and invader species, namely, specific leaf area (SLA), specific root length (SRL), leaf and root dry mass content (LDMC and RDMC) and carbon isotope fraction (δ13C). We calculated, at the plot scale, community means (CMs) for each trait, functional richness, Faith's phylogenetic diversity and functional and phylogenetic mean pairwise dissimilarities.ResultsThree out the four species showed rather extreme trait values compared to the native flora with greater impact on invaded communities. In plots invaded by ...
Linking the impacts of plant invasion on community functional structure and ecosystem properties
Journal of Vegetation Science, 2016
QuestionsMany studies report a decrease of native species richness in communities after plant invasion by exotic taxa, but the implications of species losses on community functional structure and ecosystem processes have been less explored. The questions addressed are: (1) what are the impacts of invasive plant taxa on the functional structure of the recipient community; and (2) are there links between such functional structure and ecosystem properties representing key ecosystem processes?LocationCostal habitats of Mallorca and Menorca, Balearic Islands, Spain.MethodsIn paired invaded and non‐invaded plots, species frequencies and ecosystem properties related to biogeochemical cycles (soil C and N content, soil moisture and decomposition rate) were assessed. For every native species we obtained values of several functional traits (plant height, woodiness, N fixation and evergreenness). Then we calculated indices of community functional structure (community‐weighted means for each tr...
Are island plant communities more invaded than their mainland counterparts?
Journal of Vegetation Science, 2010
Questions: Are island vegetation communities more invaded than their mainland counterparts? Is this pattern consistent among community types? Location: The coastal provinces of Catalonia and the para-oceanic Balearic Islands, both in NE Spain. These islands were connected to the continent more than 5.35 million years ago and are now located o200 km from the coast. Methods: We compiled a database of almost 3000 phytosociological releve´s from the Balearic Islands and Catalonia and compared the level of invasion by alien plants in island versus mainland communities. Twenty distinct plant community types were compared between island and mainland counterparts. Results: The percentage of plots with alien species, number, percentage and cover percentage of alien species per plot was greater in Catalonia than in the Balearic Islands in most communities. Overall, across communities, more alien species were found in the mainland (53) compared to the islands (only nine). Despite these differences, patterns of the level of invasion in communities were highly consistent between the islands and mainland. The most invaded communities were ruderal and riparian. Main conclusion: Our results indicate that paraoceanic island communities such as the Balearic Islands are less invaded than their mainland counterparts. This difference reflects a smaller regional alien species pool in the Balearic Islands than in the adjacent mainland, probably due to differences in landscape heterogeneity and propagule pressure.
2006
We investigated the relationships of vegetation communities to environmental variables and compared the relative contribution of native and introduced species in extant forest communities on St. John, US Virgin Islands, using an island-wide forest vegetation inventory and monitoring network of permanent plots. We detected 2,415 individuals of 203 species, 5 percent of which were introduced. Cluster analysis, Indicator Species Analysis, and Nonmetric Multidimensional Scaling (NMS) ordination detected four broad species communities divided primarily by moisture and disturbance gradients. Group 1 was characterized by rocky, low-to-mid elevation dry scrub forest on soils with fairly low soil nutrient content; Group 2 was distinguished by low soil nutrient content, high-elevation moist basin forests on steep slopes; Group 3 was indicative of disturbed communities on a wide range of elevations with gentle or no slope across a range of soil types; and Group 4 represented mid-elevation moist forests across a range of steep slopes on nutrientrich soils. Though introduced species are present and widespread on the island, they do not appear to be dominating most plant communities. Exceptions may be those communities with long-standing histories of human disturbance. Achieving an adequate sample of forest types of limited extent or linear spatial patterns such as mangroves and gallery moist forests is difficult with a systematic design. Future sampling should consider some form of stratification targeting these under-sampled forest types.
