Patterns of functional diversity along latitudinal gradients of species richness in eleven fish families.

Background/Question/Methods

As we enter an era of major biodiversity loss, understanding large-scale biodiversity patterns is crucial for ecology and conservation. Often, conservation priorities are based on biodiversity metrics derived from species richness, yet recent works highlight that other biodiversity metrics are also critical for maintaining ecosystem function, and services. Among these latter is functional diversity, which describes the range of roles and functions being performed within an ecosystem. Here, we aim to improve our understanding of large-scale biodiversity patterns by testing the hypothesis that species richness can predict functional diversity along the latitudinal gradient of species richness in fish. Using full-body geometric morphometrics to estimate functional diversity, we compared the predicted functional diversity based on species richness, to the observed functional diversity within eleven fish families distributed along the latitudes from 0 o to ± 76o. We then fitted a brokenstick regression onto the observed distribution of functional diversity to illustrate any significant shifts in functional diversity along this gradient.

Results/Conclusions

We found that species richness regularly over- or under-estimated functional diversity along the latitudinal gradient of species richness in evaluated fish, with an average predictive accuracy of only 16.6%. We also show that in most families, there is a pattern of stable functional diversity from the equator through the tropics that abruptly shifts with an inflection point occurring on average at ~ ± 32o. We suggest this pattern may be linked to changes in environmental factors such as global temperature and/or habitat availability beyond tropical latitudes. However, these concepts require additional confirmations. This analysis highlights the importance of further studying and considering functional diversity in conjunction with other biodiversity metrics, such as species richness, when developing conservation priorities and policies.