Botany Photo of the Day

Thank you to buildingadesert@Flickr, aka Claire W, for sharing today's photographs via the UBC Botanical Garden Botany Photo of the Day Flickr Pool (original image 1 | original image 2). Much appreciated!

Hemimeris racemosa is a small annual (from 3-50cm tall) native to southern Africa from Namaqualand to the Eastern Cape province. It is one of five (or six) described species of Hemimeris, all of which are endemic to the southern Africa. Of these, at least four are only found in the fynbos (fire-prone shrubland with hard, evergreen leaves) vegetation zone within the Cape Floristic Region biodiversity hotspot.

Flowers of Hemimeris are pollinated by bees that seek the oils secreted by glands in the floral spurs. These bees are typically (wholly?) within the genus Rediviva. In South Africa, flowers are in bloom from July to October.

I don't know if Claire purposefully photographed an interesting phenomenon with this particular species. Intentional or not, the two photographs display inversostyly, a stylar polymorphism that was perhaps first described in 2005 by Anton Pauw in Inversostyly: a new stylar polymorphism in an oil-secreting plant, Hemimeris racemosa (Scrophulariaceae) (Am. J. Bot. 92:1878-1886). In the first photograph, the style points to the upper part of the flower (though the tip is hidden by a lobe) (aka style-up) while the two pollen-producing stamens point downward. In the second photograph, the inverse occurs (aka style-down).

Interestingly, the stylar arrangement is correlated with the abundance of pollinators. In areas of high pollinator populations, the percentage of style-up flowering individuals is at its highest. As pollinator populations decline, the percentage of style-down flowering individuals increases. A third morph, where both the style and stamens are clustered in the down position, is found in areas where the oil-collecting bees are fewest in relative numbers (and in these populations, there is the highest amount of autogamy, or self-fertilization).