Correlated evolution of thermal niches and functional physiology in tropical freshwater fishes

Abstract

The role of ecology in phenotypic and species diversification is widely documented. Nonetheless, numerous nonadaptive processes can shape realized niches and phenotypic variation in natural populations, complicating inferences about adaptive evolution at macroevolutionary scales. We tested for evolved differences in thermal tolerances and their association with the realized thermal niche (including metrics describing diurnal and seasonal patterns of temperature extremes and variability) across a genus of tropical freshwater fishes reared in a standardized environment. There was limited evolution along the thermal niche axis associated with variation in maximum temperature and in upper thermal limits. In contrast, there was considerable diversification along the first major axis of the thermal niche associated with minimum temperatures and in lower thermal limits. Across our adaptive landscape analyses, 70% of species exhibited evidence of divergence in thermal niches. Most importantly, the first two major axes of thermal niche variation were significantly correlated with variation in lower thermal limits. Our results indicate adaptation to divergent thermal niches and adaptive evolution of related functional traits, and highlight the importance of divergence in lower thermal limits for the evolution of tropical biodiversity.

Evolutionary and environmental drivers of species richness in poeciliid fishes across the Americas

“…This finding agrees with the general explanation for species richness gradients under niche conservatism, with higher species richness in ancestral environments compared with non‐ancestral ones (Wiens & Donoghue, 2004). For example, poeciliid species occupying seasonal and low‐richness regions that could be considered non‐ancestral environments have been shown to have evolved physiological tolerances to withstand cold temperatures in high latitudes and elevations (e.g., Xiphophorus ; Culumber & Tobler, 2018). However, such an explanation based on niche conservatism for the Poeciliidae LDG needs to be tested formally across the whole family.…”

Contrasting Patterns of Climatic Niche Divergence in Trebouxia—A Clade of Lichen-Forming Algae

“…Both of these findings are consistent with previous work. For instance, a greater range of lower thermal limits relative to upper limits was detected in animals ( Araújo et al, 2013 ), and subsequent work integrating evolutionary the age and relationships of a diverse range of animals and plants has further revealed phylogenetic constraints on thermal limits, with lower limits evolving faster than upper limits ( Muñoz et al, 2014 ; Culumber and Tobler, 2018 ; Liu et al, 2020 ; Bennett et al, 2021 ). We emphasize that these limits may represent hard physiological boundaries that may restrict the potential for lineages to adapt in situ to changing climates.…”

Ecology and the diversification of reproductive strategies in viviparous fishes

“…Most importantly, it remains to be tested whether metrics of resource availability, competition, and predation used here to facilitate continental-scale analyses accurately reflect selective regimes experienced by different species. The challenges of quantifying complex variation in biotic interactions across the spatial and phylogenetic scales covered in this study highlights the need for microevolutionary analyses and experimental approaches on broader phylogenetic scales that allow for a better understanding of causal relationships (Culumber & Tobler 2018). For example, while there is experimental evidence for the fitness costs of matrotrophy under fluctuating resource conditions (Pollux & Reznick 2011), we still lack any empirical evidence indicating that matrotrophy provides fitness benefits over lecithotrophy under high and stable resource conditions (Pollux et al .…”