Connectivity of green and blue infrastructures: living veins for biodiverse and healthy cities

strawbAIRies!

Strawberries and bacon-and-eggs: breakfast? No, citizen science!

BIOVEINS is starting a citizen science project in its cities. The strawbAIRies project, led by the Antwerp team, hopes to collect data on air quality and at the same time, data on pollination services. While this citizen-science project has already been organized successfully in Belgium for a few years, for the first time it will now take place simultaneously in Tartu, Poznan, Zurich, Antwerp, Paris and Lisbon.

The research teams in each participating city have been sent seeds of strawberry plants and bird’s-foot trefoil, also known as bacon-and-eggs or Lotus coriculatus, which they have sown and are growing in preparation for the project. Participating city dwellers will be sent one pot with a strawberry plant and one pot with two Lotus corniculatus plants to raise on window ledges in May and June.

The ideal placement for the plants is on the window ledge on the first floor of a house or apartment, facing the street. This will give exposure to polluted air currents from the street, as well as access for flying pollinating insects. Anskje Van Mensel, who will be using data from this project for her PhD thesis at Antwerp University, hopes to get at least 50 participants from each city.

There are three kinds of samples that citizen scientists will collect for strawbAIRies: leaves, fruits and seeds.

Participants will collect strawberry leaves and send them, via the research group of each city, back to Anskje’s lab, where she will measure air pollution by magnetic analysis of the leaves.

Participants will also report on the shape of their strawberries (before eating them!). The strawberry is not technically a fruit, but what is called an “aggregate accessory fruit” meaning that the mass of it is not made from the fruiting body, botanically speaking, but from another part of the plant. Each apparent seed on the outside of the strawberry is a fruit in the botanical sense, inside which are the actual seeds. The strawberry flower has multiple pistils (the female parts of the flower that extend out from its center). When a pistil is pollinated by one or more of the polinators passing through, then the “receptacle” underneath will grow, and the strawberry will develop and swell out at that point. That means the better the total effort of pollination, the rounder the strawberry. When you see a side of a strawberry that is kind of scrunched up, disinflated, and colourless, that is the part where it wasn’t pollinated.

The interesting thing about this, is that this makes a strawberry a possible indicator of pollinator abundance or diversity, since each insect might make contact with the flowerhead differently, thus pollinating different parts of it. Even insects that are hunting other insects on the flowerhead can help shift pollen around, and thus help pollinate more of the pistils. You might hope to see honey bees, bumble bees, other wild bees, hover flies (syrphids), butterflies, and beetles on your strawberries. For some more information and nice photos from the North American context, see here: https://entomology.ces.ncsu.edu/strawberry-pollinating-insects/

This is what strawberries look like as they grow from flower to fruit:

And, if you still need reasons to be interested in strawberries, they are a good example of a cosmopolitan plant. The modern commercial strawberry is a cross of a European species, Fragaria virginiana, and a species from the Pacific coast of the Americas, Fragaria chiloensis (“strawberry from Chiloe”. This is Chiloe, considered by many Chileans to be the most special part of Chile, ecologically and culturally: https://youtu.be/SNIjHBrLQrw ) Modern commercial strawberries were first bred in France in the 1750s. Wait, you say, I thought two species couldn’t make a viable hybrid? Well, this is not really true, even for animals, so the strawberry is also a theoretical anomaly that can help us rethink the species concept, as we watch it grow.

Anskje also hopes that the Lotus corniculatus plants will flower and set seed before people go on vacation for the summer, so that they can send in the seedpods. These look like small pea pods. Anskje plans to count the number of pods and the number of seeds in each pod and will try to link this to the pollination services. They are mainly pollinated by bumblebees and wild, solitary bees. Although a large proportion of pollinated flowers do not form seeds in this species, research has shown that the more abundant the pollinators are in a particular area, the more seedpods are formed. And as you can appreciate clearly in the illustration above, each flower forms one seedpod.

Here’s what a Lotus corniculatus looks like as it grows: https://youtu.be/bX1Ns_fg49U. If you want to see it flower and form seedpods, you’ll have to grow your own!

Each strawberry and Lotus corniculatus plant will be geolocalised, so that its distance to the nearest parks and green areas can be calculated using the fragmentation data we aleady have for each city. This will allow the research team to understand how fragmentation in cities affects air pollution and pollination. Anskje hopes that, as part of her PhD, the air pollution data and the pollination data will be integrated with the other biodiversity and ecosystem data from the project. For example, the data on bees nesting in the bee hotels, and the data on nocturnal insects from the bat study (http://www.bioveins.eu/blog/data-collection-for-bioveins-part-1), can be integrated with the strawberry and seedpod data to get a richer set of proxies for pollination services in cities.

If you live in a BIOVEINS city and you want to participate, you can register HERE: https://www.uantwerpen.be/en/projects/strawbairies/participate/

Bibliography:

https://www.quantamagazine.org/interspecies-hybrids-play-a-vital-role-in-evolution-20170824/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2909262/
http://www.inia.org.uy/sitios/lnl/vol34/sareen.pdf

--Meredith Root-Bernstein 8 April 2019