Hi, Tom here. After a very busy year starting at Manchester University and moving house, I have become somewhat quiet here on the FrogBlog. However, I have just returned from a week’s fieldwork on comparative and adaptive biology on the sunny island of Mallorca, and felt this would be appropriate time for an orchid-filled return.
Mallorca is a rather unique island, with an interesting mix of European, African and Endemic species. The island owes its existence to uplifting of limestone rock due to micro-tectonics. The presence of this limestone has created a rather nutrient poor, alkaline environment, in which Orchids appear to thrive.
The main Orchids abundant on the limestone Serra de Tramuntana mountain range, in the north of Mallorca, is the genus, Ophrys. This genus is often referred to as the “Bee Orchids” because the lower petal, known as the Lebellum has been highly modified through millions of years of selection to imitate the thorax of a female bee, or wasp. This method of pollination is known as “sexually deception”, because the flower itself does not provide a nectar reward to its pollinator, but more of a devious misidentification for a bee trying to have an intimate time. Even more interestingly, the flower releases a chemical signal identical to a female insect’s pheromone, and once a male has been attracted to the flower of the Orchid, it attempts copulation. During this vigorous act, pollen is attached to the males head using a sticky appendage called a Pollinia.
As you can see from the images, each Ophrys species has co-evolved to mimic a specific insect. This specificity is rather adaptively disadvantages, as with the British O. apifera, the bee that once pollinated it has become extinct in the UK.
Fortunately the pollinators are still abundant in Mallorca, and as part of my fieldwork I counted the presence of pollinia within the flowers of O. bombilyflora, O. lutea and O. speculum, and whether their flowers had or hadn’t been visited by an eager male bee. What we discovered was that no matter what size the population of Orchids was at different sites approximately 20% would have been visited by bees.
Ophrys species also show a high degree of variance between individuals. The flowers may exhibit completely different coloured petals, or Lebellums of distinctly different shapes. One highly variable species is O. fusca, which was observed at several locations, the specimen photographed may represent the subsp. dyris, but this is uncertain. Another species, O. speculum, is by far the most spectacular of Mallorca’s Ophrys, with its brightly coloured blue mirror and fuzzy perimeter. Although this species doesn’t show much variance, we unexpectedly stumbled across an example that had a rare mutation for albinism. Early in the week a specimen was observed with a white mirror, but this one exhibited a completely un-pigmented flower. This incredibly rare specimen was the pinnacle of a great week, of flowers, fun and Mediterranean sun.