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.

The subfamily Acidocerinae

I haven't got to know acidocerines well yet, but there is something intriguing about them, something that calls you to dig deeper in order to get to understand why are they so different (at genus level, at their ecologies and biologies) and yet so (almost frustratingly) similar (at species level- at their external morphology at least).

According to Short & Fikáček (2013), the Acidocerinae are "relatively uniform and difficult to characterize", it is probably due to the fact that members of the subfamily exhibit "an extremely broad range of habitats: many occupy ‘typical’ aquatic habitats such as ponds, marshes, forest pools and stream margins. Some (Agraphydrus, Dieroxenus) are known to occupy hygropetric habitats. Quadriops has never been taken in an aquatic situation and one series was taken from a sap flow in Costa Rica", because as it is expected, different ecologies, may require variations on the structures, which is possibly the reason why you can find so many characters converging along the whole phylogeny.

The subfamily is currently composed by 14 genera and 291 described species:
*In parentheses the number of species per genus

Acidocerus Klug (1)
Agraphydrus Régimbart (37)
Chasmogenus Sharp (43)
Dieroxenus Spangler (1)
Globulosis García (1)
Helobata Bergroth (13)
Helochares Mulsant (180)
Helopeltarium d’Orchymont (1)
Horelophopsis Hansen (2)
Peltochares Régimbart (1)
Quadriops Hansen (6)
Radicitus Short & García (3)
Tobochares Short & García (4)
Troglochares Spangler (1)

In the molecular phylogeny presented by Short & Fikáček (2013), Acidocerinae is the sister clade to the 'Sphaeridiinae lineage' (Rygmodinae+Sphaeridiinae), which is the 'mostly terrestrial group' of hydrophilids. This relationship is strongly supported by the molecular data, but there are currently no morphological synapomorphies for the clade.

(Slightly) Modified from Short & Fikáček (2013).

One of my challenges as an aquatic beetle person would be to find morphological traits that lead to support or question those molecular data.


References

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

• Short, A. E., & Fikáček, M. (2011). World catalogue of the Hydrophiloidea (Coleoptera): additions and corrections II (2006–2010). Acta Entomologica Musei Nationalis Pragae, 51(1), 83-122.
• Short, A. E. Z., & Fikáček, M. (2013). Molecular phylogeny, evolution and classification of the Hydrophilidae (Coleoptera). Systematic Entomology, 38(4), 723-752.

Hydrophilids to begin

I'm now starting as a Ph.D. student at Kansas University at the Department of Ecology and Evolutionary Biology. I will be working on aquatic beetles systematics, using morphological and molecular data, at the Short Lab.

To be honest, this is my first time working on a group different to broad-nosed weevils, so my knowledge about hydrophilids was very limited until a couple of weeks ago. Two of the things that I know now in general terms of taxonomy are:

- The most influential work on hydrophilids is "The Hydrophiloid Beetles" by Michael Hansen, published in 1991. There he provided, even for genera, diagnoses, descriptions and keys, along with drawings and a phylogenetic analysis. The classification proposed in this publication has been longly used, but a recent molecular analysis published by Andrew Short and Martin Fikáček in 2013, revealed a different configuration ath the subfamily level.

- Not all the so called scavenger water beetles are actually aquatic: of course there are many aquatic species, but there is also a large terrestrial group, and there are also species that occupy intermediate habitats. If you absolutely need to draw a line (and it would not be a straight one... probably would also be diluted), it could be possible to say that the subfamily Sphaeridiinae is mostly composed by terrestrial species and the remaining subfamilies (Hydrophilinae, Chaetarthriinae, Acidocerinae, Rygmodinae and Enochrinae) are represented majorly by aquatic species. These are the subfamilies established on Short & Fikáček's paper.

One of the objectives of my project will be to take a closer look at the morphological characters that grant scavenger water beetles the ability to dive under water, and to see how those characters vary given the different niches that the beetles occupy. In order to tackle this goal, I need to familiarize first with the particular morphology of the group. Fortunately I already have experience with beetle morphology!.

My first aim is to review the genus Helobata (Bergroth, 1888), which has an odd appearance for a hydrophilid... soon I will tell you more about it!


References

• Hansen, M. (1991). The hydrophiloid beetles. Phylogeny, classification and a revision of the genera (Coleoptera: Hydrophilidae). Biologiske Skrifter, 40, 1–367.
• Short, A. E. Z., & Fikáček, M. (2013). Molecular phylogeny, evolution and classification of the Hydrophilidae (Coleoptera). Systematic Entomology, 38(4), 723-752.