A take on Quadriops

If there is one thing clear to me now regarding Neotropical acidocerines is that, for the most part, genera are fairly easy to recognize by their external morphology, but when it comes to species the challenge can get a lot harder.

Here I am, starting a new revision (a third one, with the previous ones in standby for different reasons) this time Quadriops, which is an exclusively Neotropical genus described in 1999 by Hansen. It has six described species:

Quadriops amazonensis García, 2000: 59 (Venezuela: Amazonas)

Quadriops dentatus Hansen, 1999: 134 (Venezuela: Bolívar)

Quadriops depressus Hansen, 1999: 136 (Perú: Loreto; Ecuador: Napo)

Quadriops politus Hansen, 1999: 135 (Perú: Loreto)

Quadriops reticulatus Hansen, 1999: 135 (Costa Rica: Puntarenas; Panama: Chiriquí)

Quadriops similaris Hansen, 1999: 136 (British Guiana: Ikuribisi; Venezuela: Bolívar)

Hansen offers a key to his species (translated to Spanish by García 2000). There is one species (Q. dentatus) in which the elytral punctures are not aligned in striae, all the others have aligned punctures (see image below).

The characters used by Hansen to separate the species with aligned punctures are mostly related to the presence or absence of shallow reticulation of the frons, clypeus and pronotum.

For me at this point, with the specimens I have seen, I would dare to say that all of the species with aligned punctures might be only one widespread species, given that:

- The species described so far are based on only a few specimens (usually one or two; seven at most)

- The males are known for four of the species and the differences on the illustrations for three of them are only slight.

Of course more observations are needed, also because I think differences on the shallow reticulations could be attributed to development for example, and not necessarily reflect interspecific differences.

References

• García, M. (2000). Una nueva especie de Quadriops Hansen, 1999 (Coleoptera: Hydrophilidae: Hydrophilinae) de Venezuela. Boletín del Centro de Investigaciones Biológicas, 34(1).

• Hansen, M. (1999). Fifteen new genera of Hydrophilidae (Coleoptera), with remarks on the generic classification of the family. Insect Systematics & Evolution, 30(2), 121-172.

More characters!!

So I've been keeping coding "new" morphological traits and including more taxa in the matrix. I stopped with the Chasmogenus species at sp. 9, so there are 12 Chasmogenus species included in the matrix so far. I've also included related genera, one species each: Agraphydrus, Globulosis, Quadriops, Radicidus, Tobochares and three undescribed genera, as well as one species of Cymbiodyta and one species of Sphaeridium, which as expected (for it being the only truly terrestrial included so far) is strikingly different.
As before, new characters and character states appeared, and some characters had to be split, so the matrix is now 230 characters and 28 taxa.
Here a small sample of variation on characters of the hind legs (and also an spoiler of my poster for the Evolution meeting 2016). You can see variation in the proportions, the size of the spines and area covered by hydrofuge pubescence. Images not at scale.

I also started my first full disarticulations to look at mouthparts, thorax (mesofurca, metafurca, tergum), wings, abdominal segments (tergites, laterosternites, terminal segments), male and female genitalia... thing is that the available specimens for that at this moment belong to the Hydrophilinae: Tropisternus, Berosus, Hydrophilus and Oocyclus. So far, having dedicated more time to careful fragmentation rather than to detailed observation (as I don't have a microscope yet), I have already seen interesting features that might be useful for phylogenetic purposes.
Here also just a sample (with not as pretty pictures, not at scale either) of the mandibles, showing very prominent differences, where the mandibles of Tropisternus are apparently the more common condition (at least for Hydrophilines); mandibles were illustrated by Hansen (1991, figs. 167-170), but it is astounding to see them in real life. It is the first time that I see brushes of setae on mandibles!!

This is only the tip of the iceberg, just a quick preview of many more structures to explore, to see, to compare, to code... this is still interesting!!


References

• Hansen, M. (1991). The hydrophiloid beetles. Phylogeny, classification and a revision of the genera (Coleoptera: Hydrophilidae). Biologiske Skrifter, 40, 1–367.

