Wednesday, January 13, 2016

Dombeya acutangula ssp. rosea flowering at Trinity College Botanic Garden

Dombeya acutangula Cav. (Malvaceae) is a taxonomically difficult taxon.  Some sources state that it is endemic to he Mascarene Islands (Mauritius, La Reunion, Rodrigues and associated islets) of the Indian Ocean, while the IUCN Redlist ( claims it is endemic to Mauritius.  Other sources give a distribution that includes Madagascar and all three of the main Mascarene islands (e.g. Le Péchon et al., 2010), while Seyani (1991) took a broader view and included specimens from Zambia, Mozambique and Tanzania in D. acutangula.  Part of the problem may lie in the variability of the taxon, with differences in leaf dissection, flower colour, pollen production and fruit set reported. 

In the Mascarene Islands, the genus Dombeya has speciated widely, with several endemic species which are often locally distributed.  The molecular work of Le Péchon et al. (2010) indicates that the Mascarene D. acutangula has colonized from Madagascar, but has not given rise to further species, though different subspecies and varieties have been described; several other Dombeya species described from Reunion but which are not currently recognized are considered to be part of the variation within D. acutangula.  The other Dombeya in the Mascarene Islands are thought to be the result of at least three separate colonisations from Madagascar.  The genus itself is taxonomically uncertain, with different sources stating between 80 and 250 species, and the relationships between Dombeya and related genera such as Trochetia and Ruizia are unclear.

Dombeya acutangula ssp. rosea Friedmann is restricted to the south-western parts of Mauritius, where it is critically endangered, with less than 50 individuals remaining; threats include habitat loss, range contraction and competition from invasive non-native species.

The photograph here is a composite of 28 different images focused on different areas and combined in focus stacking software – there is no other way to have all of the inflorescence in sharp focus.  The image shows the yellowish nectar accumulating at the base of the stamens, and the hermaphrodite flowers with stamens and a pistil: most other Mascarene Dombeya are dioecious, with separate male and female plants.  The Trinity College specimen was collected as a cutting in 1985 by John Parnell, Peter Wyse Jackson and Quentin Cronk during a TCD plant conservation expedition to Mauritius.

Dombeya is named after the French botanist Joseph Dombey, who made collections in South America for the Jardin des Plantes in Paris.  One set of his specimens was captured en route to Paris by the British and added to their own collection at the British Museum.  His return from Chile to France, with replaced specimens, took him through Cadiz, where he was promptly imprisoned and his collections again empounded, half of them this time being transferred to Madrid.

Le Péchon, T. et al. (2010).  Multiple colonisations from Madagascar and converged acquisition of dioecy in the Mascarene Dombetoideae (Malvaceae) as inferred from chloroplast an nuclear DNA sequence analysis.  Annals of Botany, 106: 343-357.

Posted: Steve Waldren

Wednesday, January 6, 2016

Postdoctoral Research Fellowship: Saltmarsh Ecology

Impacts of eutrophication on saltmarsh vegetation in Ireland and consequences for ecological assessment under the Water Framework Directive.

The School of Natural Sciences, Trinity College Dublin, invites applications for a Postdoctoral Research Fellow position, funded by the Environmental Protection Agency (EPA) Research Programme 2014-2020. The position is for a period of 18 months and will commence on 1st March 2016. The project is being undertaken by an academia-industry partnership of Trinity College Dublin and Botanical, Environmental and Conservation (BEC) Consultants.

The position comprises work as part of a team on the SAMFHIRES project (Saltmarsh Function and Human Impacts in Relation to Ecological Status). This project seeks to link anthropogenic pressures to changes in saltmarsh communities and investigate the ecosystems services and ecological functions of saltmarshes in Ireland. Areas of investigation include the impacts of grazing livestock and eutrophication on vegetation communities, biodiversity and net primary productivity. By integrating the outputs of this research, SAMFHIRES will refine the tool developed by the recent SMAATIE project (Saltmarsh Angiosperm Assessment Tool for Ireland – see for the purposes of the Water Framework Directive (WFD) in coastal and transitional waters.

The successful applicant will be based within the Botany Department at Trinity College and supervised by Professor Steve Waldren. They will also have access to the facilities (including laboratories) of Trinity’s Centre for the Environment. Resources available at the offices of BEC Consultants, based in Dublin close to Trinity College, will also be made available. The BEC team is co-ordinated by Dr Philip Perrin.

Closing date for applications: 12 Noon on 22nd January 2016

For further details contact professor Steve Waldren

Thursday, December 17, 2015

What do insects have to do with eating, drinking and kissing this Christmas?

We don’t often associate insects with Christmas. However, without them, we wouldn’t have many of our Christmas foods, drinks and decorations. This is because many of the plants that produce our Christmas treats rely on insects pollinating flowers earlier in the year. Without these insects, we wouldn’t have bright red holly berries to decorate our Christmas puddings, mistletoe with its characteristic white berries to kiss under, cranberries to liven up our turkey, chocolate, marzipan or many of the spices and other goodies we associate with Christmas. This is because insects are needed by most plants for cross-pollination, which results in the production of fruits and seeds. Since plants cannot move to find mates themselves, they rely on insects to bring male and female together.

