In short- or long-term relationships, size does matter: body size patterns in the Mesostigmata (Acari: Parasitiformes)

ABSTRACT

We examined a dataset of body sizes comprising 3209 species of Mesostigmata to test two hypotheses regarding body size patterns: that species living in symbiotic relationships differ in size compared with those that are free-living, and that mite species show geographic body size gradients. We found that Mesostigmata in symbiotic relationships are considerably larger than those that are free-living, but the type of symbiosis (commensal versus parasitic) had little influence on body size. We also found that free-living mite species fit a Bergmann size cline (larger species in cool climates), but mite species in commensal relationships show a converse Bergmann size cline (larger species in warm climates) while no pattern was found for parasitic species. These results fit a resource-based explanation for both patterns. We hypothesize that animals that use more easily obtainable resources grow larger, through resource pulses in temperate zones for free-living mites and use of concentrated resources for commensal and parasitic species. Available microhabitats could also promote smaller sizes in free-living Mesostigmata: i.e. soil and plants offer more and smaller microhabitats to exploit and are hence occupied by smaller species.

KEYWORDS:

• Bergmann cline
• commensalism
• ecogeography
• microhabitats
• parasitism
• phoresy
• symbiosis

Acknowledgments

This work was partially inspired by the work done by Owen Seeman on the Megisthanidae, which was a project funded by the Australian Biological Resources Study, grant number RF215-07. We also thank Heather Proctor and Dave Walter for their interesting comments and corrections that helped improve our manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This project was partially funded by the Australian Biological Resources Study, grant number RF215-07.