Hadrurus discussion

[SeanCasey]

I find that the more I learn about scorpions the more questions I have. They are such facinating creatures.

Lately I have been trying to learn about the different Hadrurus species and have made a few observations, and asked around regarding some thought. I'd like to receive input from others.

I originally was attempting to determine the difference between H. arizonensis and H. obscurus. The only material I found originally was THE TAXONOMY OF THE GENUS HADRURUS BASED ON CHELA TRICHOBOTHRIA (Soleglad, 1976) and images of each species. Based on this I noticed that H. obscurus chela trichobothria more closely matches that of the H. spadix instead of H. arizonensis.

I also have been looking at some pictures and it looks like on the H. obscurus the "mask" is forward of the position of the typical H. arizonensis "mask" and is less clearly defined and more wedge shaped instead of crescent shaped.

Also it seems that there is some overlap in the ranges of these species. This thought led me to the idea that perhaps the H. obscurus could be the result of a natural mixed breeding of the H. spadix and H. arizonensis.

I asked a few people and eventually was put in contact with Dr. David Sissom who provided me with some interesting information as well.

One comment he made I thought was quite interesting: "H. obscurus does seem to be genetically and morphologically very close to spadix (and may be a synonym of that species), but doesn’t seem to show suspicious intermediacy between spadix and arizonensis."

To me this hints that perhaps H. obscurus is a (for lack of better terms) "pallidus" form of H. spadix.

Another interesting comment was: "However, obscurus could overlap with both spadix and arizonensis and still be a separate species."

So my understanding is that even if H. obscurus is a cross between H. spadix and H. arizonensis (if it is proven to not be a synonym of H. spadix), then it would stand as a seperate species as the traits are unique to that particular grouping of scorpions.

I was also referred by Dr Sissom to Systematics and Biodiversity 6 (2): 205-223, Phylogeny and classification of the giant hairy scorpions, Hadrurus Thorell (luridae Thorell): a reappraisal. Issued June 6th, 2008. A very interesting read that answered a lot of questions regarding Hadrurus.

What are your thoughts on this?

[barkscorpions]

Sean,

And with growing knowledge will come a host of questions that for the most part can only be answered anecdotally, fragmentarily, or not at all! LOL

Cheers,
Luc

[Chad Lee]

Hi Sean,

You need to get a copy/xerox of Stan Williams' paper:

Williams, Stanley C. 1970c. A systematic revision of the giant hairy-scorpion genus Hadrurus (Scorpionida: Vejovidae). Occas. Pap. Cal. Acad. Sci., 87: 1-62.

I have an original print in storage, and if I remember correctly, he provides discussion into the population aspect between 'species' and zones.

Cheers,

Sinc. Chad

[Kari McWest]

Good discussion,
Whatever Dr Sissom says is pretty much gold.

I would have to add that spadix and obscurus have the chela trichobothria that arizonensis does not (I forget off-hand, but one group has 3 trichobothria on the inside of the chela palm, and the other have 5; of these counts, spadix and obscurus are the same). This difference almost makes arizonensis in a different "group" than spadix and obscurus, which means the likelihood of a successful hybridization between arizonensis and either spadix or obscurus extremely slim. On the other hand, the likelihood of successful hybridization of spadix and obscurus is more probable.

Zach might be better able to corroborate this part, though, that when in the same vicinity, spadix tends to inhabit rocky terrain, like cliffs and talus slopes, whereas obscurus will dominate in the flats, which might support a synonymy of the two: the carapace pattern on obscurus might be an adaptation of burrowing in the desert environment in which the interocular triangle becomes more pale, like in arizonensis.

Chad's suggestion to get Williams' paper is excellent! In it, Williams provides photographs of the different color patterns and excellent distribution maps.

[SeanCasey]

It does seem that obscurus and spadix are extremely closely related. I'll have to track down some habitat photos for the spadix to better visualize their natural environment.

I am also in the process of searching for a copy of Williams' paper, it sounds like it will be a very useful source of information.

[Kari McWest]

If mine wasn't packed, I'd scan it and send PDF to you. I'll do that when I can find it, but it might be a while.

[Zach Valois]

Originally Posted by Kari McWest

Zach might be better able to corroborate this part, though, that when in the same vicinity, spadix tends to inhabit rocky terrain, like cliffs and talus slopes, whereas obscurus will dominate in the flats, which might support a synonymy of the two: the carapace pattern on obscurus might be an adaptation of burrowing in the desert environment in which the interocular triangle becomes more pale, like in arizonensis.

Kari hit the nail on the head with this comment. I have collected both of these species all over the south-western US and this phenomona is charateristic in pretty much all of the overlapping areas that I have seen the two species (obscurus/spadix) occupying. In areas that H. obscurus occurs somewhat near the distribution of H. spadix, they still retain the tendency to occupy low flats with varying degrees of soft alluvium or rock, even when provided with seemingly ideal rocky outcrops. Then eventually taking advantage of rockier habitat. Some very important areas remain unsuccessfully sampled for these taxa for the AMNH projects we assist.

[SeanCasey]

Intersting. Do you find that the H. spadix to be as much of an obligate burrower such as the H. arizonensis, or does it tend to be more opportunistic?

[Zach Valois]

In my field work, about 60% of the H. spadix I have seen are not near uniform burrows or even scrapes. They are simply wandering around or sitting at the edge of a niche or fissure within a rock outcrop. This is not to say however that they are not occupying burrows, they may simply be going back to them or creating new scrapes (or just sheltering in cracks when activity desists as mentioned later). This can relate to a number of reasons, particularly seasonal activity patterns, a need or reason to move around (e.g. finding a conspecific in which to mate with or active surface foraging during times of high prey density). Many seem to spend much of the year simply in cracks and fissures within rock, though they do seem to prefer cracks in which debris has collected. Debris such as soil/sand and branches and foliage of such vegetation as junipers' and creosote. Debris and soil that allow them to burrow—which they almost always will if provided so—between rocks seem to be an important part of long term(especially during winter months) shelter utilization.
Both H. obscurus and H. spadix basically occupy the same type of habitat, and both exhibit similar variation in regards to habitat/microhabitat/shelter selection—in some cases, seemingly influenced by the intraspecific taxa, as discussed in an earlier post— adaptability, and exploitation. I have found both species on vertical rock walls and open, flat, sand/gravel composite soil.

An interesting subject to say the least. I may choose to work on similar projects during my undergrad work in Utah. Further investigating annual, monthly, and daily activity and movement patterns within populations, metapopulations, and at the individual level.


well back to homework,

Zach