{"id":3192,"date":"2014-11-28T02:14:42","date_gmt":"2014-11-28T07:14:42","guid":{"rendered":"http:\/\/www.biodiversityinfocus.com\/blog\/?p=3192"},"modified":"2014-11-28T02:14:42","modified_gmt":"2014-11-28T07:14:42","slug":"black-fly-day-how-about-cyto-monday","status":"publish","type":"post","link":"http:\/\/www.biodiversityinfocus.com\/blog\/2014\/11\/28\/black-fly-day-how-about-cyto-monday\/","title":{"rendered":"Black Fly Day? How about Cyto Monday!"},"content":{"rendered":"\n

When identifying insects, the further you want to identify them, generally the smaller the morphological characteristics you need to look for are. For instance, to recognize the taxonomic order Diptera, you need only count the number of pairs of wings an insect has (usually…), but to identify a fly to species, you may need to hone in on the presence or absence of a single bristle on its thorax, or middle leg, or genitals. But what about species or populations where even these characters may be too similar to confidently tell distinguish, and where you could potentially be overlooking and unknown amount\u00a0of diversity, better known as the elusive cryptic species? Well, you could look at their DNA, and try to see if there are any differences there, or, if you work on black flies, you could\u00a0literally<\/em> look at their DNA. Like, actually looking at the shape and patterning of their chromosomes, specifically special clumps of DNA found in larval black flies called polytene chromosomes.<\/p>\n

Polytene chromosomes are the jumbo-sized versions of normal chromosomes only found in cells involved with secretion, and for whatever reason, are only present in springtails (Collembola) and true flies (Diptera). Rather than replicating and then splitting themselves up amongst a series of daughter cells like normal chromosomes, polytene chromosomes replicate themselves over, and over, and over again, sticking together in clumps of hundreds to thousands of complete chromosomal\u00a0strands all woven together into a thick rope of genetic instructions. By banding together like this, these special chromosomes reveal all kinds of fascinating information about species and speciation.<\/p>\n

Starting in the 1930’s, while scientists were only just beginning to understand what chromosomes were and the role they played in genetics and heritability, dipterists began to notice that polytene chromosomes provided an untapped source of morphological characters to work with. Black fly taxonomists in particular latched onto this new dataset, largely because these over-sized chromosomes were easy to find in the silk glands of larval black flies, and provided a simple and low cost means of identifying species. Patterns of black and white bands, the locations and sizes of\u00a0bulges, blisters, and rings of Balbiani all appeared to be conserved within populations and species, and with only 3 chromosomes to deal with, taxonomists, already tuned to look for the slightest differences\u00a0and similarities between specimens, began to find all kinds of useful information; specific banding patterns that would be\u00a0inverted in some species, but not in others; whole arms of chromosomes getting spliced onto the “wrong” chromosome; all three chromosomes getting jumbled up and stuck together in the middle like a genetic pinwheel with what they called a chromocenter.<\/p>\n

\"Black-fly-cytology-diagram\"<\/a><\/p>\n

By studying these “macrogenomes”,\u00a0Simuliidae experts have been continuing to refine what a black fly species\u00a0really\u00a0is,\u00a0and are beginning to unlock the mysteries of cryptic diversity.<\/p>\n

Take, for example, work recently published by a group of black fly experts\u00a0on the Old World\u00a0subgenus\u00a0Simulium <\/em>(Wilhelmia<\/em>). These flies originally came to the group’s attention due to an outbreak of black flies in Turkey which was driving down livestock production and tourism due to the sheer numbers of biting adults (those in Northern Canada can surely commiserate), and in order to figure out what species was responsible, decided to take a closer look. A much, much closer look, specifically at their polytene chromosomes.<\/p>\n

After\u00a0sampling larval black flies from across Europe, they discovered that what had recently been considered one generalist species\u00a0found from England clear across the continent to at least Kazakhstan, Simulium\u00a0<\/em>(Wilhelmia<\/em>) lineatum<\/em>, was actually at least 3 species, each with unique differences in their chromosomes, and which replaced each other in streams as you head East!<\/p>\n