Friday, 25 May 2012

Lobelia flowers

A while ago, I wrote about the spectacular Lobelia physaloides and its relationships to other New Zealand Lobelias. At the time I didn't have good pictures of the flowers, so I illustrated that post with pictures of a fruit.

Last summer I managed to photograph flowers in the Wellington Botanic Gardens (if you're local, you can see this plant beside the path about 20m uphill from the duck pond).
Lobelia physaloides in the Wellington Botanic Gardens.
Also in the gardens I saw a red-flowered plant that I took to be L. cardinalis, the type species of the genus Lobelia.  There are a huge number of ways a big genus like Lobelia could be divided up, but whichever grouping contains L. cardinalis must retain the name Lobelia.

Red Lobelia, male phase presenting pollen.
When these flowers first open, they present their pollen first.  The stigma helps push the pollen out of the joined anthers, and then later it opens out to receive pollen.

Red Lobelia, female phase, stigma expanded to receive pollen.
Apart from their colour difference, you might think these large flowers are quite similar, especially if you compare them to the sort of little white flower that's more common among New Zealand's Lobelias, like this L. arenaria from the Auckland Islands...
Lobelia arenaria, Enderby Island, Auckland Islands.
... or this Lobelia ionantha from the Kettlehole Bog at Cass, North Canterbury.

But molecular phylogenetic research has shown L. physaloides and L. cardinalis are not particularly closely related and in fact their morphology also suggests they're not close.  Some botanists take a wide view of Lobelia and include L. physaloides, and that's the position I took in my earlier post.  However, the earliest branches in the family tree of Lobeliaceae could just as easily be classified as separate genera, and in this case L. physaloides might be called Colensoa physaloides or perhaps placed in another genus.  It seems its nearest relatives are in Australia and Africa, so it's not closely related to our other native species.
Diagram of evolutionary relationships in the family Lobeliaceae (based on Antonelli 2008).  It shows that plants classified as Lobelia are found in many different lineages.  Most New Zealand species are in the C7 clade.
However L. physaloides is classified, one thing is not negotiable for me: it must be classified in such a way that its nearest relatives aren't classified in a separate genus along with species that are more distantly related.


Antonelli, A. 2008. Higher level phylogeny and evolutionary trends in Campanulaceae subfam. Lobelioideae: Molecular signal overshadows morphology.  Molecular phylogenetics and evolution 46: 1–18.

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