Background: Animals and plants have a wide range of colours, and these different colours play different roles in different species. Some species might be signalling to potential predators that they are toxic (like a wasp’s stripes), others might be trying to hide (like a moth’s speckled grey wings), and others might be trying to signal to the opposite sex that they are high quality mates (like a peacock’s train). However, while there are clear functions in principle, the relative importance of different signals might vary depending on the context within which the animal or plant finds itself. For example, male ebony jewelwing damselflies (Calopteryx maculata) have very dark wings and this is thought to allow females of the same species to choose appropriate mates (i.e. to avoid mating with the wrong species). However, the dark pigment can also play a role in temperature regulation. Damselflies cannot generate their own heat and so rely on absorbing heat from the sun, which is helped by the dark pigment. I was interested in how the darkness of the wings varied between locations which experience different temperatures.
What I did: I wanted to collect specimens of this species for analysis from across its entire range in North America, but the range is so large (Florida to Ontario, and New York to Nebraska) that I wouldn’t have been able to travel to sufficient sites within the one season that I have available. Instead, I asked a lot of local dragonfly enthusiasts to catch and send me specimens from their local sites. I am extremely grateful to all of them for helping, as this could not have been done without their kind volunteering of time and energy. I ended up with a substantial dataset of animals from 49 sites across the range. The wings of the animals were clipped from the bodies and scanned using a flatbed scanner, and then the amount of pigment was calculated from the image. I showed that the amount of pigment was pretty constant across the range apart from when the species was found with a similar species: the river jewelwing damselfly (Calopteryx aequabilis). This suggests that there might be an optimal level of pigmentation that is independent of temperature, but that if females start to struggle to identify males of their own species there might be an advantage to changing the levels of pigment.
Importance: There have been a lot of local experiments on the benefits and costs of pigment in animals (including damselflies) but there have been far fewer studies that have looked at large scale patterns in pigmentation. These sorts of studies are essential to describe biological phenomena in the field and to reveal initial patterns in nature that might indicate interesting or novel evolutionary processes.
This is part of a series of short lay summaries that describe the technical publications I have authored. This paper, entitled “Continental variation in wing pigmentation in Calopteryx damselflies is related to the presence of heterospecifics”, was published in the journal PeerJ in 2014. You can find this paper for free at the publisher.
Image credit: That’s one of mine!
Background: One of the fundamental questions in ecology is “what drives changes in the numbers of species in time and space?” We can look around us today and see that there are generally many more species in the tropics than nearer the poles. However, another way in which we can look around ourselves is to delve into the fossil record to look back in time. Dani Fraser is a PhD student at Carleton University working on large-scale patterns in fossil mammal biodiversity. Dani was interested in looking at spatial patterns and how they changed through time, but rather than just calculating the number of animals living in each area at each time, we looked at the rate at which the communities changed as we moved further north. The idea is that when climates are relatively stable and warm there is little variability in climate and so there is gradual change in species as you move north. However, as the climate becomes more polarised (i.e. colder at the pole relative to the tropics) the rate of change in animal communities becomes more pronounced.
Background: When we build ponds in urban areas, they can play a number of important roles: managing floodwater, cooling the urban environment, removing pollution, improving the appearance of built-up areas and providing a habitat for wildlife. However, these different functions often require different forms of management, and so urban managers typically prioritise one or a small number of purposes. We were interested in the biodiversity value of ponds in Bradford in the UK.
Background: The management of water in urban areas can be a problem, because rainfall rapidly runs off impervious surfaces like pavements and roads. This means the water quickly enters rivers and streams, which then flood. City managers reduce the rate at which water enters rivers using stormwater management facilities, which often include ponds to hold back the stormwater. These ponds are usually managed just for water retention, but they could potentially form a very useful habitat for aquatic plants and animals in cities.
Katatrepsis 