基于功能性状的外来植物入侵预测模型框架构建

预测外来植物的潜在入侵性已成为生物多样性保护研究的重要内容,外来植物与乡土物种间的亲缘关系是预测外来植物能否成功入侵的一个重要途径。然而,达尔文归化难题却预测了两种截然不同的结果(即达尔文归化假说和预适应假说)。该研究解析了达尔文归化难题的内涵,提出了基于功能性状的外来植物与乡土群落间的相似性关系应该是进行外来植物入侵预测的重要切入点,而功能性状的种间分化与种内变异可能是外来植物成功入侵的两种不同生态策略。在此基础上,该研究还通过物种功能性状的多维超体积构建了外来植物与乡土群落间的相似性,提出了基于这种相似性的外来植物入侵预测的研究框架和基本流程。该模型框架的建立有助于理解外来植物的入侵机制,对外来植物的潜在入侵性预测提供了理论依据。当然,要实现外来植物能否成功入侵的准确预测,不仅依赖于功能性状的选择,还要考虑入侵的生境依赖性、空间尺度的重要性以及乡土群落的可入侵性等,未来的研究重点是通过控制实验对该模型进行验证和进一步完善。     

A phylogenetic analysis of the British flora sheds light on the evolutionary and ecological factors driving plant invasions

Darwin's naturalization hypothesis predicts that invasive species should perform better in their novel range in the absence of close relatives in the native flora due to reduced competition. Evidence from recent taxonomic and phylogenetic‐based studies, however, is equivocal. We test Darwin's naturalization hypothesis at two different spatial scales using a fossil‐dated molecular phylogenetic tree of the British native and alien flora (ca. 1600 species) and extensive, fine‐scale survey data from the 1998 Countryside Survey. At both landscape and local scales, invasive species were neither significantly more nor less related to the native flora than their non‐invasive alien counterparts. Species invasiveness was instead correlated with higher nitrogen and moisture preference, but not other life history traits such as life‐form and height. We argue that invasive species spread in Britain is hence more likely determined by changes in land use and other anthropogenic factors, rather than evolutionary history. Synthesis. The transition from non‐invasive to invasive is not related to phylogenetic distinctiveness to the native community, but instead to their environmental preferences. Therefore, combating biological invasions in the Britain and other industrialized countries need entirely different strategies than in more natural environments.     

基于功能性状多维性理解外来物种入侵的达尔文归化难题

达尔文归化难题是进行外来物种入侵预测的重要理论依据,然而,达尔文归化假说和预适应假说却预测了2种截然不同的结果。事实上,达尔文归化难题争论的焦点是物种间的差异性还是相似性促进了外来物种的成功入侵,究其原因可能是忽略了功能性状的多维性。所谓功能性状的多维性,就是不同的功能性状可能代表着不同的生态功能轴,外来物种的入侵是多个维度上不同生态过程的综合结果。本研究以现代物种共存理论为基础,构建了一个基于环境过滤和适合度差异2个维度的入侵预测模型框架,不同维度对应着不同的功能性状以及不同的种间相似性关系。该预测模型表明,在环境过滤维度上与本地物种性状趋同,同时,在适合度维度上与本地物种性状趋异的外来物种是潜在的入侵物种,而其危害程度主要取决于本地群落的构建过程。该模型框架可为外来物种入侵预警提供理论依据,也可为生物多样性保护、外来物种的防治与管理等提供实践指导。     

Similarities between invaders and native species: Moving past Darwin's naturalization conundrum

Darwin's naturalization conundrum states that successful invaders must be closely related to native species to possess the traits to tolerate that environment, but distantly related enough to possess traits allowing exploitation of underutilized niches, thereby minimizing competition. Although influential, this hypothesis is based on several simplistic assumptions. In particular, the relationship among phylogenetic relatedness, similarity, and competition is more complex than assumed and changes with spatial and phylogenetic scale. Competitive interactions are determined by limiting similarity and trait hierarchies associated with separate traits. Successful invaders thus need to be similar to native species in some respects, but different in others. This combination of similarities and differences is unlikely to be conserved. Further, many invasive species are represented in their novel range by genotypes with extreme trait values or plasticity relative to the species mean. Selection for these genotypes may alter the similarity between invasive and native species, thus obscuring the relationship between competition and phylogenetic relatedness. As environmental filtering and competition often act on different spatial scales, approaches assessing how individual traits relate to invasion at these scales (species pools vs local community) may improve our understanding of the relationship between similarity and invasion.     