What about the molecules?

It is very likely that every person that has asked me about my research has come to a comment like "yes, I love beetles and morphology but I don't really like molecules... and I know I will have to deal with them at some point"

My experience with molecular data is very limited at this point in time. I have performed maybe one or two extractions and maybe just one full protocol composed of DNA extraction, electrophoresis and PCR, without ever knowing the final product, just for the technique and it was maybe in 2009 during my Master's at the Biology Department at UPRM, and then, when I joined the Short Lab in August 2015, I knew that working with molecules was going to happen!

The lab has been working actively with molecular data, so by December 2015 a full set of amplified samples were sent for sequencing, and by mid January this year it was my duty to take a look at the sequences and edit them when necessary in order to produce clean alignments. All the visualizations, edits and alignments were done using Geneious R-8, which I consider a friendly and efficient tool.

The process (which may be obvious for those familiar with this kind of data) starts with files to be imported into the Program. At this time we had for each gene of each specimen, two sequences: forward and reverse. Those two sequences needed to be matched to get one Assembly for each specimen. On the Assembly (composed of two strands) it is necessary to check for ambiguities, for example when one of the strands says A, but the other says G, and make a decision (based on the height of the peak and the probability on each strand) to call one chain as G or A to match the other one. You can check the image below to see what I'm trying to explain. For this edition process, we created files with a track of all the modifications made in the sequences, in case it is necessary to check for errors some steps ahead.

Screenshot of Geneious R-8: Edit of COI sequence.

After you get your editing done (and documented), it is time to convert the file into a Consensus Sequence, which contains only one strand, longer than either of the previous file, as it contains the forward and reverse tails of the amplified fragment. You need to do that for all of the specimens. Once you have all the edited Consensus sequences, you can align them (see image below) and ask the Program to highlight the base pairs that differ among sequences. You need to watch out for sequences that might be reversed, which causes them not to be properly aligned.

Screenshot of Geneious R-8: Edit of COI sequence.

At this stage you check for gaps and 'misplaced' bases, which strongly depend on which gene are you working with. Then you might return to the Assemblies in order to see if the gaps are real and if the odd bases are the product of one of the previously resolved ambiguities (here is where the notes come in handy). Finally, you can ask the Program to produce a tree with selected Consensus sequences (see image below).

Screenshot of Geneious R-8: Raw COI tree.

As far as I can tell, Geneious would produce a raw result that allows visualization. It also allows to run sequences through BLAST when you suspect contamination or you amplified something else by accident. I still don't know if you can run formal analyses and models of molecular evolution in the program... I haven't got there yet.

One of the 'extra' lessons learned from this process is that consistency (apply the same rules to everything), order and documentation are fundamental for an efficient development of this kind of work.

Morphological character's matrix

During this past couple of months most of my time at the lab has been dedicated to build a matrix of morphological characters in order to analyze the Acidocerinae. The focal group at this time the genus Chasmogenus which with 40 described species is a little bit of a mess itself.

At some point Chasmogenus was considered a subgenus of Helochares, and according to Hebauer (1992), the species of Chasmogenus can be separated in two groups (subgenera): Chasmogenus  sensu stricto (composed of the American species with 8 antennomeres and simple aedeagus) and the Chasmogenus Crephelochares (composed by the non American species with 9 antennomeres and "more differentiated" aedeagus). Regarding distributions, 17 species are Afrotropical, 5 Oriental, 3 Palaearctic and 15 Neotropical (see Hansen 1999). Hebauer also mentions affinities of Chasmogenus with Enochrus, which at this time is placed in a separate subfamily (see Short & Fikáček 2013).

As it happened with Helobata, the external morphology of Chasmogenus is very homogeneous, but not as extreme, so I started my matrix with the characters used by Short (2007) on the second chapter of his Dissertation: "Systematics and biology of the endemic water scavenger beetles of Hawaii (Coleoptera: Hydrophilidae)", which contains 55 characters, most of them associated with external morphology, knowing that it is very likely that not all the characters might be informative for my group. I also included characters from Hebauer (1992) and Clarkson & Ferreira (2014).

