Regional databases demonstrate macroecological patterns less clearly than systematically collected field data

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..., During August 2018 and August 2019, ten samples were taken from each of fifteen beaches using 50 x 50cm (0.25 m2) 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 s..., , # 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 S...