Variation in epiphytic microcommunities (tardigrade-lichen-bryophyte assemblages) of the Cincinnati, Ohio area

Abstract

Corticolous (bark-inhibiting) lichens and bryophytes were studied in several deciduous forest study area as biological indicators of urban impact and as microhabitats for meiofaunal invertebrate colonizers. Bryophyte and lichen species richness are greatest in high-humidity, ‘clean air’ sites. Urban environmental conditions were characterized by decreased humidity, rapid humidity depression and decreased air quality. Differences in the bryophyte community at study sites best reflect their openness to light penetration and patchiness of microhabitats. Reduction in the number of lichen species found in sites is best explained by the study area's proximity to the city and ambient air quality. Variation in the frequency of occurrence of tardigrade species living on corticolous mosses and lichens indicates differential tolerances to aspects of climate altered by urbanization. Tardigrade species richness is greatest in high-humidity, ‘clean air’ sites. Correlation methods were utilized to illustrate the relative effects of habitat conditions on the representation of species within epiphytes collected in these monitored study areas. Tardigrade species richness was best explained by site humidity regime; however, the frequency with which some species were found in sites appears to be related to air quality. Two common species are characterized by different environmental preferences. Diphascon scoticum Murray predominates in urban park sites, characterized by low air quality and reduced humidity. The prevalence of D. scoticum may be related to this protococcal algae feeder's adaptation to low pH substrates. Such low pH conditions are more frequent in urban moss habitats. Minibiotus intermedius Plate is found more often in humid, rural sites, and is apparently intolerant of faster evaporation rates which may occur in more xeric environments.