DOI: 10.5061/dryad.3n5tb2rcp
title: Data from: Marine latitudinal diversity gradients, niche conservatism, and out of the tropics and Arctic: climatic sensitivity of small organisms

description: Aim The latitudinal diversity gradient (LDG) is a consequence of
 evolutionary and ecological mechanisms acting over long history, and thus
 is best investigated with organisms that have rich fossil records.
 However, combined neontological-paleontological investigations are mostly
 limited to large, shelled invertebrates, which keeps our mechanistic
 understanding of LDGs in its infancy. This paper aims to describe the
 modern meiobenthic ostracod LDG and to explore the possible controlling
 factors and the evolutionary mechanisms of this large-scale biodiversity
 pattern. Location Present-day Western North Atlantic Taxon Ostracoda
 Methods We compiled census data from ostracods living in shallow marine
 environments of the western North Atlantic Ocean. Using these data, we
 documented the marine LDG with multiple metrics of alpha, beta (nestedness
 and turnover), and gamma diversity, and we tested whether macroecological
 patterns could be governed by different environmental factors, including
 temperature, salinity, dissolved oxygen, pH and primary productivity. We
 also explored the geologic age distribution of ostracod genera to
 investigate the evolutionary mechanisms underpinning the LDG. Results Our
 results show that temperature and climatic niche conservatism are
 important in setting LDGs of these small, poorly-dispersing organisms. We
 also found evidence for some dispersal-driven spatial dynamics in the
 ostracod LDG. Compared to patterns observed in marine bivalves, however,
 dispersal dynamics were weaker and they were bi-directional, rather than
 following the “out-of-the-tropics” model. Main Conclusions Our detailed
 analyses revealed that meiobenthic organisms, which comprise two-thirds of
 marine diversity, do not always follow the same rules as larger,
 better-studied organisms. Our findings suggest that the under-studied
 majority of biodiversity may be more sensitive to climate than are
 well-studied, large organisms. This implies that the impacts of ongoing
 Anthropocene climatic change on marine ecosystems may be much more serious
 than presently thought.
description: 1.  <em>Present-day
 </em>shallow marine ostracod
 data We constructed a
 comprehensive, equator-to-pole compilation of ostracod censuses from the
 western North Atlantic and the Arctic Oceans. We standardized ostracod
 taxonomy and integrated census data from previously published studies,
 which involved restudy of previous collections. We obtained complete
 ostracod census data from the original faunal slides from the US
 Geological Survey’s collections, including those of Hazel (1970),
 Valentine (1971), Cronin (1983), Cronin (1990) and Lyon (1990). Taxonomy
 was based on Cronin (1990) with additional information for high latitude
 species from Yasuhara et al. (2012) and Gemery et al. (2015).
 In addition to the census data from the USGS collections, census
 data from Kontrovitz (1976), Teeter (1975), and the Arctic Ostracode
 Database (Gemery et al., 2015) were added to our dataset after
 standardizing taxonomy using SEM pictures and descriptions from the
 literature. Locality information (longitude, latitude and water depth) was
 obtained from the original cruise reports and literature. 2. Environmental
 parameters Environmental
 parameters were obtained from various databases (Appendix 2 and Table S3).
 Mean annual values (1955 – 2012) for temperature (°C), dissolved oxygen
 (ml/L) , and salinity were obtained from the World Ocean Atlas (Baranova,
 2015). pH data were obtained from the Global Ocean Data Analysis Project
 Bottle Data (version 2) (Olsen et al., 2016). Mean sea surface net primary
 productivity (NPP, in mgC/m<sup>2</sup>/day) data (1998-2014)
 were obtained from Oregon State University Ocean Productivity Centre
 (http://www.science.oregonstate.edu/ocean.productivity/) (Behrenfeld and Falkowski, 1997). Sea bottom environmental parameters were interpolated for each standard depth [based on World Ocean Atlas (Baranova, 2015)] using the Triangulated Irregular Network (TIN) interpolation from the plugin “interpolation” of QGIS (QGIS Development Team, 2016) with geographic range: latitude = 0 – 90°N; longitude = 100°W – 30°E. Interpolated environmental raster layers were overlaid with ostracod sites in QGIS (QGIS Development Team, 2016) and Point Sampling Tool was used to extract the values of environmental parameters at each site.