Andean orogeny and the diversification of lowland neotropical rain forest trees: A case study in Sapotaceae

Abstract

Understanding how species diversify and evolve in species-rich areas like the lowland rain forest in the Neotropics is critical for conservation in times of unprecedented threats. To determine how the Andean uplift, the formation of the Panama land bridge, and Pleistocene climatic fluctuations affected dispersal and diversification in the Sapotaceae subfamily Chrysophylloideae, we collected 146 Chrysophylloideae accessions in previously under-explored areas, generating one of the most geographically complete data sets for neotropical Sapotaceae. Sapotaceae is a good model to test diversification hypotheses in lowland neotropical rain forests as it predominantly occurs <1000 m altitude, and it is an abundant and species-rich group in this biome. We generated a time calibrated phylogeny of 123 Sapotaceae species based upon the nuclear ribosomal internal transcribed spacer region that suggests migration between lineages to the east and the west Andean Cordilleras occurred before and after periods of major uplift, indicating that the Andes did not represent a significant barrier to dispersal for Sapotaceae, although it may have promoted vicariance in some cases. Dispersal between South and Central America occurred mainly prior to the formation of the Panama land bridge, suggesting that this event did not affect migration patterns in Chrysophylloideae. We inferred diversification rates and detected three shifts in the phylogeny, but they are not congruent with tectonic movements during the middle Miocene and climatic changes during the Pleistocene. Finally, some species with restricted distributions appear to be phylogenetically nested within species with broader ranges, suggesting ancestor descendent relationships and insights into patterns of speciation in rain forest trees.

Reassessment of generic boundaries in Neotropical Chrysophylloideae (Sapotaceae): Eleven reinstated genera and narrowed circumscriptions of Chrysophyllum and Pouteria

“…Nuclear sequences of C. scalare were recently obtained and blasted in GenBank, indicating a 99% similarity to R. sanguinolenta. Moreover, a phylogenetic analysis based on a single locus conducted by Serrano & al. (2021) included both C. bombycinum and C. scalare, placing them in a clade that corresponds to Ragala.…”

“…& Pellegr., and Stephanoluma Baill. were included in Micropholis by , and analyses based on ITS sequence data support this decision for Crepinodendron and Stephanoluma (Serrano & al., 2021). As indicated above, we also treat Syzygiopsis as a synonym of Micropholis.…”

“…Moreover, a phylogenetic analysis based on a single locus conducted by Serrano & al. (2021) included both C. bombycinum and C. scalare , placing them in a clade that corresponds to Ragala . On this basis we reinstate Ragala and make necessary combinations.…”

Patterns in the genetic structure of 49 lowland rain forest tree species co‐distributed on opposite sides of the northern Andes

“…Widely distributed species often share broad similarities in genetic structure across their geographic ranges, reflecting similar demographic responses to climate change and landscape features (Avise, 2009; Hickerson et al., 2010). In lowland Neotropical rain forests, landscape features such as large rivers (Gascon et al., 2000; Naka & Brumfield, 2018; Nazareno et al., 2019), dry forest corridors (Costa, 2003), and mountain ranges (Bemmels et al., 2018; Frost et al., 2022; Serrano et al., 2021) frequently structure species distributions and spatial patterns of genetic variation. Mountain ranges have long been hypothesized to represent especially strong dispersal barriers to lowland rain forest species due to the high degree of specialization to narrow, stable climatic niches exhibited by tropical taxa (Janzen, 1967).…”

“…, and mountain ranges Frost et al, 2022;Serrano et al, 2021) frequently structure species distributions and spatial patterns of genetic variation. Mountain ranges have long been hypothesized to represent especially strong dispersal barriers to lowland rain forest species due to the high degree of specialization to narrow, stable climatic niches exhibited by tropical taxa (Janzen, 1967).…”