It takes one to know one: Similarity to resident alien species increases establishment success of new invaders

Aim

Darwin's naturalization hypothesis states that dissimilarity to native species may benefit alien species establishment due to empty niches and reduced competition. We here add a new dimension to large‐scale tests of community invasibility, investigating the role that previously established alien species play in facilitating or hindering new invasions in plant communities.

Location

Permanent grasslands across France (including mainland and Corsica), as a receding ecosystem of great conservation importance.

Methods

Focusing on 121 alien plant species occurring in 7,215 vegetation plots, we quantified biotic similarity between new invaders and resident alien species (i.e., alien species with longer residence times) based on phylogenetic and trait distances. Additionally, we calculated distances to native species for each alien species and plot. Using multispecies distribution models, we analysed the influence of these biotic similarity measures and additional covariates on establishment success (presence/absence) of new invaders.

Results

We found that biotic similarity to resident alien species consistently increased establishment success of more recently introduced species. Phylogenetic relatedness to previous invaders had an equally strong positive effect as relatedness to native species. Conversely, trait similarity to natives hindered alien establishment as predicted by Darwin's naturalization hypothesis. These results highlight that various mechanisms may act simultaneously to determine alien establishment success.

Main conclusions

Our results suggest that, with greater similarity among alien species, invasion success increases. Such a pattern may arise either due to actual facilitation among invaders or as a result of weaker competitive interactions among invaders than between native and alien species, leading to an indirect facilitative effect. Alternatively, recent environmental changes (e.g., eutrophication, climate change) may have added new environmental filters. Determining how initial invasions might pave the road for subsequent invasions is crucial for effective multispecies management decisions and contributes a new aspect to our understanding of community assembly.

     

Darwin's naturalization hypothesis: scale matters in coastal plant communities

Darwin proposed two seemingly contradictory hypotheses for a better understanding of biological invasions. Strong relatedness of invaders to native communities as an indication of niche overlap could promote naturalization because of appropriate niche adaptation, but could also hamper naturalization because of negative interactions with native species (‘Darwin's naturalization hypothesis’). Although these hypotheses provide clear and opposing predictions for expected patterns of species relatedness in invaded communities, so far no study has been able to clearly disentangle the underlying mechanisms. We hypothesize that conflicting past results are mainly due to the neglected role of spatial resolution of the community sampling. In this study, we corroborate both of Darwin's expectations by using phylogenetic relatedness as a measure of niche overlap and by testing the effects of sampling resolution in highly invaded coastal plant communities. At spatial resolutions fine enough to detect signatures of biotic interactions, we find that most invaders are less related to their nearest relative in invaded plant communities than expected by chance (phylogenetic overdispersion). Yet at coarser spatial resolutions, native assemblages become more invasible for closely‐related species as a consequence of habitat filtering (phylogenetic clustering). Recognition of the importance of the spatial resolution at which communities are studied allows apparently contrasting theoretical and empirical results to be reconciled. Our study opens new perspectives on how to better detect, differentiate and understand the impact of negative biotic interactions and habitat filtering on the ability of invaders to establish in native communities.     

外来种-本地种亲缘关系对外来植物归化和入侵的影响

达尔文归化难题描述了外来种-本地种亲缘关系促进(预适应假说)或阻止(达尔文归化假说)外来种成功入侵的悖论。目前, 在中国仍缺少针对达尔文归化难题的研究。为系统研究外来种-本地种亲缘关系对中国外来植物入侵的影响, 该文利用线性混合效应模型从省级、市级和群落3个空间尺度以及归化、扩散和入侵3个阶段探究了外来种-本地种谱系距离和外来植物表现的关系。结果表明: 在省级和市级(区域)尺度上, 与本地种亲缘关系较近的外来植物更有可能在当地归化和扩散, 符合预适应假说的预期; 而在群落(局域)尺度上, 外来种-本地种亲缘距离与外来种是否在群落中成功定居及其入侵程度无关。该研究结果表明与本地区系亲缘较近的外来种和本地种的竞争并不强烈, 却能较好地适应本地气候环境而具有更强的归化和入侵潜力。因此, 在今后的外来植物管理和治理中需要尤其重视与本地区系亲缘关系较近的外来植物。     

