Following Peter O'Byrne's (et al) comments about Dendrobium schulleri, I thought Neville Howcroft, resident of Rabaul PNG, might be interested and passed them on. Here is Nev's reply, reproduced with his consent:
> From: Neville Howcroft > Sent: Wednesday, 19 January 2005 8:48 PM > To: Stephen Kemp > Subject: natural hybrids Dear Steve, I have not read this yet in the OGD and I would, on what you have sent me, make a few comments and observations also. First, I use the following terminology: Provenance of the species eg D. tangerinum Markham provenance - plants from the Markham valley, D. tangerinum Snake River provenance, D. lineale Bulolo sub provenance and Morobe provenance - specifically from the Bulolo region within the Morobe province and generally from some location in the Morobe province. Fly island provenance. Hybrids - generally assumed to be between two different species and: provenance hybrid - same species crossed but each parent from a different provenance. eg. Phal amabilis from Indonesia crossed with Phal amabilis from PNG. If they are crosses between parents of sub-provenance designation they can still be referred to as provenance hybrids. You have plenty of examples with Australian orchids from what I have read. [SK: True - we have now a classification in some Australian Native Orchid Shows: "D. speciosum Exhibition style" , referring to crosses between members of the Dendrobium speciosum complex eg. D. curvicaule x D. speciosum. Also, plants benched in D. tetragonum and D. bigibbum sections are often provenance hybrids] Ok. Many - if not all provenance and species hybrids of the same section are usually fertile enough to be capable of establishing populations in the wild and i have seen examples myself from the Fly islands the putative parents being D.lineale, D. sylvanum and D. mirbelianum. Possibly, conanthum could be included. The "postulation" that the plant is a hybrid is based on similarities and dissimilarities in the first instance. I think the next step in establishing if it is a hybrid would be chemical analysis and chromosomes etc. We have found plants of D. antennatum parentage but with another parent involved growing in the upper crown of a very large rain tree in Lae. The putative other parent is D. tangerinum. - However, the hybrid I refer to could also be an F2 hybrid and not a primary F1. I think in the Fly islands there are F2 and F3 hybrids which have re-combined or selfed and thus establishing a real muddled up set of populations. So I can follow and understand everyone's comments about hybrids. It is a worry when the genetic integrity of a local species is at risk. Man's introductions no doubt have an influence but you cannot rule out nature and this is where we start getting "new species". Once the hybrid processing settles down (stabilizes) then we are all happy to say we have a variable species but without doubt a species!?? Often when working with my peers in tree breeding with pines I hear the comment that all species are really hybrids. In fact I was challenged by my mentor and teacher Dr. Garth Nikles when I declared a tree a hybrid between Pinus taeda and P. elliotii. "How do you know?" he challenged - so I had to defend my statement. Later I found out I was correct as they had done it artificially. But further I found pines in north Qld that I suggested strongly were hybrids between P. oocarpa and P. caribaea. "Impossible - they belong to different sections!".Later the P. oocarpa became P. tecunnumannii and then P. patula ssp tecunnumannii - but later again they crossed it with ease to P. caribaea. So I felt my suggestion and earlier observations were on the right track. Vanda Miss Joaquim started off as a natural hybrid and could reproduce itself in the wild and we have Phal. Intermedia, a hybrid from the Philippines that keeps popping up in the wilds. I have that here. D. schullerii generally is a broad petaled flower and yellow with some brown veins some times. I have seen the Noemfor and Biak specimens. They are undoubtedly related to D. mirbelianum which is also a somewhat variable species but usually easily recognised. So again if anyone crossed these two then I would expect fertile F1 generations with the capabilities of out-crossing and reproducing either F1 or F2 hybrids. [Postscript from Nev in a following email: What I meant to say was that D. schullerii and D. mirbelianum share characters that make them related and form a group of their own like D. antennatum and several others form a group; or D. conanthum, D. kajewskii and D. soriensis form another group and so it goes on] However, how variable are the provenance populations over their range? Is the variation over their distributional range variable?? If the populations have been hybridising with other species for centuries then I guess there would be alot of variation. With provenance hybridization often practiced and growers getting plants with insufficent information on origins of the plant on hand , as well as a lack of understanding about the implications of provenance hybridisation, the reintroduction of a "species " into the wild to save a species threatened with extinction due to habitat destruction or over collecting such well meaning efforts at conservation may result in the destruction of the species provenance and genetic integrity that in turn could weaken the remnant true provance population's survival chances rather than improve it. - I am thinking of the provances acquired adaptation/ survival abilities. Spathoglottis plicata is a weed species and it will cross naturally with other species that in comes in contact with. This happens here and I have indentified at least three hy brids here with S. paulinae, S. portusfinschii and S. parviflora. Hybrid swarms have been noted in my masters research field work. They share a common pollinator and largely the action occurs where the species come in close proximity. S. plicata usually like the protection of secondary regrowth and wet creek banks while on the periphery in the rank short, annually burnt, grasslands on shallow drier soils we have S. portusfinschii, prpbably less than 15 meters away. You can expect to encounter hybrids between the two.I have seen some obvious natural hybrids between S.plicata and s. pulchra recently in a collection. To the untrained eye they just look like another form of S. plicata. However, the labullum characters are intermediate and variable as well, More S. pulchra than S. plicata howvever. Peter's observation of Casar type hybrids is interesting as I have only been introduced to plants from New Ireland. I will be on the lookout. Some times I treat these observations with caution as the locals like plants and introduce them to the village. Over time the village disappears and the orchids remain. I have challenged the late Norman Cruttwell on this as he claimed to have collected Phalaenanthe dendrobes in the most unlikely places - there is also the memory problem. I am acutely aware that I fall into this category some times but in the event i am unsure I try not to make rash statement. I wrote an article on variation among dendrobe species such as Pomio Brown and Talasea Mushroom Pink for the PNG Orchid journal which i gave to Steve Kami for publication, This is a while ago and I still do not know if it has been published, but I may have made some comments in that on hybrids. Steve, thanks for giving me that information. Food for thought. I will have to track down some of these areas Peter has been looking at. Hope you had a good festive season and all the best for this year. I have cc this onto Steve Kami. Best wishes Nev. _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
