Inverse latitudinal diversity gradient pattern of the trogid beetles and
the drivers
Abstract
The rare inverse latitudinal diversity gradient is almost neglected
compared with the dominant latitudinal diversity gradient, and the
underlying mechanism of this biodiversity pattern remains elusive,
especially for invertebrates. Necrophage trogid beetles are a
vertebrate-dependent family group that may potentially serve as an
environmental indicator, but comprehensive distributional knowledge is
lacking. Here, a geographical distribution dataset of 11321 coordinates
belonging to 284 species (over 80% of Trogidae) was compiled, and
pairwise dependencies of trogids and vertebrates were integrated. The
diversity patterns of Trogidae were revealed by calculating species
richness and performing endemicity analysis. To further illustrate the
underlying richness-variable relationships, the relative effects of
environmental factors on the richness of trogids were investigated by
random forest analysis. The hotspots of trogid species richness and
areas of endemism were both located in temperate zones, together
generating a rare inverse latitudinal diversity gradient in which
similar height bimodal peaks appeared in the mid-latitude temperate zone
(near 30°S and 40°N). Climatic conditions and food availability combined
to explain 21.94% of the variance in global trogid richness. This work
first reported the global diversity pattern of necrophagous beetles at
the specimen grade and supported the ‘resource-dependent hypothesis’.
And the case study in trogids provides valuable insights into inverse
latitudinal diversity gradient patterns. The loose linkage of trogids
and vertebrates is another interesting insight, with implications for
carefully using trogids as an indicator of vertebrate distribution.