Why close relatives make bad neighbours: phylogenetic conservatism in niche preferences and dispersal disproves Darwin's naturalization hypothesis in the thistle tribe

The number of exotic plant species that have been introduced into the United States far exceeds that of other groups of organisms, and many of these have become invasive. As in many regions of the globe, invasive members of the thistle tribe, Cardueae, are highly problematic in the California Floristic Province, an established biodiversity hotspot. While Darwin's naturalization hypothesis posits that plant invaders closely related to native species would be at a disadvantage, evidence has been found that introduced thistles more closely related to native species are more likely to become invasive. To elucidate the mechanisms behind this pattern, we modelled the ecological niches of thistle species present in the province and compared niche similarity between taxa and their evolutionary relatedness, using fossil‐calibrated molecular phylogenies of the tribe. The predicted niches of invasive species were found to have higher degrees of overlap with native species than noninvasive introduced species do, and pairwise niche distance was significantly correlated with phylogenetic distance, suggesting phylogenetic niche conservatism. Invasive thistles also displayed superior dispersal capabilities compared to noninvasive introduced species, and these capabilities exhibited a phylogenetic signal. By analysing the modelled ecological niches and dispersal capabilities of over a hundred thistle species, we demonstrate that exapted preferences to the invaded environment may explain why close exotic relatives may make bad neighbours in the thistle tribe.     

Historical arthropod diversity patterns direct rehabilitation targets for Robben Island,South Africa,a continental island in a biodiversity hotspot

Island species are susceptible to extinction through disturbances such as habitat transformation. Due to the small size and isolation of islands, species have limited options for refuges and recolonization, making their rehabilitation a conservation priority. Robben Island is a continental island, isolated from the mainland ca. 15 000 years ago, and has been degraded by humans and alien species for nearly 400 years. Mainland areas with similar vegetation should be good reference sites for the biological restoration of the island due to historical connectedness. However, very little information exists as to which species were lost. Here we aim to identify the best mainland sites to use as reference sites for Robben Island based on remaining arthropod diversity on the island. Sites found to be most similar in terms of arthropod diversity to Robben Island were sites north of Robben Island (Elandsbaai and Dwarskersbos) rather than the geographically closest locations. These sites therefore represent ideal reference sites for biological restoration of the island. We do not suggest the reintroduction of species from these localities, but rather Robben Island should be restored to match their vegetation height and cover.     

Effects of exotic-native species relationship on naturalization and invasion of exotic plant species

达尔文归化难题描述了外来种-本地种亲缘关系促进(预适应假说)或阻止(达尔文归化假说)外来种成功入侵的悖论。目前, 在中国仍缺少针对达尔文归化难题的研究。为系统研究外来种-本地种亲缘关系对中国外来植物入侵的影响, 该文利用线性混合效应模型从省级、市级和群落3个空间尺度以及归化、扩散和入侵3个阶段探究了外来种-本地种谱系距离和外来植物表现的关系。结果表明: 在省级和市级(区域)尺度上, 与本地种亲缘关系较近的外来植物更有可能在当地归化和扩散, 符合预适应假说的预期; 而在群落(局域)尺度上, 外来种-本地种亲缘距离与外来种是否在群落中成功定居及其入侵程度无关。该研究结果表明与本地区系亲缘较近的外来种和本地种的竞争并不强烈, 却能较好地适应本地气候环境而具有更强的归化和入侵潜力。因此, 在今后的外来植物管理和治理中需要尤其重视与本地区系亲缘关系较近的外来植物。     

Effects of exotic-native species relationship on naturalization and invasion of exotic plant species北大核心CSCD

