Latitudinal Effects on Diversity and Body Size: A Case Study with Parasitoid and Parasitic Wasps
While greater species diversity exists at tropical latitudes for many groups, certain parasitoid wasp families (i.e. Ichneumonidae) exhibit a peak in species diversity at mid-latitudes (Janzen 1981). Recently, authors have questioned the legitimacy of observed latitudinal trends in species richness, body size and biology for parasitoids, due to geographic and taxonomic sampling biases. I combined DNA barcoding data with ecological variables to quantify parasitoid diversity across a latitudinal gradient (~4.088 - 58.676°N) and to test whether enumerating diversity using DNA supports a mid-latitude peak. I also compared Ichneumonidae and Braconidae body size across the same latitudinal gradient to test whether parasitoid wasps followed the Bergmann’s rule – larger specimens found at higher latitudes. My diversity estimates suggested that the number of species was consistent across latitude, though species found at higher latitudes were more closely related to each other. Body size, specifically hind tibia length, exhibited converse-Bergmann clines.