Insect Biodiversity: Unknown – a status report

 Insects, Rant  7 Responses »
Dec 112014
 

Nature published an article this week with some nice infographics that illustrate the astonishing number of species considered threatened by the International Union for Conservation of Nature, which is pretty depressing, at least if you look at the vertebrates. In what was a nice surprise, they actually included data on insects in addition to the fuzzy wuzzy taxa, noting that there are currently 993 species of insects considered threatened by the IUCN.

993 species is quite a lot, right? I mean, mammals have 1,199 threatened species, and birds 1,373, so you’d be forgiven for thinking that insect conservation is actually not too far behind the curve. But what happens when you dig a little deeper into that data?

If I were to ask you what you thought the order of insects is with the highest number of IUCN listed species, I’d be willing to bet you’d guess moths and butterflies (Lepidoptera), or possibly beetles (Coleoptera). I know that’s what I assumed. I’ve prepared a few interactive graphs of my own to help break down what those 993 species are, and how they fit into the larger picture of insect diversity (hover over wedges to see percentages, and over taxon labels to find some of the smaller wedges). And surprise, it’s probably not what you were expecting.

That’s right, dragonflies, damselflies (the Odonata), grasshoppers, katydids, and crickets (the Orthoptera) together make up more than 50% of the 993 threatened insect species. Surprised?

Next, let’s examine the total number of species that have been assessed by the IUCN, which includes the 993 species listed as threatened, plus extinct species, species considered not at risk, and species where there is insufficient data to make any conclusions.

Somewhat unbelievably, 53% of all insects assessed by the IUCN belong to the Odonata. 53%. Talk about a massive skew in the data. For context, compare the IUCN’s assessment numbers to the total known diversity for each insect order.

Look at the relative sizes of the blue Odonata wedge and the red Orthoptera wedge across all three graphs: when we look across everything we know about insect diversity, 50% of IUCN threatened insects species belong to just two orders of insects, which together make up only 2.5% of the total insect diversity. Incredibly, nearly half of all known Odonata have been assessed by the IUCN. Compare that to some of the major orders (major both in the sense of diversity and ecological/economic impact), like flies (Diptera) where 8 (the Where’s Waldo slice of pie near the top of the Assessed Graph) out of the 150,000 160,000 species we have names for have been formally assessed.

8 species of flies.

Out of 150,000 160,000.

Wow.

What’s more, some other insect orders which you would think would be correlated to the high assessment numbers of mammals and birds, specifically their ectoparasitic lice (Pthithiraptera, here included in the Psocodea) and fleas (Siphonaptera), have been completely neglected, with only 1 louse and 0 flea species assessed. Granted not all ectoparasites have high host specificity (case in point, the Passenger Pigeon louse), but when you realize that conservationists working to save charismatic species like condors and black-footed ferrets have likely caused the extinction of their respective lice (none of which are included in the IUCN Red List by the way), and add in the fact that we’ve only described a tiny fraction of the total diversity of insects, we need to assume that the conservation status of insects is being dramatically, drastically, underestimated.

It certainly seems like conservation biologists have been preferentially looking at the bigger insects (Odonata, Orthoptera and Lepidoptera make up 75% of assessed species), and pretty much ignoring the rest. It’s hard to argue with that strategy considering how difficult it is to find, identify, and track smaller insects like beetles, flies and bugs, but if we want to give a proper status report on the state of global biodiversity, we have a lot of work left to do, and any interpretations involving insect diversity need to be taken with a goliath beetle-sized grain of salt.

And no, the goliath beetle, one of the largest insects alive today, hasn’t been assessed by the IUCN either. Go figure.

Of pigeons, extinction, and lice

 Biology, Insects, Publication  5 Responses »
Sep 022014
 

Yesterday marked the 100th anniversary of the extinction of one of our most iconic emblems, the Passenger Pigeon (Ectopistes migratorius). The web is alive with tributes to Martha, the final individual of her species, and cautionary tales of conservation and how we should be working to prevent this happening to any other species. There has also been considerable discussion and debate recently whether the Passenger Pigeon may be a candidate for “de-extinction”; the theoretical process of bringing a species back from the void through cloning and genetic engineering. Seeing how I generally dislike vertebrates dominating the biodiversity news cycle, I figured we could all use a slightly less depressing story about extinction, de-extinction, the role of natural history museums in conservation, and of course, taxonomy.

As we’re beginning to understand, no species is an island unto itself. Every individual is an ecosystem of parasites, predators and symbionts, and thus when one species disappears, its co-dependents are just as likely to vanish, usually without us even realizing it. Allow me to share the story of Columbicola extinctus, a chewing feather mite that quietly faded into the night likely years prior to Martha’s high-profile demise on September 1, 1914, and which we only learned about 20 years after that.

Columbicola columbae, a species closely related to Columbicola extinctus (it seems the differences between them are slight modifications of the head and genitalia; feel free to use your imagination). Photo by Vince Smith, used under CC-BY license.

Working from a preserved Passenger Pigeon specimen collected in 1895 and housed in the Illinois Natural History Survey, Richard Malcomson discovered and described Columbicola extinctus in 1937, noting he had only seen 15 specimens of this new louse. In what may be the saddest etymological discussion I’ve seen, Malcomson says:

“Dr. Ewing of the National Museum, Washington, D.C., suggested the name of extinctus which surely is a suitable one for the Passenger Pigeon is now extinct and probably has carried the parasite into extinction with it.”

And so humanity carried on, parading the Passenger Pigeon out as the flag-bearer for extinction, while its lowly louse faded from memory. That is, until 1999, when, like a phoenix louse rising from the ashes of its host, Columbicola extinctus out-lived its name. While reviewing the genus Columbicola, Dale Clayton and Roger Price discovered that Columbicola extinctus wasn’t found solely on the Passenger Pigeon, but was in fact still alive and well on the Passenger Pigeon’s closest living relative, the Band-tailed Pigeon (Patagioenas fasciata)! What’s more, Columbicola extinctus was found on Band-tailed Pigeon specimens collected all up and down the Pacific coast, from California to Peru! As Clayton & Price note

“Our study reveals no consistent differences between Columbicola specimens from the extinct passenger pigeon and those from the extant band-tailed pigeon, C. fasciata. Thus, there is no longer grounds for considering this species of louse extinct, despite its unfortunate specific epithet.”

It’s worth considering how bird specimens preserved and maintained in a natural history museum allowed taxonomists to not only find a species at a time when it was believed to be extinct, but to also resurrect that same species 60 years later, redefining the term “de-extinction” before it was trendy. Sure, Columbicola extinctus’ species epithet may be a little premature, but it also serves as an important reminder that while extinction is usually forever, nature sometimes finds a way.

And should someone ever succeed in bringing the Passenger Pigeon back from extinction (however unlikely that is or may be to occur), we’ll be able to reunite two species who’s lives and legacies were intimately intertwined, and who were each thought to be lost to time and humanity. A fairytale ending if ever I’ve heard, albeit one that probably won’t make it to Disney.

—
Clayton D.H. & Price R.D. (1999). Taxonomy of New World Columbicola (Phthiraptera: Philopteridae) from the Columbiformes (Aves), with Descriptions of Five New Species, Annals of the Entomological Society of America, 92 (5) 675-685. DOI:

Malcolmson R.O. (1937). Two New Mallophaga, Annals of the Entomological Society of America, 30 (1) 53-56. DOI: