Jumellea teretifolia

Plants have been growing and flowering, regardless of the change in our world, but I haven't updated the blog for a while.  But this pretty orchid is in bloom, so I wanted to upload the photos.

Jumellea is a moderately small genus with about 57 species (Rakotoarivelo et al. 2012).  Some species of Jumellea are similar to each other and difficult to identify (for me), but J. teretifolia is easily recognizable due to the cylindrical leaves (as the species epithet indicates).  The narrow and long flower parts give the elegant look.  This species is endemic to central highlands (1100-1500m) of Madagascar (Provinces of Antananarivo, Fianarantsoa, Toamasina; Cribb & Hermans 2009).

Pollination biology of this species was studied by Nilsson et al. (1987).  Three interesting observations can be highlighted.  First, this species appears to rely on a single pollinator species.  Among 6 species of hawkmoths with long probosces (straw-like, elongated mouth parts), caught by light traps, only one species, Panogena lingens, was the effective pollen carrier.  Interestingly, there are two sympatric (co-occuring) morphs of this hawkmoth, differing in the lengths of probosces (long = 11.7cm and short = 7.3cm).  The long morph was a much more efficient  pollen carrier.  A specialist pollinator is generally considered to be efficient for the plants (i.e. high accuracy of pollen delivery with small amount of reward/nectar).  The short-coming of relying on a single species is that a reduction in the pollinator population size could directly reduce the reproductive success of the plant.

Second, several orchid species seem to share this hawkmoth as the pollinator.  Six long-spurred orchids were in flower during the study (November 13-30); Angraecum arachinites, A. compactum, Neobathia grandidierana, Jumellea teretifolia, Aerangis articulata, and A. fuscata.  Five of the six orchid species appear to share the same pollinator species (P. lingens) while the pollinarium of A. articulata was not found on this hawkmoth. A note about the terminology; "pollinia" are the pollen sacs, and "pollinaria" mean pollen sacs AND associated structures (e.g. the structure connecting the two pollen sacs; see this link). As with J. teretifolia, this hawkmoth species seems to be the only pollinator of these 5 orchid species.  In other words, there is a relationship between a single pollinator species and multiple orchid species.  In some cases where a single pollinator species is shared among multiple plants, different plant species may utilize different pollen deposition location (i.e. head vs abdomen of the insect).  A. arachnites was the only one among the 5 orchids which uses this strategy; pollinaria of A. arachnites were found at the bottom side of the probosces, but other four species deposited them around the same location at the top of the probosces near the base.   This could potentially cause the undesirable inter-specific pollen transfer.

Finally, the sugar concentration of J. teretifolia was fairly low (12%) for hawkmoth pollinated flowers.  Because hawkmoths keep hovering during flower visitation (instead of perching), they were considered to be energetically expensive.  They prefer nectar with high sugar concentration because they do not want to carry the extra weight of water.  Therefore, the nectar concentration of hawkmoth-pollinated flowers is generally high. Humming birds show a similar behavior, and humming bird pollinated flowers show a similar trend.  But J. teretifolia seems to deviate from this general pattern.

I obtained this plant via Madagascar import of Louisiana Orchid Connection in April 2017.  It's been a steady, but slow grower, and this is the first bloom under my care.  It has been growing under a cool-end of intermediate temperature; the max/min daily temperature is 29/18C (84/65F) in the summer and 21/13C (70/55F) in the winter.  It is growing under a moderate amount of light (PPFD of 130 µmol m^-2 s^-1).

Literature Cited:

• Cribb, P. and J. Hermans, 2009. Field Guide to the Orchids of Madagascar, Kew Publishing, UK.
• Nilsson, L. A., Johnsson, L., Ralison, L., & Randrianjohany, E. (1987). Angraecoid orchids and hawkmoths in central Madagascar: specialized pollination systems and generalist foragers. Biotropica 19(4): 310-318. (PDF link)
• Rakotoarivelo, F. P.,  S. G. Razafimandimbison, B. Mallet, L. Faliniaina, and T. Pailler. 2012. Molecular systematics and evolutionary trends and relationships in the genus Jumellea (Orchidaceae): Implications for its species limits.  Taxon 61(3): 534-544. (link to pdf on Research Gate)