Invasion of newly constructed habitats and phenotypic shifts in the morphology and performance of the Cricket Frog (Acris crepitans blanchardii)

Background/Question/Methods

Long a topic of study among the anurans in the zoological and ecological literature, studies on the diminutive Cricket Frog date at least to 1882, and span a range of disciplines from basic natural history and ecology to functional morphology, mating dynamics and communication. In the study presented here, I examined the influence the changing landscape has had on the morphology and performance of this semi-aquatic anuran. The goal of the project was to examine responses of cricket frogs (Acris crepitans) to a dramatic change in the surface water distributions in the Great Plains. Understanding the response of a species to environmental change is a key challenge for ecology and evolutionary biology in the face of large-scale, anthropogenic changes. Over the past 50 years widescale construction of small ponds and impoundments have significantly altered regions once dominated by lotic habitats, and these novel pond habitats have rapidly been colonized by cricket frogs. In Kansas, where historically there were only occasional oxbow lakes, the balance has shifted from majority lotic habitats to majority lentic over this relatively short time span.

Results/Conclusions

Earlier studies using allozyme variation demonstrated genetic differences between cricket frog populations from stream and pond populations. Using a combination of museum collections from six populations and field collected individuals from four populations maintained in the laboratory, I compared the locomotor performance and morphology of frogs from stream and pond habitats in eastern Kansas. The results showed that while pond populations had smaller mean body sizes (SIL), they showed longer tibio-fibula lengths than stream populations. These morphological differences translated into differences in performance, as individuals from pond populations exhibited significantly longer jump distances in lab trials, and these results were highly repeatable over the duration of the study. These results suggest that selection operating in these constructed pond habitats may have favored smaller body size, relatively longer hind limbs and greater jump performance. Future work will address swimming performance and correlations between morphology and both terrestrial and aquatic locomotion in both habitats.