Aims: Darwin's naturalization conundrum describes the paradox that the relationship of exotic species to native residents could either promote or hinder invasion success through opposing mechanisms: niche pre-adaptation or competitive interactions. Previous Darwin's naturalization studies have showed invasion success could vary at stages, sites, and spatial and phylogenetic scales. Our objective was to assess the effects of exotic-native species relationship on invasion process of exotic plant species in China, where related research is still lacking. Methods: Generalized linear mixed models were used to examine relationship between exotic-native species relationship and performance of exotic species at different spatial scale (provincial, municipal and community) and invasion stages (naturalization, dispersal and invasion). At community scale, we measured environmental factors of communities we investigated to control the effect of habitat heterogeneity among them. Important findings: At the provincial and municipal scales, exotic species closely related to native flora were more likely to be naturalized and distributed, which is more consistent with the expectation of the pre-adaptation hypothesis. On the community scale, the exotic-native species relationship was not related to establishment and abundance of exotic species in the community. The results suggested that exotic species did not strongly compete with their close native relatives in communities, but were better adapted to areas where their close relatives had lived. Considering their high potential of naturalization and invasion, special attention should be paid to those exotic species that closely related to the native flora in the management of invasive species. © Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

Limiting similarity and Darwin’s naturalization hypothesis: understanding the drivers of biotic resistance against invasive plant species

Several hypotheses have been proposed to explain biotic resistance of a recipient plant community based on reduced niche opportunities for invasive alien plant species. The limiting similarity hypothesis predicts that invasive species are less likely to establish in communities of species holding similar functional traits. Likewise, Darwin’s naturalization hypothesis states that invasive species closely related to the native community would be less successful. We tested both using the invasive alien Ambrosia artemisiifolia L. and Solidago gigantea Aiton, and grassland species used for ecological restoration in central Europe. We classified all plant species into groups based on functional traits obtained from trait databases and calculated the phylogenetic distance among them. In a greenhouse experiment, we submitted the two invasive species at two propagule pressures to competition with communities of ten native species from the same functional group. In another experiment, they were submitted to pairwise competition with native species selected from each functional group. At the community level, highest suppression for both invasive species was observed at low propagule pressure and not explained by similarity in functional traits. Moreover, suppression decreased asymptotically with increasing phylogenetic distance to species of the native community. When submitted to pairwise competition, suppression for both invasive species was also better explained by phylogenetic distance. Overall, our results support Darwin’s naturalization hypothesis but not the limiting similarity hypothesis based on the selected traits. Biotic resistance of native communities against invasive species at an early stage of establishment is enhanced by competitive traits and phylogenetic relatedness.     

Fish species introductions provide novel insights into the patterns and drivers of phylogenetic structure in freshwaters

Despite long-standing interest of terrestrial ecologists, freshwater ecosystems are a fertile, yet unappreciated, testing ground for applying community phylogenetics to uncover mechanisms of species assembly. We quantify phylogenetic clustering and overdispersion of native and non-native fishes of a large river basin in the American Southwest to test for the mechanisms (environmental filtering versus competitive exclusion) and spatial scales influencing community structure. Contrary to expectations, non-native species were phylogenetically clustered and related to natural environmental conditions, whereas native species were not phylogenetically structured, likely reflecting human-related changes to the basin. The species that are most invasive (in terms of ecological impacts) tended to be the most phylogenetically divergent from natives across watersheds, but not within watersheds, supporting the hypothesis that Darwin''s naturalization conundrum is driven by the spatial scale. Phylogenetic distinctiveness may facilitate non-native establishment at regional scales, but environmental filtering restricts local membership to closely related species with physiological tolerances for current environments. By contrast, native species may have been phylogenetically clustered in historical times, but species loss from contemporary populations by anthropogenic activities has likely shaped the phylogenetic signal. Our study implies that fundamental mechanisms of community assembly have changed, with fundamental consequences for the biogeography of both native and non-native species.     

Dissecting spatiotemporal patterns of functional diversity through the lens of Darwin's naturalization conundrum

