Polyploidy, or the duplication of entire genomes, has been observed in prokaryotic and eukaryotic organisms, and in somatic and germ cells. The consequences of polyploidization are complex and variable, and they differ greatly between systems (clonal or non-clonal) and species, but the process has often been considered to be an evolutionary 'dead end'. Here, we review the accumulating evidence that correlates polyploidization with environmental change or stress, and that has led to an increased recognition of its short-term adaptive potential. In addition, we discuss how, once polyploidy has been established, the unique retention profile of duplicated genes following whole-genome duplication might explain key longer-term evolutionary transitions and a general increase in biological complexity.

/pdf/the-evolutionary-significance-of-polyploidy-3jfm5py9j7.pdf

The evolutionary significance of polyploidy

Recent comprehensive data provided through the DAISIE project (www.europe-aliens.org) have facilitated the development of the first pan-European assessment of the impacts of alien plants, vertebrates, and invertebrates – in terrestrial, freshwater, and marine environments – on ecosystem services. There are 1094 species with documented ecological impacts and 1347 with economic impacts. The two taxonomic groups with the most species causing impacts are terrestrial invertebrates and terrestrial plants. The North Sea is the maritime region that suffers the most impacts. Across taxa and regions, ecological and economic impacts are highly correlated. Terrestrial invertebrates create greater economic impacts than ecological impacts, while the reverse is true for terrestrial plants. Alien species from all taxonomic groups affect “supporting”, “provisioning”, “regulating”, and “cultural” services and interfere with human well-being. Terrestrial vertebrates are responsible for the greatest range of impacts, and these are widely distributed across Europe. Here, we present a review of the financial costs, as the first step toward calculating an estimate of the economic consequences of alien species in Europe.

/pdf/how-well-do-we-understand-the-impacts-of-alien-species-on-4wdq1viv3c.pdf

How well do we understand the impacts of alien species on ecosystem services? A pan-European, cross-taxa assessment

Invasive alien species come from most taxonomic groups, and invasion biology is searching for robust cross-taxon generalizations and principles. An analysis of 2670 papers dealing with 892 invasive species showed that all major groups of invaders are well studied, but that most information on the mechanisms of invasion has emerged from work on a limited number of the most harmful invaders. A strong geographical bias, with Africa and Asia understudied, inhibits a balanced understanding of invasion, because we might be lacking knowledge of specific invasion mechanisms from poorly studied, regionally specific habitats. International cooperation is required to achieve a more geographically balanced picture of biological invasions. Invasive species with the greatest impact are best studied, but more studies of species that are naturalized but not (yet) invasive are needed to improve understanding of the mechanisms acting during the naturalization phase of invasions and leading to successful invasion.

/pdf/geographical-and-taxonomic-biases-in-invasion-ecology-132i6pqta6.pdf

Geographical and taxonomic biases in invasion ecology

Polyploidy and genome evolution in plants

Much research has been devoted to identify the conditions under which selection favours flexible individuals or genotypes that are able to modify their growth, development and behaviour in response to environmental cues, to unravel the mechanisms of plasticity and to explore its influence on patterns of diversity among individuals, populations and species. The consequences of developmental plasticity and phenotypic flexibility for the performance and ecological success of populations and species have attracted a comparatively limited but currently growing interest. Here, I re-emphasize that an increased understanding of the roles of plasticity in these contexts requires a ‘whole organism' (rather than ‘single trait') approach, taking into consideration that organisms are integrated complex phenotypes. I further argue that plasticity and genetic polymorphism should be analysed and discussed within a common framework. I summarize predictions from theory on how phenotypic variation stemming from developmental plasticity and phenotypic flexibility may affect different aspects of population-level performance. I argue that it is important to distinguish between effects associated with greater interindividual phenotypic variation resulting from plasticity, and effects mediated by variation among individuals in the capacity to express plasticity and flexibility as such. Finally, I claim that rigorous testing of predictions requires methods that allow for quantifying and comparing whole organism plasticity, as well as the ability to experimentally manipulate the level of and capacity for developmental plasticity and phenotypic flexibility independent of genetic variation.

/pdf/rethinking-phenotypic-plasticity-and-its-consequences-for-2utegn91mg.pdf

Rethinking phenotypic plasticity and its consequences for individuals, populations and species.

BACKGROUND
Biological invasions are a major ecological and socio-economic problem in many parts of the world. Despite an explosion of research in recent decades, much remains to be understood about why some species become invasive whereas others do not. Recently, polyploidy (whole genome duplication) has been proposed as an important determinant of invasiveness in plants. Genome duplication has played a major role in plant evolution and can drastically alter a plant's genetic make-up, morphology, physiology and ecology within only one or a few generations. This may allow some polyploids to succeed in strongly fluctuating environments and/or effectively colonize new habitats and, thus, increase their potential to be invasive.


