Wed, Aug 04, 2021:On Demand
Background/Question/Methods
The latitudinal gradient in taxonomic diversity, with few notable exceptions, is one of the most pervasive patterns in biogeography. Here we describe patterns of taxonomic diversity for ground active invertebrates collected by NEON pitfall traps. We estimate taxonomic diversity across and within three phyla: Arthropoda, Annelida and Mollusca, using non-destructive meta-genomic sampling to detect species from the samples. All data is from the continental USA, Puerto Rico and Alasaka. We describe the latitudinal gradient in taxonomic diversity for these phyla at four taxonomic scales: order, family, genus and species. We also describe the latitudinal gradients in species richness for the most common taxa found in pitfall traps. Lastly, we use NEON data to describe the latitudinal gradient in species richness for NEON samples (Carabidae, Ioxodida and Culicidae) that have been identified by NEON taxonomic experts. In a canonical latitudinal gradient in taxonomic diversity, for these data, a linear regression should have a significant negative slope.
Results/Conclusions When all taxa from the three focal phyla are combined, all four taxonomic scales (i.e., order, family, genus, species) have significant reverse gradients in taxonomic diversity. Of the twelve most common taxa, 9 show significant reverse latitudinal gradients in species richness. NEON Expert identified ground beetles and ticks both a significant reverse latitudinal gradient, while mosquitos show no pattern with latitude. Across the three types of comparisons, none show the expected canonical gradient with a negative slope of species richness with latitude. It is likely that, for many of these taxa and taxonomic scales, taxonomic diversity increases again at tropical latitudes thus making gradients in taxonomic diversity multi-modal with both tropical and North Temperate peaks.
Results/Conclusions When all taxa from the three focal phyla are combined, all four taxonomic scales (i.e., order, family, genus, species) have significant reverse gradients in taxonomic diversity. Of the twelve most common taxa, 9 show significant reverse latitudinal gradients in species richness. NEON Expert identified ground beetles and ticks both a significant reverse latitudinal gradient, while mosquitos show no pattern with latitude. Across the three types of comparisons, none show the expected canonical gradient with a negative slope of species richness with latitude. It is likely that, for many of these taxa and taxonomic scales, taxonomic diversity increases again at tropical latitudes thus making gradients in taxonomic diversity multi-modal with both tropical and North Temperate peaks.