Global arthropod beta-diversity is spatially and temporally structured by latitude

Abstract

Global biodiversity gradients are generally expected to reflect greater species replacement closer to the equator. However, empirical validation of global biodiversity gradients largely relies on vertebrates, plants, and other less diverse taxa. Here we assess the temporal and spatial dynamics of global arthropod biodiversity dynamics using a beta-diversity framework. Sampling includes 129 sampling sites whereby malaise traps are deployed to monitor temporal changes in arthropod communities. Overall, we encountered more than 150,000 unique barcode index numbers (BINs) (i.e. species proxies). We assess between site differences in community diversity using beta-diversity and the partitioned components of species replacement and richness difference. Global total beta-diversity (dissimilarity) increases with decreasing latitude, greater spatial distance and greater temporal distance. Species replacement and richness difference patterns vary across biogeographic regions. Our findings support long-standing, general expectations of global biodiversity patterns. However, we also show that the underlying processes driving patterns may be regionally linked.

Fig. 1. Sampling sites and five biogeographical regions considered.

Regions are differentiated by color. White points indicate sampling locations.

Fig. 2. Diversity of BINs (i.e. species proxies) across sampling sites.

Colors shown are unique terrestrial arthropod orders with each height corresponding to the relative abundance (top) or log abundance (middle) of unique BINs across the given site. The absolute latitude is provided on the x-axis with sites arranged from low to high. Bottom panel, each circle represents a unique sampling event, with colors corresponding to the region. Each vertical line shows a unique sampling location with latitude (absolute) indicated on the x-axis. Colors correspond to regional groups following the same color scheme as Fig. 1.

Fig. 3. Impacts of pairwise distance in space and latitude on community dissimilarity.

This figure shows the species replacement and richness difference components of beta-diversity, plotted from the fitted values of a linear model of the metric in question as a function of distance in space, distance in time (here set to zero), mean absolute latitude, and the interactions mean latitude × distance in space and mean latitude × distance in time (see Table 1 for statistical significances). In this figure, we explicitly test whether spatial patterns of community beta-diversity in space (in terms of overall beta-diversity, species replacement, or richness difference) varies detectably with latitude. Regions with a significant interaction between pairwise difference in latitude and pairwise distance are indicated by an asterisk. Note the differences in the scaling of axes among the individual graphs.

Fig. 4. Impacts of pairwise distance in time and latitude on community dissimilarity.

This figure shows the species replacement and richness difference components of beta-diversity, plotted from the fitted values of a linear model of the metric in question as a function of distance in space (here set to zero), distance in time, mean latitude, and interactions between mean latitude × distance in space and mean latitude × distance in time (see Table 1 for statistical significances). In this figure, we explicitly test whether temporal patterns of community beta-diversity in time (in terms of overall beta-diversity, species replacement, and richness difference) varies detectably with latitude.