Location and seasonal differences in adult dragonfly size and mass in northern Mississippi, USA (Odonata: Libellulidae) alt-text


Size and mass are often uniformly related within individuals and populations, but the relationship may vary in time or space. I asked whether isolated adult dragonfly populations within the same environmental context (climate, physiography, ecoregion) differ in both size and mature mass, and whether earlier emerging dragonflies are both larger and heavier on average. Differences were apparent among locally separated populations (ca 130-160 km apart), with the most northerly populations containing larger and heavier adults on average. Site-level environmental variation probably exerted a larger influence than broad-based ecogeographic rules (e.g., Bergmann’s rule) at this fine scale. On average, earlier emerging dragonflies tended to outsize and/or outweigh later emerging dragonflies, a commonly observed pattern in adult odonates and other insect taxa. Size and mass did not produce the same results in every case, suggesting the size-mass relationship within dragonfly species can vary among spatially or seasonally isolated adult populations.

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