The ISME journal, 2018
Island biogeography theory is one of the most influential paradigms in ecology. That island characteristics, including remoteness, can profoundly modulate biological diversity has been borne out by studies of animals and plants. By contrast, the processes influencing microbial diversity in island systems remain largely undetermined. We sequenced arbuscular mycorrhizal (AM) fungal DNA from plant roots collected on 13 islands worldwide and compared AM fungal diversity on islands with existing data from mainland sites. AM fungal communities on islands (even those >6000 km from the closest mainland) comprised few endemic taxa and were as diverse as mainland communities. Thus, in contrast to patterns recorded among macro-organisms, efficient dispersal appears to outweigh the effects of taxogenesis and extinction in regulating AM fungal diversity on islands. Nonetheless, AM fungal communities on more distant islands comprised a higher proportion of previously cultured and large-spored ...
The New phytologist, 2018
Microbes can have profound effects on their hosts, driving natural selection, promoting speciation and determining species distributions. However, soil-dwelling microbes are rarely investigated as drivers of evolutionary change in plants. We used metabarcoding and experimental manipulation of soil microbiomes to investigate the impact of soil and root microbes in a well-known case of sympatric speciation, the Howea palms of Lord Howe Island (Australia). Whereas H. forsteriana can grow on both calcareous and volcanic soils, H. belmoreana is restricted to, but more successful on, volcanic soil, indicating a trade-off in adaptation to the two soil types. We suggest a novel explanation for this trade-off. Arbuscular mycorrhizal fungi (AMF) are significantly depleted in H. forsteriana on volcanic soil, relative to both H. belmoreana on volcanic soil and H. forsteriana on calcareous soil. This is mirrored by the results of survival experiments, where the sterilization of natural soil redu...
Ecological Research
In tropical urban areas, prone to invasions by multiple exotic species, there is a need for studies to understand the precise nature of the relationship between native and exotic species. This observational study was conducted in a rapidly urbanizing Indian metropolis. It examined the native and exotic species separately as a function of richness and abundance of two focal exotic species, namely Mikania micrantha and Alternanthera philoxeroides, to find support for the hypothesis that an overall native-exotic relationship does not provide a true picture of the community composition. The richness of exotic species did not turn out to be a good predictor for the native-exotic richness relationship even after focal exotics were considered. However, when the richness components were analysed separately, Poisson log-linear models identified M. micrantha as the community-dominant, by virtue of its extensive cover. Neither soil resource availability nor the presence of other exotics had any influence on native species richness. The negative relationship of M. micrantha cover with other exotic species could be associated with a lower risk of native species loss in a community invaded by multiple exotic species. M. micrantha appeared to be a 'passenger' of habitat alteration, but was likely to become a 'driver' once it attains high covers due to its reported superior competitive abilities. Therefore, in tropical areas there is a need to prioritize management initiatives in order to identify the dominant invader species in a community and effectively manage the dominant-homogenized plots.
Ecology, 2009
The role of native species diversity in providing biotic resistance to invasion remains controversial, with evidence supporting both negative and positive relationships that are often scale dependent. Across larger spatial scales, positive relationships suggest that exotic and native species respond similarly to factors other than diversity. In the case of island habitats, such factors may include island size and isolation from the mainland. However, previous island studies exploring this issue examined only a few islands or islands separated by extreme distances. In this study, we surveyed exotic and native plant diversity on 25 islands separated by ,15 km in Boston Harbor. Exotic and native species richness were positively correlated. Consistent with island biogeography theory, species richness of both groups was positively related to area and negatively related to isolation. However, the isolation effect was significantly stronger for native species. This differential effect of isolation on native species translated into exotic species representing a higher proportion of all plant species on more distant islands. The community similarity of inner harbor islands vs. outer harbor islands was greater for exotic species, indicating that isolation had a weaker influence on individual exotic species. These results contrast with recent work focusing on similarities between exotic and native species and highlight the importance of studies that use an island biogeographic approach to better understand those factors influencing the ecology of invasive species.