Then I selected specimens in order to start coding them on the matrix. The group of specimens at this time includes one species of Enochrus, Helobata striata, some Helochares, Chasmogenus abnormalis from Okinawa (Japan), Chasmogenus nitescens from New Caledonia, Chasmogenus ruidus from Costa Rica, and 26 unidentified Chasmogenus specimens (very likely different species, most of them undescribed) from Nicaragua, Costa Rica, Panama, Ecuador, Venezuela, Guiana, Suriname, French Guiana, Bolivia and Paraguay.

When I started looking at the specimens to code them, and as it usually happens while doing this, more characters and character states started to appear. Then I had to go back to the very useful drawings presented by Hansen (1991) and his list of characters, and at the same time get used to the terminology employed by some authors (e.g. mesoventrite to refer to the mesosternum). I have been also producing my own drawings in order to help me understand the variations and keep track of what I saw. Here are some of my schemes.

   

As of now, the matrix has 167 characters (86 binary). I know several are not going to be informative (either because all of the specimens have the same character state, or because they doesn't exhibit a clear signal) but also as soon as I start dissecting (mouthparts, wings, abdomen, male and female genitalia), many more characters are going to be added. I can't wait for that to happen!. Here is a screenshot of the matrix as it is now.

For now I need to keep coding the remainder taxa, as you can see I have only 3 out of the 26 specimens I selected, in part because every time I'm coding one specimen, new character states appear and I have to go back through all the other specimens that are already in the matrix in order to figure out the best way to code the character states, but at this time the matrix it's getting more stable.

References

• Clarkson, B., & Ferreira, N. (2014). Four new species and first nominal record of Chasmogenus Sharp, 1882 (Coleoptera: Hydrophilidae) from Brazil. Zootaxa, 3765(5), 481-494.
• Hansen, M. (1991). The hydrophiloid beetles. Phylogeny, classification and a revision of the genera (Coleoptera: Hydrophilidae). Biologiske Skrifter, 40, 1–367.
• Hansen, M. (1999). World catalogue of insects. Volume 2: Hydrophiloidea (s. str.)(Coleoptera). Apollo Books.
• Hebauer, F. (1992). The species of the genus Chasmogenus Sharp, 1882 (Coleoptera: Hydrophilidae). Acta Coleopterologica, 8(2), 61-92.
• Short, A. E. Z., & Fikáček, M. (2013). Molecular phylogeny, evolution and classification of the Hydrophilidae (Coleoptera). Systematic Entomology, 38(4), 723-752.
• Short, A. E. Z. (2007) Phylogeny, morphology, and biology of the hydrobiusine and hydrophiline water scavenger beetles (Coleoptera: Hydrophilidae: Hydrophilini). Ph.D. Dissertation, Cornell University. 219 pp.

EntSoc2015

Last week The Short Lab attended the Annual meeting of the Entomological Society of America. All members presented advances on their research, so I presented the information that is being compiled in this blog, along with other data regarding the intriguing genus Helobata. You can access the presentation via Research Gate or Academia.edu.

Database

The database of the Helobata specimens that we currently have is now complete. There are 244 specimens from 18 countries:

North America: USA (including Bahamas, 74).
Central America: Mexico (5), Belize (8), Guatemala (4), Nicaragua (1), Costa Rica (4), Panama (4).
Caribbean: Jamaica (39), Dominican Republic (5), Puerto Rico (1), Trinidad & Tobago (4).
South America: Venezuela (19), Guyana (19), Suriname (3), Ecuador (17), Peru (5), Brazil (3), Bolivia (25), Paraguay (2), Argentina (2).

You can access part of the records by browsing the lab's database at http://creac.kubiodiversityinstitute.org/collections/

A high proportion of the specimens was collected at light traps. According to Oliva (see Oliva et al. 2002) most species perform dispersal flights during the night and also during high humidity noons, which allows hydrophilids to move from a water source to another to escape desiccation. That's why they become attracted to artificial lights.