SCOPE
We synthesize current knowledge on the importance of polyploidy for the invasion (i.e. spread) of introduced plants. We first aim to elucidate general mechanisms that are involved in the success of polyploid plants and translate this to that of plant invaders. Secondly, we provide an overview of ploidal levels in selected invasive alien plants and explain how ploidy might have contributed to their success.


CONCLUSIONS
Polyploidy can be an important factor in species invasion success through a combination of (1) 'pre-adaptation', whereby polyploid lineages are predisposed to conditions in the new range and, therefore, have higher survival rates and fitness in the earliest establishment phase; and (2) the possibility for subsequent adaptation due to a larger genetic diversity that may assist the 'evolution of invasiveness'. Alternatively, polyploidization may play an important role by (3) restoring sexual reproduction following hybridization or, conversely, (4) asexual reproduction in the absence of suitable mates. We, therefore, encourage invasion biologists to incorporate assessments of ploidy in their studies of invasive alien species.

/pdf/invited-review-the-more-the-better-the-role-of-polyploidy-in-13mx9eq493.pdf

INVITED REVIEW The more the better? The role of polyploidy in facilitating plant invasions

12. Using Natural Experiments in the Study of Alien Tree Invasions: Opportunities and Limitations

Aim Acacia is the largest genus of plants in Australia with over 1000 species. A subset of these species is invasive in many parts of the world including Africa, the Americas, Europe, the Middle East, Asia and the Pacific region. We investigate the phylogenetic relationships of the invasive species in relation to the genus as a whole. This will provide a framework for studying the evolution of traits that make Acacia species such successful invaders and could assist in screening other species for invasive potential. Location Australia and global. Methods We sequenced four plastid and two nuclear DNA regions for 110 Australian Acacia species, including 16 species that have large invasive ranges outside Australia. A Bayesian phylogenetic tree was generated to define the major lineages of Acacia and to determine the phylogenetic placement of the invasive species. Results Invasive Acacia species do not form a monophyletic group but do form small clusters throughout the phylogeny. There are no taxonomic characters that uniquely describe the invasive Acacia species. Main conclusions The legume subfamily Mimosoideae has a high percentage of invasive species and the Australian Acacia species have the highest rate of all the legumes. There is some evidence of phylogenetic clumping of invasive species of Acacia in the limited sampling presented here. This phylogeny provides a framework for further testing of the evolution of traits associated with invasiveness in Acacia.

RESEARCH The evolution and phylogenetic placement of invasive Australian Acacia species

Aim Reproductive traits are important mediators of establishment and spread ofintroduced species, both directly and through interactions with other life-historytraits and extrinsic factors. We identify features of the reproductive biology ofAustralian acacias associated with invasiveness.Location Global.Methods We reviewed the pollination biology, seed biology and alternativemodes of reproduction of Australian acacias using primary literature, onlinesearches and unpublished data. We used comparative analyses incorporating anAcacia phylogeny to test for associations between invasiveness and eightreproductive traits in a group of introduced and invasive (23) and non-invasive(129) species. We also explore the distribution of groups of trait ‘syndromes’between invasive and non-invasive species.Results Reproductive trait data were only available for 126 of 152 introducedspecies in our data set, representing 23/23 invasive and 103/129 non-invasivespecies. These data suggest that invasives reach reproductive maturity earlier (10/13 within 2 years vs. 7/26 for non-invasives) and are more commonly able toresprout (11/21 vs. 13/54), although only time to reproductive maturity wassigniﬁcant when phylogenetic relationships were controlled for. Our qualitativesurvey of the literature suggests that invasive species in general tend to havegeneralist pollination systems, proliﬁc seed production, efﬁcient seed dispersaland the accumulation of large and persistent seed banks that often have ﬁre-,heat- or disturbance-triggered germination cues.Conclusions Invasive species respond quicker to disturbance than non-invasivetaxa. Traits found to be signiﬁcant in our study require more in-depth analysisinvolving data for a broader array of species given how little is known of thereproductive biology of so many taxa in this species-rich genus. Sets ofreproductive traits characteristic of invasive species and a general ability toreproduce effectively in new locations are widespread in Australian acacias. Unlessthere is substantial evidence to the contrary, care should be taken with allintroductions.KeywordsBiological invasions, breeding system, invasive alien species, pollination,reproductive syndromes, reproductive traits, seed dispersal

David M. Richardson

Papers

INVITED REVIEW The more the better? The role of polyploidy in facilitating plant invasions

12. Using Natural Experiments in the Study of Alien Tree Invasions: Opportunities and Limitations

RESEARCH The evolution and phylogenetic placement of invasive Australian Acacia species

I ntroductions o f

Spatial analysis of the main invasive plant invasions on La Réunion Island