Congeneric Predaceous Diving Beetle Species Fail to Segregate in a Floodplain System: A Case of Amplified Sympatry

Abstract

Coexistence of closely related species has long been a focus of biologists in their efforts to explain mechanisms that drive community assembly. Dytiscidae (predaceous diving beetles) are a group that shows a particularly high affinity for sympatry despite their relatedness. Our objective was to investigate the degree of overlap among Neoporus (Guignot) species (Coleoptera: Dytiscidae) in floodplains of the southeastern United States. We sampled two floodplain habitats (permanent oxbow lakes and temporarily flooded pools) of the Altamaha River (Georgia, USA) for Neoporus species over three years. Six species of Neoporus were collected during our study, and a significant amount of overlap (spatial and temporal) was documented. Analysis suggested that none of the species exhibited a preference toward one habitat type or the other. Temporally, no striking patterns of segregation emerged. No negative correlations between species were documented, but neither were significant positive correlations found. This absence of distinct patterns suggests a lack of segregation among Neoporus species in floodplains of the Altamaha River. While Dytiscidae in general appears to be a particularly sympatric group of organisms, overlap among congeneric species within the family has been documented less frequently. Our study provides new insight into the degree to which dytiscids are capable of coexisting in space and time.

Coexistence mechanism of sympatric predaceous diving beetle larvae

“…In fact, IGP events were observed only twice: H. grammicus feeding on R. suturalis and C. brevis feeding on H. grammicus (Appendix S1). McDaniel et al (2017) found that dytiscid adults of Neoporus species did not segregate spatiotemporally in the floodplain; however, our study showed that spatiotemporal segregation may occur in their larval stage, when beetles are less mobile than in the adult stage. However, predation events involving small animals may have been less detectable in our direct observations because of the shorter handling times associated with small prey.…”

Does taxonomic and numerical resolution affect the assessment of invertebrate community structure in New World freshwater wetlands?

“…This combination contributes to make the identification of Chironomidae to the genus level likely the most influential contingency impacting the observed community structure patterns ( Chessman et al, 2002 ; King and Richardson, 2002 ; Jones, 2008 ). For the highly diverse invertebrate families in wetlands, genus (or species) level resolution has been shown to elucidate finer-level ecological relationships (see King and Richardson (2002) and Chessman et al (2002) for Chironomidae; Grech et al (2019) for Culicidae; and McDaniel et al (2017) for Dytiscidae). Chessman et al (2002) showed that species-level resolution in Chironomidae data sets rendered more accurate discrimination of sampling units in biomonitoring studies.…”

“…This is rarely an option for studies of wetland invertebrate communities because most invertebrate species in these ecosystems belong to highly diverse insect orders (e.g., Coleoptera, Diptera), for which adults are frequently required to key individuals to species, and sometimes genus. Consequently, community-level assessments of invertebrates in wetlands based on species-level data are usually restricted to particular families or genera ( Chessman et al, 2002 ; King and Richardson, 2002 ; Chadd and Extence, 2004 ; Simić et al, 2007 ; Garrido and Munilla, 2008 ; McDaniel et al, 2017 ; Grech et al, 2019 ).…”

Interspecific competition amongst three species of large-bodied diving beetles: is the species with expanded distribution an active swimmer and a better forager?

“…Some sympatric Dytiscidae species can coexist within an aquatic habitat (Juliano & Lawton, 1990;Saijo, 2001) despite being congeneric and of similar body size, suggesting that they are capable of coexisting in both space and time (Pitcher & Yee, 2014;McDaniel et al, 2017). Similar-sized larvae and adult dytiscids also attack similar-sized prey items (Tate & Hershey, 2003;Ohba, 2009a, b;Pitcher & Yee, 2014;Watanabe et al, 2020), suggesting that dytiscids of differing sizes may avoid direct competition for food resources.…”