Biogeographical patterns of Myrcia s.l. (Myrtaceae) and their correlation with geological and climatic history in the Neotropics

Abstract

Many recent studies discuss the influence of climatic and geological events in the evolution of Neotropical biota by correlating these events with dated phylogenetic hypotheses. Myrtaceae is one of the most diverse Neotropical groups and it therefore a good proxy of plant diversity in the region. However, biogeographic studies on Neotropical Myrtaceae are still very limited. Myrcia s.l. is an informal group comprising three accepted genera (Calyptranthes, Marlierea and Myrcia) making up the second largest Neotropical group of Myrtaceae, totalling about 700 species distributed in nine subgroups. Exclusively Neotropical, the group occurs along the whole of the Neotropics with diversity centres in the Caribbean, the Guiana Highlands and the central-eastern Brazil. This study aims to identify the time and place of divergence of Myrcia s.l. lineages, to examine the correlation in light of geological and climatic events in the Neotropics, and to explore relationships among Neotropical biogeographic areas. A dated phylogenetic hypothesis was produced using BEAST and calibrated by placing Paleomyrtinaea princetonensis (56Ma) at the root of the tree; biogeographic analysis used the DEC model with dispersal probabilities between areas based on distance and floristic affinities. Myrcia s.l. originated in the Montane Atlantic Forest between the end of Eocene and early Miocene and this region acted as a secondary cradle for several lineages during the evolution of this group. The Caribbean region was important in the diversification of the Calyptranthes clade while the Guayana shield appears as ancestral area for an older subgroup of Myrcia s.l. The Amazon Forest has relatively low diversity of Myrcia s.l. species but appears to have been important in the initial biogeographic history of old lineages. Lowland Atlantic Forest has high species diversity but species rich lineages did not originate in the area. Diversification of most subgroups of Myrcia s.l. occurred throughout the Miocene, as reported for other Neotropical taxa. During the Miocene, geological events may have influenced the evolution of the Caribbean and Amazon forest lineages, but other regions were geological stable and climate changes were the most likely drivers of diversification. The evolution of many lineages in montane areas suggests that Myrcia s.l. may be particularly adapted to such environments.

Aridity, soil and biome stability influence plant ecoregions in the Atlantic Forest, a biodiversity hotspot in South America

“…These nuclei thus probably constitute ecotonal zones where the Atlantic and the South American dry diagonal floras intermingle, and largely correspond to previously detected floristic gradients (Oliveira-Filho and Fontes 2000, Santos et al 2012, Marcilio-Silva et al 2017. Other ecoregions correspond to naturally fragmented mountainous regions where endemism (Scudeller et al 2001, Caiafa and Martins 2010, Kamimura et al 2017, Santos et al 2017) and longdistance disjunctions with the Amazon (Zizka et al 2018) are common. Abundance ecoregions, on their turn, portray dominance patterns linked to variation in the prevalence of ecological strategies related to competitive resource acquisition, stress and disturbance tolerance (Grime and Pierce 2012).…”

“…Occurrence-based analyses gave equal weights to common and rare species (Legendre and Legendre 2012), and should thus be viewed as depicting nuclei with different rare and endemic species whose richness make the Atlantic Forest the global biodiversity hotspot it is (Myers et al 2000, Carnaval et al 2014. Other ecoregions correspond to naturally fragmented mountainous regions where endemism (Scudeller et al 2001, Caiafa and Martins 2010, Kamimura et al 2017, Santos et al 2017) and longdistance disjunctions with the Amazon (Zizka et al 2018) are common. These nuclei thus probably constitute ecotonal zones where the Atlantic and the South American dry diagonal floras intermingle, and largely correspond to previously detected floristic gradients (Oliveira-Filho and Fontes 2000, Santos et al 2012, Marcilio-Silva et al 2017.…”

“…Glacial cycles also caused altitudinal migrations, spread, contraction and fragmentation of cool-and warm-adapted species in opposite directions, driving the assembly of communities due to adaptive radiation, allopatric/parapatric speciation, extinction and priority effects (Collevatti et al 2012, Turchetto-Zolet et al 2013, Leopold et al 2015. Evidence of distinct evolutionary lineages have been reported to the Atlantic Forest in response to drought severity (Antonelli et al 2018), chilling temperatures (Giehl andJarenkow 2012, Leslie et al 2012), mountainous habitats (Perret et al 2013, Turchetto-Zolet et al 2013, Santos et al 2017, and in regions showing high degrees of biome stability during Pleistocene climatic oscillations (Prance 1982, Carnaval and Moritz 2008, Carnaval et al 2014, Costa et al 2018. Many historical patterns have been identified in the Atlantic Forest such as the formation of forested refugia in southern mountain ranges during glaciations (Carnaval et al 2014, Costa et al 2018, the restriction of old lineages such as conifers to the temperate portions of the Atlantic Forest (Giehl and Jarenkow 2012, Leslie et al 2012, Slik et al 2018, and vicariance of isolated populations at mountain tops (Perret et al 2013, Santos et al 2017.…”

“…Tropical rainforests exist in eastern Brazil at least since the Eocene (56 million years BP, Burnham and Johnson 2004), and their high species diversity resulted from high rates of net species production and intercontinental migration of boreotropical lineages mainly since the Miocene (ca 20 million years BP, Christenhusz andChase 2013, Antonelli et al 2015). The reorganization of the biota produced by glacial cycles (Collevatti et al 2012, Turchetto-Zolet et al 2013, Leopold et al 2015 has produced identifiable evolutionary patterns in Atlantic Forest lineages in response to environmental gradients of aridity, temperature and elevation (Giehl and Jarenkow 2012, Turchetto-Zolet et al 2013, Santos et al 2017, Antonelli et al 2018. The reorganization of the biota produced by glacial cycles (Collevatti et al 2012, Turchetto-Zolet et al 2013, Leopold et al 2015 has produced identifiable evolutionary patterns in Atlantic Forest lineages in response to environmental gradients of aridity, temperature and elevation (Giehl and Jarenkow 2012, Turchetto-Zolet et al 2013, Santos et al 2017, Antonelli et al 2018.…”

“…The alternation of glacial and inter-glacial periods produced oscillating temperature and rainfall and, due to niche conservatism (Ricklefs 2006, Antonelli et al 2009, Hughes et al 2013, range expansion and contraction of species associated with forest or open habitats (Carnaval and Moritz 2008, Turchetto-Zolet et al 2013, Carnaval et al 2014. The reorganization of the biota produced by glacial cycles (Collevatti et al 2012, Turchetto-Zolet et al 2013, Leopold et al 2015 has produced identifiable evolutionary patterns in Atlantic Forest lineages in response to environmental gradients of aridity, temperature and elevation (Giehl and Jarenkow 2012, Turchetto-Zolet et al 2013, Santos et al 2017, Antonelli et al 2018.…”