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Spatial genetic structure reflects extensive clonality, low genotypic diversity and habitat fragmentation in Grevillea renwickiana (Proteaceae), a rare, sterile shrub from south-eastern Australia.

ABSTRACT: BACKGROUND AND AIMS: The association of clonality, polyploidy and reduced fecundity has been identified as an extinction risk for clonal plants. Compromised sexual reproduction limits both their ability to adapt to new conditions and their capacity to disperse to more favourable environments. Grevillea renwickiana is a prostrate, putatively sterile shrub reliant on asexual reproduction. Dispersal is most likely limited by the rate of clonal expansion via rhizomes. The nine localized populations constituting this species provide an opportunity to examine the extent of clonality and spatial genotypic diversity to evaluate its evolutionary prospects. METHODS: Ten microsatellite loci were used to compare genetic and genotypic diversity across all sites with more intensive sampling at four locations (n = 185). The spatial distribution of genotypes and chloroplast DNA haplotypes based on the trnQ-rps16 intergenic spacer region were compared. Chromosome counts provided a basis for examining genetic profiles inconsistent with diploidy. KEY RESULTS: Microsatellite analysis identified 46 multilocus genotypes (MLGs) in eight multilocus clonal lineages (MLLs). MLLs are not shared among sites, with two exceptions. Spatial autocorrelation was significant to 1·6 km. Genotypic richness ranged from 0 to 0·33. Somatic mutation is likely to contribute to minor variation between MLGs within clonal lineages. The eight chloroplast haplotypes identified were correlated with eight MLLs defined by ordination and generally restricted to single populations. Triploidy is the most likely reason for tri-allelic patterns. CONCLUSIONS: Grevillea renwickiana comprises few genetic individuals. Sterility has most likely been induced by triploidy. Extensive lateral suckering in long-lived sterile clones facilitates the accumulation of somatic mutations, which contribute to the measured genetic diversity. Genetic conservation value may not be a function of population size. Despite facing evolutionary stagnation, sterile clonal species can play a vital role in mitigating ecological instability as floras respond to rapid environmental change.

SUBMITTER: James EA

PROVIDER: S-EPMC4111381 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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Spatial genetic structure reflects extensive clonality, low genotypic diversity and habitat fragmentation in Grevillea renwickiana (Proteaceae), a rare, sterile shrub from south-eastern Australia.

James Elizabeth A EA McDougall Keith L KL

Annals of botany 20140415 2

<h4>Background and aims</h4>The association of clonality, polyploidy and reduced fecundity has been identified as an extinction risk for clonal plants. Compromised sexual reproduction limits both their ability to adapt to new conditions and their capacity to disperse to more favourable environments. Grevillea renwickiana is a prostrate, putatively sterile shrub reliant on asexual reproduction. Dispersal is most likely limited by the rate of clonal expansion via rhizomes. The nine localized popul ...[more]

PMID: 24737718

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Project description:Fragmentation of natural vegetation is currently one of the largest threats to plant populations and their interactions with pollinators. Plant reproductive susceptibility to habitat fragmentation has been investigated in many species; however, the response of wild mass-flowering species is poorly known, with research limited to mainly boreal plant species.Here, we studied twelve remnant populations of the threatened mass-flowering shrub Conospermum undulatum in the southwest Australian biodiversity hotspot, each presenting different population size, level of isolation, and floral display. We assessed the impact of fragmentation on (a) fruit and seed production; and (b) seed germination. To gain a deeper understanding of factors influencing the reproductive success of C. undulatum, we performed pollinator exclusion and self-pollination treatments to experimentally assess the mating system of this threatened shrub.We found C. undulatum to be strictly self-incompatible and totally reliant on pollinators visiting with an outcrossed pollen load to complete the reproductive cycle. Further, we found that fruit production dropped from 35% to <20% as a result of decreasing floral display. A reduction in population size from 880 to 5 plants and from ~700 to 0.21 in the floral display index led to a decrease in seed output, while a similar reduction in seed output, from 6% to 3%, was observed as a result of increasing isolation index from -21.41 to -0.04. Overall, seed germination was positively related to population size, and a negative relationship was found between germination and isolation. Synthesis and applications. Our results demonstrate the important relationship between pollinators and floral morphology in plants of southwest Australia that have coevolved with native pollinators and developed characteristic flower morphologies over long time frames. Indeed, due to its characteristic pollination mechanism, the self-incompatible C. undulatum can only rely on specialized native pollinators for pollen flow and cannot rely on its mass-flowering trait to attract generalist pollinators from coflowering species; neither can it compensate for the lack of visitors by promoting geitonogamy. Consequently, fragmentation has a significant effect on the reproductive output of C. undulatum, and size, isolation, and floral display of populations are important factors to be considered when planning conservation actions for the species.

Project description:Background and aimsGlobal plant trait datasets commonly identify trait relationships that are interpreted to reflect fundamental trade-offs associated with plant strategies, but often these trait relationships are not identified when evaluating them at smaller taxonomic and spatial scales. In this study we evaluate trait relationships measured on individual plants for five widespread Protea species in South Africa to determine whether broad-scale patterns of structural trait (e.g. leaf area) and physiological trait (e.g. photosynthetic rates) relationships can be detected within natural populations, and if these traits are themselves related to plant fitness.MethodsWe evaluated the variance structure (i.e. the proportional intraspecific trait variation relative to among-species variation) for nine structural traits and six physiological traits measured in wild populations. We used a multivariate path model to evaluate the relationships between structural traits and physiological traits, and the relationship between these traits and plant size and reproductive effort.Key resultsWhile intraspecific trait variation is relatively low for structural traits, it accounts for between 50 and 100 % of the variation in physiological traits. Furthermore, we identified few trait associations between any one structural trait and physiological trait, but multivariate regressions revealed clear associations between combinations of structural traits and physiological performance (R2 = 0.37-0.64), and almost all traits had detectable associations with plant fitness.ConclusionsIntraspecific variation in structural traits leads to predictable differences in individual-level physiological performance in a multivariate framework, even though the relationship of any particular structural trait to physiological performance may be weak or undetectable. Furthermore, intraspecific variation in both structural and physiological traits leads to differences in plant size and fitness. These results demonstrate the importance of considering measurements of multivariate phenotypes on individual plants when evaluating trait relationships and how trait variation influences predictions of ecological and evolutionary outcomes.

Dataset Information

Spatial genetic structure reflects extensive clonality, low genotypic diversity and habitat fragmentation in Grevillea renwickiana (Proteaceae), a rare, sterile shrub from south-eastern Australia.

Publications

Spatial genetic structure reflects extensive clonality, low genotypic diversity and habitat fragmentation in Grevillea renwickiana (Proteaceae), a rare, sterile shrub from south-eastern Australia.

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