Darwin's naturalization conundrum describes the paradigm that community assembly is regulated by two opposing processes, environmental filtering and competitive interactions, which predict both similarity and distinctiveness of species to be important for establishment. Our goal is to use long‐term, large‐scale, and high‐resolution temporal data to examine diversity patterns over time and assess whether environmental filtering or competition plays a larger role in regulating community assembly processes. We evaluated Darwin's naturalization conundrum and how functional diversity has changed in the Laurentian Great Lakes fish community from 1870 to 2010, which has experienced frequent introductions of non‐native species and extirpations of native species. We analyzed how functional diversity has changed over time by decade from 1870 to 2010 at three spatial scales (regional, lake, and habitat) to account for potential noninteractions between species at the regional and lake level. We also determined which process, environmental filtering or competitive interactions, is more important in regulating community assembly and maintenance by comparing observed patterns to what we would expect in the absence of an ecological mechanism. With the exception of one community, all analyses show that functional diversity and species richness has increased over time and that environmental filtering regulates community assembly at the regional level. When examining functional diversity at the lake and habitat level, the regulating processes become more context dependent. This study is the first to examine diversity patterns and Darwin's conundrum by integrating long‐term, large‐scale, and high‐resolution temporal data at multiple spatial scales. Our results confirm that Darwin's conundrum is highly context dependent.     

The making of a rapid plant invader: genetic diversity and differentiation in the native and invaded range of Senecio inaequidens

To become invasive, exotic species have to succeed in the consecutive phases of introduction, naturalization, and invasion. Each of these phases leaves traces in genetic structure, which may affect the species’ success in subsequent phases. We examined this interplay of genetic structure and invasion dynamics in the South African Ragwort (Senecio inaequidens), one of Europe’s fastest plant invaders. We used AFLP and microsatellite markers to analyze 19 native African and 32 invasive European populations. In combination with historic data, we distinguished invasion routes and traced them back to the native source areas. This revealed that different introduction sites had markedly different success in the three invasion phases. Notably, an observed lag‐phase in Northern Germany was evidently not terminated by factors increasing the invasiveness of the resident population but by invasive spread from another introduction centre. The lineage invading Central Europe was introduced to sites in which winters are more benign than in the native source region. Subsequently, this lineage spread into areas in which winter temperatures match the native climate more closely. Genetic diversity clearly increases with population age in Europe and less clearly decreases with spread rate up to population establishment. This indicates that gene flow along well‐connected invasion routes counteracted losses of genetic diversity during rapid spread. In summary, this study suggests that multiple introductions, environmental preadaptation and high gene flow along invasion routes contributed to the success of this rapid invader. More generally, it demonstrates the benefit of combining genetic, historical, and climatic data for understanding biological invasions.     

The rehabilitation value of a small culturally significant island based on the arthropod natural capital

Small islands are particularly vulnerable to degradation by invasive species and often lack source populations to replace those lost during localized extinctions. Robben Island, a significant South African cultural heritage site, has a long history of anthropogenic impact. Introduced alien mammals and trees have resulted in numerous localized plant extinctions with their impact on arthropod biodiversity remaining unclear. We used Robben Island’s arthropod fauna as focal group to investigate the rehabilitation potential of this transformed island. Ground surface-living, foliage-inhabiting and flower-visiting arthropods were collected using five sampling techniques. Arthropod diversity was highest in the two ‘natural’ habitats compared to alien Eucalyptus plantations. Arthropod compositional diversity differed significantly between alien plantations and natural habitats. Nevertheless, a remarkable 17 % of all species were confined to plantations. However, when we corrected for the effect of rarity, only 15 species (4 %) were unique to alien plantations and all those identified to species level were either alien in origin or were widespread generalists only normally associated with transformed areas. This emphasizes the need to identify species that drive similarity indices to fully comprehend the conservation value of alien vegetation. Arthropods found in the remaining natural vegetation showed remarkable tolerance of long-term grazing pressures from introduced alien mammals. Only eight Orthoptera species were sampled, yet one was a rediscovery of a rare species and another a range extension. All indigenous species showed strong preferences for natural habitats. Thus, Robben Island could still hold conservation value if the natural habitats are rehabilitated and the Eucalyptus plantations removed.     

The effects of phylogenetic relatedness on invasion success and impact: deconstructing Darwin's naturalisation conundrum

Darwin's naturalisation conundrum describes the paradox that the relatedness of exotic species to native residents could either promote or hinder their success through opposing mechanisms: niche pre‐adaptation or competitive interactions. Previous studies focusing on single snapshots of invasion patterns have provided support to both sides of the conundrum. Here, by examining invasion dynamics of 480 plots over 40 years, we show that exotic species more closely related to native species were more likely to enter, establish and dominate the resident communities, and that native residents more closely related to these successful exotics were more likely to go locally extinct. Therefore, non‐random displacement of natives during invasion could weaken or even reverse the negative effects of exotic–native phylogenetic distances on invasion success. The scenario that exotics more closely related to native residents are more successful, but tend to eliminate their closely related natives, may help to reconcile the 150‐year‐old conundrum.     

