New proposal for a subspecies definition triggered by a new longhorn beetle subspecies

The discovery of a new subspecies of longhorn beetle from Scandinavia triggered a discussion on the vague organism classification rank ‘subspecies’.

As a result, a newly proposed definition of subspecies has been published along with the description of the taxon in the open access journal ZooKeys by the research team of Henrik Wallin and Johannes Bergsten from the Swedish Museum of Natural History and Torstein Kvamme from the Norwegian Institute of Bioeconomy Research.

The northernmost populations of Saperda populnea display a number of divergent traits, including a shorter male antenna and reduced pubescens. In contrast with their most closely related subspecies (Saperda populnea populnea), whose favourite host plant, amongst others, is the European aspen, the new subspecies (Saperda populnea lapponica) specialised exclusively on downy willow (Salix lapponum).

Image 2According to the once no less disputed definition of species, regardless of their unique traits, populations cannot be considered as separate species until they are no longer able to produce fertile offspring according to the Biological Species concept, this being one of a number of proposed species concepts. A consensus is emerging around the unified species concept defining species as separately evolving (meta) population lineages.

However, differentiating between subspecies nowadays is a significantly tougher task, since there is no stable definition of the rank yet. Through the years, there have been various explanations of what a subspecies is and what criteria it needs to meet in order to be classified as one.

Compared to previous definitions, the researchers decode it quite simply. To them, the only necessary attributes a population needs to possess before being deemed a subspecies are that they are a potentially incipient new species; diagnosed by at least one heritable trait; and either partially or completely isolated geographically.

Furthermore, they refute a number of factors, including reciprocal monophyly in neutral markers, the “75% rule”, reproductive compatibility and the degree of gene flow.

The concept of subspecies has been so problematic that there have been even those scientists who have argued that taxonomy needs to discard it altogether.

However, the authors note that it is already formally recognised by the International Commission on Zoological Nomenclature (ICZN 1999), “albeit without giving any advice or criteria for its recognition.”

“The concept is more than a mere academic debate as subspecies are recognized in various Red Lists and conservation programs, and hence the recognition as a subspecies or not can have legal and monetary consequences.”


Original source:

Wallin H, Kvamme T, Bergsten J (2017) To be or not to be a subspecies: description of Saperda populnea lapponica ssp. n. (Coleoptera, Cerambycidae) developing in downy willow (Salix lapponum L.). ZooKeys 691: 101-148.

The first long-horned beetle giving birth to live young discovered in Borneo

A remarkably high diversity of the wingless long-horned beetles in the mountains of northern Borneo is reported by three Czech researchers from the Palacký University, Olomouc, Czech Republic. Apart from the genera and species new to science, the entomologists report the first case of reproduction by live birth in this rarely collected group of beetles. The study was published in the open access journal ZooKeys.

Generally, insects are oviparous, which means that their females lay eggs and the embryonic development occurs outside the female’s body. On the other hand, ovoviviparous species retain their eggs in their genital tracts until the larvae are ready to hatch. Such mode of reproduction is a relatively rare phenomenon in insects and even rarer within beetles, where it has been reported for a few unrelated families only.

The long-horned beetles are a family, called Cerambycidae, comprising about 35,000 known species and forming one of the largest beetle groups.

“We studied the diversity of the rarely collected wingless long-horned beetles from Borneo, which is one of the major biodiversity hotspots in the world,” says main author and PhD student Radim Gabriš. “The mountains of northern Borneo, in particular, host a large number of endemic organisms.”

The scientists focused on the group which nobody had studied in detail for more than 60 years. They found surprisingly high morphological diversity in this lineage, which resulted in the descriptions of three genera and four species new to science.

“During a dissection of female genitalia in specimens belonging to the one of the newly described genera, named Borneostyrax, we found out that two females contained large larvae inside their bodies,” recalls Radim Gabriš. “This phenomenon have been known in a few lineages of the related leaf beetles, but this is the first case for the long-horned beetles.”

However, according to the authors, the modes of reproduction remain unknown for many beetle lineages besides Cerambycidae, so the ovoviviparity might be, in fact, much more common. Further detailed studies are needed for better understanding of the reproductive strategy in this group.


Original source:

Gabriš R, Kundrata R, Trnka F (2016) Review of Dolichostyrax Aurivillius (Cerambycidae,Lamiinae) in Borneo, with descriptions of three new genera and the first case of (ovo)viviparity in the long-horned beetles. ZooKeys 587: 49-75. doi: 10.3897/zookeys.587.7961