..actually, fossil orchid genitalia. The front cover of Nature (30 Aug 2007, also www.nature.com/podcast) has a picture of a bee in amber, with the pollinium (they say pollinarium - which is correct?) stuck to its back. The fossil comes from the Dominican Republic, the pollin-whatnot comes from the Goodyerinae group, and the ensemble from the Miocene, 20 MYBP. This is the first concrete - so to speak - evidence of orchids.
The authors (Ramiriez et al) attribute the pollen to Meliorcis caribea which they promptly name in the paper. (Why Meliorchis - an orchis stuck to a bee, melis: honey. Botanical crosswod puzzles.) Thye also publish a cladogram based on plastid DNA sequences of 55 orchid genera and 5 Asparagales. This places Zeuxine, Goodyera, Ludisia, Kreodanthus (new to me) and Microchilus - plus this new thing - in Goodyerinae, within Orchidoideae. However. all of the above are (I think) restricted to Asia whilst the ancient oddity came from the New World. They note that genetic divergence has placed orchid origins at 26, 40 and 110 MYBP. The precise date of this fossil and the cladogram allows them to say that the late Cretaceous was the habitat of the last commmon ancestor of the flowering plants in general and orchids in particular. (That's 76-84 MYBP, well into dinosaur timeframes. ) They are also able to suggest that three of the five root families with the Orchidaceae split before the end of the Cretaceous, 64 MYBP and an asteroid impact ago. Thus the Apostacioideae split from the common ancestor that diverged from the Aspagales c. 80 MYBP. The Vanilloideae and Cypripedioideae then separated from the main stream about 75 MYBP, That left the ancestor clade of the Orchidoideae and the Epidendroideae, which diverged in the early Tertiary. (That is, the other side of the dinosaur-killing asteroid impact.) These two branches now encompass 95%+ of current orchid species. Page 1044 has a diagram which shows this divergence. ______________________________ Oliver Sparrow +44 (0)1628 823187 www.chforum.org _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