Next step is to continue looking for external differences that can be coded as characters. As external morphology is highly homogeneous, we will need to appeal to internal structures, where the male genitalia will provide the most informative set of characters.

Another fact about this particular set of specimens is that in several cases they are the only specimen (or only a few) collected at the same locality. If they are only females, that is going to complicate things because so far, the female genitalia does not provide useful characters... Let´s see, we need to explore!

References:

• Oliva, L., L. A. Fernández & A.O. Bachmann. 2002. Sinopsis de los Hydrophiloidea acuáticos de la Argentina (Insecta, Coleoptera). Monografías del Museo Argentino de Ciencias Naturales. 2: 1-67

Helobata, the basics

Head of Helobata larvalis, dorsal view

The genus Helobata is restricted to the New World, with most of the species distributed in the Neotropical region. The members of this acidocerine genus are quite different in appearance to the remainder members of the subfamily: the integument is finely granulated and dull instead of smooth and shiny, and their clypeus, pronotum and elytra are laterally expanded.

The genus was originally described as Helopeltis by Horn in 1873, who designated Helopeltis larvalis as the type species. Then in 1888, Bergroth proposed the name Helobata for the hydrophilid genus because the genus name Helopeltis was already taken by a hemipteran genus (see Fernández & Bachman 1987).

From Horn 1873

The genus currently have 11 described species:
Helobata aschnakiranae Makhan, 2007 (Suriname)
Helobata bitriangulata García, 2000 (Venezuela)
Helobata confusa Fernández & Bachmann, 1987 (Argentina, Paraguay)
Helobata corumbaensis Fernández & Bachmann, 1987 (Brazil)
Helobata cossyphoides (Bruch, 1915) (Argentina)
Helobata cuivaum García, 2000 (Venezuela)
Helobata larvalis (Horn, 1873) (Argentina, Bolivia, Brazil, Paraguay, Venezuela; Guatemala, Mexico; USA; Cuba)
Helobata lilianae García, 2000 (Venezuela)
Helobata perpunctata Fernández & Bachmann, 1987 (Argentina)
Helobata quatipuru Fernández & Bachmann, 1987 (Brazil)
Helobata soesilae Makhan, 2007 (Suriname)

One of the things that constitutes the revision of this genus a challenge, is the fact that they are very similar in their external morphology: when you look at them at a certain distance, they look fairly different (also because the specimens I have on hand proceed from different countries along the continent), which makes you think you can come up with several clear characters that differentiate them; but once you get to look at them closer, those differences just vanish, because the variation of the character states is so soft and gradual, that in a certain way you could only be sure of the character state by comparing your specimen to other of a different species, which is not always what you have on hand when you are trying to identify things with a key, for example.
The good news, is that different species exhibit clear differences on the male genitalia: the shape, size and relative size of structures (among other characteristics). Actually the descriptions of Makhan species are practically limited to the description of the male genitalia.

Let's see how it goes... I'm already constructing a data matrix for the phylogenetic analysis and it will be accompanied by a database on localities for the specimens.


References

• Fernández, L. A., & Bachmann, A. O. (1987). Revisión del género Helobata Bergroth (Coleoptera: Hydrophilidae). Revista de la Sociedad Entomológica Argentina, 44(2), 1985. 
• García, M. (2000). Tres nuevas especies de Helobata Bergroth 1888 (Hydrophilidae: Hydrophilinae), de Venezuela. Boletín del Centro de Investigaciones Biológicas, 34(2): 237-246.
• Horn, G. H. (1873). Revision of the genera and species of the tribe Hydrobiini. Proceedings of the American Philosophical Society, 118-137.
• Makhan, D. (2007). Helobata soesilae sp. nov. and Helobata aschnakiranae sp. nov. from Suriname (Coleoptera: Hydrophilidae). Calodema Supplementary Paper, 14, 1-3.