Enigmatic Pycnoscelus species

[VolkswagenBug]

There are some well-documented members of the Pycnoscelus genus in the hobby (P. surinamensis, striatus, nigra, femapterus, potentially tenebrigera soon) and a bit of literature on P. indicus as well, but the rest of the genus is a complete mystery. After thoroughly searching, I found nearly no valuable information beyond geographical range on P. aurantia, gorochovi, janetscheki, micropterus, rothi, semivitreus, and vietnamensis (P. rufus was originally considered to be a distinct species, but it appears it might just be P. striatus, so it's excluded). I did find what may be a valuable article on P. schwendingeri, but I can't access the article even through my university. There is also a record of a "Pycnoscelus sp. 'Thailand'" in the hobby at some point, which may be P. conferta.

Does anybody know anything about these species? I'm particularly interested in mode of reproduction; I have a hypothesis regarding P. nigra and P. surinamensis, but it partially depends on whether these unknown species are parthenogenic or reproduce bisexually.

 

[pannaking22]

I'd be curious to see some of the taxonomy (thanks for posting what you did) since it seems like most of that is muddled. I know that P. striatus has both males and females, so presumably they aren't parthenogenetic. Unfortunately I don't know much about the other species though. @All About Arthropods @Hisserdude

 

[VolkswagenBug]

I'd be curious to see some of the taxonomy (thanks for posting what you did) since it seems like most of that is muddled. I know that P. striatus has both males and females, so presumably they aren't parthenogenetic. Unfortunately I don't know much about the other species though. @All About Arthropods @Hisserdude

Yeah, the taxonomy for the genus isn't very well-defined. The Blattodea Species File seems to have a mostly accurate taxonomy except for the inclusion of P. rufus, but it's kind of hard to say whether it is accurate because of the lack of documentation on the species I mentioned. I have a suspicion that P. nigra may not be a distinct species either or that it's more closely related to P. surinamensis than previously thought. That suspicion is why I want to know whether other species in the genus are parthenogenetic, because otherwise it would likely be a derived trait in both of those species, and it's rather unlikely that that would develop twice. The alternative to them arising independently at some point would be that they both came ultimately from the same parthenogenetic strain of P. indicus (assuming that hypothesis is correct), confirming that they have a more recent common ancestor than either have with the rest of the genus.
Also, it looks like P. semivitreus is indeed bisexual, as a male is shown here, so that's good to know.

 

[Hisserdude]

I believe that the genus is probably in need of a revision for sure, the same as many other roach genera... I don't have much to add here, but I will say that I personally believe the sp. "Thailand" in the hobby are just a new strain of surinamensis, I've kept both and personally I think that's the case. I remember in FL I found both dark and light colored adults together, (the dark ones were definitely surinamensis, not nigra), so I think both the light and dark adults in the sp. "Thailand" stock are surinamensis as well.

 

[VolkswagenBug]

I believe that the genus is probably in need of a revision for sure, the same as many other roach genera... I don't have much to add here, but I will say that I personally believe the sp. "Thailand" in the hobby are just a new strain of surinamensis, I've kept both and personally I think that's the case. I remember in FL I found both dark and light colored adults together, (the dark ones were definitely surinamensis, not nigra), so I think both the light and dark adults in the sp. "Thailand" stock are surinamensis as well.

Okay, thanks. That's somewhat disappointing, but it's good to get a somewhat more definitive answer on the conferta issue. I'll take the safe route and assume they are surinamensis.

 

[Hisserdude]

Okay, thanks. That's somewhat disappointing, but it's good to get a somewhat more definitive answer on the conferta issue. I'll take the safe route and assume they are surinamensis.

Indeed, kinda disappointing, at the same time though I'm no taxonomist, so I believe we should just keep calling them sp. "Thailand" until further notice.

 

[VolkswagenBug]

Having obtained some more information, here's an updated summary of what I know:
P. rufus is very ill-defined and a more recent paper by Anisyutkin (who's responsible for probably about half of the research on non-surinamensis Pycnoscelus species with Roth filling the other part) completely omits it in its description of the taxonomy, which otherwise includes all of the species in the genus that I mentioned. Neither Anisyutkin nor any other authors have explicitly identified P. rufus as being specifically part of striatus, although a much older paper of his (2004) identifies P. rufus as a part of the P. striatus species complex.

As far as I can tell, there is one currently 'confirmed' species complex, which constitutes the majority of the genus. The P. indicus/surinamensis complex constitutes nine species (conferta, femapterus, indicus, janetscheki (tcheki?), nigra, surinamensis, gorochovi, vietnamensis, rothi, schwendingeri). Like I said, there might be a P. striatus complex if P. rufus was merely omitted by mistake; otherwise, it seems to be on its own along with P. aurantia, micropterus, semivitreus, and tenebrigera.

Mode of reproduction is still only confirmed as bisexual for femapterus, indicus, and striatus. The presence of males doesn't actually indicate whether a species is bisexual, since apparently some strains of surinamensis produce useless males and the same could be true of other species. However, there are confirmed males of the following species for which the mode of reproduction is unknown: gorochovi, vietnamensis, rothi, semivitreus, schwendingeri. Still no idea on aurantia, conferta, janetscheki, micropterus, and tenebrigera. P. nigra and P. surinamensis are still the only clearly parthenogenetic species. However, I'm waiting on an interlibrary loan for another article, so we'll see if anything turns up there.

There are issues with the identification into these complexes and as separate species, though - most of Anisyutkin's and Roth's work on them are based on single adults or a few at most, and typically only males are looked at. There aren't any live captive cultures of most of these species as far as I know, which means getting large samples is very difficult. Additionally, their specimens are all dead. This means that they're identifying based solely on morphology, which can work as a haphazard method, but isn't very desirable nowadays with the advent of genetic technologies. Reading more about the genus solved some of my questions, but left me with more. I was considering a study to look at the relationship between P. nigra and P. surinamensis, but I think far more is needed to solve the mysteries of this genus. Unfortunately, there are so many higher-profile genera that need attention, so these little guys may remain a mystery for a while.

 

[VolkswagenBug]

I got some significant phylogeny information, for anyone interested. I found full mitochondrial genomes for surinamensis, nigra, indicus, and femapterus, which helps provide a general idea of phylogenetic relationships even though it's not super accurate. Here's the tree I generated with MEGA (base pairs aligned with MUSCLE), which also has two other blaberids and some less closely related members of Blattodea for comparison.