Wednesday, August 27, 2014

August in Michigan or Biodiversity in my Backyard

After a two year hiatus, I've somewhat apprehensively decided to have another go at maintaining this blog.  I find myself at a very convenient point in time for doing so -- I've been in Michigan visiting family before starting graduate school and have had an insanely great time naturalizing around the state.  Given the content of my last post, it seems only appropriate to start off with an exciting find in the flooded hardwoods of my parents' neighborhood.

Foraging on buckthorn

I promise it's in there...




I can still remember searching this forest constantly for Prothonotary Warblers (Protonotaria citrea) during my first summer as a birder.  Based on everything I was reading, the habitat here seemed perfect for them, but I never even turned up a migrant bird in four years of searching.  So, when my youngest brother Dawson and I heard a sharp chip note coming from a forested edge of the Grand River, I got really, really excited.  Soon we located a family of four birds (two adults and two juveniles) foraging intensely on buckthorn berries, which are really abundant here right now.  I actually hadn't heard of them doing this but, like many warblers, berries apparently become a more common dietary item for prothontaries in fall (Petit, 1999).  At any rate, I'm very encouraged by finding them here where they likely bred and really hope this continues in subsequent years.  This is a species of special concern in Michigan and is found regularly in only a few spots in Jackson County.


Another encouraging bit of news from this property is the recent discovery of an apparently healthy population of Blue-spotted Salamanders (Ambystoma laterale).  This salamander is the subject of many fond childhood memories and (I suspect) played a major role in getting me interested in biology at an early age.  I distinctly recall flipping a specific log at my grandmother's farm in the northwestern corner of the county during summer visits and seldom finding myself disappointed by the lack of one of these beauties.  How could an eight-year old child not be captivated by this animal?

A summary of my fifth through tenth year on this planet

Blue-spotted Salamanders are pretty common in the state and are capable of handling an impressive diversity of environments -- I recently found one under an old tire near a building in a heavily disturbed, dry field.  Subsequent, post-rain searches have come up empty -- did s/he move in the moist night? Interestingly, many populations in southern Michigan are all-female hybrids involving the closely-related Jefferson's Salamander (Ambystoma jeffersonianum).  They reproduce through kleptogenesis, wherein a female uses sperm from a heterospecific male to stimulate egg division, though the sperm does not actually fertilize the egg (Bonen et al., 2007).  This form of reproduction arose in this group some 5 million years ago (Bi and Bogart, 2010) and results in a high proportion of polyploid individuals with varying numbers of chromosome copies, though most are triploids.  I grew up referring to these salamanders as Blue Jefferson's Salamanders, a la grandma, until I was corrected by a friend some years later.  Who knew grandma Jackie was so well-versed in salamander hybridization?

We found many young individuals this year!
I suspect that this population is likely composed of hybrids, but I'm still not confident in my ability to determine this.  Hybrids tend to have less blue-spotting than pure individuals and also tend to have morphological phenotypes that are intermediate between blue-spotteds and various heterospecifics.  A potentially easier way of evaluating this population is to sex all individuals that I find in the field, but I don't know how to reliably sex salamanders.

Other herps have been doing very well here, such as this large Eastern Milksnake (Lampropeltis triangulum  triangulum) that my brothers found in early May.  Much of my time back home has been devoted to finding this species on the property, as king/milk snakes are my absolute favorite snakes.

Future Dr. Porter, world authority on the utility of denim jackets for herpetological research
The chorus of Wood Frogs (Lithobates sylvaticus) here is absolutely deafening in the spring
Northern Water Snakes (Nerodia sipedon) are really common here.  They are not water moccasins and will not kill you.  Please stop.
A growing interest of mine has been insects, especially Odonata (dragonflies and damselflies).  I'm increasingly struck by the subtle yet staggering diversity of morphology, behavior, and ecology in this group, most of which has been poorly studied compared to other taxa.  As such, I think a better understanding of Odonata natural history will make this an excellent group for addressing many interesting questions in my own field of evolutionary ecology.  Luckily for me, I have a canoe and Odonataphiles as my mentors of natural history, both of which have been invaluable for getting to know these things a bit better.  Here is but a small sampling of the local diversity:


Black-shouldered Spinyleg (Dromogomphus spinosus)
Dragonhunter (Hagenius brevistylus) (Photo credit: Don Henise)
Prince Baskettail (Epitheca princeps) (Photo credit: Don Henise)
Blue Dasher (Pachydiplax longipennis)


Ebony Jewelwings (Calopteryx maculata) in copula (Photo credit: Don Henise)
Violet Dancer (Argia fumipennis violacea) (Photo credit: Don Henise)
It's hard to know where to stop since there's so much more I'd like to cover here, and we still haven't left my back yard (this post was going to be a brief summary of my Michigan travels).  However, it would be downright irresponsible for me to not introduce one of the true outliers of the ode world.

During evening fishing trips to Williams Lake with Carson and Dawson, I began to notice an abnormally abundant damselfly with a light orange thorax and a blue-tipped abdomen, especially where extensive mats of aquatic vegetation were present.  I initially wrote them off as some weird immature or polymorphic female bluet which I'd have no chance of identifying.  However, one curious feature of these things was their crepuscular and even nocturnal activity.  By the time we'd pulled up the anchor and slowly started drifting home for the day, they were still madly fluttering over lily pads and even landing on our hats, fishing poles, and the canoe.  Most Odonata are most active around early to mid afternoon and vanish in evening hours, yet here these odd little creatures were dancing in the soft golden rays of dusk and even well into the night.

