[Taxacom] large animal genera

[Scott Thomson]

Yep I agree with you Doug, genera based on discriminating characters seem
to me to be the better arrangements, and those doing this tend to be
neither splitters or lumpers. Those who start pulling in "rules" such as
avoiding monotypy at all costs and only splitting in the presence of
paraphyly, this is dogma. To be of use they should be based on diagnostic
characters. I work with vertebrates, hence I tend not to see large genera
of the size being discussed here. The principal is the same though. I think
there is also something to be said for splitting being more popular in
groups of interest, ie collectors, lumping when it is more conservative and
conservation orientated. Both ends of this scale seem to me to be being
influenced by issues outside of taxonomy.

Cheers, Scott

On Tue, May 26, 2015 at 3:36 PM, Doug Yanega <dyanega at ucr.edu> wrote:

> Regarding comments on the "arbitrary" or "artifical" nature of genera,
> with implications of personal bias and idiosyncrasies of the responsible
> taxonomists; briefly, in several of the groups I gave examples of (bees and
> wasps), this clearly can't be what's going on. The same taxonomists who
> recognize and create small genera also recognize large genera, USING THE
> SAME CRITERIA. Those criteria pretty much invariably focus on the level of
> morphological variation, and the ability to recognize and discriminate
> groups of species *based on characters*. In certain lineages, the levels of
> morphological variability are so low that there are few *reliable
> characters* that allow for recognition of groups. Look at bee genera like
> Lasioglossum and Andrena, with over 1000 species (and Nomada are parasites
> of Andrena), and Perdita, with around 800; all of them have numerous
> subgenera, and the subgeneric classification of each is a dismal morass,
> with weak and often contradictory characters, giving little concrete or
> confident support for making further divisions, ESPECIALLY if one is hoping
> to follow any sort of monophyletic hierarchy. The point is that while many
> lineages can be partitioned up just fine, there are others where there has
> clearly been extensive radiation with little character evolution, and those
> lineages defy anyone's attempts to partition them further - even when they
> are the same taxonomists who DO partition up most of the remaining
> diversity in their respective areas of expertise. This is not lumpers
> versus splitters, so much as it is people who apply the same criteria to a
> wide variety of taxa, sometimes resulting in very large genera that are
> just as "natural" as small or even monotypic genera recognized *by those
> same people*. There are a few exceptions in bee taxonomy (e.g., the recent
> elevation of the subgenera of Trigona to genus level), but by and large,
> this is the pattern. There may be some pressure in the future to split some
> of these huge genera up based on molecular evidence, but here's the
> quandary: from examples I know of, the molecular divisions are not matching
> up very well with the recognized subgenera. In that situation, unless one
> has a sequence of species X, you won't be able to place it. Meaning, more
> than likely, that the genus can't be split, for all practical purposes,
> without leaving over half the described species unplaceable (since that's
> about how many will NOT have fresh specimens available for sequencing).
>
> The same cannot be said, for example, about genera like Cicindela, for
> which there are umpteen different historical classifications, ranging from
> some authors who recognize one genus with nearly 2000 species, to other
> authors who split the exact same group into over 100 genera - or Carabus,
> with something around 900 species placed either into one genus or around 90
> genera. Both these groups are super popular with collectors and
> non-scientists, and have had hundreds of different "experts" publishing on
> them, rather than a handful. That seems to put an entirely different sort
> of pressure in terms of splitting, even if there is no solid morphological
> basis for doing so.
>
> Food for thought,
>
> Sincerely,
>
> --
> Doug Yanega      Dept. of Entomology       Entomology Research Museum
> Univ. of California, Riverside, CA 92521-0314     skype: dyanega
> phone: (951) 827-4315 (disclaimer: opinions are mine, not UCR's)
>              http://cache.ucr.edu/~heraty/yanega.html
>   "There are some enterprises in which a careful disorderliness
>         is the true method" - Herman Melville, Moby Dick, Chap. 82
>
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-- 
Scott Thomson
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