Anyone know why some species of damselflies seem to have so many (>3) color morphs ?
I wanted to make a one-page figure showing some of the common species in Alberta (just for fun - drawing damselflies is relaxing*) and while looking through images of Coenagrion resolutum on BugGuide and iNaturalist I counted at least 3 different female color morphs and 5 different male morphs (pictured below - although M1, M2, and M4 are quite similar, so I might be making distinctions where there are none). Looks like Enallagma annexum also has at least 3 female color morphs as well (haven’t looked at other species yet).
I know very little about Odonata and was expecting maybe one color morph per sex. After some googling it looks like some species have “andromorph” females which resemble males (2 female morphs) and some have males which resemble females (2 male morphs) and some species that have “young” males that look different from older males (2 male morphs) but I couldn’t find an example of a species with multiple systems in play that result in >3 color morphs for the species as a whole, let alone 5.
Why all the colors? Is it just random variation in pigment deposition during development? Age? Larval diet? Geographic variation? Association with particular microhabitats? Misidentifications? Some combination of these?
I don’t know a lot about this but there are definitely some species with multiple distinct colour morphs - however it is also the case that ‘new adults’ can take some time before their colours become established, they can start off pinkish before gradually turning their proper blue for example.
Surely, with Odonata having a long and dedicated following, this MUST have been addressed, right?
With butterflies, some morphs have been tested and determined why they’re beneficial/ superior; with other butterflies, the question remains to be determined. Damselflies I’m no specialist in, so aside from a search for papers, I wouldn’t know where to start.
Nice drawings! Are they yours? If so, good work indeed.
As for color morphs, I think age of the specimen has a good deal to do with it, as @matthewvosper noted. At least with the dragonflies and damselflies I’m familiar with (New England in the US), many adults start out virtually colorless when they first emerge, gain an initial coloration as they mature out of the teneral stage (which can take a day or two, to a week or so), and then sometimes gain pruinosity or other color changes when they are fully mature and/or “old.” So first, we’d need to know the approximate age of the specimens.
Secondly, there may still be color morphs that are independent of age, the same way there are color morphs of Red-Backed Salamanders or Eastern Screech Owls or Pink Lady’s-slippers or The Joker moth. My guess in such cases is that there might be two possible explanations: 1) that they are simply random mutations with no selective benefit or detriment, that happen to become established in the population; or 2) there are selective consequences to the different colors, but there are two or more selective forces working against each other at different times. An example of the second possibility - and I am completely making this up - a late and strong freeze in May might select against green-morph Joker caterpillars or pupae, allowing brown morphs to survive better, whereas in “normal” years, green morphs are selected for because they are more camouflaged again the usual predators.
That would be interesting if there is a genetic basis to the colors, rather than being related to diet/age. If so I think there would have to be some pretty crazy balancing selection to maintain so many different colors in a single population, so I’m guessing most populations would have only a few of the possible colors (not sure if that’s the case).
Yes, the drawings are mine, although I traced the initial body shape from an iNaturalist photo.