They seem to swarm the black lining of the canoe during colder weather
I consulted Don and Robyn Henise about the possibility that I might be observing Vesper Bluets (Enallagma vesperum).  I think a combination of disbelief and excitement was on their faces that evening, as this was a species they had been unsuccessfully searching for for some time.  This instantly lowered my confidence in the true ID of the damselflies I had been seeing -- how could two ode experts living in the same county as me have missed them?  After all, they are exceedingly abundant on Williams Lake, which I don't often regard as being an exceptional ecosystem in many ways.  What was going on?

My understanding is that vespers are often highly localized within a broad region, making them somewhat difficult to find.  Given their affinity for areas with a lot of lily pads (where males defend territories), I suspect that the combination of copious vegetation and high water quality (important for the larval stage) in this area is not often found coexisting in nature, especially in an age of excess fertilizers, herbicides, pesticides, etc.  Though the factors governing their local distributions is still unclear to me, their presence here has afforded me an attempt at better understanding their bizarre phenology and the evolutionary consequences this might have for other traits.  Rather than continue to on too far with this idea, maybe it is appropriate instead to write down a short list of questions I have come up with while observing these lemon-yellow beauties.

1) Why did the nocturnal behavior evolve at all?  Reduced predation/competition with other odonata?  Exploitation of a novel niche?

2) Is the orange coloration of the thorax (an unusual trait within Enallagma) an adaptation to a crepuscular lifestyle?  Interestingly, only other crepuscular species in this genus have such coloration.  Furthermore, light becomes more red-shifted later in the day, meaning an orange-yellow thorax might reflect a lot of light relative to a blue or green thorax, which is preferable if you need to attract the attention of a potential mate.

3) Has the crepuscular lifestyle facilitated the evolution of territoriality in E. vesperum or vice versa?  During the day, the habitat that vespers utilize in late evening has a few individuals of a pretty good diversity of species such as Stream Bluets, Violet Dancers, Widow Skimmers, Slaty Skimmers, Common Whitetail, Prince Baskettails, Royal River Cruisers, Dragonhunters, American Rubyspots, Black-shouldered Spinyleg, etc. -- many potential competitors and predators, especially given the small size of vespers.  However, at dusk, the same habitat is literally covered with vesper bluets (and nothing else) at seemingly every lily pad.  And if you were to visit the same area ~2 hours before vespers come out, you'd find the area similarly dense with Orange Bluets (Enallagma signatum), which are similar to vespers in coloration and territoriality (based on my observations -- this has not been published in the literature to my knowledge).  These observations have had me wondering for some time if vespers and oranges, by virtue of utilizing a clustered resource at a time when no other odes can, regularly reach much higher densities than other bluets ever experience.  It seems to me that this is a perfect recipe for the evolution of territorial behavior.

4) Have the targets of sexual selection changed in this novel (temporal) environment?  Admittedly, I don't know much about sexual selection in dragonflies, but it seems that most visual components of courtship are likely to be difficult to detect after sunlight, when copulation is reported to peak (Moody, 2009).

5) Surely, temperatures at and after dusk are very thermally stressful for an ectotherm -- how do they manage to engage in high performance territorial defense and copulatory flights in these conditions?

6) What are the primary predators of vespers, given that most insectivorous birds and dragonflies are not regularly active during a large chunk of their flight time?  If the predators are different, how is selection for anti-predator mophology, behavior, etc. different than for other bluets?

It's rare to see two males on the same lily pad... (Photo credit: Don Henise)
Most of these questions could completely or partially answered by virtually anyone with a bit of a natural history background and, more importantly, a curiosity about the natural world.  It seems to me that the line between "professional biologist" and "amateur naturalist" is increasingly being drawn, which is a shame, given that a plethora of interesting research could be done on organisms like these bluets by people without a degree.

A supplementary post highlighting other Michigan naturalizing may follow, but I am leaving for Laramie in two days, making this somewhat unlikely.  Besides, this is my first post in years -- I'm taking it easy. However, a post on crossbills in the Upper Peninsula will definitely eek its way into existence over the next week.


Sources

  • Bi, Ke; Bogart, James P (2010). "Time and time again: Unisexual salamanders (genus Ambystoma) are the oldest unisexual vertebrates". BMC Evolutionary Biology 10: 238.
  • Bonen, L.; Bogart, James P.; Bi, Ke; Fu, Jinzong; Noble, Daniel W.A.; Niedzwiecki, John (2007). "Unisexual salamanders (genus Ambystoma) present a new reproductive mode for eukaryotes". Genome 50 (2): 119–36
  •  Moody, DL (2009). Mating Behavior and Male Territoriality in Enallagma vesperum (Odonata: Coenagrionidae) on Ponds in Ohio and Northern Michigan. Ohio Journal of Science. 109 (3): 67-70.  
  •  Petit, Lisa J. 1999. Prothonotary Warbler (Protonotaria citrea), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/408


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