Self-pollination and inbreeding depression in Acacia dealbata: Can selfing promote invasion in trees?

The ability to self-fertilise may promote invasiveness in plants by assuring reproductionwhen mate and pollinator availabilities are inadequate, provided that the benefit of increased fecundity via selfing is not outweighed by inbreeding depression. However, knowledge of breeding systems and inbreeding depression has been lacking for most introduced plants. In this study of the invasive Australian tree Acacia dealbata in its introduced range in South Africa, controlled pollination experiments indicated that the study population was at least partially selfcompatible and had a high capacity for autonomous self-pollination. However, we found substantial inbreeding depression, with seeds per fruit, progeny survival and progeny growth being lower after self- than after crosspollination. Progeny arising from self-pollination also had a higher frequency of certain traits – yellow colouration of leaves and pink or white colouration of stems – which were associated with lower rates of survival. High inbreeding depression in A. dealbata must detract from the reproductive assurance benefit of self-fertilisation, casting doubt on the hypothesis that self-fertilisation contributes to invasiveness in this species. As high inbreeding depression has also been reported in other self-compatible trees, future studies should elucidate whether selffertilisation contributes to invasiveness of trees by assessing both reproductive assurance benefits and inbreeding depression costs over the lifetime of progeny

Sport policy convergence: a framework for analysis

This is an Accepted Manuscript of an article published by Taylor & Francis Group in European Sport Management Quarterly on 30th April 2012, available online at: http://www.tandfonline.com/10.1080/16184742.2012.669390The growth in the comparative analysis of sport management processes and policy has led to an increased interest in the concept of convergence. However, the concept is too often treated as unproblematic in definition, measurement and operationalisation. It is argued in this paper that a more effective framework for examining claims of convergence is one that analyses the concept in terms of seven dimensions which can be explored through a mix of quantitative and qualitative methods of data collection. It is also argued that a deeper understanding of the process of convergence can be gained by operationalising the concept in the context of a selected range of meso-level theories of the policy process or of specific aspects of the process. The proposed analytic framework provides not only a definition of convergence but also the basis for a more nuanced investigation of hypotheses of convergence

Self-pollination and inbreeding depression in Acacia dealbata: Can selfing promote invasion in trees?

The ability to self-fertilise may promote invasiveness in plants by assuring reproductionwhen mate and pollinator availabilities are inadequate, provided that the benefit of increased fecundity via selfing is not outweighed by inbreeding depression. However, knowledge of breeding systems and inbreeding depression has been lacking for most introduced plants. In this study of the invasive Australian tree Acacia dealbata in its introduced range in South Africa, controlled pollination experiments indicated that the study population was at least partially selfcompatible and had a high capacity for autonomous self-pollination. However, we found substantial inbreeding depression, with seeds per fruit, progeny survival and progeny growth being lower after self- than after crosspollination. Progeny arising from self-pollination also had a higher frequency of certain traits – yellow colouration of leaves and pink or white colouration of stems – which were associated with lower rates of survival. High inbreeding depression in A. dealbata must detract from the reproductive assurance benefit of self-fertilisation, casting doubt on the hypothesis that self-fertilisation contributes to invasiveness in this species. As high inbreeding depression has also been reported in other self-compatible trees, future studies should elucidate whether selffertilisation contributes to invasiveness of trees by assessing both reproductive assurance benefits and inbreeding depression costs over the lifetime of progeny

Heterogeneity in local density allows a positive evolutionary relationship between self-fertilisation and dispersal.

Despite empirical evidence for a positive relationship between dispersal and self-fertilization (selfing), theoretical work predicts that these traits should always be negatively correlated, and the Good Coloniser Syndrome of high dispersal and selfing (Cf. Baker's Law) should not evolve. Critically, previous work assumes that adult density is spatiotemporally homogeneous, so selfing results in identical offspring production for all patches, eliminating the benefit of dispersal for escaping from local resource competition. We investigate the joint evolution of dispersal and selfing in a demographically structured metapopulation model where local density is spatiotemporally heterogeneous due to extinction-recolonization dynamics. Selfing alleviates outcrossing failure due to low local density (an Allee effect) while dispersal alleviates competition through dispersal of propagules from high- to low-density patches. Because local density is spatiotemporally heterogeneous in our model, selfing does not eliminate heterogeneity in competition, so dispersal remains beneficial even under full selfing. Hence the Good Coloniser Syndrome is evolutionarily stable under a broad range of conditions, and both negative and positive relationships between dispersal and selfing are possible, depending on the environment. Our model thus accommodates positive empirical relationships between dispersal and selfing not predicted by previous theoretical work and provides additional explanations for negative relationships

Does autogamy contribute to invasion in Lilium formosanum?

