Lack of congruence between fundamental and realised aridity niche in a lineage of water beetles

Abstract

1. Coping with aridity is a physiological challenge for all organisms, including freshwater ones. Aridity shapes distributions of aquatic species at fine and large geographical scales. Specifically, for aquatic beetles, the desiccation resistance of the adults is a potential constraint for the colonisation of arid regions.2. We assessed the congruence between the fundamental and realised aridity niche in eight species of a Palearctic lineage of water beetles (subgenus Lumetus, genus Enochrus, family Hydrophilidae). We also estimated the relative explanatory capacity of aridity-related versus other environmental variables in species distributions.3. Most of the species, even those most sensitive to desiccation stress in laboratory experiments, occur in areas with high aridity within the Palearctic region.Our results suggest a lack of association between the physiological (desiccation resistance) and environmental distance matrix (realised aridity niche), or between either of these and phylogenetic distances. Aridity-related variables had generally a similar explanatory capacity in explaining the distribution of species than non-related ones. 4. Our results indicate that desiccation resistance has not been an important physiological constraint for the colonisation of arid environments by this clade and suggest that other non-physiological factors are more important in shaping their distributions along aridity gradients. The studied beetle lineage might conserve a high basal desiccation resistance from relatively recent terrestrial ancestors, which could have provided a physiological advantage for the colonisation of arid areas. Further research could shed light on whether these unexpected results are common to other groups of aquatic insects living in arid areas or are particular to this group of beetles.

Linking physiology and climate to infer species distributions in Australian skinks

“…This could be likely due to phylogenetic conservatism of metabolic rates and evaporative water loss in this genus, and that these traits are not exposed to strong natural selection forces across their range (Llewelyn et al, 2016; Martins et al, 2019). Similar observations have been made for invertebrates, in which resistance to desiccation was not correlated with range size (Pallarés et al, 2022) and thermal sensitivity of metabolic rates did not change across tropical and temperate species of stoneflies (Shah et al, 2021). Our results suggest that the Lampropholis species might conserve low thermal sensitivities for metabolism and water loss (Pallarés et al, 2022), perhaps due to behaviour buffering effects of climatic variation and reducing selective pressures on thermal sensitivities (Muñoz & Losos, 2018).…”

“…This could be likely due to phylogenetic conservatism of metabolic rates and evaporative water loss in this genus, and that these traits are not exposed to strong natural selection forces across their range (Llewelyn et al, 2016;Martins et al, 2019). Similar observations have been made for invertebrates, in which resistance to desiccation was not correlated with range size (Pallarés et al, 2022) and thermal sensitivity of metabolic rates did not change across tropical and temperate species of stoneflies (Shah et al, 2021).…”

“…Our results suggest that the Lampropholis species might conserve low thermal sensitivities for metabolism and water loss (Pallarés et al, 2022), perhaps due to behaviour buffering effects of climatic variation and reducing selective pressures on thermal sensitivities (Muñoz & Losos, 2018).…”

Role of climatic variability in shaping intraspecific variation of thermal tolerance in Mediterranean water beetles

“…Therefore, hydrophilids might conserve typical traits associated to more variable, terrestrial environments (e.g., Pallarés et al. , 2022), like higher thermal tolerance. In this sense, studies across different lineages controlling for phylogenetic effects would be illuminating.…”

“…Secondary colonizations of the terrestrial medium (and back to water again) seem to have been frequent within the family Hydrophilidae (Bernhard et al, 2006;Short & Fikácek, 2013;Bloom et al, 2014), while the aquatic Adephaga (which includes dytiscids) apparently entered the aquatic environment only once (Shull et al, 2001;Hunt et al, 2007;Jäch & Balke, 2008). Therefore, hydrophilids might conserve typical traits associated to more variable, terrestrial environments (e.g., Pallarés et al, 2022), like higher thermal tolerance. In this sense, studies across different lineages controlling for phylogenetic effects would be illuminating.…”