Deconstructing the latitudinal diversity gradient of North American mammals by nominal order

Kirsten M Meltesen, Evan T Whiting, Jesús N Pinto-Ledezma, Tessa S Cicak, David L Fox, Jennifer Frey (Editor)

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North American mammals follow a well-established latitudinal diversity gradient in species richness. However, the degree to which species in different mammal clades follow the same latitudinal gradient—and to which each clade contributes to the pattern observed for all mammals remains unknown. Here, we separate the overall mammalian latitudinal diversity gradient by mammal orders and investigate the impact of climate and topography on the distribution of each major mammal clade. We joined an equal-area grid (100 × 100 km cells) of continental North America embedded with environmental variables (n = 10) with mammalian species ranges (n = 753). We used spatial regression models to quantify the relationship between species richness and latitude for all mammals, all mammals excluding select clades, and for each individual subordinate clade (n = 9). We used multiple linear regression and simultaneous autoregressive regression models to determine which environmental variables best explained patterns of species richness for each mammal order. Whereas North American mammals altogether exhibit a strong latitudinal diversity gradient in species richness, most orders deviate from the species richness pattern observed for all mammals and their gradients are weak or entirely absent. Bats (Chiroptera) exhibit the strongest latitudinal gradient—their removal from the pattern for all mammals substantially weakens the total mammalian gradient, more so than when rodents are removed. Environmental variables explain patterns of species richness well for some clades, but poorly for others. The gradient we observe for North American mammals today is likely a combined product of multiple diversification events, dispersals, and climatic and tectonic histories. todos los mamíferos y sus gradientes son débiles o están completamente ausentes. Nuestros resultados muestran que mientras los mamíferos de América del Norte en su conjunto exhiben un fuerte gradiente de diversidad latitudinal en la riqueza de especies, la mayoría de los órdenes se desvían del patrón de riqueza observado para todos los mamíferos y sus gradientes son débiles o están completamente ausentes. Los murciélagos (orden Chiroptera) exhiben el gradiente latitudinal más fuerte: su remoción del patron debilita substancialmente el gradiente latitudinal observado de riqueza de todos los mamíferos, es más acentuada que cuando se remueve el orden de roedores. Las variables ambientales explican bien los patrones de riqueza de especies para algunos clados, pero debilmente para otros. El gradiente observado en la actualidad para los mamíferos de América del Norte es probablemente el resultado combinado de múltiples eventos de diversificación, dispersiones e historias climáticas y tectónicas.

Original languageUndefined/Unknown
Pages (from-to)707-722
Number of pages16
JournalJournal of Mammalogy
Issue number4
StatePublished - Aug 1 2023

Bibliographical note

Funding Information:
The authors thank U-Spatial at the University of Minnesota for providing student access to ArcgIS software. We also thank K. McNulty, J. Cavender-Bares, and S. Broadfoot for their support and helpful discussions and insights. Finally, we thank the anonymous reviewers whose constructive feedback helped improve the manuscript during revisions.

Publisher Copyright:
© The Author(s) 2023.

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