Holly (Ilex aquifolium) is unusual in the plant world because male and female flowers occur on separate shrubs. As bees drink nectar from male flowers, they get pollen on their bodies and when they move to a female plant to continue to feed, they deposit that pollen on female flowers. The pollen causes the female flowers to be fertilized, and to form fruits (or berries) containing the fertilized seeds.

A bumblebee visits a Holly flower in Co. Wicklow in
April to drink nectar. (Photo J. Stout)

Similarly, mistletoe (Viscum album) also holds its male and female flowers on separate plants. Plants are partially parasitic and live on the branches of other trees but still rely on insects (not just bees, but also flies, bugs and beetles) for pollination and thus berry production. In fact, both mistletoe and holly fetch higher prices at market if they have berries on them, and so insect pollinators are of economic value at Christmas time as well.

Cranberry bushes (Vaccinium macrocarpon) produce both the male and female structures not just on the same plant, but in the same flower. However, they still need bees to transfer the pollen between flowers, because those male and female structures do not mature at the same time.  Large bees, such as bumblebees, which can shake the flowers at just the right frequency to dislodge the pollen (producing a distinctive buzzing sound) are the best pollinators. This is known as “buzz pollination” and is important in other crops too (including tomatoes and blueberries).

Chocolate-producing cocoa trees (Theobroma cacao) produce small flowers on their trunks, and although flowers don’t produce a scent to attract pollinators, they produce a small amount of nectar and are visited and pollinated by tiny flies (midges). Although flowers contain both male and female structures, they cannot fertilize themselves, and these midges are needed for the production of cocoa fruits, which contain the seeds from which we derive chocolate. These trees grow in the tropics and flowers and fruits are produced throughout the year, although it takes 5-6 months for them to mature before they are harvested.

Marzipan (almond paste) is made of ground almonds (and sugar). Almond (Prunus dulcis) trees bloom in early spring and are visited by bees – both managed honeybees and wild bees. In fact, almond trees in California (where most of the world’s almonds are produced) produce better yields when both honeybees and wild bees are present in orchards. This is because they complement each other in their foraging. If there are no bees at all visiting flowers, fruit set can plummet by up to 90%.

Honeybees are important pollinators of
almond flowers (Photos J. Stout)

Many of our Christmas spices, including cinnamon (Cinnamomum spp.), cloves (Syzygium aromaticum) and nutmeg (Myristica fragrans), essential ingredients in Christmas cakes, puddings and mulled wine, also need pollinating by insects. In the case of cinnamon and cloves, this is done by bees, but for nutmeg, it’s beetles that do the pollinating job.

So, as you enjoy Christmas this year, raise a glass to the insects that made all of this possible.

For more information on pollinators, their value and conservation, see the All Ireland Pollinator Plan

Posted: Professor Jane Stout

Originally published in the Independent supplement on the Science of Christmas 14th December, 2015


Wednesday, December 16, 2015

There are some things that you never get to hear about: The Botany Bake Off

There are some things that you never get to hear about.  The Botany Department at Trinity College is currently having a bake off competition inspired by the BBC TV series the Great British Bake Off.


One fascinating entry was this lovely chocolate cake of a pine stump.  Why?  Well it represents Botany PhD student Alwynne McGeever’s work studying fossil tree stumps and pollen grains to uncover when pine populations were rising and declining throughout Europe over the last 10,000 years.  It was presented at a recent departmental coffee break in the library and it tasted as beautiful as it looked.  Now you wish you did Plant Sciences at Trinity College Dublin!

Sunday, December 13, 2015

PhD student on plant collecting expedition in South East Asia

PhD student Dongwei Zhao, who is working with plant taxonomist Professor John Parnell, is currently on a plant collecting expedition in South East Asia.  He is working on Camellia species and is visiting various herbaria as well doing field work.  The image is from Loei in Northern Thailand and Dongwei is in blue.

Thursday, December 10, 2015

Genetic variation in Irish perennial ryegrass: New reserach

Irish Perennial Ryegrass

TCD botanists Sai Krishna Arojju, Sarah McGrath and Trevor Hodkinson have publish a new paper on genetic variation in Irish perennial ryegrass in collaboration with Susanne Barth Teagasc, Oak Park Carlow.

This study assessed the genetic diversity in 928 individuals from 40 diploid populations of Lolium perenne using nuclear simple sequence repeat markers, including 22 accessions of Irish ecotypes, seven European ecotypes and 11 released varieties. High levels of allelic and genetic diversity were determined, with intra-population variation accounting for the majority of the variation. The majority of the accessions deviated from Hardy–Weinberg equilibrium and had relatively high inbreeding coefficients. Two major gene pools of ecotypic accessions were defined by unweighted pair group method with arithmetic mean (UPGMA) and PCA analyses. One of these two gene pools accounted for two-thirds of the ecotypes and included most of the current Irish and Northern Irish breeding materials and about half of the European ecotypes included in this study; these European ecotypes performed well under Irish selection conditions. Population structure and differentiation analyses using Structure analysis and analysis of molecular variance confirmed the results found in the UPGMA and PCA analyses. These results will be useful for breeders who wish to exploit specific pools from ecotype collections.

More details:

Posted: Nick Gray