The Taiwanese geophyte Lilium formosanum is invasive in the eastern parts of South Africa. Although it is capable of autogamy, a pollinator, the hawkmoth Agrius convolvuli, is present. Reproduction may therefore take place both by self- and cross-fertilisation. The relative importance of these modes of pollination for seed production is evaluated using emasculation experiments. The potential contributions of outcrossed and selfed progeny to invasion are assessed in progeny performance trials

Pollinators, mates and Allee effects: the importance of self-pollination for fecundity in an invasive lily

1. Ability to self-fertilize is correlated with invasiveness in several introduced floras, and this has been attributed to its mitigating effect on fecundity when pollinator visitation and mate availability are inadequate. Cross-pollination opportunities are expected to be most limited in isolated individuals and small populations, both typical of the leading edge of an invasion. Thus, self-pollination may promote invasion in part by mitigating pollen-limitation Allee effects. 2. We used emasculation and pollen supplementation experiments to test whether the importance of self-pollination for fecundity increased as plant abundance decreased and isolation increased, in the hawkmoth-pollinated and autonomously self-pollinating invasive lily Lilium formosanum, in its introduced range in KwaZulu-Natal, South Africa. As inbreeding depression is negligible in these populations, seed production through selfing is likely to be demographically important. 3. In naturalized populations of L. formosanum, varying in size and degree of isolation, emasculation reduced seed production by two-thirds, indicating strong reliance on self-fertilization for fecundity due to inadequate pollinator visitation. However, this was not related to population size and was only greater for more isolated populations in one of the 3 years in which the experiment was carried out. Pollen supplementation experiments showed that pollen limitation was low – 12% on average – and significant in only one of 3 years, demonstrating that autonomous self-pollination was highly effective. 4. In artificial arrays, consisting of plants placed inside naturalized populations or in pairs isolated (3–702 m) from populations, the effect of emasculation on fecundity was greater in isolated plants than those inside the population in one of two populations. Isolation reduced fecundity when emasculated plants were placed next to a second emasculated plant, but not when emasculated plants were partnered with an intact plant, from which they could receive pollen. 5. We conclude that self-fertilization in L. formosanum compensates for inadequate pollinator visitation across all levels of population size and for a pollen-limitation Allee effect due to decreased mate availability in isolated plants, and may thus play an important role in invasion

Synthesis of the mixed lithium-magnesium, mixed amide (R,R/S,S)-[{LiMg(TMP)[CH2Si(Me)(2)N(SiMe3)]}(2)]: a conformationally-locked structure of five fused rings inducing two stereogenic nitrogen centres

Reaction of the magnesium amide Mg(TMP)2 with the lithium amide LiHMDS is accompanied by an unexpected, sterically-promoted hydrogen transfer/amine elimination process, to yield the novel title compound which is the first such heterometallic composition to contain a heteroleptic amide ligand set

Reproductive biology of Australian acacias: Important mediator of invasiveness?

Aim Reproductive traits are important mediators of establishment and spread of introduced species, both directly and through interactions with other life-history traits and extrinsic factors. We identify features of the reproductive biology of Australian acacias associated with invasiveness. Location Global. Methods We reviewed the pollination biology, seed biology and alternative modes of reproduction of Australian acacias using primary literature, online searches and unpublished data. We used comparative analyses incorporating an Acacia phylogeny to test for associations between invasiveness and eight reproductive 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 introduced species in our data set, representing 23/23 invasive and 103/129 non-invasive species. These data suggest that invasives reach reproductive maturity earlier (10/13 within 2years vs. 7/26 for non-invasives) and are more commonly able to resprout (11/21 vs. 13/54), although only time to reproductive maturity was significant when phylogenetic relationships were controlled for. Our qualitative survey of the literature suggests that invasive species in general tend to have generalist pollination systems, prolific seed production, efficient seed dispersal and 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-invasive taxa. Traits found to be significant in our study require more in-depth analysis involving data for a broader array of species given how little is known of the reproductive biology of so many taxa in this species-rich genus. Sets of reproductive traits characteristic of invasive species and a general ability to reproduce effectively in new locations are widespread in Australian acacias. Unless there is substantial evidence to the contrary, care should be taken with all introductions. © 2011 Blackwell Publishing Ltd.Revie