The roles of dispersal and mass extinction in shaping palm diversity across the Caribbean

Abstract

Aim: The rich flora of the Caribbean islands and surrounding mainland evolved in a context of isolation alternated with phases of terrestrial connectivity between landmasses, climatic fluctuations and episodes of mass extinctions during the Cenozoic.We explored how these events affected the evolution of the sister palm tribes Cryosophileae and Sabaleae, and how continent-island exchanges, endemic radiations and mass extinction shaped their extant diversity.Location: The American continent including the Caribbean region. Methods:We reconstructed a time-calibrated phylogeny of the palm tribes Cryosophileae and Sabaleae using 84% of the known species. We inferred ancestral distribution and tested the effect of island colonization and mass extinction on extant diversity. Results: Our results indicate that Cryosophileae and Sabaleae originated c. 77 Ma most probably in Laurasia, and their extant species started to diversify between 56-35 Ma and 19-10 Ma respectively. Biogeographical state reconstruction estimated that Cryosophileae dispersed to South America between 56-35 Ma, then dispersed to North-Central America between 39-25 Ma and the Caribbean islands between 34-21 Ma. We detected a possible signature of a mass extinction event at the end of the Eocene, affecting the diversification of Cryosophileae and Sabaleae and we did not detect a diversification rate shift related to the colonization of the Caribbean islands. Main conclusions: Species of Cryosophileae in the Caribbean islands are probably derived from a single Oligocene dispersal event that likely occurred overwater from North-Central America rather than through the hypothesized GAARlandia land bridge. Contrastingly, three independent Miocene dispersal events from North-Central America explain the occurrence of Sabaleae in the Caribbean islands. Contrary to our expectations, island colonization did not trigger increased diversification.Instead, we find that diversification patterns in this clade, and its disappearance from northernmost latitudes, could be the signature of a mass extinction triggered by the global temperature decline at the end of the Eocene.

Iriarteeae palms tracked the uplift of Andean Cordilleras

“…5 Ma (Pardo‐Trujillo et al., ). We find corroboration of distributions and diversification in palm clades in relation to the geological history of the Andes ( Aiphanes , Eiserhardt et al., ; Iriarteeae, here; Ceroxylon , Sanin et al., ; Cryosophila , Cano et al., ), showing palms tracked these highly dynamic geological systems.…”

Historical biogeography of Caribbean Podocarpus does not support the progression rule

“…Antilles, as we found for Podocarpus, has been documented in Caribbean angiosperms (Cano et al, 2018;Nieto-Blázquez et al, 2017). Continental recolonization has also been shown for Podocarpus in the Australasian region (Condamine et al, 2017), which reinforces the concept of islands acting not just as sinks but also as sources of biodiversity.…”

Adjacency and Area Explain Species Bioregional Shifts in Neotropical Palms

“…The Markov chains were run for 500 million generations and repeated three times to verify convergence and to ensure effective sample sizes exceeded 200. The divergence time analysis was constrained to incorporate robust secondary calibrations points on the root of the Arecaceae tree, as well as on three major clades of Neotropical palms: Ceroxyloideae (mean age of 52 Ma with a standard deviation of 11 Ma; Sanín et al, 2016), Geonomateae (40 ± 6 Ma; Roncal et al, 2012), and the New World Thatch Palms (41 ± 9 Ma; Cano et al, 2018). Age constraint on the crown node of Arecaceae was derived from Couvreur et al (2011) at 100 ± 4 Ma.…”