The origin of modern patterns of continental diversity in Mauritiinae palms: the Neotropical museum and the Afrotropical graveyard

Abstract

While the latitudinal diversity gradient has received much attention, biodiversity and species richness also vary between continents across similar latitudes. Fossil information can be used to understand the evolutionary mechanisms that generated such variation between continents of similar latitudes. We integrated fossil data into a phylogenetic analysis of the Mauritiinae palms, whose extant diversity is restricted to the Neotropics, but extended across Africa and India during most of the Cenozoic. Mauritiinae diverged from its sister lineage Raphiinae ca 106 Ma. Using ancestral state estimation and a lineage through time analysis, we found that diversity arose globally during the late Cretaceous and Palaeocene across South America, Africa and India. The Palaeocene–Eocene transition ( ca 56 Ma) marked the end of global Mauritiinae expansion, and the beginning of their decline in both Africa and India. Mauritiinae disappeared from the Indian subcontinent and Africa at the end of the Eocene and the Miocene, respectively. By contrast, Neotropical diversity steadily increased over the last 80 Myr. Taken together, our results suggest that the Neotropics functioned as a continental-scale refuge for Mauritiinae palms, where lineages survived and diversified while global climatic changes that drastically reduced rainforests led to their demise on other continents.

Idiosyncrasies unveiled: examining the pace, patterns and predictors of biotic diversification in peninsular India

“…Relictual Gondwanan floral lineages are yet to be identified in peninsular India, or all have gone extinct. Despite the potential role of peninsular India as an "evolutionary graveyard" for floral lineages (63), our results indicate a predominant historic stability in the landscape. One potential way to provide this stability is through rapid turnover of the forests where ecologically similar species of Asian origins replace Gondwanan lineages, as has also been suggested in earlier palynological studies specifically for the Indian landmass (64).…”

“…Relictual Gondwanan floral lineages are yet to be identified in peninsular India or all have gone extinct. Despite the potential role of peninsular India as an "evolutionary graveyard" for floral lineages 81 , our results indicate a predominant historic stability in the (which was not certified by peer review) is the author/funder. All rights reserved.…”

“…A large proportion of the current species diversity in peninsular India is of Asian origin, except for a few small vertebrates and soil arthropods (11). The plant fossil record suggests diverse Gondwanan flora in the region until at least the late Paleocene, which now has extant relatives in Southeast Asia (12, 62, 63). Relictual Gondwanan floral lineages are yet to be identified in peninsular India, or all have gone extinct.…”

Functional and historical drivers of leaf shape evolution in palms (Arecaceae)

“…But there is also evidence of aridification across continents over the past 40–50 Myr alongside temperature variation, leading to the contraction of tropical‐like forests towards the equatorial latitudes. The pollen record has revealed patterns of palm extinctions including groups such as Mauritiinae and Eugeissoneae, typical rainforest groups and pinnate‐dissected (Bacon et al, 2022; Lim et al, 2022). From our results, this period corresponds to the diversification of entire‐leaved lineages, increasing in relative frequency at the expense of pinnate–dissected palms mainly (Figure 4a,b).…”

“…The GLMMs assess shape rather than shape evolution, thus, we treat pinnate-entire and palmate-entire as entire-leaved, pinnate-dissected as pinnate, and palmate-dissected as palmate. For computational constraints, we ran every model on 42 (Adams, 1979) phylogenies randomly selected from the distribution, each as a random effect. For every model, we ran four independent chains of 10,000,000 iterations, a thinning of 5000 and 8000 burn-in.…”