Following Rapoport's Rule: the geographic range and genome size of bacterial taxa decline at warmer latitudes

Abstract

We sought to test whether stream bacterial communities conform to Rapoport's Rule, a pattern commonly observed for plants and animals whereby taxa exhibit decreased latitudinal range sizes closer to the equator. Using a DNA sequencing approach, we explored the biogeography of biofilm bacterial communities in 204 streams across a ∼1000 km latitudinal gradient. The range sizes of bacterial taxa were strongly correlated with latitude, decreasing closer to the equator, which coincided with a greater than fivefold increase in bacterial taxonomic richness. The relative richness and range size of bacteria were associated with spatially correlated variation in temperature and rainfall. These patterns were observed despite enormous variability in catchment environmental characteristics. Similar results were obtained when restricting the same analyses to native forest catchments, thereby controlling for spatial biases in land use. We analysed genomic data from ∼500 taxa detected in this study, for which data were available and found that bacterial communities at cooler latitudes also tended to possess greater potential metabolic potential. Collectively, these data provide the first evidence of latitudinal variation in the range size distributions of freshwater bacteria, a trend which may be determined, in part, by a trade-off between bacterial genome size and local variation in climatic conditions.

Connecting through space and time: catchment‐scale distributions of bacteria in soil, stream water and sediment

“…Such investigations have revealed that, across spatial scales, bacterial communities typically show decreases in community similarity with increasing distance (Bissett et al ., ; Griffiths et al ., ). Bacterial communities have further been demonstrated to conform to macroecological patterns including the latitudinal diversity gradient (Lear et al ., ) and Rapoport's rule, where the geographic range sizes of organisms increase closer to the poles (Lear et al ., ). Soil bacterial communities are strongly influenced by pH, as well as other environmental variables such as plant diversity, C to N ratios or the moisture and clay content of soils (Lauber et al ., ; Griffiths et al ., ; Terrat et al ., ), whereas stream bacterial communities are strongly impacted by physicochemical parameters including sediment grain size and surface area (Mendoza‐Lera et al ., ), and seasonal temperature change (Hullar et al ., ).…”

Microbial biogeography of 925 geothermal springs in New Zealand

“…Biogeography identifies patterns of diversity across defined spatial or temporal scales in an attempt to describe the factors which influence these distributions. Recent studies have shown that microbial community diversity is shaped across time and space 1 , 2 via a combination of environmental selection, stochastic drift, diversification, and dispersal limitation 3 , 4 . The relative impact of these ecological drivers on diversity is the subject of ongoing debate, with differential findings reported across terrestrial, marine, and human ecosystems 5 – 8 .…”

Community richness of amphibian skin bacteria correlates with bioclimate at the global scale

“…For instance, studies have found that geographic ranges of environmental bacteria decrease towards the equator following Rapoport's Rule 4,5 . In addition, composition and diversity of environmental microbiomes vary with latitude [6][7][8][9][10] , and are known to be structured by abiotic factors, such as salinity, pH, temperature, oxygen and nutrients [11][12][13][14][15] .…”