Indexing hybrids and varieties   Jess Riddle   Mar 19, 2007 19:50 PST  Ents, For measurement purposes, how should we treat hybrids and named varieties? I'm sure some people would just ignore hybrids and not divide taxa below the species level, but I just can't see this group doing that. I'm sure we'll track the maximum dimensions of hybrids and named varieties whenever we recognize them, but what about species in a Rucker Index or other indexes? Should a hybrid and a parent species both be allowed to count in a Rucker Index thus, in a sense, allowing the parent species to be counted one-and-a-half times? Should multiple varieties of the same species be allowed to count in a Rucker Index? These questions are not just hypothetical. The RHI 10 for Groundhog Creek, NC includes Saul's Oak, the white-chestnut hybrid. If the index is expanded to 11 or more "species", white oak would also qualify based on height. This post was precipitated by Will Blozan's question about Biltmore ash in the Oconaluftee watershed. The standard form of white (Fraxinus americana var. americana) and Biltmore ash (Fraxinus americana var. biltmoreana) have each been measured to 148.6' tall in the watershed. I have initially simply listed white ash in the Rucker Index. If both varieties were included separately, the index would rise 0.78'. Any thoughts? Jess RE: Indexing hybrids and varieties   Steve Galehouse   Mar 19, 2007 20:17 PST  Jess, ENTS- I think it all boils down to "lumpers" and "splitters" in a taxonomic sense; if a tree type is currently accepted as a variety or race of a species, it should count as the species as far as maximum size--if it is currently accepted as a hybrid, it should count apart and in addition to its presumed parents. Lots of room to waffle, especially with oaks that freely hybridize. Steve Galehouse RE: Indexing hybrids and varieties   Joshua Kelly   Mar 20, 2007 06:06 PST  Ents, On the subject of including varieties and hybrids in Rucker Indeces, I propose an ecological definition: If varieties and their sister taxa occur in the same conditions, I propose listing only one in the Rucker Index. If they tend to be fairly ecologically discrete, as in Fraxinus americana var. americana and F. americana var. biltmoreana (they seem to seperate by elevation and soil quaility), I think including both in the Rucker Index of a watershed, mountain range, state, or region is tenable. In the opposite case, I would be less entusiastic about including taxa that had a large ecological overlap. The case of hybrids is actually a bit more complex, because they are quite genetically distinct, yet they may share the exact same habitat as both of their parents. I don't haven't formulated a clear opinion about including hybrids. Josh Re: Indexing hybrids and varieties   Edward Frank   Mar 20, 2007 08:09 PST  Jess, I am a splitter. If there is a defined, named, naturally occurring, hybrid or named variety, I would count each as a separate type in terms of Rucker Indexes. Ed   Home