Pollen Insights into Apomictic and Sexual<i>Miconia</i>(Miconieae, Melastomataceae)

Since tropical trees often have long generation times and relatively small reproductive populations, breeding systems and genetic variation are important for population viability and have consequences for conservation. Miconia albicans is an obligate, diplosporous, apomictic species widespread in the Brazilian Cerrado, the savanna areas in central Brazil and elsewhere in the Neotropics. The genetic variability would be, theoretically, low within these male-sterile and possibly clonal populations, although some variation would be expected due to recombination during restitutional meiosis. We used ISSR markers to assess genetic diversity of M. albicans and to compare with other tropical trees, including invasive species of Melastomataceae. A total of 120 individuals from six populations were analysed using ten ISSR primers, which produced 153 fully reproducible fragments. The populations of M. albicans presented mean Shannon's information index (I) of 0.244 and expected heterozygosity (H ) of 0.168. Only two pairs of apparently clonal trees were identified, and genetic diversity was relatively high. A hierarchical amova for all ISSR datasets showed that 74% of the variance was found among populations, while only 26% of the variance was found within populations of this species. Multivariate and Bayesian analyses indicated marked separation between the studied populations. The genetic diversity generated by restitutional meiosis, polyploidy and possibly other genome changes may explain the morpho-physiological plasticity and the ability of these plants to differentiate and occupy such a wide territory and different environmental conditions. Producing enormous amounts of bird-dispersed fruits, M. albicans possess weedy potential that may rival other Melastomataceae alien invaders.

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“…; Caetano et al . ), and consequently are incapable of completing sexual reproduction, rendering them obligate apomictics (Caetano et al . ).…”

Section: Discussionmentioning

confidence: 99%

Unexpectedly high genetic diversity and divergence among populations of the apomictic Neotropical tree Miconia albicans

et al. 2017

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“…High male sterility associated with apomixis may lead to the absence or paucity of pollen available to reward bees or other insects (Caetano et al . ). Indeed, insect visitation to Melastomataceae flowers is mostly driven by pollen viability, with no changes in pollinator composition between sexual and putative facultative apomictic species (Maia et al .…”

Section: Discussionmentioning

confidence: 97%

Shifts from specialised to generalised pollination systems in Miconieae (Melastomataceae) and their relation with anther morphology and seed number

et al. 2016

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Most species in Melastomataceae have poricidal anthers related to specialised bee buzz-pollination, while some have anthers with large openings associated to non-bee pollination systems. We tracked the evolution of anther morphology and seed number on the Miconieae phylogenetic tree to understand the evolutionary shifts in such pollination systems. Anther morphometric data and seed number were recorded for 54 taxa. Pollinators (bees, flies, wasps) were recorded for 20 available species. Ancestral state reconstruction was made using Maximum Likelihood from nrITS sequences. We used phylogenetic eigenvector regressions to estimate phylogenetic signal and the adaptive component for these traits. Species pollinated by bees or bees and wasps tend to have smaller pores and fruits with more seeds. Species pollinated by flies or flies and bees and/or wasps tend to have larger pores and fruits with less seeds. Independent evolution occurred three times for anthers with large pores and twice for fruits with few seeds. We detected a phylogenetic signal in both traits, and negative correlated evolution between them. In actinomorphic small-flowered Miconieae, changes in anther morphology can be related to generalisation in the pollination system incorporating flies and wasps as pollinators and lessening the importance of buzzing bees in such process. Differences in pollen removal and deposition may explain differences in anther morphology and seed number in Miconieae.

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“…In the facultative apomictic species, the balance between apomictic and sexual events seems to be dependent on genetic (Asker & Jerling ; Hanna ) and cytological factors (Caetano et al . ,b). Facultative apomictic species such as M. hyemalis and T. sellowiana may maintain the ability to attract pollinators (Hanna ; Jefferson & Bicknell ; Koltunow et al .…”

Section: Discussionmentioning

confidence: 99%

“…) and is generally associated with polyploidy and hybridisation (Mendes‐Rodrigues & Oliveira ; Caetano et al . ,b), which in turn are related to different levels of low pollen viability or even complete pollen sterility (Mogie ; Richards ; Goldenberg & Shepherd ; Goldenberg & Varassin ). On the other hand, sexual species have high pollen viability (Goldenberg & Shepherd ; Goldenberg & Varassin ; Hoffmann & Varassin ).…”

Section: Introductionmentioning

confidence: 99%

Apomixis does not affect visitation to flowers of Melastomataceae, but pollen sterility does

2015

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Apomixis is an asexual seed reproduction mechanism thorough which embryos are originated from material tissues inside the ovules, without precedent fertilisation. It allows plants to colonise new habitats, even in places where flower visitors are scarce or where plants are isolate. Apomixis seems to be related to pollen sterility and, in species with flowers that offer pollen as a reward for pollinators, the amount or quality of the pollen offered by these species may influence the amount of the visits and specific composition of the visitors. In order to test this hypothesis, we studied breeding systems of 16 species of Melastomataceae and their flower visitors, evaluating composition and abundance of the visits to apomictic and sexual species. Apomictic plants with no viable pollen or with pollen with low viability did not receive visits from pollinators, and consequently probably produce strictly apomictic fruits. On the other hand, apomictic and sexual plants with high pollen viability do receive visits; in this case, apomictic plants may produce fruits and seeds through both sexual and apomictic methods. The species composition of insects visiting Melastomataceae with high pollen viability was similar, regardless of whether the plants were apomictic or not. It seems that pollen viability levels are important to determine visits to the flowers irrespective of breeding system.

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Pollen Insights into Apomictic and SexualMiconia(Miconieae, Melastomataceae)

Cited by 25 publications

References 30 publications

Unexpectedly high genetic diversity and divergence among populations of the apomictic Neotropical tree Miconia albicans

Unexpectedly high genetic diversity and divergence among populations of the apomictic Neotropical tree Miconia albicans

Shifts from specialised to generalised pollination systems in Miconieae (Melastomataceae) and their relation with anther morphology and seed number

Apomixis does not affect visitation to flowers of Melastomataceae, but pollen sterility does

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