DOI: 10.5061/dryad.p5hqbzm03
title: Regional databases demonstrate macroecological patterns less clearly than systematically collected field data

description: The analysis of macroecological patterns has necessitated the use of
 large, composite datasets recording local-scale species occurrences
 distributed across the globe. These datasets, however, have various
 spatial and temporal biases, including taxonomic under sampling, range
 gaps for many species, and geographic uncertainty. They have rarely been
 compared to data collected in the field across large spatial gradients. In
 this paper we use two datasets built from online repositories plus
 standardised field collections of death assemblages to reconstruct
 macroecological patterns for marine bivalves along the eastern coastline
 of Australia – spanning over 20° of latitude and the transition between
 tropical and temperate regions. We test the strength of the latitudinal
 diversity gradient using four diversity measures and identify a
 biogeographical boundary. The field collection demonstrates a strong
 latitudinal gradient, but results from the composite datasets were varied.
 Adding observation-based records to the composite dataset obscured the
 latitudinal gradient. The location of the biogeographic boundary was the
 same in all datasets, and the location mirrored two previously published
 bioregionalisations. Although broad patterns seen in the field can be
 uncovered from composite macroecological datasets, care both in dataset
 construction and choice of methods is needed to ensure robust results.
description: During August 2018 and August 2019, ten samples were taken from
 each of fifteen beaches using 50 x 50cm (0.25 m<sup>2</sup>)
 quadrats, with five samples taken north of the beach midpoint and five
 taken to the south. Sites were spaced along the coastline to ensure they
 were independent samples and therefore representative of an independent
 species pool. Sample locations within each site were chosen randomly,
 ensuring they were ≥10 m apart and between high and low tide marks.
 Sampling was carried out during clear days not following a storm to avoid
 artefacts of changes in depositional mode. The top 5 cm of sediment within
 each quadrat was processed through 16, 8, and 4 mm sieves. Valves were
 retained and counted if they were more than 50% intact and able to be
 identified to morpho-species level – although this will bias our
 collection somewhat towards species which are naturally better preserved
 it will also ensure our samples are reflective of a more recent
 deposition. Although the spacing of the sites and sampling set up will
 eliminate some degree of temporal and spatial mixing, and give the
 collection an intertidal focus, these sites will still represent a larger
 mixing of habitats and time periods.
description: # Regional databases demonstrate macroecological patterns less clearly
 than systematically collected field data
 [https://doi.org/10.5061/dryad.p5hqbzm03](https://doi.org/10.5061/dryad.p5hqbzm03) ## Description of the data and file structure ### Files and variables #### File: SiteMetadata.csv **Description:**  ##### Variables * sample: Individual beach code for use during the field collection. Can be used instead of site or beachno. * site: Beach name, according to Short (2000 or 2007) - Beaches of the Queensland Coast or Beaches of the New South Wales Coast. * beachno: Beach number, according to Short (2000 or 2007) - Beaches of the Queensland Coast or Beaches of the New South Wales Coast. * lat: Latitude of the beach midpoint. * lon: Longitude of the beach midpoint. #### File: bivalvefieldcollection\_Kerr.csv **Description:**  ##### Variables * site: Collection site. Name is according to Short (2000 or 2007) - Beaches of the Queensland Coast or Beaches of the New South Wales Coast. Matches beach name in site metadata. * sample: Quadrat (sample) number. * fraction: Sieve size (mm). * originalcode: Species code given when valve identified in the field. * newcode: Species code given when valve identified in the lab. * n: Number of valves of that species collected in that sample/fraction. * family: Family of valve. * genus: Genus of valve. * specificEpithet: Species name (only) of valve. * species: Genus and species of valve. * authority: Source used to identify valve in the lab. ## Code/software Software not needed, only csv files are presented. ## Access information Other publicly accessible locations of the data: * As supplementary information in Kerr, M. R. and Alroy, J. 2023. Body size and abundance are decoupled from species richness in Australian marine bivalves. - Frontiers of Biogeography. This source also includes measurement data.