Climate niche shift in invasive species: the case of the brown anole

Anolis sagrei, a Cuba and Bahama native lizard, is a successful invader in Florida and adjacent areas. Herein, we focus on conservatism in its climate niche axes and possible congruencies with its natural history properties. The not mutually exclusive hypotheses of the present study explaining its northern range limit are: (1) climatic conditions within species' native and invasive ranges are identical; (2) the species is pre‐adapted to novel conditions as a result of historical climate variations; and (3) only some niche axes limit the species' invasive distribution and the observed pattern is explained by an interplay between the potential niche within its native range and life‐history. Species distribution models for native and invasive distributions were built on ten bioclimatic variables. Using Schoener's niche overlap index, the degree of niche conservatism among variables was identified. Significances of hypothesis (1) were tested using null‐model approaches. Possible climatic pre‐adaptations were evaluated by comparing its actual tolerance within its invasive range with that of the Last Glacial Maximum (LGM) within its native range (hypothesis 2). Results of (1) and (2) are discussed in relation to natural history, approaching hypothesis 3. We detect varying overlaps in niche axes, indicating that natural history properties are associated with conservative niche axes. Climatic comparisons with LGM of native and current conditions of invasive range suggest that pre‐adaptations are unlikely. Possible shifts in the fundamental niche of the species may have been facilitated by enhanced genetic diversity in northern invasive populations. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 943–954.     

How strongly do interactions with closely‐related native species influence plant invasions? Darwin's naturalization hypothesis assessed on Mediterranean islands

Aim Recent works have found the presence of native congeners to have a small effect on the naturalization rates of introduced plants, some suggesting a negative interaction (as proposed by Charles Darwin in The Origin of Species), and others a positive association. We assessed this question for a new biogeographic region, and discuss some of the problems associated with data base analyses of this type. Location Islands of the Mediterranean basin. Methods Presence or absence of congeners was assessed for all naturalized alien plants species at regional, local and habitat scales. Using general linear models, we attempted to explain the abundance of the species (as measured by the number of islands where recorded) from their congeneric status, and assessed whether the patterns could be alternatively accounted for by a range of biological, geographical and anthropogenic factors. A simulation model was also used to investigate the impact of a simple bias on a comparable but hypothetical data set. Results Data base analyses addressing Darwin's hypothesis are prone to bias from a number of sources. Interaction between invaders and congenerics may be overestimated, as they often do not co‐occur in the same habitats. Furthermore, intercorrelations between naturalization success and associated factors such as introduction frequency, which are also not independent from relatedness with the native flora, may generate an apparent influence of congenerics without implying a biological interaction. We detected no true influence from related natives on the successful establishment of alien species of the Mediterranean. Rarely‐introduced species tended to fare better in the presence of congeners, but it appears that this effect was generated because species introduced accidentally into highly invasible agricultural and ruderal habitats have many relatives in the region, due to common evolutionary origins. Main conclusions Relatedness to the native flora has no more than a marginal influence on the invasion success of alien plants in the Mediterranean, although apparent trends can easily be generated through artefacts of the data base.     

Species composition,functional and phylogenetic distances correlate with success of invasive Chromolaena odorata in an experimental test

Biotic resistance may influence invasion success; however, the relative roles of species richness, functional or phylogenetic distance in predicting invasion success are not fully understood. We used biomass fraction of Chromolaena odorata, an invasive species in tropical and subtropical areas, as a measure of ‘invasion success’ in a series of artificial communities varying in species richness. Communities were constructed using species from Mexico (native range) or China (non‐native range). We found strong evidence of biotic resistance: species richness and community biomass were negatively related with invasion success; invader biomass was greater in plant communities from China than from Mexico. Harvesting time had a greater effect on invasion success in plant communities from China than on those from Mexico. Functional and phylogenetic distances both correlated with invasion success and more functionally distant communities were more easily invaded. The effects of plant‐soil fungi and plant allelochemical interactions on invasion success were species‐specific.