Researcher Bossard Consulting Huntsville, Alabama, United States
Seasonality of fleas (Siphonaptera) is often attributed to competition, prompting the idea that flea species compete for, and partition, temperature as a resource, along with correlated variables such as moisture, involving phylogenetic conservatism, character displacement, and phenotypic plasticity (Thermal-niche Partitioning Hypothesis). Do the common flea species in a community on a host show distinct, partitioned thermal niches? I compared 5 rodent-flea communities for thermal niche optima by fitting non-linear LRF (Lobry–Rosso–Flandrois) curves, and examined ecoregion and climate for each community. Hosts were Southern flying squirrel (Glaucomys volans volans), Richardson's ground-squirrel (Spermophilus richardsonii), North American deer-mouse (Peromyscus maniculatus), Midday jird (Meriones meridianus), and Wagner's gerbil (Dipodillus [Gerbillus] dasyurus). Results for mesic flea communities showed distinctly spaced thermal-niche optima, supporting the Thermal-niche Partitioning Hypothesis; however, the xeric flea communities did not. In xeric communities, rodent fleas may compete for resources other than temperature, such as moisture or host availability, and for jird fleas, varied thermal-niche widths, not optima, create flea seasonality. Variations in seasonal timing among xeric fleas may correspond with desiccation resistance, but mesic fleas appear to compete for temperature, resulting in thermal-niche partitioning and seasonality, because resources such as moisture are less limiting. Non-competition seasonality hypotheses (Environmental Filtering, Neutrality) require testing, too. Thermal niche partitioning may increase "species-packing" of disparate fleas from many families, increasing the host's flea-species richness. Thermal niches may partition insect and plant communities, so implications for biodiversity conservation and disease ecology with global warming are wide-ranging.
