Phylogenetic niche conservatism explains an inverse latitudinal diversity gradient in freshwater arthropods

Abstract

The underlying mechanisms responsible for the general increase in species richness from temperate regions to the tropics remain equivocal. Many hypotheses have been proposed to explain this astonishing pattern but additional empirical studies are needed to shed light on the drivers at work. Here we reconstruct the evolutionary history of the cosmopolitan diving beetle subfamily Colymbetinae, the majority of which are found in the Northern hemisphere, hence exhibiting an inversed latitudinal diversity gradient. We reconstructed a dated phylogeny using 12 genes, to investigate the biogeographical history and diversification dynamics in the Colymbetinae. We aimed to identify the role that phylogenetic niche conservatism plays in the inversed diversification pattern seen in this group. Our results suggest that Colymbetinae originated in temperate climates, which supports the hypothesis that their distribution is the result of an ancestral adaptation to temperate environmental conditions rather than tropical origins, and that temperate niche conservatism can generate and/or maintain inverse latitudinal diversity gradients.

Evolution of the Juan Fernández diving beetle, Rhantus selkirki (Coleoptera, Dytiscidae)

“…Our study supports the exclusion of several species from Rhantus , as recently proposed based on molecular data (Balke et al., ; see also Morinière et al., ). According to our results, the genus Rhantus as conceived previously to Balke et al.…”

“…The subfamily Colymbetinae is monophyletic in our analysis, in agreement with previous studies based on various data sets (Beutel, Ribera, & Bininda‐Emons, ; Burmeister, ; Michat et al., ; Miller, ; Miller & Bergsten, ; Morinière et al., ; Ribera, Hogan, & Vogler, ; Ribera et al., ). The support obtained was moderate (Figure ), and no unambiguous synapomorphies were discovered (Figure ).…”

Knitting patterns of biodiversity, range size and body size in aquatic beetle faunas: significant relationships but slightly divergent drivers

“…Finally, mean body size in diving beetle assemblages decreased with increasing latitude, showing a trend opposite to that suggested by Bergmann's rule (Bergmann, 1847;Blackburn et al, 1999). Also, some smaller clades of diving beetles may peak at mid latitudes (Morinière et al, 2016). The LDG is typically assumed to result from three main groups of hypothesised mechanisms (Hurlbert & Stegen, 2014).…”

The global latitudinal diversity gradient pattern in spiders

“…Taxa that conform to this negative association between taxonomic richness and absolute latitude include birds, corals, freshwater arthropods, mammals, mangrove trees, marine arthropods, marine protists, molluscs, reptiles, terrestrial arthropods and terrestrial plants (Hillebrand, ; Kinlock et al., ; Willig et al., ). Only a minority of taxa show multimodal, positive or non‐significant relationships with absolute latitude, and these largely consist of parasitic species, aquatic floras and faunas and taxa with narrow latitudinal ranges such as subarctic forests (Marshall & Baltzer, ; Morinière et al., ; Willig et al., ). Some notable exceptions to the classical pattern include turtles, with a peak at 25° N (Angielczyk, Burroughs, & Feldman, ); ichneumonids, with a peak at 40° N (Timms, Schwarzfeld, & Sääksjärvi, ); grasses, with a strongly bimodal pattern (Visser, Clayton, Simpson, Freckleton, & Osborne, ); and Permian therapsids, with a positive association (Brocklehurst, Day, Rubidge, & Fröbisch, ).…”