Adaptations to new environments, native species, and new types of prey.
While undergoing range expansion into new areas, non-native aquatic species will oftentimes experience novel environmental conditions (e.g. variable water flows, new prey) that can affect survival. To help overcome some of these challenges, and ultimately become established in the new environment, non-native organisms may exhibit morphological changes that will facilitate the species' ability to forage, navigate and reproduce.Pumpkinseed (Lepomis gibbosus) are a North American species of centrarchid that were introduced into Europe more than a century ago. The species has since spread throughout the continent, and is particularly invasive in the Iberian Peninsula.
My doctoral research examines how morphological traits differ between native and non-native populations of pumpkinseed, and how differences in phenotypic plasticity between these populations may facilitate the spread of this sunfish through the Iberian Peninsula and other areas in southern Europe.
In 2007, adults from two populations in Spain were successfully introduced into artificial ponds in Canada. They have since produced viable offspring.
One laboratory experiment revealed that some pumpkinseed populations from Europe possess morphological traits (e.g. pectoral fin length) that are different, in terms of size and position, than those found in pumpkinseed from some North American populations. These changes could be the results of adaptations that have been inherited by subsequent generations over the course of the species' expansion through Europe. Introduced species would be expected to develop and pass on morphological changes that would help future generations to overcome some of the more difficult attributes of novel environments.
Adult pumpkinseed exhibit adaptive plasticity under different environmental conditions. However, until now there have been few morphological
comparisons using early pumpkinseed life stages, let alone populations from different geographic ranges. Over the past few years, I have been testing the phenotypic plasticity of Iberian pumpkinseed to environmental changes related to swimming, foraging and interspecific competition.
Behavioural responses in round goby.
Conspecific signals and spawning behaviour.
Mean time spent by juvenile round goby in the area of the flume containing paired egg odour stimulus. Trials were conducted using conspecific (yellow bars), heterospecific (pink bars), and control lake water (blue bars) stimuli.
The round goby (Neogobius melanostomus) is an invasive fish in the Laurentian Great Lakes of North America. Females spawn repeatedly between May and September, while males often nest in cavities or artificial substrata on natural reefs or shipwrecks. Once a nest is established, males become territorial, interacting aggressively towards intruders. During this period, researchers have observed non-reproductive round goby attempting to enter parental nests, and in most cases, the intruder consumes the eggs that have been deposited inside.
Several types of heterospecific (e.g. rainbow trout, Oncorhynchus mykiss) eggs are also consumed by round goby, but no particular species is targeted. A portion of my MSc research examined the behavioural resonses of juvenile round goby to egg odours. Fish prefered egg odours from their own species over odours from either rainbow trout egg, or control water.
In another laboratory experiment, I tested if reproductive female round gobies were attracted to a combination of olfactory and visual stimuli, representing reproductive and non-reproductive
male round gobies. Females spent significantly more time at a nest with a black reproductive male model compared with a mottled non-reproductive male model. Knowledge of these reproductive habits may enable researchers to develop a method of control for this invasive fish.
Spawning behaviour in the round goby:
The following video is the first documented example of round goby spawning in a laboratory setting. In this clip, the female (lighter fish) can be seen inverting to deposit the eggs on the nest ceiling.
For more information, see our 2009 publication in the Journal of Great Lakes Research.
Dr. Lynda D. Corkum MSc Advisor Aquatic ecology and invasive species
Dr. Michael G. Fox PhD Advisor Fish ecology and fisheries management
Dr. Corkum's research interests include behaviour and ecology of freshwater fishes (in particular, the round goby), and life history strategies of the burrowing mayfly.
Dr. Fox's research interests include life history adaptations, feeding and bioenergetics of young-of-year fish, and exotic species introductions.