Myrteae phylogeny, calibration, biogeography and diversification patterns: Increased understanding in the most species rich tribe of Myrtaceae

Abstract

Myrteae (c. 2500 species; 51 genera) is the largest tribe of Myrtaceae and an ecologically important groups of angiosperms in the Neotropics. Systematic relationships in Myrteae are complex, hindering conservation initiatives and jeopardizing evolutionary modelling. A well-supported and robust phylogenetic hypothesis was here targeted towards a comprehensive understanding of the relationships within the tribe. The resultant topology was used as a base for key evolutionary analyses such as age estimation, historical biogeography and diversification rate patterns. One nuclear (ITS) and seven chloroplast (psbA-trnH, matK, ndhF, trnl-trnF, trnQ-rps16, rpl16 and rpl32-trnL) DNA regions for 115 taxa representing 46 out of the 51 genera in the tribe were accessed and analysed using maximum likelihood and Bayesian inference tools for phylogenetic reconstruction. Dates of diversification events were estimated and contrasted using two distinct fossil sets (macro and pollen) in BEAST. The subsequent dated phylogenies were compared and analysed for biogeographical patterns using BioGeoBEARS and diversification rates using BAMM. Myrteae phylogeny presents strong statistical support for three major clades within the tribe: Australasian group, Myrtus group and Main Neotropical Lineage. Dating results from calibration using macrofossil are an average of 20 million years older and show an early Paleocene origin of Myrteae, against a mid-Eocene one from the pollen fossil calibration. Biogeographic analysis shows the origin of Myrteae in Zealandia in both calibration approaches, followed by a widespread distribution throughout the still-linked Gondwana continents and diversification of Neotropical endemic lineages by later vicariance. Best configuration shift indicates three points of acceleration in diversification rates, all of them occurring in the Main Neotropical Lineage. Based on the reconstructed topology, several new taxonomic placements were recovered, including: the relative position of Myrtus communis, the placement of the Blepharocalyx group, the absence of generic endemism in the Caribbean, and the paraphyletism of the former Pimenta group. Distinct calibration approaches affect biogeography interpretation, increasing the number of necessary long distance dispersal events in the topology with older nodes. It is hypothesised that biological intrinsic factors such as modifications of embryo type and polyploidy might have played a role in accelerating shifts of diversification rates in Neotropical lineages. Future perspectives include formal subtribal classification, standardization of fossil calibration approaches and better links between diversification shifts and trait evolution.

Estudo taxonômico das espécies de <em>Eugenia</em> L. (Myrtaceae) da Reserva Natural Vale - Linhares, ES

“…A tribo Myrteae (incluída em Myrtoideae) engloba quase todos os táxons da região neotropical pertencentes a Myrtaceae, exceto Metrosideros stipularis Hook.f., que pertence a Metrosidereae (Myrtoideae) (Vasconcelos et al 2017, Pillon et al 2015. Myrteae circunscreve aproximadamente 2500 espécies, número que a caracteriza como a tribo mais rica da família (Wilson et al 2005, Lucas et al 2007, Wilson et al 2011, Vasconcelos et al 2017.…”

“…Myrteae circunscreve aproximadamente 2500 espécies, número que a caracteriza como a tribo mais rica da família (Wilson et al 2005, Lucas et al 2007, Wilson et al 2011, Vasconcelos et al 2017. As características morfológicas que a distinguem das demais tribos são a presença, geralmente, de tricomas unicelulares, folhas opostas, flores com estames numerosos, ovário ínfero, sistema vascular transeptal e frutos indeiscentes e carnosos (Schmid 1972, Wilson et al 2001, Wilson et al 2005.…”

“…Eugenia está circunscrito em um dos dez grupos definidos para a tribo Myrteae por Vasconcelos et al (2017), denominado informalmente de "Eugenia group", juntamente com Myrcianthes, Hottea, Pseudanamomis e Calyptrogenia. O "Eugenia group" se destaca pelo número de espécies, cerca de 1100, além de ser o único com distribuição pantropical (Lucas et al 2007, Mazine et al 2014, Vasconcelos et al 2017, WCSP 2017 e se distingue dos demais grupos em Myrteae principalmente pelos cotilédones parcialmente a completamente fundidos, com testa macia, óvulos originados no mesmo ponto da parede (septo), ausência de placa escalariforme e presença de inflorescências em racemos, dicásios, fascículos ou glomérulos (Lucas et al 2007).…”

“…As espécies neotropicais pertencem à tribo Myrteae, a mais rica da família (Wilson et al 2005, Lucas et al 2007, Wilson et al 2011, Vasconcelos et al 2017.…”

“…Dentre os dez grupos de Myrteae, encontra-se o "Eugenia group", com aproximadamente 1100 espécies, das quais cerca de 1000 estão circunscritas em Eugenia L. (Lucas et al 2007, Mazine et al 2014, Vasconcelos et al 2017, WCSP 2017. Maior gênero neotropical da família, Eugenia se destaca também com o maior em número de espécie na flora brasileira (BFG 2015).…”