Survey data matter: predicted niche of adult vs breeding Odonata

Assessing and categorizing habitat needs or population trends of organisms with complex life histories, such as Odonata, is challenging. All Odonata have aquatic nymphs and terrestrial adults. As a consequence, their use as indicators of ecosystem health or as umbrella species in conservation plans may be misleading if data from a particular life stage does not reflect actual residency at a freshwater site. We explored this question with an extensive data set for Odonata from Oklahoma, USA, to determine if ecological niches modeled from records of adults (i.e., lacking any evidence of breeding) differed from niches modeled for records indicating breeding (tandem pairs, ovipositing females, larvae, teneral [recently emerged adults], or exuviae [shed exo-skeletons of larvae]) at surveyed sites. We predicted that models would be comparable if adult presence strongly indicates local breeding but would be dissimilar if adults occupy many more sites than those at which the species breeds. Our results supported the latter prediction. Adult models were broader geographically and had a wider, more equitable (higher evenness) balance of contributing environmental variables (niche dimensions) than did models for breeders, which tended to be more ecologically specialized. These findings suggest that surveys of adult Odonata, which are relatively easy to obtain because of organized efforts to encourage observations by citizen scientists, can paint a misleadingly broad picture of a species' ecological niche. We recommend that evidence of breeding, especially presence of tenerals or exuviae, be used to outline ecological requirements when questions of conservation or population monitoring arise.